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Home My WebLink AboutCT 06-16; CARLSBAD BOAT CLUB AND RESORT; WATER QUALITY TECHNICAL REPORT; 2006-06-01�_ � � i � !�'f I�I 1 ` . � �/ �� ,o �. .�; �,� < O �Ji y�2 �, y1 �/� / -�� r� �d �/ � 0��S�� ✓` O WATER QUALITY TECHNICAL REPORT CARLSBAD BOAT CLUB 4509 Adams Street Carlsbad, CA EXCEL ENGINEERING 440 State Place Escondido, CA 92029 (760) 745-8118 ��.�� 6 - Zs -o G obert D. Dentino RCE #45629 Exp. 12/31/06 ��, �� Il �� ; -, � For: - Carlsbad Boat Club . 4509 Adams Street Carlsbad, CA 92008 June, 2006 0 � ��,o�ss�o'y�r� �� %�� '��Om �, �,�;,_� � e� �� \OF �p�1F�/ i aC .� , :; -; ,� _; I� � I �_ � TABLE OF CONTENTS i. 2. INTRODUC'1'ION ..............................................................................................................1 PROJECT DESCRIPTION .......................................................................1 Topography and Land Use . ... ... ........ . ....... .... . ... . ... .. . . . . ... .. .. . . ..... . . . . . ........1 Watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Post-Construction Storm Water .............................................................3 Cond.itions of Concern ................................................. ...................... 4 � ,� 3. POLLUTANTS AND CONDITIONS OF CONCERN ..........................................5 Treatmant�Control BMP Selection Matriac ................................................5 Anticipated and Potential Pollutants Table .. ... .... . . ... .... . . ... ... .. . . .. ...... .. . ... ....6 ,� �� i �� , �, DrainagePattern .........:............................................... .... ..................8 WaterQualiy .........................�........................................................,8 �nvironmental Analysis, Hydrology/Water Quality .............. . .......................8 Concerns of Receiving waters . ....... ....... ..... .. ... . ... . .... . . ...... .. ... ... . .. ... .......9 Beneficial Uses .............................................................................. 10 Impaired Bod.y of Water ..........................................� ......... ................10 4. STORM WATER BEST MA,NAGEMENT PRACTICE5 ....................................10 SiteDesign BMP's .................................................. ... ....................11 SourceControl BIViP's ......................................................................1 l Project Specific BMP's .....................................................................12 i -� �, �� 5. PROJECT BMP PLAN Il�IPLEMENTATION ................................................12 Recommended Post-Construction BMP Plan Option .. . . . ... . . . . . . ... .. . . . . .... .... ..12 Operation and Mai.ntenanca Plans .......................:.... ............ ................13 Mai.ntenance Responsibility ..................................:.. ...... ....................13 �� i � �; 1 I 1 � APPENDI�CES 1: Storm Water Requirements Applicability Checklist 2. Vici.nity Map 3. Site Control BMP's 4. Source Control BMP's 5. Drainage Study 7. Drainage Map r, � _1 i; f 1. INTRODUCTION This Water Quality Technical Report (WQTR) was prepared to recommended project Best Management Practice (BMP) options that satisfy the requirements ident'ified in the following documents: City of Carlsbad — Storin Water Standards Manual; . County of San Diego Watershed. Protection, Storm Water Management and Discharge Control Ordinance (County Ordinance), Sta.ndard Specifications for Public Works Construction; NPDES General Permit for Storm Water Discharges Associated with Construction Activity; and . San Diego County NPDES Storm Water Permi� Specifically, tlus report includes the followi.ng: Project description and location with respect to tha Water Quality Control Plan for the Carlsbad Boat Club. � BMP design criteria and water quality treatment; Recommended BMP options for the projec� �BMP device information for the recommended BMP options; ;�� LI Operation, maintenance, and fundi.ng for the recommended BMPs; 2. PROJECT DESCRIPTION ,! The exi.sting site is approxi.mately 1.0 acre in size, with approximately 0.10 acre being within the '- � ridal zone. The existing residenceJboat club structure is to be removed. In its place will be a new 3 _ story boat club and time share with under ground parking for vehicles and small boats. Three i floors wi.11 be visible from the La.goon and only one floor will be visible from Aciams, Street. The -� site will be accessed from Adams Street via a driveway, which starts out at 5% and at its steepest __ point reaches 19%. ,, i� � � (; i �s ! , The land currently has a large residential structuxe which is being used for boat club purposes. The majority of the site drains southerly into the Agua Hedionda Lagoon without any treatment. There is a little storm runoff that flows onto the property from the west and east. This runoff will not be allowed to cross onto the subject property. It will not be diverted and will reach its final destination, which is the Agua Hedionda Lagoon. Site looking north " .__��f S '- q� �' ."""'" � Y�,� � .�a� �g,� � �� . � � �: E _. �' . .�,: " ....�.. . . .•. .�� l Si� The proposed storm drain for this project will tie into a proposed detention facility consisting of four 27-inch CMP's , which will provide 314 cubic feet of storage for the proposed development. i �� 5 ;h�,'�"'��5 ci`,}jz`='":: .�tt(dF, -2- Site looking northeast r�.� � - Runoff will exit the site from three points. The first point is from the boat ramp located on the east side of the property. This outlet will discharge the runoff-generated from the pedestrian walkways and the boat ramp area. The second point will be from the location of the club house and boat dock area, the majority of this area is sand. The third area is the main storm drain system which will detain and treated runoff before discharge into the Agua Hedionda Lagoon. This storm drain services the rooftops, hardscape, and landscaped areas. When the site is fully developed with structures, landscaping and sidewalks. There will be an increase in the runoff generated. However, since the difference in impervious surfaces only increases from 57% to 63% the differential run-off is minor. Pre construction runoff was calculated to be 3.94 cfs. The post construction runoff was calculated to be 4.25 cfs; an approximate 0.31cfs increase in runoff. Additionally the site will no longer be discharging untreated run-off into the Agua Hedionda Lagoon. The onsite soil consists of an upper loose and compressible alluvium of silty, gravelly sand. This soil type is categorized as moderately well drained and the run-off is low and erosion hazard is slight. There are no rock outcroppings on site. -3- � ;�.x;; .-�. . . . .�4.F y�-� l"l.+y � � � � ,M.S �� -� . ( � M` 3w"_»� s c`�-�+eo y� t:`. ".,.r.,....�,�,,,�„��..�,�„ � �_ en �. r.. ffi- +� � '�� w .-- . . . ,. � .. .. . . . .. �. . ... S1�_,"-C: dr _ _ . . .. . , ,. . �_ —_. . All runoff from this project will ultimately proceed southerly and into the Agua Hedionda Lagoon. According to the 1998 303d list published by the San Diego Regional Water Quality Control Board, the Agua Hedionda Lagoon is an "impaired water bod}i'. Pre- and post-construction BMPs are mentioned in this report for this project and will be detailed in the project's future SWPPP. Currently in City of Carlsbad runoff from building roofs, driveways, patios, sidewalks, streets, and alleys, etc. is characterized as low, intermittent, seasonal flow and poor water quality. Water quality is degraded by urban runoff. The greatest, and generally only, flow occurs during the winter months. -, _ Looking east along the lagoon. 1 } 3. POLLUTANTS AND CONDTTIONS OF CON,CERN As shown on the "Storm Water Requirements Application Checklist" (Appendix 1) this project is �- '� subject to the "Priority Project Permanent Storm Water BMP R.equirements." Per table 2(Page 7 '_� of this report), this project f�all.s into the following project categories: 1) Attached Residenti.al. Development ; j 2) Restaurants � ;� 3) Hillside Development over 5,000 square feet The anticipated and potential pollutants generated by this type of development include: • Sediment � � • Nutrients� � � • Trash and debris • Oil, Grease and Heavy Metals i � • Oxygen demanding substances ' "• Bacteria and Viruses • Pesticides Per the 303D list, the Agua. Hedionda La.goon is impaired by bacteria and sedimentation/siltation. Therefore, these will be a polluta�rt of pri.mary concern, with the rem ��ng pollutants being of secondary concem. �, , A review of table 4(next page), "Structu.ral Treatment Control BMP Selection Matrix", indicates �; infiltraxion basins and filtration are the only treatment controls BMP for bacteria and Viruses to achieve a high to medium removal efficiency. � For this project our primary treatment BMP will be filtration in regards to our pollutant of primary concem. This offers a medium'removal efficiency for sediments. This BMP also treats all secondary pollutants with a high to medium removal rating. � There will be two variations of filtration used on this project; one will be the sedimenta.tion time �"! used in the proposed detention facility and the other will be a gravel and sand strip on the west � side of the driveway (see detail below). `� , i - . �; , .�. ,i ,_ ;I �! �� :� �rr� �rs � The sand filter ca.ptures and treats the design runoff in a two part system, first a straining area, then a filter bed. The strai.ni.ng area collects large sediment and prevents these objects from clogging the filter bed.. The sand bed then strains the water, removi.ng soluble and patticulate pollutants. The treated water is conveyed �rough the perforated pipes and into an underground detention facility which allows more filtra.tion and sedi.mentation before final controlled discharge into the Agua. Hedionda I,agoon �� J �� ,'f f l l t �, ; � ! ; , � i� I y� Table 4. Treatment Control BMP Selection Matriz Pollntant of '�atmeat Controi BMP Categorles Concern B1oIIlters �nUon Inflltrat(on Wet Pond� or Drainage Hydrodynamte Baains Bailas�� Wetlswda Inaerb Filtrxt3on �arAtor Syatemi�� Sedim�t M H H H ' L H M Nutrients L M M M L M L fieavy Metals M M M H L H L �° U U U U L ' M L Compounds Trash and Debris L � H U U M FI M �� Domanding L M M M , L M L Substances Bacbe�ia U U FI U L M L Oil and Cmase M M U U L H L Pesticidea U U U L U L (1) Inctuding trenches and porous paveme�t . (2) Also lmown as hydrodynamic devices and bafflo boxea. L: Low removal eff ciancy _ M: Medium removal e�icieney E3: ffigh t�emoval officiency U: Unlmown re�oval effici�cy Soum.es: C�luidance Speaifying Msnagemaut Measares for Sourcas ofNou�►oint Polfition in Coasffi1 VJate�a (1993), National Stonnwater Bast Msaagement PtacHces Databesa (2001), and Guide fnr BMP Soleation in Urban Developui Areas (2001). 6- � l �-J , I '__ �,� � � ( ( , i , l � � �j � � � _� Table' 2. Anticipated and Potentlal PoIlutants Generated by Land Use Type Gener�l PoIlntant G►tegorie� Prlodty Project Heavy prganic '�ash �3'g� OIl and Bac� Categoriea Sedimenb Nutrienb Metale Componnds and Dems►nding Grease and Pestlddee DebrL Snbatances Vicvees D�ached Reaidential X X X X X X X Developmeut Attached Rasideatial X X X P�l� P� P X Development Commencial Develo�ment>100, P�� P�I� P� X P�� X P�3) P�� 000 ft. . Automotive Repair X Jt�4x� X X Shops Rostaurants � X X X X � H'illsido . Dovolopmemt X X X X X X >5,000 ft.2 Parking Lote Pt�� P(i� X . X P�i> X p(t) Streeta, Highways X P�l� • X X�� X P�� X and Freeways X = anticipated P m potential (1) A potential pollutant if landscaping ezists on-site. (2) A potential pollutant if tha project mcludas uncovered parking areas. (3) A poteutial poltutant if land nsa involves food or animal wasta products. (4) Inclnding petroleum hydrocarbons. (5) Includ'mg solv�ts. -�- � � ! �- � �- � i � � Drainage Pattern Runoff from the site would ulti.mately flow into the Agua Hedionda La.goon. ;� `; Therefore, the proposed project would not result i.n: an alteration of the coutse or flow of rai.n ', __ i waters, nor is it anticipated exposing people or property to water-related hazards, such as flooding. Impacts associated with flood hazards would not be significa.n� Impacts of the proposed Boat (� Club project on local water resources may include an overall reduction i.n polluted urban ninoff � into the Agua Hedionda Lagoon. Approximately 57 percent of the site is currently covered by impervious surfaces. The site will become approximately 63 i.mpervious once developed. Impacts !�� associated with surface runoff would be less than significan� � �_: Drai.nage patterns withi.n the project area would not be modified; therefore, no significant impact would occur. �� ,i Water Qnality The quality of water comi.ng from the proposed new Boat Club site would be enhanced when compared to the use of the existing Boat Club site. Consistent with the Regional Water Quality Control Board's (RWQCB) San Diego Urban RunoffMunicipal Permit, the proposed project would ensure tha.t appropriate measures to control pollutants from the new development would occur. Such measures i.nclude, but would not be limited to, the incorpora.tion of runoff collection and treatment such as filter strips and on=site detention prior to its release from the site. The use of these devicec� would reduce the amount of polluted or contaminated wa#er released into the Agua Hedionda Lagoon. Environmental Analysis, Hydrology/Water Qnality i_c Currently there are no mechanical devices on site to process the nmoff, which result in runoff going straight into the Agua Hedionda Lagoon without preliminary treatmen� Based on this ��, discussion, i.mpactg associated with water quality for the life of the proposed project would be less � ', i than significan� �" �; I� �-� �; -8- j, Concerns in Receiving Waters The Carlsbad Boat Club project is located adjacent to the Agua Hedionda Lagoon. According to the 1998 303d list published by the Regional Water Quality Control Board, the Batiquitos Lagoon (Carlsbad Water Shed HU 904) is an "impaired water body." The sections below provide the beneficial uses and identification of impaired water bodies within the project's hydrologic area. Beneficial Uses The beneiicial uses of the inland surface waters and the groundwater basins must not be threatened by the project. Tables 1 and 2 list the beneficial uses for the surface waters and groundwater within the project's hydrologic area TABLE 1. BENEFICIAL USES FOR INLAND SURFACE WATERS Surface z� U U� p�� W W a t e r � z C� C� O� W �'"' � 1 � 3 � � Batiquitos N E E E N E E E E E E E La oon TABLE 2. BENEFICIAL USES FOR GROUNDWATER Hydrologic Unit, Hydrologic Area MIJN AGR IND Carlsbad Watershed (HU 904) Ex N N Notes for Tables 1 and 2: Ex: Excepted from Municipal E: Existing beneficial use P: proposed beneficial use N: Not a beneficial use IND - Industrial Services Supply: Includes use of water for industrial activities that do not depend primarily on water quality including, but not limited to, mining, cooling water supply, hydraulic conveyance, gravel washing, fire protection, or oil well re-pressurization. NAV — Navigation: Includes uses of water for shipping, travel, or other transportation by private, military, or commercial vessels. REC1 - Contact Recreation: Includes use of water for recreational activities involving body contact with water where ingestion of water is reasonably possible. These uses include, but are not limited to, swimming, wading, water-skiing, skin and SCUBA diving, surfing, white water activities, fishing, or use of natural hot springs. -9- i t � 1 � '� I ,_,� � REC2 - Non-Contact Recreation: Includas use of water for recreation involving proxi.mity to water, but not normally �� involving body contact with watar where ingestion of water is reasonably posaible. Thesa �isea include, bnt are not limited to, picnicldn.g, sunbatiung, hiking, camping, boating, tide pool and marina life study, hunting, sightseeing, or ��`� " aesthetic enjoyment in conjunction with the above activities. � ,, COMM — Commercial and Sport Fishing: Includes the usae of water for commercial or recxeational collection of fish, -- shellfish, or othar organisms including, but not limited to, uses involving organisms intended for human consumption � �' or bait purposes. I � BIOL — Preservation of Biological Habitats of Special Signi.ficance: Includea uses of water that support designated areas or habitats, such as established refuges, patks, sanctuaries, ecological reserves, or Areas of Special Biological Significance (ASBS), whare the preservation or enhancement of natura.l resources requires special protection. EST — Estuarine Habitat: Includes uses of water that support estaari.ne ecosystems i.ncluding, but not limited to, preservation or enhancamemt of estuarine habitata, vagetation, fish, shellfish, or wildlife (e.g., estaarine mammals, waterfowl, shorebirds). � ,�� WII.D - Wildlife Habita� Includes uses of water that su�port terrestrial ecosystems including but not limited to, � 1�' preservation and enhancament of teaestrial habitats, vegetation, wildlife, (e.g., mammals, birds, reptiles, amphibians, _ _ � . inveatebrates), or wildlife and food sources. RARE — Rare, Threatened, or Endangered Spacies: Includes uses of water that support habitats necessary, at least in part, for the survival and successful maintenance of plant or animal speciea e.smblished imder stata or federal law as rare, threatened or endangered. MAR — Marine Habita� Includes uses of water that support marine ecosysbema including, but not limited to, preservation or enhancement of marine habitats, vegetation such as kelp, fish, shellfish, or wildlife (e.g., marine mAmmAls, shorebirds). " ,_ I MIGR — Migiaxion of Aquatic Organisms: Includes usea of water that support habitata necessary for migration, acclimatization betwcen fresh and salt water, or other te�porary activities by aquatic organiams, such as anadromons � , fish. SHELL — Shellfish Harvesting. Includas nses of water that support habitais auitable for the collection of filter-feeding shellfish (e.g., clams, oysters and mussels) for human consumption, commarcial, or sport purposes. . - Impaired Water Bodies !� Section 303(� of the Fedaral C1ean�Water Act (CWA, 33 USC 1250, et seq., at 1313(d)), requires States to identify and list waters that do not meet water quality standards after applying certain required technology-based affluent lim.its (i.mpaired water bod.ies). The list is known as the Section '� 303(d) list of im�aired waters. ,� .- �; . �`,� 4. STORM WATER BEST MANAGEMENT PRACTICES The Storm Water Standards Manual requires the implementation of applicable site design, source . control, project-specific, and structural treatrnent control BMPs. _� ; ; �[�r , � ,, � I �_ 5 �� _; �� IF ,� �' � �� _� ,, ,� � �_i ; -7 � i, �' �' Site Design BMP's " The followi.ng BMP's are considered in the project design process: 1. Reduce impervious surfaces especially in the boat ramp area (see appendices 3), 2. Sand filtration for treatrnent of 85�' percentile flows (see appendices 3), 3. A detention facility to allow reduction in nanoff and provide sed.i.mentation treatment, 4. A cross gutter at the entry of the new Cazlsbad. Boat Club preventing offsite polluta.nts migrating onto the site, � 5. Well landsca.ped slopes to reduce erosion, see bio retention (see appendices 3), Wherever possible, the use of i.mpervious surfaces was lim.ited to walkways around buildi.ngs, boat ramp and the parking area. In addition, the use of efficient landscaping incorporated in the area design to assist i.n the filtration and reduce the runoffs contamination with sediments, nutrients, heavy metals and to some extent oils and grease. � 5ource Control BMP's The following BMP's were considered in the project design process: 1. Spill prevention and control (see appendices 5), 2. Trash stora.ge (see appendices 5), 3. Include storm drain stenciling and signage (see appendices 4), 4. � Include properly designed outdoor material and trash storage areas (see appendices 4), 5. Parking lot sweeping (see appendices 4), . 6. Inlet trash barrier cleaning (see appendices 4), 7 8. Professional landscape maintenance (see appendices 4); Efficient irrigation, and Integrated pest mallagement principles (see appendices 4), 11. Prompt removal and disposal of trash waste and debris from open areas. An appendix 5 contains all of the pertiuent i.nformation relative to the Source control BMP's listed above. However, item eleven requires that the Carlsbad Boat Club maintenance staff will implement a source control best management practice that requires the da.ily trash removal from the facilities grounds and beach area. This will eliminate the `�vashing away" of any debris into the Agua Hedionda Lagoon during a storm event. � �-� �: � Project-specific BMPs The Storm Water Sta.ndards Manual requixes specific BMPs for this project. The following are incorporated into the design: . � �k ; � 5. PROJECT B1VFP PLAN IIVIPLEMENTATION � i This section identifies the recommended BMP options tb.at meet the applica.ble storm water and " water quality ordinance requirements. This includes i.ncorporating BMPs to minimi�.� and mitigate for runoff contauL__�ion and volume from the site. Note that BMPs other tha.n those j identified in the plan ma.y be used during final engineeri.ng. . . The followi.ng sections address the use of construction- and post-construction BMPs. Recommended Post-Construction BMP Plan OpHon � Since the site is geometrically constrai.ned, it is not practical to create an above ground detention basin near the outfall. Long-term maintenance of a detention basi.n would also be problematic. ;� This site proposes to detain the peak runoff and the 85� percentile flows with an underground �; detention facility: This will be designed. for a gradual discharge to allow sedimentation and, if possible infiltration. Also, as a means of reducing the discharge of hydrocarbons and other debris �' 1 into the Agua Hedionda I.agoon, the site drainage will be filtered by a sand filter. Runoff from the ', ,� roofs will also be directed through the detention/sedimentation facility before discharge into the Agua Hedionda Lagoon. Additionally the sites underground detention system will serve as ;; �� "settlement area for �y debris in the runoff and provide for possible infiltration, however, we are ;� not counti.ng this for the purposes of this report. � j` • Collection of debris in the catch basin '�-, • Treatment of roof run-off � • Detention area for predevelopment runoff release ;� '�1 i't , , ,z_ r -, �, ;, � '_; r `�, �� ? i i � 1 '� � Operation and Maintenance Plan and Maintenance Responsibility As a contract for the City of the long-term maintenance requ�rements of proposed BMPs and a ', f description of the mechanism tha.t will ensure ongoing long-term mai.ntenance. The maintenance �_ or the parking and enclosed trash a.reas and sweeping of the rooftop . and maintaini.ng of the mechanical BMPs are the responsibility of the Carlsbad Boat Club. These items will be included `' ' in the annual mai.ntenance activities for the facility. � Name of Project: Carlsbad Boat Club � j Owner: Carlsbad Boat Club , 4509 Adams Street ; CarLsbad, CA 92008 � `-'; ,, i i i �I ' f i � i �J � � ,` , ,-� ;� �f 'i ) � _. ! L � -13- , �°�_ � �` "+� APPENDIX 1 � 1� Storm Water Requirements Applicability Checklist STORM WATER REQUIREMENTS APPLICABILITY CHECFa.IST ;� �I �_, _� �; � �i �`� , s �' ,'- s 1 � ' _? , -, 'r � _I I ` � G' .� � , 1: ,�� i � , � 'i ,[ ,�� , Section 1. Permanent Storm Water BMP Requirements: If any answers to Part A are answered "Yes," y�our project is subject to the "Priority Pro}ect Permanent Stam Water BMP Requirements," and "Standard Permanent Stortn Water BMP Requirements" in Section III, "Permanent Storm Water BMP Selectlon Procedure' In the Storm Water Standards manual. If all answers to Part A are °No," and any answers to Part B are "Yes,' your proJect Is only subJect only to tf�e Standard Permanent Storm Water BMP Requlrements. If every question in Part A and B Js answered "No," your proJect Is exempt from permanent storm water requlrements. � . Part B: Determine Standard Permanent Storm Water Requlreme Does the proJect propoae: • 1. New Impervfous areas, such as rooftops, roads, parking lots, drlveways, pethf 2, New pervlous landscape areas and lrrigatlon systems? 3. Permanent structures withln 100 feet of any natural water body? 4. Trash storage areas? ' � 5. Llquld or solld mafierlal loading and unloading areas? 6. Vehlde or equlpment fueling, washing, or melntenance arees? � 7. Requlre a General NPDES Permit for Storm Water Dlscharges Assoc(ated wH (Except'construcdon)?' � S. Commerclal or Indusfiial waste handling or storage, excluding typical offlce or -14- and sldewalks? �/ ✓ ,/ - ✓ ✓' ✓ � Industr(al Activltles � iousehold waste? �/ , , k � �'-� I �, i I �' � � � _, ,� ,) �t ��-� � _� ,i ,; t_ 1 �_ ti ,� �1 Section 2. Consttvction Storm Water BMP Requlremerits: If the answer to questlon 1 of Part C Is answered "Yes," your project Is subJect to Section IV, "Constrvctlon Storm Water BMP Performance Standards," and must prepare a Storm Vllater Pollution Preventlon Plan (SVIIPPP). If the answer to ques�on 1 is "No," but the answer to any of the remaining questlons Is "Yes," y�our pro)ect Is sub)ect to Section IV, 'Construction Sfiam Water BMP PerFormance Standards," and �must prepare a Water Pollu�on Control Plan (VI/PCP). If every question ln Part C is answered 'No," your project is exempt from any construcdon storm water BMP requirements. If any of the answers to the questions In Part C are "Yes,` complete the constructlon site prloritfzatbn in Part D, below. . Part C: Determine Construction Phase Storm Water R ulrements. Would the proJect meet any of these criterla during constructlon? Yes No 1. Is the proJect subJect to Califomla's statewide General NPDES Perr�it for Storm Water Discharges � Assocfated Wfth Constructlon AcUvftles? ' 2. Does the proJect propose grading or soil disturbance? �/ 3. Would sfi�rm water or urban runofP have the potentlal to contect any portlon of the constructlon area, including washing and staging areas? - 4. Would the proJect use eny construc�fon materials that could negatively effect water qualfiy if disc#�arged from tt�e site (such as, palrtb, sotvents, concrefe, and stucco)? Part D: Determine Constructlon Sfte Prlority ✓ ✓ In accorciance wlth the Munidpal Perm�, each construclion stte with consfivction storm water BMP requlremerrts must be designated with a priority: high, medium or low. This priori�zation must be completed with thts form, noted on the plans, and induded in the SWPPP or WPCP. Indicate the project's prioriiy in one of the check boxes using the criterfa below; and-existlng and surrounding condf�ons of the proJect, the type of activi�es necessary to complete the construction and any other extenua�ng arcumstances that may pose a threat to water qualtty. The City reserves the right to adJust tt�e prbrity of the proJects both before and during constructlon. [t�ae: me construc�ior, ptiorlty aoes IVor c�enge construc�ton eMP requ�rernerns that apply to proJects, ap construc�lon BA� requlrementa muek be Identlfled on a c�se-bjr-case baels. The construdfon prlority does affect'the frequency of fnspectlons thet wlll be �ed by C�ty s�i. See 3ectlon N. 1 for more details on constrix:Uon BAAP requirements.] k� � �,l '�� i � �`� �� t� � s� i , ._ r r- ti, + �t� �-� ,� � i 1 �, A) Htgh Prlorily . 1) Projects where the site is 50 acres or more and grading will occur durfng the wet season 2) Projec�s 5 acres or more and tributary to an Impaired water body for sediment by the most currer�t Clean Water Act Sectlon 303(d) Ilst (e.g., Penasquftos watershed) 3) ProJects 5 acxes .or more withln or dlrectly adJacent to or discharging dlrectly to a coastal lagoon or other receiving water withln an water qualtty sensitive area .. 4) Projects,, active or Inactive, adjacent or tributary to sensltive water bodies B) Medlum Prlorlty 1) Capftal Improvement ProJects where grading occurs, however a Storm Water Pollutlon Preverrtlon Plan (SWPPP) Is not required under the State General Construction Permft (Le., water and sewer replace+nent proJects, intersectlon and street re-allgnments, widening, comfort statlons, etc.) 2) Permit proJects In the publ� rlght�f-way where grading occurs, however SWPPPs are not required, such as Installatlon of sidewalk, substantlal retaining walls, curb and gutter for an en�re street frontage, etc. -�s- � '� � 3) Permit proJects on private properly where grading permtts are requlred (i.e., cuts over 5 feet, �� fills over 3 feet), however, Not}ce Of Intents (NOIs) and SWPPPs are not required. ' � ❑ � C) Low Pr�orlty � 1) Capital Projects where minimal to no grading occurs, such as signal light and loop , j instanations, street Ilght lnstalla�ons, etc. !_� 2) Permit projects In the publ(c rtght-of-way where minlmal to no grading occurs, such as pedestrian ramps, dfireway addltions, small retalning walls, etc. �" ; 3) Permit projects on prfvate property where grading permlts are not required, such as small ;� retafning walls, single-family homes, small tenant Improvements, etc. S �k i A � � �_�� i ' � _ i � � 4 i � . } , -� i � y , 1 (� , � � -� t i -16- � r � � � APPENDIX 2 Vicinity Map ��"��,� .� � ��- � a �� ,e� ;;r.r�^ , . .�. � ,*,,,` , �� "-. c� y. pg . a . � .. .. � �" �A. < r fi� r - � i � �n�' �' F�`" t � ' N yr ��. . . . � � . . lt a�0% '� :i� � � � �� L- �r�:- ��t -:s , � ., '? , a. ` a`„". �'P �"1:, .< < .. a � 11 : ' �j_ , ' N , '. `'$� � J,p ',��' : `� p_ ' -�'1 � �'' �S;l .�'y.�, , ' .. �. ,r� ' _2 � ,� �y�� r ' 'f� � l`fdy �� 4�r �. . �+ r y ';, s^ � a � a, � `�: ;►,.�i�; ` ''� yt P, -;o , �'' � f,�: ;�• � �.�, , ta `c n r s�l�' � � �kp ` 4� . � L� a � ' ' c :. `�. ��, yt' �,�8r� � �q �, � � � .. �Q . w,�i� � 3 c : � - �f.`. _... t'�ti�•� .�`��•�" , o �-. ,r.✓ '�� _ .�� .�.� 7 -� ; ' . . : � p ' o�a : �, �: � 1?:�� ; t� . . , „ ��¢ � � �ta yL � � _ . ,+.7�, "� . , � � PJyc �"0,,� J� � � F�`,�. �vidqnClt� A�e '• �G,: Cry � : - � � � � - - _ � `�: � �� , '�_ . �. �; _-�4 .. F� ., � p6 ,, . . ��: a� ,. `r'0��1��Rr, a:, t �. �4 a � ` . . �� ,� � � �. � � � - � � . �> -.,. 'r^ °,� i _ .'',.� �� . �_� . !� .� y� �� (1� . �u `��i t6 � { 'j:rl � c� .�dy v , ' ` r :�;.. ��y`� ^,�f��;�.�,y •� {fy;ti'�5�� i; ,, ,.�av� ��,, �r�,�of { � ' f ' Gr a� f5 .",� � ��.< � � � � , ,Sy ` � � � °�Y G� : �'X S` t. �ir� �� ": { sV� '. -,S*� F`� m/ ° �s3 � " � r � ,�A� . � g ''� E ' � � � �� h4 � p•h ., ��t'.� ��. �.'4 j {�, ��,�, s pfy'' � ' �'r �. � .. gy�� ti�"�', t ��'0'3�a �� " � t� ;. ��(jp : � ` a • Qf � �% t'� -_.. �;'�': � ��'�� A� � �:� � � �r � � ° � �'�"�y ,, 4 � �� o a� 1 -` yg a'� �' .r ,y b - ;� ,�ua v�,� o ' � , �` ��t A...� �%•:i 'ss � .� a `�j° "� q '. u�� . �" v1- :y . li . : :��',� 7 u �y,a ' �,'c` . " ,�a. 'p .. do . 'P �j�. p �, � . �, _ � ,,o � �"t' -y � � C� � ati + � -� u � a �. � � � �'i' �ry��a� `' ' � �� , V.. ��Ot�yii 4 . � , �Q �q+ t E'�' '� $ - -.� ��" * SITE� .� " �. }',� ` _ �c 4 � a , �m - � � nor� ft � C� 2QGe '� a^ o c' f n� �;, �2a`CB hi�VTEQ v- 2002 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED SEGMENT ApprovedbyUSEPA: r„r,� zoo3 SAN DIEGO REGIONAL WATER QUALITY CONTROL 130ARD CA•LWA`LER YO'1'EN`L1AL TNtDL ESTL1�iA'I7•:la YROI'OSED Ti1i>L RE�,I(N� 'TYPE N:�1�LE W'ATEKSF�P:D �POLLC'"t'AN7ISTKESS.Q1Lt SOUI�CES I'RTORI'T1' SI'I,E AFPEC1k:D C0IIPLETFO:V 9 li Agua ]lediouda Creek 90=131000 Total Dissolved Solids Low 7 Miles 9 � Agua Hedionda Lagoon 90431000 Bacteria lndicators Sedi m entation/Siltation 9 R Aliso Creek 90113000 Bacteria lndicators Medium Urban RimotT/Storm Sewers Unknown point sourcc Nonpoint/I'oint Source Phosphorus Low /mpairnrent loeated at lou�er 4 miles. Urban Rw�ofUStorm Sewers Unknown Nonpoint Source UnknoHn point source Toxicity Low Urban Runuf�Storm Sewers Unknown Nonpoint Source Unknown point sourcc 9 E Aliso Creek (moutl�) 9 E Buena Vista Lagoon 90113000 Bacteria lndicators Urban RunofUStorm Sewers Unknown Noopoint Source Unknown point source Low Nonpoint/Point Source Low Nonpoint/Point Source Nonpoint/Point Source 6.8 Acres G.8 Acres 19 Miles 19 Miles 19 Miles Medium 0.29 Acres 90421000 Bacteria lndicators Low \ionpoint/Noint Source Nutrients Low Estimated si_e of imparrment is I50 acres locuted in upper portion of lagoon. Nonpoint/Point Source Sedimentation/Siltation Medium Nonpoint/I'oint Sourcc 202 Acres 2U2 Acres 202 Acres Page 1 oj 16 � �� ' li � - -� � �� , �i � �, i! 1-. �� 1 �_� ,�� ,� N-, � � 4 r -ti 1 '�. Y il I' i�f i`- f 0 APPENDIX 3 Site Control BNiP's � I l' � 0 r � a � , � �� e' r �.� ��4 _ - �. �:� 3t� � � '�:� �x ^�'��,�� . � °:� �. ,,,� �-- , - -� a �- �- �� 4 �` � �� , ,�, � ''� � � ��, � � �� , � . � � �^ '� '� , � r � � ��r � � +�; � �� ' �� ,� ,� ' � :� � � . � � j � � : � ��` � '"�` � � �s �1' � F . r � +� ,, ,� ,; �, � � ��; � � � },��M � � � �° ��: � �,��i _ � ,� �► �° i � :.� �. � �� f � � ��. f�� , � � � ��. � �, �V � : �AR�I�RTE� � Concrete Eroslon Contro/ Systems � �.� � ARMORFLEX� Armorflex mats consist of machine compressed cellular concrete blocks of a unique interlocking shape which are made up into mats for easy handling on-site. The blocks are cabled longitu- dinally by means of galvanized steel aircraft or polyester cables. ARMORFLEX FEATURES Factory Made and Assembled Sophisticated purpase-built machinery gives consistent quality and economic production. Quality Concrete Specification • 4000 psi concrete • sulphate-resistant to ensure durability • excellent freeze and thaw resistance Up to 20 Percent Open Area Permits free drainage of ground- water thus preventing a destabiliz- ing build up of back-pressure behind the revetmenfi. Flow Efficiencies Designed with open or closed cell blocks, Armorflex provides the ideal combination of unit weight and surface roughness. The Armorflex Manning Rough- ness Coefficient, n, has a value ranging from 0.026 to 0.034, depending on the block used. Vegetation The open cells of Armorilex pro- vide the perfect environment for vegetation. Grass and small shrubs The open cell structure of Armor- flex concrete revetment systems nurtures plant life, providing quicker grawfh and rnore stable revegetation. can penetrate the filter, providing an attractive, pennanent anchor for the system. When vegetation is not desired, install Armorflex with closed cells or fill open cells with stone. Access Armorflex is free of dangerous projections, so pedestrians, animals, vehicles and boats all have convenient, safe access to the water. Stability Serving as an articulated mattress, Armorflex provides continuous erosion protection against the destructive forces of water. The proper Armorflex class is determined by the design hydraulic conditions to which it will be subjected. Flexibility Armorflex blocks are interconnect- ed by flexible cables, providing articulation between adjacent blocks. Block walls are designed with beveled relief to allow far flex- ibility in all directions. Permeability When placed on filter fabric or a conventional graded �Iter, the per- meability of the revetment system relieves hydrostatic pressure in the subgrade. The system's capability for soil retention Open-cell 8/ock Closed-cell 81ock � � � � OPEN-CELL BI.00K � �� ,� - � -�_- - - •Nx�a =----- - o 0 �mrn B EN� VIEW AREf PPFA - �� -•---- 'romn.,.---- - CI - ��_ "_ "_i �_-q-.> - iuexu - TOP VIEW SIOE VIEW CLOSEQ-CELL BLOCK (WfY 9�'FX _ � � ARE� NiCA c.aF ------ - - =nxrn.i = =- O B ENO VIEW _ ,,,,,F . __ _ _ - I � = 'mrwi""'c' � ' C/�yF ' ___ __. ♦ �-A-= - - tunna = - - ' _ TOP V�EW ' SI�E VIEW prevents leaching of subsoils through the installation. DESIGN Since 1980, Armortec has initiated and participated in a wide range of research projects to evaluate the performance of Armorflex, includ- ing the following: 1. Tetratech model tests - California, U.S.A. 2. Leylstad field trials, Netherlands - Rijkswaterstaat Directorate of the Zuiderzee Project, 1982. Armorfiex Block Specifications (Typical Values) Nominal Gross Conaete Specific Compressive Dimensions Area! Block Weight" Open Block Weight Strength Maximum �� Blcek Area Class Ibs.lcu. ft. Ibs./sq. in. Absorption A B C sq. ft. Ibs. Ibs./sq.ft. % S-Class 30S 130-150 4000 121bs./cu.ft. 13.0 11.6 4.75 0.98 31-36 32-37 20 Open Cell 50S 130-150 4000 12 Ibs.lcu. ft. 13.0 11.6 6.0 0.98 45-52 45-53 20 S-Class 45S 130-150 4000 121bs./cu.ft. 13.0 17.6 4.75 0.98 39-45 40•45 10 Ciosed Cell 55S 130-150 4000 121bs./cu.ft. 13.0 11.6 6.0 0.98 53-61 54-62 10 40 130-150 4000 121bs./cu.ft. 17.4 15.5 4.75 1.77 62-71 35-40 20 Open 50 130-150 4000 121bs./cu.ft. 17.4 15.5 6.0 1.77 81-94 46-53 20 Cell 60 130-150 4000 121bs./cu.ft. 17.4 15.5 7.5 1.77 99-113 56•64 20 70 130-150 4000 12 ibs./cu. ft. 17.4 15.5 9.0' 1.77 120-138 68-18 20 45 130-150 4000 12 Ibs./cu. R. 17.4 15.5 4.75 1.77 78-89 43-50 10 Closed 55 130-150 4000 121bs./cu.ft. 17.4 15.5 6.0 1.77 94-108 53-61 10 Ce�� 75 130-150 h000 12 Ibs.lcu. ft. 17.4 15.5 7.5 1.77 120-138 66-78 10 85 130-150 4000 12 Ibs./cu. ft. 17.4 15.5 9.0' 1.77 145-167 82-95 10 ' Block height may vary by approxrmately 0.5" based on loca! manu(acturer's capabilifies. `" B/ock weight may vary by 2% based on the specific gravrty of local/y available aggregate material. 3. Wave Attack Tests, Report No. M1910 - Delft Hydraulics Laboratory, 1982. 4. Hartel Canal Trials - Rotterdam Public Works Department and Delft Soil Mechanics Laboratory. 5. River Waal Breakwaters, Arnhem - Rijkswaterstaat, 1983. 6. "Design of Reinforced Grass Waterways," CIRIA Report 116, 1987 7. "Minimizing Embankment Damage During Overtopping Flows," FHWA Report-RD-88- 181 prepared by Simons, Li and Associates, Inc., November 1988. 8. "Hydraulic Stability of Articulated Concrete Block Revetment Systems During Overtopping Flow," FHWA Report-RD-89-199 prepared by Simons, Li and Associates, Inc., July 1989. Research Proven Performance Armortec has carried out exten- sive research into wave and open channel flow conditions on Armortlex in the United States and the Netherlands. Design manuals and computer programs are available to assist in the proper Armorflex block selection for your hydraulic conditions. Design recommendatians can thus be made on the basis of specific research data and sound engi- neering principles. Please call Armortec Corporation for design manuals and software. ARMORFLEX INSTALLATION Armorflex arrives on-site as a system of factory-assembled mats. These articulating mats con- sist of interlocking blocks held together by cable. Armorflex is placed on a site specific geotextile which has been placed on a pre- pared subgrade using conventional construction equipment. RESEARCH AND �� Delivery $ Unloading Mats are supplied on 40-foot trailers, up to 1600 square feet per truck. Delivery can be phased so that mats can be off-loaded directly from the raad vehicles onto the prepared subgrade, if the site layout permits. Anchorage The mats may slide on the geo- textile fabric until the system set- tles and seats. Temporary anchor- age can be achieved by driving wood stakes on two-inch centers along the top of the mat. Permanent anchorage can be achieved by connecting the mat cables to patented anchors such as "Helix" or "Duckbill". Finishing Mats subject to wave attack should be blinded with a � n �� ;; �` � - E_�, � ,� � � � �. ��3 �, :� ,, �c � ��`+ � -r r i '; " �jr� R. �•.'!�. � � �}. � - ��' � ir � �,,. ti�m � � �r ~ � ,4 ,��..'>.- _. . ,.. �� ed to give a"green" effect. ARMORFLEX APPLICATIONS Channel lining River Bank Protection Drainage Ditch Lining Pipeline Protection Boat Ramps Reservoir Slope Protection Lake Shoreline Protection Bridge Abutment Protection Dikes and Levee Protection Disclalmer The information presented herein will not apply to every insta/lation. Dimensiorrs and quantifies shown are approximate only and wil! vary as a result of srte conditions and installafton procedures. IVo warranry or guarantee expressed or implied is made regarding the perfor- mance of any product, slnce the manner of use and handling are beyond ARMORTEC 3260 Pointe Parkway, Suite 200 Norcross, Georgia 30092 (770) 409-9002; (8Q0) 305-0523 Fax (770) 662-5819 411�/ 11� 6L� •�i ` Ai �`�f.�.- . � , ��111Z ! �11� y;n"'. sand/gravel mixture. Above normal waterline mats may be topsoiled and seed- Laying Mats Mats can be handled with a lifting beam, which picks up mats from both ends. Dam Crests and Spillways Weirs and Overflow Channels Media Filter MP-4� � Description Starmwater media filters are usually twachambered including a " preireatment settling basin and a filtex bed filled with sand or other absorptive filtering media. As stormwater flows into the first chaxnber, large particles settle out, and then finer particles and other pollutani� are removed as stormwater flows through the filterix�g media in the second chamber. � There are currently three manufacturers of stormwater filter systems. 'I�vo are similar in that they use carl�.id,ges of a sta.ndard size. The cartrid,ges are placed in vaults; the number af carlridges a function of the design flow rate. The water flows - laterally (harizontally) into the cartridge to a centerwell, then downward to an underdrain system. The third praduct is a flatbed filter, sim.ilar in appearance to sand flters. California Experience There are currently about 75 facilities in California that use manufact�ed filters. � r, Adva ntages ■ Requires a smaller area tban standard flatbed sand filters, wet ponds, and constr-ucted wetlands. ■ There is no standing water in the units between storms, minimizing but does not entirely eliminate the opport�mity for mosquito breedin,g. ■ Media capable of removing dissolved pollutants can be selected. ■ One system utilizes media in layexs, allawing for selective removal of pollutants. ■ The modular concept allows the design engineer to more closely match the size af the facility to the design storm. j�Design Considerations'�� .�.��Design Sform �.��..��....._.�..�.,�_..� ■ NlediaType ■ Maintenar�ce Requiremenf Targe#ed Constituents ,�. C� .�.riSedi menta��,-_,��u..�a_�,� ��, Q Nutrients Q Trash C1 Metals Bacferia Q Oil and C�rease C� Organics Removal Effectivoness See New Development and Redevelopment Hancbook-Section 5. ■ As with all filtration systems, use in catchments that have sigiuficant areas of non-sffibilized soils can lead to premature cla,gging. -�£� Y � � � J�uary 2003 Callfornla Stormwater BMP Handbook 1 of 3 New Development and Redevelopment www, c� mph�dbooks. com Li mitations ■ As some of the manufactured filter systems function at higher flow rates and/or have larger media than found in flatbed filters, the former may not provide the same level of performance as standard sand filters. However, the level of tr�eatment may still be satisfactary. ,d ; -4 � ,� �; �� n , t,; ,�i +i �� ,s�, �1 � i �- - � �� ;�, ±� ;� r� �� ,r �} ;�i1 � � � _� MP-4� Media Filter. Desl�n and Sizin� Duidelines 'liiere � e ciurently three man.ufacturers of sbormwater filtier sysbems. Filtem System A: 'I]�is syst�m. is si milar m. appearan.ce t� a slow-rabe sand filfier. However, the media is cellulose mat�rial treated to enhance its ability bo remove hydmcarbons and oth�r [�rgA, ntc compoimds. The media depth is i2 mches (go cm). It operates at a veayl�igh ratie, 20 �m/ft2 at peak flows. Normal operating raties are much lower as �s� no that the stoa�mwates caveerss the ent�e bed at flows less t�.an. the peak rabe. The system uses vaa�tex separatia�. for pa-etreatrnent As the media is mtiended bo remove sedimeats (with at�.ched pallutan�} and �ga, nir compounds, it would not be expected to remave �issolvedpollut�.ts such as nutrieuts and mete]s unless tiiey are complexed with the orgenic compowids that are remaved. Filter System B: It uses a�le vertical fYt6er ca�isting of 3 mch dia.me�ber, 3o inch high slotted .plastic pipe wrapped with fabric. The stand� d fabric has nomm.al ope�mgs of 10 microns. The sta�rmwaber flows intio -the �e:rtical fither gipes and. out t3�rough an im.derdrai.n system. Several �mits are placed veriically at 1 foat inte:rrvals to give the d�esired ca�adty. Pretrea�ent i.s typicaIly a dry exbended deb�ntion basm, with a de�tenti� time a� about 3o hours. Sto�rmwa�ex is retain�ed in t�e basin by a bladder that is autiomaticaIly iuflabed `vhen radnfall begins. 'T7�is actian st�ts a timer which opeas the bla.dder 30 ltioiu�s later. The fil�ber bay has an emptyin,g time of ia to 24 how.s, or about i bo 2 gpm/fi� of filt�er � ea This pa�ovides a tiotal elapsed time of 42 tio g4 ha�s. Gaven ti�at the media is fabric, the syst�m �oes not remove dissalved polluta�ts. It does remove poIlutants attached fio the sediment that i.s removed. ' Filte� System C: The system use vertical �idges m which sfiormwaber e�ntieis ra�iaIly to a ceatiex wdl wit�in the flte� writ, flowing dawnward � an imder�am system. Flow is cao�trolled b� a passive float valve system, which p�evienis water from passing through the csrtr idge until the wate� level m the eault rises to the top c� the carlridge. FuIl use a�f the entQe fil�r s�nface area an.dtl�e valume ofthe cartiidge is assiuedby a passiee sip)�on mec,hanism as the water suiface recedes below the to�p a� the cartrid,ge. A balance betwe� hydrostatic forces ass�es a ma�e aa� less equal flow po�rtial ac��oss the vertical face a� the fi1�6er s�face. Hence, the �l.�eer sutface receaves sus�pended solids eee�nly. Absent the float valve and siph� syst�ems, the amowit c� water tr�eat�ed over time per tmit ar+ea in a ve�ti.cal filter is nat caa�stant, decreas�g with tl�e filter ha�ght; fiu�lhermore, a filter would clog tmevenly. Restriction of the flow us�g orifices ensures cor �+�t h��aulic caazdwctivity of the carlridge as a wl�ole by allowing the orifice, raii�.er than the medi.a, whose hydraulic con�cti.vi�y decreases over time, to control flow. . � The man�act�e,r offers seve;ral. media used. smgly or in combmatiaas (dual- or multi-mec�ia}. Total media thi.cluzess is about � in,ches. Some me�ia, su�ch as fabric andpe;rlite,.remove amly suspended solids (with atiached poIlutant�). Media that also remove dissolv�ed. inca.ude compos� zeolitie, and iron-infused palymer. Pretrea�ent occt�s in. an. upstream imit and/aa� the vault � within which the cartridges are located. Wateer quality volume or flow rafie (depen�ing a� the particular product) is det�-mined by local govemme� or sized so tbat 8�36 a� the annual run�off volume is treat+ed Constructlon/Inspectlon Considerations ■ Inspect one a�r more times as ivece.gsaty dw.ting the first w�t seasaai of operati�. to be certain that it is drai.ni.n,g properiy. 2 of 3 Califomla Stormwater BMP Haidbook Januery 2003 New Developrnent and Redevebpm�t www, cabrr�phan�ooks,com � ��} y I `• I I � r, ; ,. � �� l. �, Media Filter MP-4a Performance � The mechaaisms of pollutant removal are essentiaIly the same as with public domain fil-�a.s (TC -40) if o# a�milar des�gn.. Whe�ther remaval of �issolved pQIlutalrts or,ciu�s depen.ds on the media. pexlitie and fabric do not remove dissoTved palhrt�n.1�, wh�reas for eacamples, zeolites, compos� activatied caifia�, and peat have t3�is capability. , , As most man�actiu ed filtier systems fundion at h�gher flow rabes and have large:r media tban fowzd in $atb ed filte� th�y may na� pravide t3�e same level of performance as standand sand "� __I fili�eis. However, the level of treatinent may still be sat�'acbory. Sitinp Criteria There are no umque siting critieria. � i 4 Additional Deaiyn Guidellnes FoIlow guidelmes p�ravided by the man�acturer. � Maintenance . � ■ M.ain.tes�ance activi.ties and frequencies are spec�.c tio each p�oduct Annual maintenance is ' typdcal. ,�j ■ Mauufact�ed.filtexs, like standardfilters CTC-4o), require more fieqwent maurtien�ce ti�an �, i', . most standerd trea�.ent systems l�e wet paoids an.d constructed wdiffids, typicallY ` annuallyfor most sites. ,1 ,� L� ■ Prert�eatinent systems ti�at may pa�ecede the filter �i.t shauld b e maintained at a frequ�acy fil r spec:ified for the particul� process. � Cos't �, . Manufactl�s pi�vide cost� for ti�e �its mcluci�g delive�y. InstaIlatiam costs are genexally on the ordes of 5o tio ioo % af t�e manufad�a's costs. � �� Cost Considerc�ions ■ Filters are g�neraIly more exge�is,ive tio mavltain than swales, pa�ds, and ba�ins. ��' ■ The modularity of the manufact�ed systems aIlaws ti�e d,esign e�gi.neer to closely match the �. �- capaaty a� t�e fac�7ity tio the design sborm, maa�e so than with most other m�.ufa�d Prodt�cts • . I� � ' �� _t References and Sources of Additional Information � Atintion, G.R, 2002, Stormwate�'I�ea�e� Bi.ological, C�emical, and Engmeering PrmciPles, RPA Press, q.i6 p�gea. -{ :� January 2003 Callfromla Stormwat� BMP Hendbook 3 of 3 , , New Devebpm�t aid Redevelopment ' ,' www.cabrnpha�dbooks,com � f *�, ?-�n��a��C'i8 �� x �� "�t'e` � � � &4ra . . . '� a c `�'�',�'e;., r�w ; c ' � . ,� q<�' +'�»i..na+w��u.ra�rsoiw�rairv�a�a�pi�rMl�ir'"' � � f `�'^` �� { }'_,. 1��'��..�,,��#��! ,�. � '".�a,�,a„x �� , ' �i-�.� �,A�'�. ��",,,c�lt �'1�� `�.�< �_�� .�' . {�; .eL�^-` � +� � "� �i�'�S'•ax..�� .:�« �,: ''�. �'4 *"..""� � 4 `�'r� 4 � 1 t� `�'k' *�A a< r - . s"" " ,.,.. r�:+.• ��s� '�.. ��' �� i , . yy,t .....n . ry "'"'y_ 6r"` '_'1 . . . . � . . . �.� ..� :w'..a��-� � l..:p'u" "`'° - i�.:.t ' ;'s. _ : {.,: " �'�_"`:i-.^». ;,�" . ¢, ;..:�::i ,v �': r f IR��V'��Mk�� RS � �M��It� �MsiR�� The FIQ-GardT�" Trash & Debris Guard is often the only practical option to filter stormwater leaving sites with little fall from a parking surface, through a parkway culvert to curb and gutter outfall. It is designed to remove debris and has an optional Fossil Rock pouch for hydrocarbon removal. Based on site conditions, the flow capacities shown may be derated by a safety factor of 0.50 to 0.75 to account for severe debris buildup between maintenance cycles. � Specifications: Wldth Helght Ftltered Flow Bypass Model (�� n� Depth (In Cap. (cfs) Cap. (eta)• FG-TDG24 24 6 0.75 0.45 0.62 FG-TDG36 36 6 0.T5 0.67 0.94 FG-TDG42 42 6 0.75 0.78 1.10 FG-TDG48 48 6 0.75 0.88 1.26 FG-TDGBO 60 6 0.75 1.11 1.58 Approximate — may vary with location and debris loading between maintenance Questions? Conract Krisrar at (800) 579-88i 9. 09/04 I� 4 `� �, ,� �� • "� ' ,; �� 1 � �� f A Motmtlng 's�de" b�cket �� --�� t-NVIV I V1tVY � 8edhnent screen {9 mesh) C / TOP VIEW -T- �� APPLICATIQN CHART �DEL N0. A B C FQ-TDQ24 32.00" 6.D0" .7b' Fti-TQQ38 d4.00' � 8.00' .7b' FCi-TOQ42 64.00' B.Od' .7b' FQ-TDC348 58.001" 6.�0" .76' FQ TD(360 BB.00' 6.00" .7b' F4TD(3-CUST As req'd As req'd NOTES: � . 1. All metal cornp�ents st�etl be conskucted lrom s� s�el 2. �atrlTMlteah attd DNxfe (3uard ahaJl be mo�utted to Ute tace � aub, ecross the diefn op�fng. Mottnttng brackets shaU be secured to tlte tace o� curb tstig tYw 3l8' x 2-12' s�less atee�l expa�ion ar�dtas end tamper reslstant bo�. 3. MauMing bredcais sl�l ba st�p�ed arAh �ampar resls�rd e� s� securty bo�. 4. Fleter to ap�atfon ct�art ior starxierd hedgh� erid wimhs far Flo(?ardTM iYssh and Debiis �uard. (�wn slzeg al'e avef�ble 6. FI� Tiash and Q�brfs Guand Is sup�ed v�Ait a removable (B meshj sedknent screen. Alterr►ate stte semment saeens may be spec�fied to rataln tlie perlk�e size an�aa�d fir each spedflo s�a. 8. FIoC�ndTMllrssh end Deb�ie Quand may ba epe�tlfed wM Fosell RodcTM idtar medfum patxh 1or tlte co�ec�on ot os end preas�. 7. FbCiat�IT"Tfash and [�9� Gua�d should or�ly be used on saes thet Rxwrpotate a comprhet�atve rt�@enance program that fnc�dea �� 9 � �� TYPICAL INSTALLATION Parkway Culvert , �� ;� � \ �� j FRONT VIEW a°� � a . _„"'�..A.., p� �v•0 � � D V � �♦ 4 +dJ� • O , •� E , a' � a � �a � SIDE VIEW �s�i� RocKTM pouuc�„ FLOGARD�' TRASH & DEBRIS GFJARD ,R i ;� �r ��, �r�., santa �a, ca, tsoo> �rg.sa,m � i i � .� i � , �' i � �. y � � b � � � r�1�. \ � �� il BOIf ti] (H09 Of CUIti TOP NEW FLO-GARD'� .TRASH & DEBRIS GUARD tc�r �,t�t�, i►x., s�,t� �, cA (soo> 5rs-ea� s os�oa �_ � il � �- screen Absa�ber� Pouch Tetl,erin9 CUp � FRONT VIEW 1 �� , 31DE H�W e . . :, • : :v . :, .. •. •... �. •.•.. •. • .. .. . .. .. . .. .. . .. .. . . � •..'.V .�. D '..'.Q .°. � '..'.Q ;�, C •.•..V .� V_ ' •'V .•°• p. ^ �'V .�• p. ".•V : � .:. . . • . .'•.V••".•.P'•.V�•:':.�'•.V^:':.P�•.V••:'.•.P'•.V••:'.•.P�•.V••:'.•.P'•.V••:':.P'•.V^:'.•.P'•.V••:'.•.P'•.V••:'.•.��•.V••:'.•.P'•.Q'.' Q^:'.•.V . •0. : ,o . •� '. o . •v• • .v . • 'v • .v . • 'd• • .v . • 'o• • .v . • 'v • ,v • • 'v• • •v • ' 'v' ' .o -' 'o. '-p • ' 'p� ' •p • �0�18� /4I7801b9flt POUCh FLO-GARD'� 1RASH � DEBRIS GUARD ��y c�rc o-,�i�nor,� xdsc�r �, i►,�., s�,c� r�a c,a (soo� �s-se� s I 0�04 Site Design & �andscape Planning SD-1� . ...:�.�=�:�R_.�...,.�..�.�u.r. «..u.�rt,. � �..4.�,.m..,.�,�.�.. Design O6jectives .� ...�..._..,�._..w,_...�.,��.��.. r, Q Ma�amize Infiltratia� C�1 Provide Retention [� Slow Runoff Q Minimize Impervious Land Coverege Prohibif Dumping of Improper Materials Confain Pollutants Coilect and Convey Description Each project site passesses unique topographic, hydrologic, and vegetative features, some of which are more suitable for development than others. Integratir�,g and incorporatin,g appropriate landscape planning method,ologies into the proj ect design is the most effective action that can be done to minimize stu�face and groundwater contamination from starmwater. Approach Landscape plannin4g should couple consideration of land suitability for �ban uses with consideratian of commurrity goals and projected growii�. Proj ect plan designs should conserve natural areas to the extent possible, maximize natural water storage and infiltr�ation opportunities, and protect slopes and channels. Suitable Applicetions Appropriate applications indude residential, commercial and industr�i.al areas planned for develapment or redevelopmerrt. Design Considerations Design requirements for site design and landscapes plannin,g should conform to applicable standards and specifications of ageneies with jurisdiction and be consistent with applicable General Plan and Local Area Plan policies. - �;�„� �� ' /' January 2003 Callfornla Stormwater BMP Handbook 1 of 4 New Development and Redevelopment www, cabmphandbooks, com �� SD-1� Site Design & Landscape Plar�ning ' ;' Desig�.ing New Ixstal[ations Begin the development of a plan for the landscape imit with ati�ntiam. to the foIlowu�,g geaeral. princiPles: � �; ■ Formulatie the plan on the basis of clearly aiticulatied commtmity goals. C�efuIly ide�tify — confiict� �.d clwices betwees� retamin�g and Fratecti�g desu ed. resatirces an.d commimity _ �� ■ Map and assess l�d suil�hilit�* for �ban uses. Include t�+e fdlawing l�d9cape fea�r�s in the assessmeut: wooded land, open unwaoded land, steep slopes, erosi�.-prone sails, foimdatiam. stritability, soil suitability for wastie �isPosal, aquife�s, a4uife�' rec�arSe areas, wetiands, floodplains, siuface waters, agri.cult�al land.�, and various c�tegories of �ban landuse. Whe�n aPP�P�� the assessment can hi, h� l�.t rn,tstan�;,,� lacal or regional resaurces that the commtmity dete�mmes should be pinte�teci (e�g., a scemc area, recreational area, threatien+ed species habitat, farmland, fish nm.). Mappir�g and assessment should recognize not a�ly t�ese resrnu�es but also add�iamal areas need.ed fa�r th� sustea�e. Proj ect p1an. des�ns s�wuld couse:rve natiu'al areas to the extent possible, m aximi ze nAt►„�1 water sborage and infiltrati.oai oppaa�tunities, and prote�t slopes and c,hannds. ConserveNc�zmatAreas duriRg Landscape Plcuuang If applicable, the faIlowi�,g items are required and must be i.mplem�n�d in the sitie layaut , duri.�g the subdiei�aai des9gn. and appa�oval �essy cansisteat with applicable General. Plan and ' � Local Area Plan policies: � . 'i � i-� ■ Qustier developmeut on least-se�n�i.tive porti.ons of a site wlule leavixig the remaiuir�g land in a natival im�isturbed condition. ■ Iami.t clearing an�d gradin,g of native vegetation at a s�te to the �mmimum amotmt needed tn build lots, aIlow access; and p�ovide fa e protectiam. . ■ Ma�mize trees and ot�.er vege�tation at eac,�. sit�e bY Flan�,g ad�itional vegetation, clu�,g iree areas, and pa�omoting the use of native �d/aa� dmught bolerant plants. ■ Promote nat�al vegetation bY usi.ng Parking lot islands and ather landscaped areas. ■ Presel.ve riparian areas and wetian.ds. Mcraomize Ncitural Water Starage andlnfiJiration Opportrmi.ties Within the Landsca�e Itnit ■ Promote the ca�servation a� forest cover. Buildin,g a� land that is ah eady deforested affects basin hych�ology to a lesse� exteat than conv�errti.ng forestied land. Loss a� faa�est cov� reduces in.t�ception staa�age, �d�ntion in th,e aiganic farest floor lay�er, and water losaes by evapotr�an.spiration, resulting in large peak nmoff inr.rPAAes and either their negativ�e effecLs or the expense of caunt�r.u�,g thiem with str�al solutions. ■ Maintain na.t�al storage reseraioa s and �ainage corridors, incluc�ng depressi.oa�s, areas c� permeable soils, swales, and mtermitten.t s�eams. Develop and implement policies and I�� 2 of 4 Callfnmla Stamwater BNP Hendbook January 2003 New Development and Redevelopm�t - - wtivw,c,abrnphanci�oaks,com �� +� ; Site Design & I.andscape Planning SD-ia � �, f 1` regulat�.ons tio discotaage th,e clearmg, fill;no and channelizatio� of these featiu es. Utilize i; them in ��ge ndwa�ks m. preference bo p�pes, culae�ts, and e�gineered �tches. ■ Eealuati.ng infiltr�ation opp�m.ities by r�ferrmg to the sbormwate� ma.nagement mar.n�al for � � the j�i.sdicti.oaz and pay particular atbention ib the selectia� criteria for av • inu �- graa�ndwater co�n,;T,Aticu�., Poa� soals, and hY�'ogeological can.�itions t�at cause these faalities to faiL If necessary, locate de�velopments with large amoimts of impervious �� s�mfaces � a po�atial to produ+ce relatively cont;ammatied rimoff away from gro�dwatier ..� recharge areas. Protection of 57opes cuid ChanneLs dwzng Lcmdsoape Design ■ Cao�vey rim� safely from t3�e tops of slopes. ,, ■ Avoid dist��bi.n,g stieeg or unsta�le slopes. , , ■ Avoid dist�bi�g natural channels. ■ Stabilize di�abed slapes as quickly as possible. ■ Vegetate slopes with native or drought tiolerant vegetation. � f ■ Ca�ntrol and ti�eat flaws in landscapi_ng and/oa� other contr ols pa�ior tio reachi.n,g e�ist�g � na.t�al c�rn'�e systems. . i i ■ Stabili.ze temporaty andpermane�t channel c�ossin.� as quickly as passible, and ens�e that increases in rim-off veloaty andfrequen�cy causedby the project do nat erode the chauneL ��_�, . ■ Install energy dissipa.t�eers, such as riprap, at the oudeta of new storm ch�ams, culv�rrts, � � conc�its, aa� cb.�nels ti�at entier imlmed channeLs in accaa�dance with applicable '� specificatiaris to m;nim;�e e�sion. Energ,y diss�atiexs shall be i.nstalled in such a way as tio .J minimize jIl1PgC1B 1D TeCe1VID,g Wg�i'S. • . l I ■ Iane on-site couveyance chaunels where appropa�ia�e, tio reduce erosion caused by mcrea.sed � . flow �elocity due to in rre�ses m tribut�ry impeTvious area. �.e first c�ace fcu' lmin,gs —. s�.auld be grass or some other veg�tative sutface, since these mat�rials not, only rec�ce � � r�maff velocc�iies, but also provide watier quality ben�.ts from filti ation and infiltr atic�. If —� velocities in the cbannel are lrigh ena�gh bo eradie grass or othe� vegetative linangs, riPrap, -, concrete, soil cemen� or geo-grid stabilizati.a� are ot�.er altiernatives. � J ■ Con.sidc� other design Pa�inc�es that are comparable an.d equally effective. , -, RedevelopixgExistinglnstacUations � �- ' Various j�isdictional stiorm.water man�gement and miti,gation plan.s (SUSMP, WQMP, etc.) '� -� deCne "redevelopme�.�' in tierms af amoLts of additional impervious area, increases in gross �-- � floor area and/or e�cteri.or canstruction, and ]and dist�bing a.ctivities with s�uct�al a� �� , impervious suifaces. Th,e definitio�n of ° redevelapmen�' must be consulted tb detiermine whd:her o¢� not the requaements fo�r ne�w development apply t�o areas inteuded for redevelopment If tl�,e definitiam applies, the sbeps oudmed under "desiguu.rig new mstallations" �� I above sl�ould be fa�➢.owed. � �� Jarx�ary 2003 Callfornla Stormwater �1P Hendbook 3 of 4 New Davelopment and Recievelopment -- www.c�mphancmoolcs. com � � �; i� � �� SD-iQ Site Design & Landscape Plannirig , Redevelopmen.t may pa�esart significant oppommity bo add featiu�es whi.ch had not previousl.y ' been implem�ated. Examples include in�orpaa�ation of de�pressions, areas a� permea.ble sails, a1� SWales i11 TI�eW�y iaedevie�ed Bl�as. While Some site crn1Str ain may earist due bo the status �� a� already �isti.n,g infiastrwct�e, aPPort�mities should not b e missed to m axi mi � mfiltration, . slow rimoff, re�ce i.m.per.vious areas, �iscx�nnect �ectly camnected i.mpexvious areas. Other R�ources A Manual faa� t� Standard Urban Stiorm.water Mitigation Plan (SUSMP), I.os Ar�geles Caunty Depa�e;at of Public Waa�ks, May 2002. � � Sbormwate,r Management Manual for Wes�em W�shington, �Vasbmgtion St�te De�pai�ent of ��BY� AuSust 2orn. � . Mode1 St�ndard Urban Stnrm Watier NTiti�tion Plan. (SUSMP} far San Diego Coimty, Port of San Diegq and Cities in San Diego Cotmty, February 14, 2002. � Model Watier Quality Managemen.t Plan (WQMP) far Cotmty � Ora�ge, Orange Colm.ty Flood Camtrol I}isirict, and the I�corporatied Cities of Orange County, Draft February 2003. `�� Vent�a Co�tywide Technical Guidan�ce Mauual for Stiormwata Quality Contr� Measlu es, July 2002. J . . � a_ �� 4 of 4 C�Ifomla Stormwater BMP Han�ook ��rY �3 � New Development and Redevelopment — warw, cabmphan�ooks.com Efficient Irrigation SD-12 � ,�w �, �?'�. u_Design ObjectivesYF.. R.,. , , � t �: ,� z � _ �. . �.�...,..�.�.,.M_.rt_ � . K, .. . �.. u. . .. ., . ��"i��. +} k�rF�'� . � h`k. � � * � `�� , t��w . �:�� ;, - � �. �,.�� ' '� � ,-�.; 4 � . � �� , �� , _ � � �� ,� r � ; �- , r �, � � °� *�.��t� .. � ,_ �., _ _ ��.,�.,..�-��r_4x...�.�.�. �_,..��:. ., _��„�. W..�. _ _ _ � _. . �.�.. __, _ . _�:..-��.��.: , �x Cd Maximize Infiitration C� Provide Retenlion I� Slow Runoff Minimize Imper�nous Land Coverage Prohibit Dumping of Improper Mafenals Confain Pollutanis Collect and Convey Description ��..�,.�,�.�� ,_nw�_ _1��,... �� Irrigation water provided to landscaped areas may result in excess iirigation water being canveyed into stormwater draina,ge systems. Approach Project plan designs far development and redevelopment should include application mei�ods of irrigation water that mir�imize runoff of excess irrigation water into the stormwater conveyance system. Suitable Applications Appropriate applica.tions include residential, commercial and industrial areas planned for development or redevelopment. (Detached residential singl.e-family homes are typically excluded from this requirement.) Design Considerations Designing �Vewlnstalrations The followin,g methods to reduce excessive iir�gation runoff should be cansidexed, and incorporated and implemented whexe determined applicable and feasible by the Permittee: ■ Employ rain-triggered shutoff devices to prevent irrigation after preeipitation. ■ Design irrigation systems to each landscape area's specific water requirements. ■ Include design featurin.g flow reducers or shutoff valves tr iggered by a press�e drop to contml water loss in the event of broken sprinkler heads or lines. ■ Implement landscape plans consistent with County or City water conservation resolutions, which may include provision of water sensors, programmable irrigation times (for short - cycles), etc. �� M � 1 i- _ January 2003 Callfornla Stormwater BMP Handbook i of 2 New Development and Redevelopment www.cabmphandbooks. com �� SD-12 Eff cient Irrigation �� ; ■ Desi,gn timin and appli.cation methods of irrigation wat� to �m»� the rimoff of excess �_'� ur�gation water into the storm. water drai.nage system. ■ Group pl.an.ts with sim�lar water requirements m order to re�ce excess irrigation rimad'f and promo�be siuface filtratiaaz. C�wose plant� with low'rri,gaiion requu�ements (for esamPle, native aa� draught tiolexant species). CQnsider des�gn features such as: - Us�g mulches (such as wood chips or bar) in glanter ai�eas withaut grotmd oover to mi ni mi�.e� g�m�t lIl riII10� � - InstaD.mg appropriatie pl.�t ma.t�rials for the location, in accordance with amo�mt a� �' -� stmli�h_t and climatie, and use n.ative plant matierials where possible and/or as recommended by the landscape architect - Leaving a vegetatiee barrier aloIIg t�e propei#y boimdary and mterior watercrnuses, ta act as a pollutant filtier, where appropa iate and feasible - Choosing plants t}�a.t m;n;mi � or eliminate the use of ferh7izer or pesti.cides to sllst&Lu �� . ■ Emplay othes comparable, eqt�all.p effective methods t�a reduce irri.� � watier �maff. ' ' ��P�9 Bxis iing IxstaIIactio�es � Various jurisdictional staa�mwaber management and mitigation plans (SUSMP, WQMP, eix.) ;- define �redevelopment" m terms a� amoimts of aaditional im�eavious area, increases in g�ross • flooa� area and/or exterior comstructic�, and land dist��bumg activities with stiruct�al or - i.mperviaus s�mFaces. The defimtion a�" red�velopment" must be consultiedto detes�;nP whethe� or not the requirements for new development apply tio areas in�nded for � � redevelopment. If the de�'mi.tion appli.es, the steps outimed imder "desi,gniv,g new installation�' ' - � abave shouldbe foIlowied Other Resources � � AManual fcu� the Standard Urban Stiormwater Mitigation Plan (SUSMP), Los An,geles Cowsi.y De�pari�n�nt a� Public Waa�ks, May 2002. Model Standard Urban Stiorm Wat�er Ni'iti�tion Plan (SUSMP} for San. Diego Coimty, Port of San Diego, and Caties i.n. San I?iego Coimnt�y, Februaiy i4, 2002. Model Wa�r Quality M��gement Plan (WQMP) for Coimty a£ Orange, Ora�ge Cowzty Flood Control District, and the Incorporated Citi.es of Orange Cotmty, Draft Febniary 2003. Vent�ma Coim.tywide Tec3�nical Guidanice Mam�al for Sbormwate� qualiiy Control Meastu�es, July �002. � � � �,--� 2 of 2 Callfwr�a Stormwater BMP Fiarx�ook Jan�ary 2003 ' �� New Developrrient and Redevelopment ' www,cafxr�phand�od<s.00m I` �_J � �� .; �� Outlet Prot�ectionNelocity Dissipation Devices S-10 Standards and ■'I'here az'e many types of energy dissipaters, with rock being the one that is Specificatlons 1eP��ted in the figure on Page 3. Please nota that this is only one example and the RE may approve other types of devices proposed by the contractor. ■ Install riprap, grouted riprap, or concrete apmn at selected outlet. Riprap aprons are best suited for temporary use during construction. ■ Carefully place riprap to avoid damaging the filter fabric. ■ For pmper operation of apron: - — Align apron with receiving stream and keep straight throughout its ; � length. If a curve is needed to fit site conditions, place it in ngper section . of apron. — If size of apron riprap is large, protect underiying filter fabric with a gravel blanke� _ � -1 �� ■ Outlets on slopes steeper than 10% shall have additional protection. Maintenance and ■ Inspact temporary measures prior to the rainy season, after rainfall events, � Inspection �d regularly (approximately once per week) during the rainy season. ■ Inspect apron for displacament of the riprap and/or damage to the underlying fabric. Repair fabric and replace riprap that has washed away. ■ Inspect for acour beneath the riprap and around the outle� Repair damage to slopes or underlying filter fabric immediately. �� ,f i'i �� , � _� -, �i � —� i ; ■ Temporary devices shall be completely removed as soon as the surrounding drainage area has been stabilized, or at the completion of construction. ;. Cafh'ans Stam Weter QuafltY Handbooks Sectlon 3 Constructlon Site Best Managemertt Practices Manuel Outlet ProtectioNVelocfty Diaslpatlon Devices 53-10 Maroh 1, 2Q03 2 of 3 �� Outlet ProtectionNelocity SS-10 � �� Dissipation Devices � ij �-� �� , �� __� ''� �J �� _� �— � r� � t �j 'i W La ii � � 0% i i =- 1.2 W (min) Pipe outlet to well defined channel Key in 150-230 mm, (6-9 in.) recommended for entire perimeter. �1.5 dia. ro ck (max), placed � at 150 mm �" min. depth Filter FabricJ SECTION A-A N TS �� Pipe Dlameter Discharge Apron Length, La Rlp Rap mm m3/s m D�. Diameter Min mm • �� 0.14 3 100 028 - 4 � 150 450 p.2g 3 150 0.57 5 200 O.g5 7 � 300 1.13 8 400 �pp O.g5 5 200 1.13 8 200 � 1.42 8 300 1.70 9 400 For la er or hl he� flows consult a R istered Clvll En ineer Source: USDA — SCS ` Caltrans 3torm Water Qualfty Handbooks s�O� 3 � Constrvctlon Site Beat Managemertt Practices Manual OuUet Protectlor�/eloclty DisslpaUon Devlces S3-10 Mer+ch 1, 2003 3 of 3 i �_ PLAN VIEW N TS ;'�t��,R'�- O �'� / �'�j s� � �� f ' j i �nT"".- �i i` �� 74� %/ '� ,y �, � f� �. ,. r `��'�1T ;R��/O.%" Policy on the Use of Hydrodynamic Separators to Achieve Compliance with NPDES Provision C.3 Donald P. Freitas Program Manager Hydrodynamic separators, when used as a sole method of stormwater treatment, do not meet the "maximum extent practicable" requirement for stormwater treatment effectiveness with regard to compliance with NPDES Provision C.3 in Contra Costa. The following types of facilities, if sized and designed as described in the Stormwater C.3 Guidebook, can meet the "maximum extent practicable" standard for stormwater treatment effectiveness: • Swales, planter boxes, bioretention areas, and other facilities using filtration through soil or sand (sized according to the flow-based criterion). • Dry wells, infiltration trenches, infiltration basins, and other facilities using infiltration to native soils (sized according to the volume-based criterion). • Extended detention basins, constructed wetlands or other facilities using settling (sized according to the volume-based criterion, with a detention time of 48 hours). Hydrodynamic separators, including vortex separators and continuous deflection separators ("CDS units"), are substantially less effective than any of the above-listed facilities for removing stormwater pollutants of concern. This difference in effectiveness can be inferred by comparing design criteria and mode of operation and by analyzing the relative capability of each type of facility to remove small particles. The difFerence in effectiveness can also be validated by reviewing available results of taboratory and field tests. Experience to date has shown swales, planter boxes, bioretention areas, or other effective treatment facilities can be successfully applied to Contra Costa development sites. Lack of space, in itself, is not a suitable justification for using a less effective treatment device since uses of the site and the site design can be altered as needed to accommodate a swale, planter box, bioretention area, or other effective BMP. In most cases, effective BMPs can be fit into required landscaping setbacks, easements, or other unbuildable areas. Hydrodynamic separators can be used to remove trash and coarse sediment from stormwater upstream of detention basins or other treatment facilities designed to remove pollutants of concern to the maximum extent practicable. Installations of hydrodynamic separators are subject to the Provision C.3.e requirements for operation and maintenance verification. Planned inspection and maintenance of hydrodynamic separators must be documented in a Stormwater Treatment Facilities Operation and Maintenance Plan prepared in accordance with Appendix F of the Stormwater C.3 Guidebook. Each installation should be coordinated with the Contra Costa Mosquito and Vector Control District prior to final design. (11/16/2005) 255 Glacier Drive, Martinez, CA 94553-4897 • Tel: (925J 313-2360 Fax (925) 313-2301 • E-mail: «cleanwnterC�Dpw.co.contra-costa.ca.us �Progrom Purticipanls: Anfioch, 8rentwood, (layton, foncord, Danville, EI Cerrito, Hercules, Lnfayetfe, Martinez, Moroga, Oakley, Orinda, Pinole, Plttsburp, Pleosant Hill, Richmond, San Pablo, San Ramon Walnut (reek, (ontro (asta (ounty and Conira (osta Caunty Flood [ontrol 8 Water Conservatlon Dlstrlct �_f r �, , � �� _� �� ;f ��_� �^ � �� l� i i� To: C.3 Planaing /Permitting Work C�mup aad C.3 Technical Work C�roup From: Dan Cloak Subject: IIse of Hydrodynamio Separaton to Achieve C.3 Compliaace Date: 3 November 2005 Iatroductioa Frovision C.3 (Water Board, 2003� of the atormwater NPDES permit requirea Contra Coata mun{cipalitiea to make atormwater treatment - measures, sottrce control measurea, a.nd aite design meaeurea a condition of approval for new development a.nd significa.nt redevelopment projects ao that'polluta.nt discharges are decreased to the maximum extent practicable. Some applica.nts for plannin.g and zoning approvals have propoaed inatalling hydroctynamic separatora including contlnuous deflecttve separatora, or "CDS units,A to achieve compliance with the treatment requirements. In addition, manufacturers' representativea of these devicea have communicated with municipal ataff and have atated the devicea meet the °maximum extent practicableA criterlon. The C.3 Pla.nning/Permitting Work (�roup and C.3 Technical Work Group requested technical review and preparation of draft guiciance on the uae of hydrodynamic aeparators to comply with Provision C.3. The guida.nce will be incorporated into the next edition of the Contra Cos�a Stormwa.ter C.3 Guidebook Hydrodyaamic 8eparaton ' USEPA (1999a) describea hydrodynamic aeparators as °`flow-through atructurea with a aettling or separation unit to nemove aedimenta." The separatora depend on the energy from flowi.ng water, no outeide power source is needed. They can be located beneath parking lots or etreeta. USEPA (1999a) identifies and descrlbes the following apeciflc brands of hydrodynan�ic aepa.rator: m Continuoua Deflective Separator (CDS unita) � Downstream Defendef�'°� � Sto 'rmceptor� ' . � VortechsT"d Additional bra.nds of hydroctyne.mic aeparator are identified in Caltrans (2004aa. CDS unita uae a$ne acreen to acparate aolida from water. Flow ia directed tangentially to the acreen to prevent blocking or clogging. Settlea.ble solida accumulate in a contain.ment sump. Floating material circulatea at the water aurface until the water level dropa (Wong, 199'�. i)an Cl+o-a� �n�roamQ+Ttal Conmulti� 7 of 9 �_� �.l I { , -� i � _1 I � _� � ; �_, ' ( �t I� ;� � ` ;; �r"� �� f" � �_f �_, Hydrodynamtc Separaton 9 Novembor 2003 Vortecha separatora uae awirling motion inaide a chamber, and a baffied outlet, to encourage aettling of solida (Vortechnica, 2004). Other brands have aim�ar features and mode of operation, although deaigns differ. Pollntants of Coacern aad Particle Sizes Proviaion C.3 apecifiea neither the polluta.nts to be removed nor the effectivenesa of �reatment. Proviaion C.3.d does provide criteria for sizing treatment facilities. Finding 7 of the Water Board's February 19, 2003 Order adding Frovision C.3 (Water Board, 2003) provides examples of the types of pollutanta the Board intends treatrnent facilitiea to capture: ...PAHs which are producta of internal combustion engine operation end other aources; heavy metals, such as copper fr'om brake pad wear and zinc from tire wear; dioxins as producta of , combuation; mercury result�ng from atmoapheric deposition; and natural-occurring minerals fro�i local geologp. Finding 7 atates further. All of these pollutante, and othera, may be depoaited on paved aurfaces and roof-tops as fine airborne particlea, thus yielding atormwater runoff pollution that ia unrelated to the perticular activity or use associated with a�ven new or red.evelopment project However, Diachargers can implement treatment control measures, or require developera to implement treatment control meaeurea, to reduce entry of these pollutante into atormwater and theii� discharge to receiving watere. The Water Board is also preparing TMDLe for mercury and PCBs and a water quality atteinment strategy (WQAS) for copper and nickel. Airborne psrticlea derive from chemical converaion of gases in the atmoaphere and fi-om windblown dust, The latter particles are larger, with a peak in the aize distn"bution (by mass) at around 10 }�m diameter. The size diatrlbutlon falla off to near zero at around 100 um (DEFRA, 2001). � USEPA (1999b) has developed a generaliud particle aize diatribution to be uaed in modelin.g air depoaiiion from induatrlal sourcea. In the diatribution, eighty-seven percent of total masa is associated with particlea amaller than 15 }im. As amall airbome particles gather on impervious surfaces and are aubsequentl,y transported in runoff, the3' tend to agglomerate to form larger particles or may also become attached to larger particlea eroded by the flow of water. Therefore, pollutants derived from very emall particlea in air deposition may be assodated with eomewhat larger particlea in runo$ entering a treatment device. In aed.iment suspended in urben runoff, the diatrlbution of particle sizes is variable. It has been noted that eampling equipment may fa.il to capture larger particle sizes, creating an inherent bias in the particle aize diatribution (HI.I, 2002). Studies by USEPA (��mmari�prl in Rinker Materials, 2004) show 80-90% of total suepended sedi.ment mass ia in particles amaller than 100 }im. Some data from other aources ahow larger particle aizea predominating. z�s ��l , __� '' I Hydrodynam{c Separators 3 Nmrombor 2005 �' l The difference in results may be in part due to different characteriatica of '� the tributary area sampled. Runoff from highways or open spaces aeema more likely to include lazger particles, which may be derived from automobilea, decomposirig pavement, and run-on from unpaved areas, i i when compared to particles in runoff from rooftopa, parking lota, and ' low-volume streete, which moatly originate from air depoaition. ; � �Site design guidance in the Contra Casta Stormu�a.ter C.3 C�,cidebook (CCCWP, 2005)�empha.ajzes techniques to separate la.ndscaped a.nd pervious areae by creating �aelf-retaining areas.A This would tend to reduce the ]ikeli.hood of findi.ng subatantIal amounta of larger-sized particles in the runoff from impervious areae that reaches treatment fa.cilitlea. � In aum, Provision C.3 aima to control the tranaport of toxic pollutante �- i associated with very fine particlea deposited by air depoaition and � windblown dust on paved areas and rooftops. This can be accompliahed �.� � by facilities capable of removing particlea in a range from sub-micron to 100 }im (Rinker Materials, 2004). Urbonas (2003j suggeats that an effective BMP should be capable of removing particlea sinaller than 60 ' ' _1im• i� , , � _r Relative Treatmeat Effectivaness Provlsion C.3.d spedfles alternative ways to determine the runo$ flow or volume that fadlities muat be designed to treat without liypassing or overtlowing. To comply with Provision C.3, thia runoff flow or volume must be treated to remove pollutante to the "maximum extent practicable," which ia the atandard for control of runoff pollutanta establiahed by the Clean Water Ac�t. In thia context, °maximum extent practicable" meane leas-effective treatrnent may not be aubatituted when it ia practicable to provide more- effective treatment - �� Independent assesaments of the performance of atormwater treatment '� devicea either evaluate the application of engi.neering principlea used in -� the design of the device (rational.evaluation) or evaluate samplea of �- -� device effluent, sometImes with comparlson to influent samplea I 4 (empirical evaluation). ti Rational Evah.cation ��l r ! � � � i � �-- I �1 � _� � Salvia (2000) categortzed treahnent devices as gra.vity aeparators or filters and evaluated manufacturers' claima by comparing the deaign of the proprletary devicea with generally accepted engineering deaign � 'procedures and crltcrla for the treatment of atormwater or wastewater. In water and wastewater treatment engineering, settling columns are . typically used to determine the design settling rate for waters to be treated. Studies cited by Schueler (198'� ueing aettling columns indicate that 60-70% of aed.imenta in urban runoff settle out within 6 hours, and the remaining sediment may take as much as two days to aettle. The California Stormwater BMP Handbooks (CASQA, 2003) recommend a 48- hour detention time for stormwater treatment detention basina. F��] ��i i� �J Hydrodynam{c Soparators S November 2005 — I � _ ., , -� � --� , �� J �� i '�f -� � J ,--, I� '� '�_ �l i � �.P _ �` 1 Using the CASQA methodology, a 48-hour aettling time, and typical Contra Coeta rainfall patterns, a settling basin suitable for treating runoff from a completely impervfous area would require a basin volume of approximatcly 3000 cubic feet per acr� (CCCWP, 2005). By comparison, the manufa.cturera of hydrodynamic aepara.bora propoae their devices ca.n effectively treat runoff within a aubata.ntially amaller volume. The flow patterns and aettling dynamics of hydrodynamic aeparators are poorly underatood. It is not establiahed that hydrodyttamic aeparators can remove very amall particlea in a ahorter d'etention time than ie required for quieacent settling basina. Public environmental agencies are evaluating these cla.ima empiricalty. Stvalea, planter boxes and bioretention areas uae ffitration through a bed of granular media—the Stormwater C.3 Guidebook apecifies a sandy loaui—to remove particles from stormwater. In deep-bed filtration, water transports particlea via aettling, diffuaion, and' hydrodynamics into the interatices of between mcdia granulea. The pazticle then attaches to the medium by electroatatic interactiona, chemical brldging, or adsorption (Weber, 1972). The effectiveneBa of removal is governed by the surface application rate and the eize of the media.. The Cruidebook (CCCWP, 2005) specifles a sandy loam with an infiltration rate of five inches per hour and a depth of 18 inches, allowin.g at least two to three hours for removal to occur. In a sand Slter, particlea accumulate itt deeper layere of the ffitration media, increasing head loss and eventually causing'breakthrough and losa of filter effectivenesa ff the ffiter is not periodically backwashed (Weber, 1972). In a biologically a�ctive soil filter, the action of bacteria, , insecta, and earthworms are believed to promote agglomeration of aoil particlea with the soil media, maintaining the poroaity of the media and, over tlme, increasing, maintaining or reatoring the soil's ability to abaorb additional pollutant particles. Becauae of the multiple mechaniama at work, and the absorptive capacity of the aoil, it is expected that effiuent from a soil ffiter will contain very low leveTe of particulatea. Neither filtration nor settling will remove all diasolved pollutanta conaistently and effectively. Biologlcal filters may remove aome d.isaolved pollutanta through ion exchange and abaorption. On the other hand, some disaolved constituenta, auch as nitrogen and phoaphorous, may be released from the soil filtration medium. Effiuent concentraiiona may sometimea exceed influent concentratlona, particularly in the startup pha.se of operation. . Em�irical Euahtations In the last few yeara, public agencies have begun to independently evaluate perforniance claims. Empirical evaYuationa of treatment BMP effectiveness are hampered by the following. � D�'erent target constituents. Total suapended solids (TSS) is typically used as a stand-in for pollutanta of concern because data are available and becauae the concentration of aome pollutants tends to be roughly proportional to TSS. However, measurement of TSS is subject to anomalies and also m�y not be proportional to concentrations of aome pollutants of concem. � 4of9 � J( i � ;-M , � '_1 Hydrodynunic Saparators 3 November 2005 � No standard for how to meastcre performance. Percent removal of load or concentration, calculated�from measurementa of influent and effiuent, is the most typical measure. However, uaing this measure, higher influent concentratfona tend to produce higher percent removals. Effiuent concentration alone has been propoaed as a better indicator of performance (Urbonas, 2003). � D�}'ering quatities and chara.cteristics of in}2uent. Urban runoff influent varies with location, from one event to the negt, and during events. Treatment results obtained under different conditions may not be fairly comparable. 86 Difj"erent flow rates. Stormwater flows are highlp varlable. Published test reaults mqy reflect high pollutant removals achieved at very low flow ratee. ,r 4 � Manufacturera of hydrodynamic separatora have varying claima regarding the effect�veneas of treatment. The manufacturera of CDS units � claim only �...an abflity to capture and retain aolids ia.rger than 100 �zm..." (FYancis, 2005, emphasis added). Hydro International claima their �� Downstream Defender can achieve 80% removal of a 50 }im meau ;� particle aize sa.nd at apedfied�ratea of flow (Washington Dep.artment of Ecology, 2005). The Vortecha system, at apecifled rates of flow, claima a ,-- 64% removal of coarae ailt particlea, ranging from 38 }im to 75 }�m, in ; f laboratory etudiea (New Jeraey Department of Environmental Protection, ) 2005). In each case, public agencies have requested additional information and testa to detemaine whethcr claimed removal ratea reflect r` � � the diatrlbution of particle aizes actually typical of atormwater or to verify �{ the flow ratea uaed are reasonable. ;- � �l �� I-�, ,� -� Reports of the effectivenesa of biofiltera include data from °`wet" awalea and filter strips, where the primary modea of treatment are settling and contact with vegetation, rather than flltration through soil. Data from the National Stormwater BMP Database preaented by Urbona.s (2003) ahow typical effluent concentra.tions near 10 mg/L, well below that produced by hydrodynamic devices. Bioretention faalities using soil 5ltration to treat atormwater are believed to be conaiderably mpre effective than °wet" swales and are capable of producing effiuent nearly fiee of lead, with removal rates of 98-99% (Haieh and Davis, 2003; Center for Waterahed Protection, 2000). It is likety aimilar results can be achieved for other heavy metals and for hydrophobic organic pollutants auch as PCBa. Teehnical Feastbility aad Operability The Caltrana (2004b) BMP Retrofit Pilot Study providea the most current, comprehensive, and regionally applicable information based on actual construction and operation of a variety of treatment BMPs. CDS units were the only hydrodynam.ic separators tested by Caltrans. They were highly succesafui at removing grosa pollutants but no signi$cant reduction in auapended solids was obaerved. Because theq are efficient at capturing vegetation, excesaive maintenance frequency may be required to avoid clog�ng of unita inatalled where there ia aubstantial leaf fall. Moaquito breeding wae repeatedly observed at the two CDS installationa monitored by Caltrana, as it was for the multi-chambered treatment train (MCl�.� and wet pond installations. To implement the 3 of 9 l � , � '� 1 � Hydrodynemic Separaton S November 2005 ; f southern California trash T�SDL, Caltrans is developing non-proprietary � designa for devicea that remove grosa polluta.nta (Caltrana, 2004c). � Agency personnel have egpreased concern that hydrodynamic aeparators, ' becauae they are in underground vaults identified only by manhole ', 1 covera, could become �out of aight, out of mind,A and not be adequately mai.ntained. Given the relatively amall number of inatallationa, this ,, concern can only be evaluated by anecdotal esperience. . '_� , �- . �_� _� ��l� � �� — i _.j �1 i �.� �� _� r-} � � ; 't � � Urbonas (2003) recalla inspecting a number of underground off and grease trapa in Denver. Deapite being subject to mai.ntenance agreements, nearly all the traps had not been maintained for years. Some had manhole covera overlain with asphalt paving. Coats In their compilation of fact sheets attached to the Storm Water Treatrnent BMP Technology Repork Caltrans (2004b) rates all hydrodynamic separators as havi.ng low coats and low effectiveness compared to a , detention basin. Luliaic (2002) dtes the initial cost of the smalleat concrete CDS unit, capable of serving a 25-acre catchment, as $13,200, with a cost for each clea.n-out aervice of $300 to $4-00. By comparlson, a detention basin serving 25 acres of impervious area ahould have a volume of 1.75 acre-feet (CCCWP, 2005). Uai.ng the formula in CASQA (2003), the construction, design, and permitting cost a basin can be eatimated at $63,700. CASQA (2003) eatimatea the cost of maintaining a detention basin at $3,100 per year, moatly for mowing and other vegetation manAgement CASQA (2003) dtes conetructlon costa for bioretention areas at $3 to $4 per square foot. Using the aizing criteria in CCCWP (2005), adequate treatment of runoff from 25 acres of impervious area would require 1 acre of bioretention area; therefore conatruclion coats would be roughly $150,000. However, the landeeape amenity provided by a bioretention area ahould also be considered when comparing coats. Coata of maintena.nce may be the same as landacape covering the same area. Suazmary aad Coaclnaioaa The following types of facilitiea, if sized and 'desigaed as described in the Stormwa.ter C.3 Guidebook (CCCWP, 2005), can meet the "maximum extent practicable" atandard for atormwater treatment effecttvenesa: ■ Swalea, planter boxes, bioretention areas, and other facilitiea using flltration through soil or sand (sized according to the flow-based criterion) . ' � s� Dry wella, infi].tratlon trenches, inflltration basins, and other fadlitiea uaing infiltration to native aoils (aized according to the volume-based criterlo�. � F�ctended detention basins, constructed wetlends or other facilitiea using aettling (sized according to the volume-based criterion, with a detention time of 48 hours). Hydrodynamic separato�, including vorteg separators and continuoua deflection aeparatora (�CDS unita'�, are aubatantially lesa effective than any of the above-listed facilitiea for removing atormwater pollutanta of 6of8 t ��t � � � I r�, :�-� i i I 1 i � � �1� � �_ � ,�� Hydrodynamlc 8eparaton 3 Novembor 2008 concern. Thia difference in effectivenesa ca.n be inferred by comparing deaign criteria and mode of operatlon and analyzing the rela.tive capability of ea.ch type of fadlity to remove amall particles. The ciifference in effectivenesa can also be validated by reviewing available reaults of laboratory and field tests. F�perience to date has shown swales, planter boxea, bioretention areas, or other effective treatrnent facilities ca.n be succesafully applied to Contra Coata development aites. La.ck of apace, in itself, ia not a suitable juatification for uaing a leas effective treatment device aince uaes of the site and the aite design can be altered as needed to accommodate a swale, planter box, bioretention area, or other effective BMP. In moat casea, effective BMPs can be flt into required landacaping aetbacka, easementa, or other unbuildable areae. Operation and maintenence of btydrodynamic aeparatora ie more coatly and more prone to problema than maintenance of awales, planter boxes, bioretention areas, detention basina, inflltration trenchea, and other effective treatment facilities. Separatora require frequent maintenance, are.prone to clogging, and are more likely to promote mosqufto breeding than a.ny other treatment device except (posaibl� con'structed wetlands. Hydrodynamic aeparators have lower initial coat; however, higher maintenance costa over the life of the project aubetantially reduce and may eventually overcome this initial cost advantage. ' Costs of effective treatment facilities may be higher than for hydrodynamic separatora, but are not likely to be ao high as to threaten the economic feasibility of a development project. � Becauae practicable alternatives are capable of providi.ng more effective treatment of atormwater pollutants of concern, hydrodyna.mic separators do not meet the °maximum egtent practicable" requirement for stormwater treatment effectiveneas as that requirement applles to compliance with Provision C.3 in Contra Costa. Hydrodynamic aeparatore can be uaed to remove groas pollutants (trash and coarae sediment) from atormwater upatream of detention basins or other treatment fac�itiea designed to remove pollutanta of concern to the maximum extent practicable. Inatallationa of hydrodynamic separators are subject to the Provieion C.3.e requirements for operation and maintenance veriflcation. Each inatallation ahould be coordinated with the Contra Costa Moaquito and Vector Control Diatrict prior to final design. References Cited Caltrans. 2004a. California Department of Tranaportation, Diviaion of Environmental Analyeis. Storm Water Treatment BMP New Technology Report, November 2004. SW-04-069.04.02. Caltrana. 2004b. BMP Retrofit Pilot Program Final R.eport. January 2004. CTSW-RT-O 1-050. Caltrana. 2004c. �Groas Solida Removal Fllot Studies,A July 6, 2004 _ _, . update. ht*a•//www dotc:a.�ov/ha/env/stormwater/onQoinsr/r�arcLAilot studv/i � � nd . �tm � ;� �} 7of9 t ''� I '� � �� j ,�' � Hydrodynernic Saparators 3 Nmromber 2005 CASQA. 2003. California Aasociation of Stormwater Quality Agencies. Ca.lifornia Stormwater BMP Handbook New Development and Redevelopment Chapter 5. www.cabm�handbool�s.oz� � � � Center for Waterahed Protection. 2000. °Comparative Pollutant Removal , Capability of Stormwater Treatment Practices.° Article 64 in The Practice of Watershed Protedion. Center for Waterahed Protection, Ellicott City, Maryland. www.cwa.org �� ' � ��' } CC�CWP. 2005. Contra Coata Clean Water Program. Stormr.uater �3 Guiclebook, Second Edition. www.cccleanwater.org DEFRA. 2001. Department for Environment, Food, and Rural Affaira, United Kingdom. Expert Panel on Air Quality Staudarcls. Size Distribution and Chemical Nature of Airborne Pa.rttcles. Francis, Scott. 2005. "CDS C.3 Complia.nce,° Auguat 29, 2005 memorandum to Marlo Camorongan, City of Concord, CA. CDS Technologies, Morgan H�71, CA, � KLI. 2002. Ki.nnetic Laboratories, Inc., in cooperation with EOA Ina Joint Storm.water Agency Project to Study Urban Souroes of Meracry, PCBs, and Organochlorine P�.siic;ides. (Year 2) www.eCVt1rPDU.orr� Lukaic, Rachel. 2002. "An Upda.te of the 1999 Catch Basin Retroflt Feasibility Study Technical Memorandum.° Santa Clara Valley Urban Runoff Pollution Prevention Program. Haieh, Chi-Hsu and Allen P. Davis. 2003. "Multiple-L�ent Study of. Bioretention for Treatment of Urban Storm Water Runoff.p Diffuse Pollution Conference, Dublin 2003. New Jersey Department of Environmental Protectton. 2005. `Conditional Interim Certiflcat{on Findings: Vortecha� Stormwater Treatment S�atem by Vortecha, Inc." inkPr Materials, Ina 2004. "Particle Size Diatribution (PSD) in Stormwater Runoff.'° Info Series, June 2004. Salvia, 3amantha. 2000. "Application of Water Quality Engineering F�andamentala to the Aasesam.ent of 3tormwa.ter Treatment Devicea.'° Santa Clara Valley Urban Runoff Polluiion Prevention Program. Scheuler, Thomas R. 1987. Controiling Urban Runo�`: A Practical Manual for Plarere{ng and Designing Urb�m Bll�s. Mehopolita.n Washington Council of dovernments. ' `,�� Urbonaa, Ben. 2003. aEffectiveneas of Urba.n Stormwater BMPs in Semi- �� Arid Climates." Preaented at the regional conference on: Experience with -' Best Management Practices in Colorado. April, 2003. r- , USEPA. 1999a. United,Statea Environmentel Protection Agency. Storm ;� Water Technology Fact Sheet Hydrodynamic Separators. EPA 832-F-99- � 017. September 1999. �--� USEPA. 1999b. Screening Level Ecologlcal Riak Assesament Protocol, Chapter 3: Air Disperaion and Depoaition Modeling. i_� Vortechnics. 2004. Vortechs System Fact Sheet: www.vortechnics,cpm �� Washfngton Department of Ecology, 2005. �General Use I.evel � ' Deaignation for Pretreatment (TSS) Pilot Use Level Designations for Basic �- (TSS) and Oil Treatment for Hydro Intemational's Downatream ; ? Defender�l. Updated June 1999. �, 8 ot 9 1 �� I �r � �"� r �_ ,� Hydrodynamla S�parators 3 Novwnbor 2003 +( ( � Water Hoard. 2003. Califomia Re�onal Water Quality Control Board for i j the San Franciaco Bay Region. °Contra Coata Countywide NPDES Municipal Stormwater Permit Amendment.'° Order No. R2-2003-0022. , -. � www.waterboards.ca.gov f Weber, Rlalter J. 1972. Physioochemical Processes for Water Quality �� Control. Wiley-Interscience, New York. Wong, Tony H.F. 1999. "Continuous Deflective Separation: Its ` i - Mecha.niem and Applicationa.' Department of Civil Engineering, Monash Univereity, Auatralia ,� �l �� + � � 1 ` , � I 9of9 I , i 3he lournai far S�rfate Water ituality Prafesatonals r.�.�r� 1 t„�,lC,�i� _ ��..:� _. ��V1S1tlI l+�' � .,K,. >>,. .,.: �.��E -� S r . . . .. � " ,''. � � . � . .. , �''� � �- Y ;. y . � L J i� �l, F�rst o# four pcxrts: Basins #or Stormwater Trecxtmen� Systems By Gary R. Minton It has been 25 years since the first community in the United States established the requirement for the post-development treatment of stormwater from new developments. Since then, local, regional, and state governments have published many manuals and handbooks identifying acceptable treatment systems (structural best management practices, or BMPs) and design criteria. Initially, few of these design criteria were supported by laboratory or field research. Absent such data, engineers were forced to use best professional judgment in choosing design criteria. With numerous studies completed over the past two decades, it is timely to reexamine some of these criteria. Furthermore, our treatment strategy is rapidly evolving. The focus has been the general removal of pollutants using total suspended solids (TSS) as the surrogate for all pollutants. However, there has been a recent shift to consider specific pollutants. Some states now emphasize the removal of total phosphorus (e.g., Virginia, Washington, New York); total nitrogen (e.g., Maryland, No�th Carolina); and dissolved metals (e.g., Washington) in particular situations. With this more complex management strategy, a particular design criterion may differ depending upon the targeted pollutant. This article is the first of a four-part series on design criteria. The first three articles consider three generic types of treatment systems: basins, fine-media filters, and vegetated swales and strips. The fourth article is devoted to the removal of dissolved pollutants. Differences in design criteria to target specific pollutants are also examined. , Table 1 provides design criteria for basins from representa�ve manuals and handbooks. � � Design criteria related to size and configuration are discussed for extended detenfion ponds and vaults, wetponds and vaufts, and constructed wetlands in their many variant ` forms. On the East Coast, the initial focus was on extended detention ponds, in some cases modi�ed flood control fadlltles. These basins were expected to be empty after each storm. For many jurisdictions, the basic type has evolved to include some form of ' wet pool, elther covering the entire bottom area orjust a small pool, called a micropool, at the ou�et. In contrast, on the West Coast, the starting point was wet basins, expected to retain stormwater befinreen storms. However, some manuals now.include an extended detention layer in the deslgn. Convergence of concepts appears to be occurring, although the perspective differs. On the East Coast the perspective focuses on extended detention basins with wet pools; on the West Coast, on wet basins with an extended ; deten�on layer. Basln Volwne In thls flrst article, basln volume is considered with respect to the removal of sediment and attached pollutants such as metals and nutrients. The last article�of this series considers the volume required to achieve a signfflcant removal of dissolved pollutants.0.45 The volume of extended deteniion basins (s commonly deflned by specifying the depth � � of runoff to retaln and treat Initlally, the specffication was 0.5'inch, based on a philosophy of capturing the "flrst flush" of pollutants. It was reasoned that the majority of � pollutants are present in the first 0.5 inch of runoff. Some jurisdic#ions began to state a management goal of capturing and trea�ng "X" percent.of the volume of stormwater over ' � time, typically 85% - 90%. This led to an Increase in runoff depth to 1 Inch or more, as indicated In Table 1. With a volume capture goal of 85% -�90°�, the relevance of first flush becomes problema�c. Not commonly recognfzed is that the slzing of an extended detention basln involves finro questions: the depth of runoff to divert and the volume of the basln. These are finro separate but related questions. It is common to assume that the volume of the basin is equal to the desfgn depth of rvnoff that fs to be dlverted to achfeve the, management obJective. However, for many Jurisdlctions, the volume of the basln must be larger than, not equal to, the runoff depth that is to be dlverted. Why? It ls Important to recognlze that some stormwater might�at times remafn in the basin as the next storm arrives. Hence, how much larger the basln must be depends on two factors: the design drawdown time and the interevent �me, or the time between runoff events. The required basln volume � Increases as the Interevent time decreases and as the specified drawdown tlme at brimful increases. The above effects are understood from the work of Guo and Urbonas (1996) and related articles. Their methodology solves dlrectly the relationship between the management goal and the size of the basin for a particular climafic reglon. The concept Is illustrated In Figure 1. They proposed that the selected basln volume be equal to the max(mized water-qualiiy capture volume (WQC�, shown (n Figure 1. The WQCV is defined as the pofnt on the curve where an inc�emental increase�in the storm volume captured and treated begins to decrease significantly with the incremental Increase in basin volume. At the WQCV, the amount of stormwater captured over tlme is on the order of 80% - 95°/a, depending on the community, and is therefore close to the management goal of many communities. The normalized WQCV in Figure 1 is all events divided by a value of runoff depth equal to the 99.5 percentile runoff depth for each community. Normalization allows comparison between communities. �1C#U�� . Pc�rtray�� of th� CQn�t of guo ar�a Ur�o;n�s �t9��) 1 � a.� � o.s w �' a.� �, � a.s � a.� � u.�a � � � o.a � � az o.y �� Representative results from Guo and Urbonas (1996) are presented in Table 2. Here the volume of the basin is specified as a multiple of the depth of the mean annual runoff event. The mean annual runoff event is the total annual runoff divided by the total number of runoff events (Driscoll et al. 1989). For example, assume a community has a mean annual storm runoff depth of 0.7 inches and a sizing ratio of 2. The volume of the extended detention basin is 1.4 inches times the tributary area and the runoff coefficient. ' TABLE 2 Maximized Detention Volume Ratio for Various Cittes a, b Drawdown i Boston , Cincinnati � Denver � Seattle ( Tampa ! Sacramento j ASCE ; � , 12 hours I 1.67 j 1.13 ; 1.21 ', 24 hours � 1.79 � 1.46 ; 1.36 I ; _ . _. _ _ _ ; _ . _. .__ _ . __ ._-- --. _ _ _ ..._ _ __ _._ . . ' 48 hours ! 1.89 ( 1.52 i 1.49 I a. J. Guo and B. Urbonas 1996 � b. Based on 95% impervious surface 0.99 � 1.65 � 1.00 I 1.31 1.34 � 1.76 � 1.50 _. __ ___ __ _ _, . _ � _ ; _ � 2.29 � 1.95 � 2.31 ' 1.58 1.96 Table 2 shows the incremental effect on basin volume of increasing the drawdown time at brimful from 12 to 48 hours. It shows that increasing the drawdown time increases the required volume for the basin. This point is typically not recognized. Why must the volume be increased? Because the longer the drawdown time the more likely there will be stormwater in the basin when the next storm arrives. The effect differs significantly between communities. The incremental effect is minor for Boston, Tampa, and Denver. 0 0.� o.a o.s a.� � N�rmaiazed �ater•Quaiity Gapture Vol�me + ;'. � Conversely, it is'signtflcant for Seattle and Sacramento where the interevent times are -° relatively short during the wet season. For a given community, the aggregate volume of _ water captured over time is the same irrespective of the drawdown time speclfled at ` j brimful. But the basln must be larger wlth greater design drawdown times. The ratios in . Table 2 do not account for inflltra�on or evaporation. �� For the specffied storm depths presented in Table 1, the ratio of volume of the basin to _� the runoff volume of the mean annual event (VbNr) ranges from 1.5 to 3. While the _ - rafilos lie within the vicinity of the WQCV values suggesteci In Table 2, It is unlikely values currently specffied in many manuals that are the most appropriate for their regions. This � is because, as noted previously, it is commonly assumed that the volume of the basin is ` equal to storm depth to be diverted. . Also presented in Table 2 are nafional values (ASCE 1998) based on the work of Guo. Glven the substantial climatic d(fferences between regfons, apparent in Table 2, using average national values may result In elther an undersized or oversfzed faclllty depending on the community. , Other methods for determining the WQCV have been proposed, such as.the Califomia Stormwater Quality Associa�on (CASQA 2003); Goforth et al. (1983); fGng County (1998); Nix et al. (1983); Pitt, R. (2000); and Roesner et al. (1991). These methods have not been compared to ascertain whether they provide outcomes similar to Table 2. It is likely dlssimllar results will be fourid. A professional dialogue Is needed to ascertaln the most appropriate method. For that reason, thls author Is not suggesting the approach by Guo and Urbonas (1996). Rather, it is presented �to make the point that Interevent �me, the selected drawdown time, and the selected management objec�tive interrelate to, affect the deslgn volume of a basln. As such, the selection of the drawdovm tlme and the management objective are not separate dedsions. With respect to wet baslns, Table 1 Indlcates that It Is common practice to spedfy a volume that is the same as that specifled for extended detentlon basins. Some manuals specify a larger volume. However, It is intuitive that a wet basin can be smaller than an extended deten�on bagin if the desired removal effidency or effluent concentration of TSS Is the same. This is because additfonal settling occurs in wet basins between storm events. A synthesis of data of wet basin pertormance, Figure 2 suggests a VbNr of 1 is sufFiclent (Strecker 2003). F(gure 2 plots effluent concentra�on as a functlon of the VbNr. The plot indicates Ifttle further reduction In the effluent concentratlon beyond a ratio of 1. Comparison of Figure 2 to Ta le 1 suggests that communffies oversize wet pool, basins If sediment and attached pollutants are the �only obJectivve. The data in Figure 2 reflect what is settling from the stormwater and the growth of plankton algae. Hence, TSS do not approach zero even with large basln volumes. It was prev(ously observed wlth extended detention baslns that maxlmlzation of the removal of particulate metals and nutrients Ilkely requlres a larger basin than if TSS removal is the sole objective. This may also be the case for wet basins. Hence, a VbNr on the orcler of 1.5 may be deslra6le. . �r 1� _� ,ry ,� r , _� �. -;, `, _N ,, �. �- ,, ,, ,_� „ %, �� '� C � �- �� : � ��il�� ,�� 1�k�f�1' ��t� �i1t� �f�u�er�� '�'�� r�c�cer ��}��} � � � �� -- � c � � � . ¢ � ��' � . c� � � . � e a � �� 4 ° � � � a � �l � a � �2 3 �. 5 � 7 �,8� 9 �Q� �►�� v�►u,�� I1�itc�tf �tr�aium��w�ter�ti r�sr�� With respect to the West Coast perspective, the ques�on arises as to the benefft of placing an extended detention layer atop a wet pool. Most manuals suggest splitting the design volume in haff: half wet pool and half extended detentlon layer. A few suggest increasing the design volume to add an extended deten�on layer. The relative beneflts of thls approach are discussed later In this article. . � Drawdown Time � Drawdown time is the fime required to empty an extended detention basin or layer from brimful, the elevahon of overflow. As noted previously, the design drawdown fime at brimful affects the size of an extended defentlon basin; its specification Is therefore important Table 1 presents a signfficant range of drawdown fimes, from 24 to 72 hours at brimful. The first recommendatlon for.drawdown time was 40 hours at brimful, averaging 24 hours for all events (Grizzard et al. 1987). The recommendatlon was derlved from a fleld study of one converted flood control detention pond and laboratory column tests. The �e �� _[ -; � �I ,, '� laboratory studies showed little addifional removal of TSS beyond a settling time of six to �"�� 24 hours depending on the Initial TSS concentration. A more recent study of a field basin �, -�i (Keblin et al. 1998) found negligible improvement in TSS reduc�on at drawdown times in � excess of 24� hours. As settling velocity distributions of sediment in stormwater can vary '� reglonally because of varying soil types, the appropriate drawdown time may also vary - reglonally. For example, ln New England, where a slgnlficant fractlon of the sedlment ;�� may be deicing sand, a lower drawdown time ls Ilkely needed than in the Padflc - Northwest to achleve the same pertormance goal. Other pollutants need to be , considered. Generally, metals and phosphorus associate primarily with the fine �� sediments, necessitating relatively longer drawdown times to achieve hlgh, removal of �� the particulate forms. The work of Keblln et al. (1998) suggests that achleving the highest praciical removal efficiency of particulate metals may be twice that of only the ` �� sediment. It appears that tlie average drawdown time should be at least 24 hours. However,� 48 ,� hours is likely prudent ln most reglons. This results In drawdown tlmes at brimful on the � order of 40 to 72 hours. There is little reason not to specify a greater drawdown time in � communities, such as Boston, where the effect on basin volume Is minor. If the effect of t-� the declsion is signiflcant, as with SeattJe and Sacramento, local studles of the �� relatlonship befinreen performance and drawdown �me should be conducted. This `'� suggests that the analysls of the relatlonship between drawdown �me at brimful and bas(n volume needs to be extended beyond 48 hours. '�� The above discusslon Is relevant to extended detenfion basins that dry completely between storms. However, most�manuals now encourage induslon of some form of � �' permanent wet pool. This raises the ques�on as to whether very long drawdown tlmes �= are necessary. One manufactured product, the�StormVault, uses the combfned wet , pooUextended detention layer conflguration. It appears to provide satlsfactory treatrnent `� with a drawdown time at brimful of onfy six hours. The contrlbution of the wet pool to' �i_ � performance is likely slgnificant. Drawdown Rate Although drawdown time has been in use for finro decades, (t is not necessarily the �� correc# design criterion. The more appropriate crlterion may be the drawdown rate; that ��, is, the rate at which the water level drops in the basin. Consfder two basins, Identfied as A and B, both with the same design volume and drawdown time at brimful. They differ ln � that Basin A has an average depth at brimful one-third that of Basln B. Hence, Basln A has three tlmes the sartace area of Basin B. It follows that the average drawdovm rate of ' Basin A is one-thlyd that of Basin B. As a consequence, Basin A removes particles that -, are much smaller, with lower settling velocltles, than Basln B. Conceptually, the perspective is to recognfze that"all particles with settling velocmes greater than the fall - rate of the water will reach the bottom of the basln before the water exfts the basin. The slower the fall rate, the smaller the particle that reaches the bottom. The fall rate In an �� '� extended detentlon basln is akin to the hydraulic loading rate (HLR). The HLR Is -�' expressed as cubic feet per second per square foot of basin surface area. It will be noted that the units of cfs/ft� are also ft/sec: the unfts of the settling velocity of a particle. N The relevance of the HLR has been recognfzed in� water and wastewater treatment for a a_ E century (Hazen 1904) and Is the basis for sizfng sedimentation basins (AWWA 1990; ;� Metcalf and Eddy 1991). Its appropriateness has also been recognized for stormwater treatment (Small and DiToro 1979; USEPA, 1986; Dorman et al. 1996). � Is there a benefit of specifying drawdown rate rather than time? Table 2 suggests it depends upon the community. The advantage of specifying the drawdown rate is that the needed drawdown time and therefore basin volume decreases with a shallower basin, compensating for the larger area required of a shallower basin. For example, assume the local jurisdiction selects a drawdown rate of 0.15 ft/hr. For a basin with a depth of 7.2 feet, the drawdown time is 48 hours at brimful. If a depth of 3.6 feet is selected, the drawdown time need only be 24 hours. According to Table 2, the required basin volume is only about 5% less for Boston and Cincinnati, 10% for Denver and Tampa, but approximately 40% for Seattle and Sacramento. What is the appropriate drawdown rate? Figure 3 summarizes information for several studies of extended detention basins. The data are from facilities in California, Maryland, North Carolina, Virginia, and Texas. Shown is the effluent concentration versus drawdown rate. Basing the choice of drawdown rate on effluent concentration may be more valid than efficiency, because efficiency tends to be lower at lower influent concentrations. However, efFluent concentration is not independent of influent concentration, complicating the analysis. F1�IJR� 3. Effluent T� Cancer�tr�tian as Refated to Av$r$r�e �7ravr�dc�vrm Rat� at 8�mful t4� �zo � f� c� � 8� t�i �" 6� � c w � � � 20 0 Q�awdown A�te �fflhrj As the data are scattered, the appropriate drawdown rate is not readily obvious. Some of the scatter is due to highly varying median influent concentrations. It is also noted that the performances observed in each study reflect drawdown rates that are much lower than that at brimful because most storms in each study did not fill the respective basin. Given the scatter in Figure 3, one might conclude we should continue to use drawdown �.00 �0��0 1,i�Q 1.50 �.� '� � � '� � , � ' ;, time. However, to be fair, tF the abscissa in Figure 3 were plotted against drawdown time, a sfmilar scatter would be found. It would be )ust as difflcult to select a drawdown time from such a scatter. Figure 3 suggests that below 0.30 ft/hr, the Incxemental benefit is problematic. Based on the work of Keblln et al. (1998) previously cfted, this value should be halved to 0.15 ft/hr to achieve the maximum practical, removal of attached pollutants. Thls value represents the average drawdown rate from brimful The slze of particle that settles faster than a drawdown rate of 0.15 ft/fir is about 5 to 15 microns, depending on water temperature and the spec�c gravity and shape of the particle. However, particles smaller than thls slze range will be found on the bottom of the basin for two reasons. First, during all events the fall rate is for much of the time less than the average rate at brimful. Secondly, the stormwater as it enters the basln is thoroughfy mixed vertically. As a consequence, many partldes less than the 5- to 15- mlcron range reach the bottom before the basin empties because they are close to the bottom as they enter the basln. � , Is deten�on time Irrelevant? Drawdown rate is relevant to partides that are discrete. That -- Is, as they fall, coagulation does not occur when two particles make contact. Silts and 1- �, sands are discrete $uspensions, whereas clays coagulate given sufficient �me. By { conventlon, clay particles are smaller than 5 microns. Hence, at a drawdown rate of 0.15 ' I ff/hr, much of the day suspension mlght not reach the bottom before the basin empties unless ft coagulates into larger partides. It is possible at Influent sediment concentrations less than about 50 mg/L the clay fraction is significant, In which case �me � for coagulation may be important. Griaard et al. (1986) found at these tow concentra�ons lt took on the order of 48 hours to reach a percent removal slmilar to that �� achieved in only two hours when the Inl�al TSS concentratlon was on the order of 100 ,,_� mg/L. This suggests extended time is needed for coagulation at very low inmal concentrat(ons. However, it is questionable as to whether high .levels of performance are +, � relevant at such low initlal concentra�ons. Some manuals spectfy a drawdown �me of 24 ' hours for the average condition, but this average condition Is not typically deflned. � Regardless, it is likely that.even with this specification, days have Insufficlent time to , satisfactorily coagulate. Hence, there may be an inherent limitation for extended �' deten�on baslns if day Is a signiflcant frac�on of the Incoming sediment As such the ' beneflt of a wet pool becomes apparent The long residence �me between runoff events -�� provides sufficient time for the clay to coagulate in the wet pool and to reach the bottom ; of the basln. These issues again polnt to the importance of understanding local '� cond�ions and influent concentrations when selecting an appropHate dKawdown rate. _ Lengtli-to-Wldth Ratlo The purpose of specifying a length-to-width (UW) ratio is to improve hydraulic efficiency r�'' by reducing short-circuf�ng and dead zones. Wtth respect to wet basins, hydraul(c �:�; efflciency is deflned as how well fresh stormwater exchanges with older water in the basin. Table 1 indicates a large range in deslgn values. Specifying an UW ratlo for '? extended detentlon baslns is likely unnecessary as these_baslns operate essentially as : flll-and-draw systems. The constricted outlet tends to force incoming stormwater Into all areas of the basin. A comparison of six extended detenfion basins (n wtilch the UW ratio �r� varied from 3 to 10 fotand no difference in pertormance (Caltrans 2004). Whether � performance is affected by ra�os in the range of 1 to 3 is unknown. � ,_ , � �� I !� '� While a high UW ratio may maxlmize hydraulic efficiency, it may also create a geometry '� that is difficult to fit into many developments. Furthermore, excessivefy narrow basins 'J may induce the resuspension of sediments because of greater throughput water � velocitles. The experlence from wastewater treatment (s to have substantial L/W ratios, 1-�' on the order 10 to 20 or greater depending on the unit operation (e.g., sedlmentation, ,_ chlorinatlon). Such hlgh L/W "ratlos are not necessary in stormwater systems because , the rate of inflow is generally lower relative to the basln volume than In wastewater � ' systems. . ,i � �i ,; �y Y. �; 7 � � �, � �i '� � , �, ' �1 �; � f e �-,, ., �_ ' �, � � One study of the relatlonship between the L/W ratio and hydraulic effidency suggests a ratio above 2 provides little additional benef�. Figure 4 is an interpretatlon of Walker (1998). It shows the effect of increasing the UW ratlo on hydraulic efficiency. Figure 4 suggests modest benefit of incremental lncreases of the ratio above 2. It also suggests the approprlate LJV1/ ratio likely differs with the size of the basin as deflned by the VbNr value. For baslns with large VbNr values a UW ratio of 2 is Ilkely satlsfactory. If the VbNr of wet basins is on the order of 1 as recommended fn thfs article, the LIW ratio should be greater, perhaps 3 to 4. The storm Intensity common to the region may also be relevant to this decislon. In the Southeast, with high-Intensity storms, the incremental benefit of increasing the UW ratio is likely greater than the Pacific Northwest with its mild storms. This dffference Is suggested by contrasting the results of Persson et al. (1999) and Persson (2000) to Walker (1996). In the former studles signlficant benefit was found up to a ratio of 5. However, these studles were conducted at higher flow rates. �Gi��L �4. ��# +� Ler�g�h-ta-Wici�h f�o on 1lVater �lok�tme E�tcrh�ge �rafr�r Vilalkei-1�58� '� 0 � � � � Y a� 0�8 Q7' � � o:s o� 0�1 0 � Stn�m b.S � p�or�d miume Si�rm � �qt�l t� pertd v�me 2 4 6 8 1J4�1 f�a Poor hydraul(c efficlency has been found not to be an issue with poorly configured large wet baslns with VbNr values on the order of 10 (Pitt 2000). Thls Is not likely the case with smaller VbNr ratlos. Baffles were added to a pond with .a VbNr of about 1.5, increasing the UW from 1.5 to 4.5 (Mathews et al. 1997). A slgnificant improvement in hydraullc efficlency was observed. � �� ' An UW ra�o of 1 is Ifkely valid for small wet basins if an extended detention layer is � included on top of the wet pool. Restric�ng the outlet causes stormwater to "badc into" �_ areas that would otherwise be dead zones such as comers or areas of dense _ � vegetation. The deslgner may be allowed the flexibilfty of using elther a wet pool only �_'' with a large UW ratio, or a combination extended detention/wet pool with a smaller UW ratlo to meet slte constralnts. For pure extended detention basins a UW ra�o of 1 Is ,� likely sufficlent. , As with the UW ratio, the beneflts of an extended detentlon layer may differ with the �, s cl(matic region: The concept may be most beneflcial in the Southeast with its short, high- ;, intens(ty storms and high rates of inflow. In contrast, the concept may be of less benefit on the West Coast where average storm Intensities are much less. ' �I ' The above discussion does not take into consideratlon the poten�al adverse effects of " . thermal or denslty (from deicing salts) stratlflcatlon on hydraulic and therefore t,` � pertormance efficiency. The efFect of strattflca�on is poorly understood. Thermal � !� stratification reduced the detention tlme of a small wet basln by half (Timmins et al. -�' 1999). The signiflcance of stratification to performance is unknown, as is the effect of the ,� � energy of incoming storrns to temporarlly destratlfy the basfn. One study concluded that ;� summer storms abetted stratfication due to tlie incoming stormwater being hlgher in -- temperature than the pond water (McBean and Bum 1983). �', Stra�fica�on should not reduce performance during storms. As established above, - performance Is a function of hydraulic loading r�te, whlch remalns the same Irrespective _ of stratiflcation. However, stratlflcation reduces the exchange of fresh stormwater with � water present in the bas(n. As a consequence, stratfflca�on in effect reduces � �_` performance befinreen storms with respect to fine sediments and dissofved pollutants. _ Increasing the L/W ratio might decrease the potential for stratificatlon by increasing flow �, velocities within the basin. SubsurFace discharge to the lower half of the wet pool and/or �}� entrance baffles might have a greater mitiga�ng effiect than a large UW. A flnal note of Interest Is that fn the study clted above, thermal stra�flcatlon occurred in the top 10 �, inches of the wet pool. This suggests that the common recommendafion (Table 1) to Ilmit the ma�dmurn depth to avold strafification may not be effeciive. More studies on thls ' subJect are needed. � Multlple Ponds or Cells , ,..� Several manuals suggest incorporatfng multiple cells, either as separate basins�in series ��' or by separation of one basln Into two or more cells wfth a berm extending above the � water surface. Mul�ple cells can signiflcantly increase space requirements. The ,� purported benefft is more effective treatment. However, there are no data substan�ating � thls claim. Some conceptual designs like tfiat shovm fn Flgure 5 may result in poorer '��'' performance than one basin of equal volume. Whlle aesthetically pleasing, mul�-ponds _ with irregular shapes Increase short-clrcul�ng and dead zones. Thls decreases hydraulic '� efficiency and, as a consequence, performance efficiency. An extended detention layer . � may minim(ze this effect. .� �-� � ,� -� I� -'"� � I , �/ i �l � 1 5 � � � � i� �� L ;� R I � �, � � C ,� r � � �� i i, . t ', '� ' :i ,f �� r, ,, 0 ` "°� ' ' � �'�`. �-� � � � ��, . `'� . . �,u �� . Y1. ,. - 1 �4� �� `"�r�T'.� 1�y, - , . i �ar�{y{��y� .. �� . L1 k^ f,�� _i. 1 ' ' .. L` ^�T^�� :, { � - �-1 ^ 1_ }� rt� � ��y�� . L . , `- } i ; � � � !`I�1!f� . . F ',y: a c ^ � .� w . Ikit3� . � �: ' �`, v.,' ;. >;� . . • �C�'l47 . �� - , �a ' . � ; '�� _ �, ;; � . ��, � - ; � ` � �,..;,� ' . . . , ,. . c - aYe�ilair tvfttex�! ' . . .• . � . . �� id��✓' � wt i `�S' J�/y��' . ` _ \ / ; , � , �t�� ` ` .� � ' �� y^ , , � � ' 4�+4�'�• . � FlqUl�� . A.Crina�piu� [�sigf,i far C`�ori�-�wt�i 1Matt�ri� Vegetation Coverage � � For wetponds, a shallow safety bench of 10 to 15 feet in width is commonfy recommended. The benches become covered by emergent vegetatfon. For wetlands, manuals usualiy specify a depth regime that resutts in vegetation coverage on the arder 60% - 85% of the surtace area. Concepts of vegetation configurations are frequently included in manuals (Figure 5). . Depending on fts degree and location, emergent vegetation may enhance or degrade hydraulic efflciency and therefore pertormance efflciency. If the basin is configured so as to produce an open area down the middle of the basin, hydraullc efficiency and therefore performance is reduced. Water, finding the path of least resistance, moves through the center of the basin, with little exchange wfth "old" water Iri the densefy vegetated areas along the sides of the basfn (Persson et al. 1999). In shallow marsh wetlands, low-flow channels may have a similar effect. As the wetland ages, a patfem of uneven plant densities may create channels of less resistance, decreasing hydraulic efflclency. A more appropriate configurat(on might be open fore- and after bays wfth a shallow intermedlate marsh area and no low-flow channel. To use less space, the intermediate area could be of wetpond depth. The interface befinreen the central area and the fore- or after bays can be a berm, but with the top below the water and covered by emergent vegetation. This berm conflguration could more evenly spread incoming water across the lateral cross-section of.the pond. Altematively, as previously noted, an extended detentlon layer mlght compensate for the adverse effects of frfnge vegetation on hydraullc efficiency. Sedtment Storage The common criterlon is to either add 1 foot of depth or increase the basin volume by 20% above that calculated for pertormance. The added cost is not trivial. However, once constructlon of the development is complete, the accumulation rate of sediment is ` . � modest, on the order of 0.25 to 0.5 in/yr. Furthermore, most of the incoming sediment - settles in the forebay. It is suggested that this requirement be eliminated, particularly if a forebay is inherent to the design. Furthermore, a more cost-effec�tive aftemative to the earthen forebay might be a large standard.manhole, a small manufactured wet vault _,, (e.g., Stormceptor), or a vortex separator. Even if the iNtial cost Is greater, the life-cycle cost might be lower glven the greater ease of maintenance of these devices. � _� . � Flnal Observatlons 1��, The discussion suggests that wet basins and extended detention basins are not ._ �- separate types but opposite ends of the same type. A continuum exists between the two extremes, depending on the climate of the particular reglon and the design volume. The discusslon further suggests that extended detentlon basins should perform as well as ,� wet basins, although they must be larger to achleve slmilar pertormance with respect to `f the removal�of sediment and particulate pollutants. As previously noted, particles as �� small as 5 to 10 microns should be readily removed at current drawdown rates. �� ' However, performance studles suggest otherwise, as implied in Figure 3. TSS in the �` effluent of wetponds are typically on the order of 10 to 20 mg/L, whereas they are on the .� ` order of 20 to 40 mg/L. for extended detention basins. This dlscrepancy is due in 'part to , weiponds having volumes equal to or greater than those of extended deten�on baslns ' (Table 1). It may also be due in part to the likely inablllty to induce the coagulatlon of day _, even with a specifled drawdown time for small storms. a . �� Design aspects other than volume and drawdown tlme might contribute to a less-than- expected perFormance for extended detentlon basins. The most likely reasons are 7 adverse inlet and outlet condffions. Resuspension of previously deposited sediment and ,�° erosion may occur In the Inlet area during the infrequent high-Intens(ty storms if energy disslpatlon is insuffident Resuspended clays might have insufflcient �me to re- � coagulate and as a result exit during these events. The more likely candldate for subpar I u perfonnance is the outlet structure. In a water or wastewater basln, e�ating water Is gathered along an effluent weir that extends the wldth of the basin. This minimizes , approach velocities to the welr. By contrast, the outlet strvctures of extended detention ' basins 'are very small relative to their end-cross sec�ons. As a consequence, stormwater �" "rushes" toward one relatively small point in the basin. Approach velocifies near the ,M outlet are excessive rela�ve to the settli�g veloclty of silts and clays, and even fine sand. � j, The effectfvve HLR In the vlcinity of the outlet Is substantially greater than the nominal '' �HLR of the basin. Sediments that should be removed based on the nominal HLR, or . drawdown rate, are lost through the�outlet. This condl�on Is exacerbated if the bottom ', i around the outiet fs bare, allowing for eroslon at the hlgh approach velocltles. Whlle wet basins also have narrow outlets, the effect is less severe. With wet basins the water exiting each storm is "old" water�that Is relafively clear of fine sediments, given the � reteniion time befinreen storms. One or a combination of design elements may mitigate the effect of small outlet � stnictures. Several outlet risers tied to an e�at manifold may help. However, the issue of clogging very small orifices arlses. A shallow wet pool or mlcropool at the outlet may � counter the effect of excessive approach velocities by preventing scouring of -' accumulated sediments at the bottom of the basin in the vianity of the rlser structure ;-, (Fennessey and Jarrett 1997). Some have found that withdrawal at the surface improves performance (Ward et al. 1979; Millen et al. 1997) whereas others have not (Keblin et al. ,._ � _� _G I �'� 1998). Spacing, size, and the location of pertora�ons on the riser may affect - performance (Ward et al. 1979). However, another study found no significant difference in performance between a single bottom oriftce and a perforated vertical riser � (Fennessey and Jarrett 1997). It is possible that while the riser configuration reduces approach veloci�es, the reduction may not be sufflclent to signtflcan�y affect . perFormance. Certalnly, however, a riser structure with a series of vertically placed holes ; should reduce erosion and/or resuspension in the immediate vicinity of the outlet A cone of gravel around the bottom of the outlet structure has been found to signiflcantly Improve performance (Engle and Jarrett 1995). More studies on this issue are needed. ��, Basins sized as suggested here should be able to meet the general criterion of 80% �; removal of TSS, a specficatlon of most manuals. They sfiould also be able to meet the specfficatlon of 40% removal of the total phosphorus (TP) inasmuch as 75% - 90% of the ,- phosphorus is typically bound to the sedlments. Meeting the goal of 40% removal of � nitrogen Is less certa(n given that it is more soluble than phosphorus. These ques�ons `�" are considered in the fourth artlde of thls series. _ ,� � , It is common to specify a minlmum drainage area, under the thesis that a base flow of water Into the basin is needed to keep a permanent pool. Thls limits the use of wet basins for larger areas, on the order of at least 10 to 25 acres depending on the region. The concem Is that the wet basln will not fully function without water. ,Thls is not the case. There Is no need for the basln to "work" between storms. Pollutants migrate to the bottom as water evaporates and into the soll with infiltration. Allowing the pond to dry may reduce mosquito problems. Infiltration Is good for the hydrologic cycle. However, drying may solubilize some pollutants, which might be lost in subsequent storms. If the removal target Is solely TSS and attached pollutants, this Is no concem. Even if dissolved pollutants are of concem, the pond or wetland fills with the next storm, at whlch time the solubilized pollutants likely renew attachment to inorganic and organlc sediments. Constructed wetlands can withstand extended periods of dryness without harm to the vegetation. Specifacatlons as to the ma�amum length of dryness to avoid thls problem may be prudent and wlll vary with the climatic region and vegeta�on specles. It is also important to recognlze that a constant base flow can reduce the performance with some pollutants. One 'study found a negafive net removal of phosphorus (Oberts 1997). Removal during storms was ofFset by loss in base flows during dry periods. �-, The concepts dfscussed In this article are also relevant to manufactured basins such as Stormceptor, BaySaver, EcoStorm, and Stormvault. Regardless of how they may be �-� configured, they are essentially wet vaults. ' " Summary . �'• - ,�,} The data suggest wet basins can be smaller than currently specified. They also can be � smaller than extended detention baslns if the sole objec#ive is the reductlon of sediment �' >� and attached pollutants such as metals, pesticides, and nutrients. In most situa�ons this "basic" level of trealrnent is Ilkely sufflclent A dead storage volume equal to the runofF of ,� the mean annual event<that Is, a VbNr of 1 to �1.5<Is likely adequate for wet.baslns. A � larger volume may be necessary where slgnificant removal of dlssolved pollutants is also desired. This aspect is considered in the fourth ar�cle of th(s series. , �� `�� To achieve reasonably equivalent performance, extended detention basins must be larger than wet basins with a Vb/Vr on the order of 2 to 2.5, depend(ng on the region. ;'� , . �, � _ �� 1 Y; �( The speciflcation of volume must also take into considera�on the spec(fled drawdown time at brimful and'the interevent iime for the locality. A longer specfied drawdown �me . and shorter interevent time requfres a larger basin volume to achieve the same � management objec�ve wlth respect to the aggregate volume of water treated over time. . The effect of infiltratlon and evaporafion could be included in thls analysis. � Drawdown rate rather than drawdown time is the correct deslgn criterion for extended �, detention basins. In some regions, in particular the West Coast, recognitlon of drawdown rate as the correct crtterion �esults in more cost-effective sizing. Current data suggest '� ` the specfflcation for the average drawdown rate from�brimful be on the order of 0.15 ff/hr. .�% Although,there Is considerable uncertainty with this spedfication, the same uncertainty exists with the current speclflcation for drawdown time. Regardless, even if changing from drawdown tlme to rate fias little efFect on basin volumes for much of the nafion, the ', .� use of drawdown rate will ensure that field studles gather the appropriate Informatlon � �� that has been ladcing in most previous studles. ;' Drawdovm tlme may be relevant to the extent that clay Is a signiflcant fracfiion of the - incoming sedlmen� Local studles are needed to ascertaln the relevance of clay as are - � more studies on the relationshlp befinreen fime, coagula�on, and settling. The data �,� suggest; however, that the issue of clay mlght not be the most sfgnificant factor in what appears to be less-than-expected pertormance of dry basins. ,� , There may be an Inherent Iimltation of extended detention basins to perform as well as - wet baslns (rrespective of the drawdown rate or time. Deslgn aspects other than volume and drawdown time must be considered, in par�cular the outlet structure. Modiflcat(ons ', ', to current outlet design speciflcatlons are neederl to reduce approaching ve{ocfties and � the potential for resuspenslon and/or eroslon In the vidnity of the outlet. The limitations of these bas(ns can be mitlgated through the Incluslon of a wet pool. However, at some ! point the questlon arises as to what is being deslgned:,an extended detention basln with '}� a wet pool or a wet basin with an extended detention layer. It follows that at some polnt the relevance of an extended deten�on layer becomes problemafic. � The length-tawidth ra�o is an Important design parameter for wet basins, but it is � probabfy not particulariy relevant to extended detention baslns. A ratlo on the order of 2. �� to 4 is likely sufflclent for wet baslns. The appropriate ratio depends on the selected Vb/Vr and general rainfall intensity. A rafio of 1 is likely sufficient for extended detentlon � basins. Oddly configured baslns or fiasins with varying bathymetry adversely affect - fiydraullc efficiency and therefore performance efflclency. The adverse effect of such �� conflgurations can be reduced by Increasing the slze of the syste�m and/or by Indudfng ;% an extended deten�on layer. However, as these relationshlps are little understood, it is � advisable to carry out the appropr(ate studies before Imposing such requirements. ' Care must be taken with emergent vegetatlon. Depending on location and density, emergent vegeta�on can be counterproduchve. Vegeta�on along the sides of a wet '' basfn, wlth open water down the center, reduces hydraullc efflclency. Thls can be b_� countered by lateral berms with emergent vegetation and/or an extended detention layer. The sign�icance of this observation is greater in reglons,with high-intensity storms �; such as the Southeast. Y. '�i ��!� -- 1 . Additional laboratory and fleld studies are needed to better define the significance of the observafions and recommendatlons made in this article. Being aware of the relevant � design criteria and how thelr selecfiion may afFect pertormance leads to studies in whlch � the most relevant characteristics of performance are evaluated,such as hydraullc � efficlency, water level fluctuations, and the size distributions of incoming and outgoing sedlments. References American Soclety of Civll Englneers (ASCE), 1998, "Urban Runoff Quality Management," Manu'al and Report of Engineering Practice 87, Reston, VA ,� Amerlcan Water Works Assoclation (AWWA), 1950, Water Quality and Treafinent, F.W. Pontius (ed), McGraw-HIII, New York; NY. , . Barrett, M., 1999, "Complyfng with the Edwards Aqulfer Rules: Technical Guldance on Best ; Management Practices," Texas Natural Resource Conservatlon Commisslon, Austin, TX. Califomla Departrnent of Transportation (Caftraiis), 2004, "BMP Retrofrt Pilot Program, Flnal . Report," CTSW-RT-01-050. Califomia Stormwater Quallty Assoclafion (CASQA), 2003, "Stormwater Best Management Practice Handbook," New Developmerrt and Redevelopment. Dorman, M.E., M.E. Hartigan, J.P. Steg, and T.F. Quasebarth, 1996, °Reten�on, Detentlon, and Overland Flow for Pollutant Removal frorn Hlghway Stormwater Runoff," FHWA-RD-095, US Federal Hfghway Adminlstration, McLean, VA. � Driscoll, E, G.E. Pelhegyl, E.W..Str�ec�cer; and P.E. Shelly, 1989, "Analysls of Storm Everrt Characterls�cs for Selected Ralnfall Gauges Throughout the United States;" prepared fo� USEPA. � � Engle, B.W., and A.R. Jarrett, 1995, 'Sedlment Retentlon Efflclencies of Sedimentatlon Filtered Outlets;" Trans. Amer. Soc. Agri. Engrs, 38, 2, 435. Fennessey, L.A., and A.R. Jarrett, 1997, 'Influence of Principel Spfllway Geometry and � Permanent Pool Depth on Sedlment Retentlon of Sedlmentatlon Basins,° Trans. Amer. Soc. Agrl. • Engrs.; 40, 1, 53. � Goforth, G.F., J.P Heaney, and W.C. Huber, 1983, 'Comparison of Basfn performance Modeling Techniques," J. Environ. Engr., 109, 5, 1082. � � Grlaard, T:J., 1987, "Flnal Repork London Commons Extended Detentlon Faclltty Urban BMP f Research and Demonstra�on ProJect,' Vlrglnla Tech Unfversity, Occoquan Watershed Monitoring Laboratory, Manassas, VA. - � ' Griaard, T.J., C.W. Randall, B.L. Weand, and K.L. Ellls, 1986, "EffectNeness of Extended Detention Ponds In Urban RunofF Qualfty<Impact and Qualfty Enhancement,' B. Urbonas and L.A. Roesner {eds), American Soclety of Civil Englneers, New York, NY. Guo, J., and B. Urbonas, 1998, "Maxlmlzed Detenfion Volume Dete�mined by Runoff Capture Ratfo," J. Vllater Res. Plan. and Manage., 122, 1, 33. '�� '�i i� �� ,� Hazen, A., 1904, 'On Sedimentabon," Trans. Amer. Soc. Civil Engr., 53, 45. Keblin, M.V., M.E. Barrett, J.F. Mallna, and R.J. Charbeneau,� 1998, "The Effectiveness of Permanent Highway Runoff Controls: Sedimenta�on/Filtration Systems," Research Report 2954- 1, Center for Transportation Research, Unfverslty of Texas, Austln, TX. � King County, 1998, Surface Water Design Manual, Department of Natural Resources, Seattle, WA. Mathews, R.R., W.E. Watt, J. Marsalek, A.A. Crowder, and B.V.C. Anderson, 1997, "Extending Retention Times in a Stormwater Pond wfth Retrofltted Baffles," Water Qual. Res. J. Canada, 32, 1 73. McBean, E.A., and D.H. Bum, 1983, 'Thermal Modeling In Urban Runoff and the Irnplications to Stormwater Pond Deslgn," In Intematlonal Symposium on Urban Hydrology, Hydraulfcs and Sedlment Control, University of Kentucky, Lexington, KY. Metcalf and Eddy Inc., 1991, WastewaterEnglneering: Treatmenf, Disposal, Reuse, McGraw-Hlll, New York, NY. � Mlllen, JA., A.R. Jarrett, and J.W. Falrcloth, 1997, "Experimental Evaluation of Sedimenta�on Basfn Performance for Altemative Dewatering Systems," Trans. Amer. Soc. Ag. Engrs., 40, 1087 Mlnton, G.R., 2002, Stormwafer Treatment 8bloglcel, Chemical, and Engineering Princlples, RPA Press, Seattle, WA, www.stormwate►i�ook.com., Nbc, S.J., J.P. Heaney, and W.C. Huber, 1983, °Analysls of Storage/Release Systems in Urban Stormwater Quality Management: A Methodology," 1983 Intematlonal Symposlum on Urban Hydrology, Hydraullcs and Sedlment Control, Unfverslty of Kentucky, Lexington, KY. Oberts, G., 1997, Lake McCarrons Wetland Treatrnent System—Phase III Study Report,' Metropolitan Councll of the Twin Ciiy Areas, St Paul, MN. - Persson, J., N.L. Somes, and T.H. Wong, 1999, "Hydraulic EfFlc(ency of Constructed We�ands and Ponds,' Water Sd. Tech., 40, 3, 291. � Persson, J., 2000, The Hydraulic Performance of Ponds of Varlous Layouts, Urban Water, 2, 243. Pltt, ,R., 2000, "The Design and Use of Detetrtion Fadl�ies for Stormwater Management Using DETPOND," University of Alabama. � —� Raasch, G.E., 1979, "Urban Stormwater Deter�tlon Slzing Technique, In Intema�onal Symposlum �, on Urban Storm Runoff," Unlverstty of Kentucky, Lexington, KY. Roesner, L.A., Burgess, E.H. and Aldrich, J.A., 1991, "Hydrology of Urban Runoff Quallty Management,' Proceedings of the 18th Natlonal Conference on Water Resources Planning and Management, Symposium on Urban Water Resources, New Orleans, LA. Small, M.J., and _D.M: Dltoro, 1979, "Stormwater Treatment Systems," J. Envlron. Engr., 105, 3, 557. ,I �� Strecker, E., 2003, presentation to the Independent Science Panel regarding its review of the technical adequacy of the State of Washington Stormwater Management Manual for Westem Washington. � Timmins, K., T.L. Koob, M.E. Barber, and D. Yonge, 1999,'Thermal Stratiflcation Impacts on Wetpond Pertormance," Intematlonal Water Resources Engineering Conference; ASCE, Seattie, -. WA. IJSEPA, 1986, "Methodology for Analysis of Deten�on Basin for Control of Urban Runoff Qual(ty,' USEPA 440/�87-001, Washington, D.C. Walker, D.J., 1998, 'Modeling Residence Time in Stormwater Ponds,° Ecol. Engr., 10, 247. �� Ward, A.D., C.T. Haan, and B.J. Barfleld, .1979, "Predlctfon of Sediment Basln Performance," _� Trans. Amer. Soc. Ag. Engrs., 22,1, 126. � �' Whlpple Jr., Wllllam, Hunter, Joseph V., 1981, "Setdeabllity of Urban Runoff Pollut(on,' J. Water � Pollutlon Control Federatlon, Vol. 53, No. 12, pp. 1726 -1731. . �, Gary Minton, Ph.D., P.E., !s an independent consultant on stormwafer treafinenf i wifh Resource Planning Assoclafes. He is author of fhe book Stormwater Treatment: Biological, Chemlcal, and Engineering Principles � � - (www. stormwatenbook. com). � SW November/December 2004 ; Part 2: Fine-Medla Filters By Gary R. Minton �, This is the second of a four-part series examining deslgn criteria for stormwater ;; treatment systems. In the flrst of this series (Stormwafer, November/December 2004, � sw 0499 revisitin4.htm�, basins were the,focus. Now we shlft our focus to fine-media �— filters, which are filters that use fine�rained media simllar to those used for potable water treatment The concept of using flne medla for stormwater treatrnent was first � �dopted by the Cfty of Austin, TX, in the late 1970s. The most commonly used medlum _ . Is sand, although other medla are dlscussed in this article. Not consldered In this article are manufactured stormwater fllters, whlch commonly use coarser medla. Slnce communities in the United States flrst began requiring post�ievelopment treatment � � of stormwater from new developments 25 years ago, local, regional, and state '-- govemments have publlshed many manuals and handbooks identffying acceptable treatment systems (structural best management practices) and design criteria. As noted �� in part 1 of thls series, few of the criteria were Ini�ally supported by laboratory or field i. J research, and engineers relied on their best professlonal judgment In� choosing design ��I a! ,� �� criteria. In light of the many studies completed in the past 20 years, it is time to reexamine some of these criteria. In addition, treatment strategy is evolving from a focus on the general removal of pollutants using total suspended solids (TSS) as the surrogate for all pollutants to a more recent trend to consider specific pollutants. Some states now emphasize removal of total phosphorus, total nitrogen, and dissolved metals in certain situations. A particular design criterion can vary depending on which pollutant is targeted. Table 1 provides design criteria for fine-media filters from representative manuals and handbooks. Sand filters are a commonly used treatment system in Texas and the Chesapeake Bay area, and are particularly attractive for the removal of sediment (TSS or suspended sediment concentration) and attached pollutants. They can be expected to give consistent performance irrespective of the size of the storm and flow rate, unlike many other systems such as swales and vortex separators. They also may provide relatively consistent effluent quality with respect to TSS and attached pollutants, irrespective of the variation in influent concentration (Caltrans 2004). Despite these advantages, sand filters are rarely used outside the two areas mentioned above. This likely occurs for two reasons: First, sand filters can be fairly large, particularly if the available head is modest given site topographic constraints. The second concern is maintenance. This article discusses how the selection of design criteria directly affects surface area and maintenance frequency. Alternative criteria a�e suggested that may result in wider use of fine-media filters. YaEttr:� t, f'`»r� y�,iS�ia:t r�i f:rr,�i��n f,`ri?rri-� � _. , ,. . , , � � � �. . . `��9. . . - . . f �,Yn � .... � ' _' _ � . _ . ".... _ _' _ �t .... t_. .... _ h {c ,; F„ . f i .:�'i § � t : . «� :� ,r�i:a 1 >.a � �,r� �i:f ; ;�i � '� � : 3' i , d t. . _ _ . . ..,.,.a-:,... _ ._.. �. . , , .. �.: . _ „ " � '.i i$� 1' . _.�i � �}xe i �r�7�: � I�e' � -�ti�� 66 �� 9'1�.� � f' '€� - � »�. . � �:� �� y j 4 i. a .. -± ° .: t �� . �� .Ti.�c 4.r�# - _ � .. � , .,�, �s�.�,: � ta�'f .� s� t .n� -� _.. �� .._ j_ _ Y - � . � itii �S , �� :��y- � ' a. At influent TSS less than 100 mg/L, the requirement is effluent of 20 mg/L. b. The incremental increases in loading is to be reduced by 80%. The goal of other manuals is usually 80% reduction in the concentration or loading of TSS for the water that rs treated up to and including the design storm irrespective of the predeveloped concentration or loading. c. No specific goal is established; rather, removal expectations are provided for each type of system, ranging from 10% to 65%. d. Capture and treat the complete volume of 80°/a of the storms, ,� � representing small and moderate-size storms, while treating a portion of � - the larger stonns. e: For 100% (mpervlous surface. In most manuals, ma�dm�m storm i depth captured or sizing storm decreases with increase.in previous i_I surtace fraction. With the exception of Washington, the volume treated by the sand filter is the same as the volume calculated for an extended � � , detention basin. ;; f. Varies �with the extent of the development of the site prior to the current development -, g. Implied in the sizing equation. Pretreatrnent It Is common practice to pretreat stormwater before It enters the �fter bed. The obJective ' is to reduce solids loading on the fllter bed, thereby extending the time between �, �� necessary maintenance events. Subsurface fllters commonfy use a wet vault chamber , separated from the filter bed by a common wall. The most common pretreatment method '� for surFace filters is an extended deten�on basin. Wet�onds are used where in some '� cases the filter is actually the outJet berm of the pond and not a separate unit. Flow- _ through grass swales have also been employed. However, wetponds and grass swales may not be the most appropriate choice for pretreatment given the potent(al for clogging 1 of the filter bed—from algae (n the case of ponds and eroded sediment In the case of swales. However, no problems have been published in this regard. Media Type and Size Dlstributlon As previously mentioned, sand is the' most commonly used filter medium. Mlxtures of sand and a second medium are used, although infrequently. The obJective is the removal of d(ssolved pollutants: Added media in full-scale facfl�les have included peat (for removal of inetals), activated carbon (organics), calctte (phosphorus), and fron filings (phosphorus). There has been laboratory- or pllot-scale experimentation wlth dolomlte (phosphorus) and soybean hulls (metals). An alterna�ve Is to coat the sand wlth an oxide of iron, manganese, or aluminum to remove dlssolved metals. �"� The size dlstribu�on commonly specified today is ASTM (Amerlcan Society of Tes�ng -- and Materials) C33. This is the� speciflcation for fine aggregate for use in c�ncrete. Its ready avaflability reduces the cost. It Is, cofncldenthr, falrly slmllar to the speclflca�on of ' sand for water treatment Early manuals had a slmple specffication of "0.20 to 0.�0 and fines are acceptable." It is believed that thls specffica�on has caused premature dogging , of sand beds, somefimes through the entire depth of the bed. Medla Depth . I � '-� Initially, the Ciiy of Aus�n specifled a depth of 36 inches, mimlcking the depth commonly used in potable water treatment. It was soon changed to '18' inches, Iikely because of the ' recognition that almost all of the removal of TSS and attached pollutants occurs on or '! near the surface of the bed. Substantial media depths are used In potable water treatment given the need to consistently and�rellably meet a very strict potable water . standard. Such a standard, less than one unit of turbidity, is not required of stormwater treatment. ��N�'' �. The relevance of inedia depth relates to the area required of the filter to pass the design event. The greater the depth of the media, the greater the surface area of filter required to meet the specified drawdown time as shown in Table 2. Eighteen inches is taken as the standard with a unit area of one. Reducing the media depth from 18 to 6 inches reduces the required area of the filter by about 50%. Conversely, a filter depth of 36 inches increases the filter area by about 30%. How the relationships in Table 1 were produced is presented later in this article. � � � Sand filters with 18 inches of inedia appear to perform more effectively than other stormwater treatment systems, in particular extended detention basins and swales. Therefore, some may consider it acceptable to reduce the depth of the media in a sand filter even if performance degrades somewhat. One study (Amini 1996) found that increasing the media depth from 6 to 12 inches, the maximum depth evaluated in this study, increased the removal efficiency of TSS by only 5%. A study of bacteria removal found little improvement with media depths above 12 inches (Bellamy et al. 1985). In a recently completed study (Caltrans 2004), several sand filters with 18 inches of inedia performed substantially better than a single filter that had only 12 inches, with mean effluent concentrations of about 6 and 12 mg/L, respectively. However, 12 mg/L is acceptable. While the results of these studies are inconsistent, they do indicate that shallower bed depths are acceptable in most situations, certainly 12 inches and possibly 6 inches. A depth of 6 to 12 inches is likely impractical with large filters where mechanical methods are used to maintain the filter bed. Heavy equipment could damage the underdrain system. But it may be acceptable for small filters, less than a few hundred square feet, where cleaning by hand occurs. Also, more frequent cleaning may be feasible with small filters. Alternatively, where 18 inches is specified, the depth of the design storm could be reduced, commensurate with the higher efficiency of sand filters over other treatment technologies (Barrett 1999, King County 1998). A shallow filter bed is likely acceptable where the objective is the removal of TSS and attached pollutants. It may not be appropriate if the objective is the removal of dissolved species. Removal of dissolved pollutants is discussed in the last of this series of articles. Hydraulic Conductivity Sometimes referred to as the coefficient of permeability or the filter factor, hydraulic conductivity describes the ability of water to pass through media. Its value is inherent to the particular medium, its size distribution, and sediment accumulation. Hydraulic Cf�� c�� e+�ia �e�t� conductivity is not to be confused with the infiltration rate, which is the actual rate of flow through the filter. Confusion occurs as both have the same units (feet or inches per hour or per day). The filtration rate increases with the depth, or head, of water above the filter bed, whereas the hydraulic conductivity is unaffected by head. Hydraulic conductivity, however, decreases with the accumulation of sediment. Specified design values have ranged from 1.8 to 3.5 feet per day. The effect of its selection is shown in Table 3. The more conservative value of 1.8 feet per day increases the filter area by about 90%, a significant increase. What does the selected hydraulic conductivity - -�-� � �� ,- �-�-��- represent? The hydraulic conductivity of clean '' ' ; '� , sand is on the order of 2 to 5 feet per hour. The values in Table 3 are 5%-10% of clean sand. These values therefore represent a filter almost totally clogged: the time to clean the filter. If the filter is not cleaned promptly, the management goal of treating, for example, 90% of the stormwater over time, is not met. The greater the selected hydraulic conductivity the smaller the filter area, but the more frequent the maintenance. The value chosen is arbitrary within a reasonable range, and represents the tradeoff between filter area and the frequency of maintenance. In effect, its selection represents a tradeoff between initial construction costs and long-term maintenance costs. Elevation Drop ��J�G'� �. E�GG'� A major limitation in the use of fine-media filters is the available elevation drop—that is, the difference in the elevations of the development and of the public drainage system to which the development discharges. Table 4 illustrates the effect of the available maximum water depth over the top of the filter, called the head. As the head increases, the surface area of the filter decreases. Hence, the feasibility of fine-media filters increases with increasing head. However, the decrease in filter surFace area corresponds with the required frequency of cleaning. It should also be noted that reducing the bed depth also reduces the elevation drop required of the site, and therefore the potential feasibility of a fine-media filter. Drawdown Time Note: 18 in of inedia, 4-ft water depth The design drawdown time affects the size of the filter. Therefore, its specification is important. Table 1 presents a significant range of 24 to 48 hours. Drawdown time affects filter area by its definition of Q, the average "'��1� 3. Ef��t c�fi ��i�r� Nyc�ra��Eics Cic�ncluc�ivi��r �� - � � � fittration rate during the design storm. The greater the allowed drawdown time, the lower `- ) the fiitration rate and therefore the smaller the filter area. i Avoiding anaerobios(s in the fllter bed Is the common reason given as to why a �^ ' maximum drawdown time must be specffied. Bacteria attached to fhe filter medla � consume dissolved oxygen as they use organfc matter and ammonia fn the incoming � stormwater. The concem (s that under anaerobic conditions, dissofved phosphorus and -- metals previously removed may be released. An addltlonal benefit from specifying a. drawdown �me may be to Inhibit the excesslve growth of bacteria that might clog the � filter. Drying of the fllter bed between storms fnhibits growth. '_ � The relationship between drawdown time and either anaerobiosls or excessive bacteria ' growth has no# been establlshed. Nor has the slgnlflcance of pollutant release been �_ I deflned. Whether release occurs depends on the mecha�ism of removal. A possible mechanism of dissolved phosphorus removal is sorptioNpreclpitation to ferric b�ade �� present on the surface of the sand. Under anaerobic condi�ons, ferric iron changes to �; ferrous, disassociating the complex and releastng the pollutants. One study found a constant anaeroblc condition In the bottom of the filter (Shapiro 1999). The conditions of ; F the study are likely the most extreme that wlll be faced. The filter had a media depth of � � 36 inches and a typical drawdown time of 72 hours. Furthermore, it was located (n a �- region with long storms and short interevent times, conducive to crea�ng anaerobic 1 conditions. Flnally, iron filings were added to the sand to promote the removal of �� dissolved phosphorus. The transformation of the filings under anaerobic conditions - appears to have caused sand pardcles to bind. The fllter was found to be constantly anaerobic in the bottom 24 inches. However, despite this condition the filter removed on �� the order of 50% of the dissolved phosphorus as well as dissofved metals. All of the -, removal was likely occurring in the upper 12 inches of inedia that remalned aerobic. �� If nitrogen removal is the objective, a temporary anaerobic condition is desirable. l � Bacterla change ammonia to nitrate in the presence of dissolved oxygen,�but the net reduction of nitrogen Is zero. Other bacteria under anaerobic condltions change the �J' nitrate to nitrogen gas. The Ideal operafion is for the upper area of the fllter to be aerobic �__� and the lower area to be anaeroblc. '- ` � Speafication of the drawdown fime Is therefore a function of the pollutant-removal � �; objective, the interevent tlme befinreen stoims, and the time needed for the filter to dry. If � the objecctivve Includes dlssolved phosphorus and/or metals, a low drawdown �me, �-� , perhaps on the order of 24 hours, is approprlate. If not, 72 hours may" be satisfactory. A � � long drawdown time may also be deslrable if nitrogen removal fs the management - objecthre. JAn altemative to a"�ghY drawdovm �me may be to Incorporate aluminum into the sand. Aluminum oxldes may be an effective remover of dissolved phosphorus and/or metals (Minton 2002). Unlike ferric oxide complexes, aluminum oxide/phosphorus/metal � ; complexes will not disassoclate under anaerobic conditlons. � � Determin(ng the Filter Bed Area and Live Storage Volume 1� � '�� , i� �+q�sar�ivn A � � I-{�d,"� i 11� 1Vhc�a: r3. � �cs nf t�er 1 a fpa:t er�tDl� d� d � r►�,�cifn�mi uul �!. Manuals employ the same equation (Equation 1) for sizing the filter bed area, although the speciflc form of the equa�on varies with the units used. The average flltratlon rate Is equal to the runoff volume of the deslgn event dtvlded by the drawdown �me at brimful. For example, assume a design runoff depth of 1 inch. The volume of runoff is the multiple of 1 inch, the dralnage area, and the runoff coefflcient. If a 4&hour drawdown tlme Is selected, the average flftratlon rate, Q, is half that if the drawdown time is 24 hours. Hence, Equation 1 states that a drawdown time of 48 hours requires a fllter area that is half that for a 24-haur drawdown time. Previous observations in this article about the relatfonshlp between bed depth, hydraulic conducfrvity, drawdqwn time, available water depth, and filter.surface area are understood with the examination of Equation 1. Hence, the selecfion of the values for the key desfgn aiteria must be considered as a whole, payfng particular atten�on to the eifect of these declsions on maintenance frequency. ' It Is important to recognlze that the available live storage volume above the�filter itsetf Is usually less thah the volume of the deslgn event to be captured and treated. Commonly, ; the pretreatment unit provides the addi�lonal live storage volume. In effect, while a longer specified drawdown time deceases the fllter area and the volume above it, it does not decrease the total storage volume that is required. Furthermore, Equation 1 fails to cons(der the combined effect of the lnterevent �me and the cholce of drawdown time on the potential for some stormwater to be present in the � treatment system when ttie next stotm arrlves. This aspect was �discussed in the flrst article of this series with respec# to extended deten�on basins. Slmilarly, the Interrelated effects of Interevent time and drawdovm �me should be considered when specifying � sizing criteria for the total live volume of the comb(t�ed pretreatment-filter system. One manual recogn[zes this point (CASQA 2003). �A flne-media filter can be v.iewed as an extended deten�on basin wtth a system of underdrains rather than oriflces. . � Counterbalancing this relatlonshlp Is the recognitfon that the actual hydraulic conductivity � is greater than the design hydraulic conductivity through much of the malntenance cycle. The only proper way to define the flfter area and the live storage volume Is through continuous simula�on with a program that recognizes the gradual change in hydraullc conductivvity as solids accumulate in the filter. A complementary methodology sizes the area of the fllter based on solids accumulafilon, thereby relating.filter area to the desfred maintenance cycle (Lenhart 2000, Minton 1995 -' and 2002, Urbonas 1999). There are two key elements to this approach: The flrst Is the loading rate of sediment (TSS) to the fllter, as pounds or kilograms per year. The sec;ond . element is the amount of sediment that accumulates on the fllter before the design __ hydraulic conductivity (s reached, as pounds per square foot or kilograms per square meter. � Equations 2 and 3 express the methodology. Equation 2 considers concentration. The analysis can also be tiased on annual unit loading—#hat is, pounds per acre or,kilograms per hectare of drainage area per year (Minton 2002). ��i�'1 �� . � xc�r�r- �> - "r� wn��: �, = m� ��u� �� r�� t�ry� � �� Q � � �e��i�,G t�� a� �� '� � m�an czan�ntrni}cttr +�f�SS in s�nw�ir.r (s�OE�� `� � t�u Conaes►trs�iau +��"�'S'� in tll�uc�i' {�ct�(I.,�j k� cne�ric �com^cusS+� �ac�ir � i�rmatria, b2.di�.i�0.t� to� Im�orikrl �u��g�n �r ,� m �' � � . ' The solids-accumulation method explia�y considers the desired malntenance frequency. The area of the filter is calculated with both the flow and solids-accumutation methods. The larger area is selected. Altematively, the selectlon of the fllter area Is based on ' Equafion 1. Equa�ons 2 and 3 are then used to specify the malntenance frequency for the particular development. A regulatory agency could assume the same sediment concentration or unit loading for each type.of land use. It could then specify maintenance , frequency as a functlon of the maximum water depth over the filter. This relationship � recognizes that as the available water depth Increases, the fl�ter area decreases, and in turn the maintenance frequency (ncreases. Flnally, the two methods can be contrasted to determine the approprlate values for the drawdown tlme, hydraulic conductivity, and media depth for a parficular c�imatic region. Publlshed data suggest that design hydraulic conductivity is reached at approximately 0.25 to 0.50 pounds of sedlment per square foot of flfter area (1.2 to 2.4 kg/m2) (Clark and Pltt 1999, Keblln et al. 1996, King County 1996, Shapiro 1999, Urbonas 1999). More field studles are needed. Final Observafions Maintenance costs may be reduced, while performance is enhanced, by plaang a suitable geofabric on the sand surface. The geofabric may extend the length of the malntenance cycle (Graham et al. 1994). Its replacement after dogging with most of the removed sediment may ease maintenance time and therefore costs. This approach Is suggested for small filters, particulariy if the medla depth is reduced to between 6 and 12 Inches. � . `, Field inspection during construc�on is particulariy important with fine-media fliters. Care must be taken in the selectlon and protection of flne medla when located onsite, and - before placement in the fllter bed. The hydraullc cond�ion of the fllter must be checked if �; the fllter was used during constrvct(on of the development , � It is likely that fine-media filters are more attractive in regions with low annual rainfall. � �, There are finro reasons: The first is the unattracttvveness of�treatment systems that rely on �-' water to sustain their performance, such as wetbasins and flow-through swales. Secondly, fn drier climatic regions the amount of sedlment readiing the filter is less over the typical year than in wet cllmafiic regions. Hence, the maintenance frequency will likely be less than In wetter climates. '� Anecdotal information suggests that vigorous surtace vegetation extends the � maintenance cyde. The author knows of one sand filter fn the Pacifiic Northwest In which . a thldc growth of grass was intentionally promoted. Although over five years old,�the filter surface has never had to be cleaned. Otherfifters in the�same area have required semi- �; annual malntenance. Sediment Ilkely accumulates in the grass rather than the surface of the sand. Vegetation ls known to enhance the infiftration capacities; more studles are , needed on this questlon. Promo�on of surtace vegeta�on may be particulariy attractive ,, , In wetter climates where fifters experience a hlgher annual solids loading and longevity of agricultural solls (Minton 2002). Some manuals suggest that flne-media filters not be used for drainage areas in excess of 10 acres (Table 1). However, sand filters are serving much larger areas without issue. The author is famlllar with a dual-fifter system that serves a residential area of 250 acres. �' � Washout of accumulated fine particles that are toxlc has been observed under laboratory conditions (Clark� and Pitt 1999). Whether this accurs under fleld conditions �S� not knovim. - � Summary �; The effect of the chofces of key design crfteria, their Interrelationship, and thelr combined �� - effect on filter area and maintenance frequency must be consldersd. There Is no one appropriate value forthe hydraullc conductivity. The value that Is selected should be j�� based on the deslred frequency of maintenance, with consideration to the eifect on filter i_; surface area. Where the objective is the removar of sediment and attached pollutants, a media depth of 12 inches and posslbly as little as 6 Inches is likely suffldent in most �- , sltuations. While performance will be less with the shallower bed depth, the effluent �' concentra�ons will be similar to that produced by other treatment systems such as � basins and swales. A shallower�b�ed depth allows for a smaller fllter surface area. A � shallower bed depth also reduces the elevatlon drop.requlred of the design. However, a smaller filter area, whether from a.reductlon in the bed thlckness or by the greater ' avallable elevatlon drop, may result in unacceptable frequency of maintenance, , particulariy in wetter dimates. The se7ec�on of the drawdown time may dfffer depending on the pollutant-removal obJective, but should take Into consideratlon interevent �me . �' . particulariy In wet climates with frequent storms. It would be prudent to use both the flow and sollds-accumula�on methods to determine the fllter area. More studies are needed on the relafionshlp befinreen solids accumulatfon and hydraulic conductivity, and the -� effect of surtace vegetation on the maintenance cycle. � � References Amini, F. 1996. Effect of fllter thickness on sand fltter pertormance. Water Qua/ Res J Canada 31, 4, 801. � , Barrett, M. 1999. Complying wffih the Edwards Aquffer rules: Technical guidance on best management practfces. Aus�n: Texas Natural Resource Conservation Commission. Bellamy, W.D., G.P. Sllverman, D.W. Hendricks, and G.S. Logsdon. 1985. Removing Giarclia cysts with slow sand flltration. J Amer Water Works Assn 77, 2, 52. Califomla Deparlment of Transporta6on (Caltrans). 2004. �BMP retrofit pilot program, final report, CTSW-RT-01-050. Califomia Stormwater Quality Assoclation (CASQA). 2003. Stormwater best management praciice handbook, new development and redevelopment. �' Clark, S. and R. Pitt. 1999. Stormwater treatrnent at crftical areas, evaluation of filtratlon media for stormwater treatmen� US Environmental Protection Agency, EPA/600/R-00/010. � �� . `. Graham, N.J.D., T.S.A. Mbwette, and L. DlBemardo. 1994. Fabric protected slow sand fiftra�on: A revfew. In Slow sand flltrstion, eds. M.R. Collins and M.:1.D. Graham. Denver: American Water Works Assacia�on. Keblin, M.V., M.E. Barrett, J.F. Mallna, and R.J. Charbeneau. 1998. The efFectiveness of permanerrt highway runoff controls: Sedimentatlon/flftration systems, research report 2954-1. Austin: Center for Transportation Research, University of Texas. � � bng County. 1996. Determina�on of Inflltratlon rates and hydraullc conductivity for varlous sand � filter media. Seattle. fGng County. 1998. Surface water deslgn manual. Seattle: Deparlment of Natural Resources. Lenhart, J. 2000. A suggested methodology for the prellminary evaluation of stormwater flltra�on systems. Pordand, OR: Stormwater Management Inc. Mlnton, G.R. 1995. Stormwater treatmerrt by medla flltratlon. Short course, Unlverslty of Washington, Professlonal Development Program. ,, '� Minton, G.R. 2002. Stormwater treatrnen� Bfologlcal, chemlcal, and englneering prinGples 416 � pages. Seattle: RPA Press. � Shapiro and Assoctates and the Bellewe Utilitles Departrnent. 1999. Lakemorrt storm water treatrnent facllfiy monftoring report. Bellevue, WA. Urbonas, B. 1999. Deslgn of a sand fllter for stormwater quality enhancement. Water Environ Fed 71, 1, 102. ,-, Gary Minfon, Ph.D., P.E., is an independent consultant with Resource Planning ;' Assoclates in Seattle, WA. He is author of the book Stormwater Treatment: Blological, `� Chemical, and Engineering Princlples. �f � �, I' I �i ! � � � 1 - i � 1 1 � �_ J , 0 APPENDIX 4 Source Control BMP's 0 n Spill Prevention and Control M_ , \\ :' :` . =-�--� , �� ---. _� a ��` � , J�,. . .. � � -�*�; "� ,� � � "�' � � � � ;%„ �� BMP ObJectives o Soil Stabilization o Sediment Control o Tracking Control o Wind Erosion Control • Non-Storm Water Management • Materials and Waste Management Definition and These procedures and practices are implemented to prevent and control spills in a Purpose manner that minimizes or prevents the discharge of spilled material to the drainage system or watercourses. Appropriate This best management practice (BMP) applies to all construction projects. Spill Application control procedures are implemented anytime chemicals and/or hazazdous substances are stored. Substances may include, but are not limited to: ■ Soil stabilizers/binders. ■ Dust Palliatives. ■ Herbicides. ■ Growth inhibitors. ■ Fertilizers. ■ Deicing/anti-icing chemicals. ■ Fuels. ■ Lubricants. ■ Other petroleum distillates. To the extent that the work can be accomplished safely, spills of oil, petroleum products, substances listed under 40 CFR parts 110, 117, and 302, and sanitary and septic wastes shall be contained and cleaned up immediately. L�Caltrans Storm Water Quallty Handbooks Section 8 Constructlon Slte Best Management Practices Manual Spill Prevention and Control WM-4 �� March 1, 2003 1 of 4 i ,� : � �� __� Spill Prevention and Control Limitations ■'This BMP only applies to spills caused by the contractor. M- ■ Procediu�es and practices presented in this BMP are ganeral. Contractor shall identify appropriate practices for the specific materials used or stored on-site. Standards and ■ To the extent that it dcesn't compromise clean up activities, spills shall be Specifications covered and protected from storm water nm-on during rainfall. � ■ Spills shall not be buried or washed with water. I11 ■ Used clean up materials, contaminated ma.terials, and recovered spill material � that is no longar suitable for the intended purpose shall be stored and disposed of in conformance with the special proviaions. � ; i ■ Water used for clea.ning and decontami.nation shall not be allowed to enter `� � � storm drains or watercourses and shall be collected and disposed of in accordance with BMP WM-10, "Liquid Waste Managemen�" `` ■ Water overIlow or minor water spillage shall be contamed and shall not be allowed to discharge into drainage facilities or waterconrses. ;; ■ Proper storage, clean up and spill reporting inshuction for hazardous materials stored or used on the project site shall be posted at all ti.mes in an ; F open, conspicuous and accessi�le location. ' ■ Waste storage areas shall be kept clean, well organized and equipped with �-- _ � ample clean-up supplies as appropriate for the materials being stored. ., Perimater controls, containment structiu�es, covers and li.ners shall be repaired � -� or replaced as needed to� maintain proper function. Educat�on �� _ i �1 � �J ;� � �� -ti i _� � Educate employees and subcontractors on what a"significant spill" is for each material they usa, and what is the appropriate response for "significant" and ��insignificani" spills. ■ Educate em}�loyees and subcontractors on potential da.ngers to humans and the environmant from spills and leaks. � � ■ Hold regular meetings to discuss and reinforce appropriate disposal procedures (incorporate into regular safety meetinga). ■ Establish a continui.ng education program to indoctrinate new employees. ■ The Contractor's Water Pollution Control Manager (WPC1Vn shall oversee and enforce proper spill prevention and control measures. �� Storm Weter Quality Hendbooke , Sectlon 8 Constructlon 31te Beat Maoagement Practicea Manual 3plll Preventbn and Control WM-4 � March 1, 2003 ' � 2 of 4 f �, � Spill Prevention and Control � �.4 � ,-� . �� 't �_ � Cleanup and Storage Procedur�es ■ Minor Spills � �; - — Mi.nor spills typically involve small qua.ntities of oil, gasoli.ne, paint, etc., 1 which can be controlled by the first responder at the discovery of the spill: . � � `� �, - ,� r — iJse absorbent ma.terials on sma11 spills rather tha.n hosing down or � bluyin8 the spill. — Remove the abaorbent materials promptly and dispose of properly. — The practice commonly followed for a minor apill is: — Contain the spread of the spill. — Recover spilled materials. — Clean the contaminated area and/or properly dispose of co�tamin_A±ed materials. ■ Semi-Significant Spills r�f — Semi-significant spills still can be controlled by the first responder along ; � with the aid of other personnel such as laborers and�the foreman, etc. � This �response may require the cessation of all other activities. . � �� — Clean up spills immediately: — Notify the project foreman immediately. The foreman shall notify the Resident Engineer (RE). � — Contain spread of the spill. — If the spill occurs on paved or impermeable surfaces, clean up using "dry" methods (absorbent ma.terials, cat litter and/or ra.gs). Contain the spill by encircli.ng with absorbent materials and do not let the spill apread widely. � — If the spill occurs in dirt areas, immediately contain the spill by . constructing an earthen dike. Dig up and properly dispose of conta.minated soil. — If the spill occurs during rai.n, cover spill with tarps or other material to prevent contaminating runoff. � � � Caltrans Stom� Weter Quality Handbooka Sedlon 8 - � Conatruatlon Slte Best Management Prac:tices Nlanual Splll Preventlon and Contrnl WM-4 �� March 1, 2003 3 of 4 �� • �� , • � . '�J Spill Prevention and Control �- �, . si�ificanr�xazaraous sPills i ,k '. � . ; � {� — For significant or hazardous spills that cannot be controlled by personnel in the immediate vicinity, the followi.ng steps shall be taken: — Notify the RE immediately and follow up with a written report. — Notify the local emergency response by dialing 911. In addition to 911, the contractor will notify the proper county officials. It is the contracto�a responsibility to have all emergency phone numbers at the construction site. — Notify the C�overnor's Office of Emergency Sarvices Warning Center, (805) 852-7550. — For spills of federal reportable quantities, in conformance with the requirements in 40 CFR parts 110,119, and 302, the contractor sha11 � notify the National Response Center at (800) 4248802. — Notification shall first be made by telephone and followed up with a written report. — The services of a spills contractor or a Haz-Mat beam shall be �` a obtained immediately. Construction personnel shall not attempt to clean up tha spill until the appropriate and qualified staff have arrived � . at the job sibe. _� 1 .-. . � _. ; ��a � — Other agencies which may need to be consulted include, but are not li.mited to, the Fire Daparfinent, the Public Worics Deparhment, the Coast Quard, the Highway Patrol, the City/County Police Deparhnent, Department of Toxic Substances, California Division of Oil and Gas, CaUOSHA, RWQCB, etc. Maintenance and ■ Verify weekly that spill control clean up materials are loca.ted near material Inspect(on ��80� ��s� �d use areas. . ■ Update apill prevention and control plans and stock appropriate clean�p materials whenever changes occur in the types of chemicals used or stored onsite. � �P 1� � Caltrane Storm Water Quallty Handbooke Sectlon 8 - � Constructlon Slte Best Management Practices Manual Splll Preventlon and Control WM 4 �� Mer+ch 1, 2003 . i i � � �� Trash Storage Areas SD-32 Description Trash stor�e areas are areas where a lrash receptacle (s} are located for use as a repository for salid wastes. Stormwater runaff from areas where tr�ash is stored or disposed of can be polluted. In addition, loose lrash and debris can be easily transported by water or wi.nd into nearby storm drain inlets, channels, and/or creeks. Waste handling operations that may be sources af stormwater pollution include dumpsters, litter control, and waste piles. Approach T�iis fact sheet contains details on the speeific measures required to prevent or reduce pollutants in stormwater runoff associated with trash storage and handling. Preventative measures includi.ng enclosures, containment structures, and impervious pavements to mitigate spills, should be used to reduce the likelihood of contamination. Suitable Applications YDesign iObjectivesyY. .+� , ...,.._..,,.�._.�...,�.... ..�._,_.�....._.�..,�_...._....�. Ma�mize Infiltration Provide Retenfion Slow Runoff Minimize Impenrious Land Coverage Prohibit Dumping of Improper Materials l� Contain Pollutanis Collecf and Convey Appropriate applications indude residential, commereial and industr�ial areas planned for development or redevelopment. (Detached residential single-family homes are typically excluded from this requirement.} Design Considerations D esign requirements for waste handling areas are governed by Building and Fire Codes, and by current local agency ordi.n.ances and zollirig requirements. The design criteria described in. this fact sheet are meant to enhance and be consistent with these code and ardinance requirements. Hazardous waste should be handled in accordance with legal requirements established in Title 22, California Code of Regulation. Wastes from commercial and indus�ial sites are typically hauled by either public or commeraal carriers that may have design or access requirements for waste storage areas. The design criteria in this fact sheet are reoommendations and are not intended to be in conflict with requirements established by the waste hauler. The waste hauler should be contacted prior to the design of your site tr�ash collection areas. ConfLicts or issues should be discussed with the local agency. Designmg Newlnstallations Trash storage areas should be designed to consider the followin,g sfructural or treatrnent con�ol BMPs: ■ Design tr�ash container areas so that drainage from adjoining roofs and pavement is diverted around the area(s) to avoid run-on. This might include berming or grading the waste handling area to prevent r�m-on of stormwater. ■ Make siu�e trash containex areas are screened or walled to prevent off-site transport of trash. y'A:i .'�ryaa��y � ' � �y; : VT-- . �'#�. = �,.s �; ' �is+�- . January 2003 California Stormwater BMP Handbook 1 of 2 New Development and Redevelopment www.cabmphandbooks. com �� ,� SD-3� � Trash Storage Areas ,; ■ Use lined bins or i�mpsters bo reduce leakir�g a�liquidwaste. - ■ Provide roofs, awnings, or attacased }i.ds on aIl tr�ash co�taine,rs ta n,;n;m; ze direct pa�ecipi.tatiam andpreventramfall from e�t� contgmes�s. , ,' ,' ■ Pave traah sborage areas with an i_mpervious st�face to mitigate spulls. , ■ Do nat loca�be storm �ains m. i.mmediate vic�i.ty a� the tra.s�. stiarage area. �� ,� ■ Post s�gns am aIl dumpsbeis infarmi�g useTs tl�at hazardous mab�rials are not to be disposed of therein. � R,ede�elopingBxisting Ixstallationa Various j�msdi�ional sta�-mwa�ex ma�gement �d mitigation plans (SUSMP, WQMP, etic.) de�me �redevelopmeirt" in. terms of amowits of acic�itianal imgervious anea, inc,�reases m. gross floor area and/aa� exterior comsh�uctiam, andland dist�u�b�g acti�ities with str�uctiu�al ar i.mpervious stnFaces. �e definition a�" redevelapment" must be consulted to determine whether or not the requiremea.ts for n,ew development apply fio areas mxended for redevelogment. If the definition applies, the steps oudined imder °desi.gnvzg new instaIlatia�s" above sriauld be followed � , �ldditionel Information , Maintenmtce Cmesideration.e The iutegrity a� stiructtmal eleme,nts that are subjectto dam.�ge (i.e., screens, cove�s,'and signs} � must be maintained by tl�e owner/operata�r. Mainten�_c� �eements be�tween the local a�ency , and the owne�/operator may be required Some ageacies will require mamte:aance deed restrictioms tio be recorded of the pa�opes�ty ti$e. If required by the local ageacy, ms�intpm ance ,� � �eements or deed restr�i.cli.ons must be execirted by the owner/operatior before improv�eme�t � � plans are app�roved. . . Other Resources �� f r-^. ?� k � A Manual for the Standard Urban Stormwa.tier Mitigation Plan (SUSMP), Las Ar�geles Coun�y Depa�._�►t- a� Public Wa�rks, May 2oa2. � . Mode1 Standard Urban Stiorm Water Nfitigation Plan (SUSMP} for San Diego Coimty, Part of San Diego, and Cities m San Diego Co�mty, _Februaiy i4, 2002. Model Wai�r Qua}ity M�.agement Pl�. (WQMP) for Cnimty a� Orange, Orange Coimt,y Flood. Ca�ntrol District, and the Incorporai�ed C�ties of Orange Crninty, Draft Febivaiy 2ao3. Vent�u a Cotm�ywide Technical Guidance Manual for St�ormwater Qualittiy Ca�n.tr ol Meas�es, July 2002. � ,� 2 of 2 , Callfixnla Stormwater BMP Handbook January 2003 : Naw Developtnent �d Redevelopment -� www, cabrnphan�ooks,00m • 1 i L� Pervious Pa�ements S D- 20 Des�g nv Object�ves �C( Maximize Infiltration Q Provide Refenfion C� Slow Runoff � Mini mize I mpen�ous Land Coverage Prohibit Durr�ing of Improper Mafenals Confain Pollutants Collect and Convey Description Peivi.ous pavir�g is used for light vehicle loadir� in parkin� areas. The term des�ribes a system comprising a load-bearing, durable s�mface together with an underlying layered structure that temporarily stores water prior to infiltration or drainage to a cantr�olled outlet. The surface can itself be parous such that water infiltrates across the entire surface of tl� material (e.g., grass and gravel surfaces, porous concxete and porous asphalt), or can be built up of impermeable blocks separated by spaces and j oints, through which the water can drain. This latter system is termed `permeable' pa.ving. Advantages of pervious pavements is that they reduce runoff volume while providing treatment, and are �obtivsive resulting in a high level of acceptability. Approach Attenuation of flow is provided by the storage within the underlying structure or sub base, together with appropriate flow oontrols. An underlying geateattile may permit gro�mdwater recharge, thus conhibuting to the restoration of the natural water cycle. Alternatively, where in�iltration is inappropriate (e.g., if the ground�vater vulnerability is high, or the soil type is unsuitable), �e surface can be constructed above an impermeable membrane. The system offers a valuable solution for drainage of spatially constrained urban areas. Significant attenuation and improvement in water quality can be achieved by permeable pavements, whichever method is used. The surface and subsurface infrastr-ucture can remove both the soluble and fine particulate pollutants that occur within urban runoff. Roof water can be piped into the storage area directly, addin,g areas from which the flow can be attenuated. Also, within lined systems, there is the opportunity far stored runoff to be piped out for reuse. Suitable Applications Residential, commeraal andindustrial applications are possible. The use of permeable pavement may be restricted in cold regions, arid regions or regions with high wind erosion. There are some specific disadvantages associated with permeable pavement, whic,h are as follows: ' � �- � � . . `,r�:�''' . ;d#l�{� . January 2003 Callfornla Stormwater BMP Handbook i of 10 New Development and Redevelopment www.cabmphandbooks. com �, SD-2� Pervious Pa�ements - ■ Permeable paaemart can become clogged if improperly installed or ma�tair�ed. However, this is coimtered by t�.e ease with whic,h amall areas a� pavm.g can be cleaned aa� replaced. when block�ed or damaged. �� ■'Th�ir application should be limited. to highw&ys with low traffic v�olumes, axie loads and speeds (less than go mph limit), car ParkmB areas and other l�d.y tr�af6.ck,ed or non- " trafEicked areas. Permeable surfaces are a�ently n,at consid,ened suitable for adoptable - roads due tio the risks �assoc�ated with failure on h�gh speed roads, the safety implications of ponding, and disruption arismg fram recams�uction. ■ Whm usm,g im.-]ined, in�ltratia� sysfiems, there is some rislz of contaminatmg groimdwater, ' de�pendir�g on soil conditiao�s �d aquifer susceptitrility. Hawever, this ri.sk is lik�ly to be , smaIl because the areas drained t�n.d tio have mherently low pollutant loac�ings. ■ 17ie use of permeable pavemeut is restricted tio ge;ntle alopes. + ■ Porous block pavin,g has a lrighe� risk of abrasion and dam�ge than solid blocks. � Design Considerations " � DesigxixgNewlnstaliatio�es If the grades, subsoils, drainage cbarac�ristics, andgroimdwatier oonditions are suitable, pei�eable pavirig may be substituted for conventiamal pavement on parkin,g areas, cul de sacs and other areas with light tr-af6.c. Slopes should be flat or very geaiie. Scottish experience has � `� shown tbat pe�-meable pav�g systiems can be �lled in a wi.de range of groimd conditic�s, and the flow atber.u�ation perfarmance is exc,�llent ev�en when the systems are l,n�- The suitabilitly af a pes�vious sysbem at a particular paveme� sitie w�l, hawevex, depend on the loa�ing criteria required of the pavement � � Whe�e the system i.s tio be used faa� i�fillrating dramage watiers into the grolmd, the wlnera�ty of local groimdwater so�ces to pollutioai from the sate shou].d be low, and the seasonal h�gh , water table should be at least 4 feet below � s�face. Ideally, the pe��vious s�face s�,ould he-horizaaztfll in order to intiercept local rainfall at so�ce. pn slopin�g sites, P�rviaus surfaces may he �raced tio accommodate differences in levels. ' Design Gr.d de�i nes � 'Ihe desiga of each layer a� the pavement m�t b e dex�rmined by the likely tr�affic loadings an.d � their required. operational }ife. To grovide satisfac�ol.y perfarm�ce, the follow�g critieria should be considered: , ■ The subgrade should be able to sustam traffic loadi.ng wrthout e�cce.ssive deformation. '- ■ Thie granular arpping and sub-base layers should give s�ficient load-beari�g to pa�avide an , ad�equate cons�an platform and base for die over�yi�,g pavement lapers. ■'Ihe pavement m.aterials ahould not crack of s�fer �sive rtritin,g imder the influ�n�ce a�f traffie. Zhis is controlled by the horizontal te�1e str�ss at the base a� these la.yers. 2 of 10 Callfnrnla Stormwater BMP Handbook January 2003 New Development and Redevelopment www, c�mphancf�ooks, com � -, Pervious Pa�ements � SD-�0 ., ,, ; There is no current structiu�al des�ga method specfficaIly for peivious pa.vements. AIlowances °, should be considered the fallawing factors in. the des�u. and speGificaiion a� mate�ials: ' ■ Pervio�s pavem� iase mateaials wrth high perm.eab�ity and eaid space. All tl�e ciurent UK = ti pavement des�gn me�thods are based on the use of conv�tiamal materials that are de,�se.and rela.tivel� i_mpez�eable. The stiffness of the materials must therefore be assessed. �_, . ■ Wai�eer i.s preserrt witl�in the c�ction and can sdtea and weaken materials, and t3�is must �� be allowedfor. . ■ Egisting de�iga methods assume fuIl friction between lay+ers. A�y geotextil.es aa� geomemhranes must be carefully spec�fied tio mm;m; �.� loss of friction between laye�s. � . . � ■ Porous asphalt loses a�esson and becomes britde as air pa.sses through the voids. Its . divabilrtyis thereEare low�r ti�an caaiventional mater.�a]s. '� The sin,�e sized gra�ing of materials used means that care should be taken to e�me tbat loss of � finer par�r].es be�twe�n unbo�md layess does not occ�m. �i_ �� P ositiami�qg a geotextile near t�,e s�face of the pe;rvious cons�iction should ena.ble padlutants tio � be tr�a.pped and re�tained dose � tl� s�face a�f the cons�trudion. This has bath advant�ges and � disadvan�ges. The mafri disadvantage is tbat the filb�a.�g of sediments and i� associated pollutants at tbis level m�y hampe� pe;rrcolation a�f waters and can even�ally lead to s�mfa.ce ', _; paa��in,g. One advant�ge is tbat e�vea if eve�tual ma;,,te„Anc�e is required•to rebzstatie infiltratf c�, onty a limited amo�t of the construction need� t�o be distlu�bed, since the sub-base �� below the geotex�le is protecbed. In ad,�i.tion, the poll}rtant ca�cen.tration at a h�gh. level m the sh�u+ctiu�e allaws faa� its release over time. It is slowly transported. in the sbormwat�er tio lowpx '' levels where chemi.cal and biological proce.sses may.be operating to retam or degrade pallutants. �� The d,esi.gn should e�.sw.�e tUat s�t'icti.eat v�oid space e�sts for the stbrage of sedime.�ts to limit •� the peri.od between rem.e�ial worl�. �� ■ Pervious paveme,nts require a single size gradi.ng to giv�e apen voids. The chadce of matierials i� is the�fore a compa�omi.se befiween stiffn,ess, p�meability and sbor�ge capaci�,y. , ■ Because tive sub-base and cappir�g will be in camta�t with water for a large part of the time, ;, the str�agth and d�ability of the aggregate �c].es when sa.t�a�ecl and subj ectied to - wetb�g,and dryi�g sh,ould be assessed. �-� ■ Aimiformly graded sm.gle size material. c�nnot be �ompactied �.d is liable to move when. � caazstruction tr�afficpasses bve� it This effect can be re�cedby the use of an,gular civshed ., rock m.at�rial with a bigh s�uface frictioai. j In pollution co�ti ol terms, th�ese lay�s re�pa�ese�t the site of long tierm chemical and biological " pallutant retes�tion and degradatiom processes. The c;onstruiction mateaial.s should be selected, ,- in adc�ili.on tio their �t,,,rt,�,�l strength pat�pe.rties, fca� their abili�y 1�o sustain such proces.se.g. In. � gen�ral, t�is means tl�at matx�ials should crea�e neutr�al or slightiy alkalme ca�.�itions and they _• should provid,e favorable sites fc� colo�ri.zatiam by mic�obial populations. � �� ,� -- January 20Q3 Callfornla Stormwater BMP Flendbook 3 of 10 � ;� New Development axi Redevelopment ' ' w►+rw,cabmphandbooks,can • �, _� .;, ., :u , �� 'r SD-20 Pervious Pa�ements ■ The bloc,ks sh,ould be lain level co��on�r��on ��ae�mo� ■ Permeable s�mfaces can be laid wit}�out cross-faIls or langituc�al gradieats. . ■'I�iey should nat be used for stor�ge o� site mateaials, unless the s�mface is well psotected fibm deposition af silt and a�her spillages. , ■ Th�e paveme�.t s�.ould be camstru�cted m. a si�le operation, as-a�e a� the last items tio be buil� on a devel.opmeat site. I.andscape develapment shr�uld be completed before pavement constr�uction to avcrid contaminatiam by s�7.t aa� soil firom tbis san�ce. ■ Suifaces drauming to the pavement ahould be stahi.lized befaa�e constniction of t3�e pavemeut ■ Inapprapriatie �ans�iction equipment ahould be k�ept away from the pavemeat to prevent ' damage 1�o the s�mface, sub-base or sub-grade. M�ntencmce Requirements �' � The mr��-� requII.�ements of a pervious siuface shauld be reviewed at the time a� des�gn �, , and should be clearly apeafied.. Main�ce is requ�ed to prev�t dog,gioig of the pervious � suiface. 'T9�.e factiors to be considiered whea defimng m�ance re�irements must include: � ■ Type of use , _ ■ �� '� ■ Le�el of traf5.cking �; ;� -, � ., ;� ` ;t ��. '� � �� ■ The lacal envinonment and any ca�ttr�uting catichnvenl� Studies in the UK have shown sati.s�factory operation of poraus pavem�t systeems without mambenance for ov� io y�.-s andrecent wox� by Imbe et al. at gth ICUD, Pardand, 2002 desc�ibes systems opera�g for over 2o years without m�;rn�n�c�. However, performance imder such regimes could not be gua.rantieed, Table � shows t,ypical recomm.ended maintenance regimes: 4 of 10 Callfornla Stormwater BMP Haxxtook Jax�Y 2003 New Develapment and Redevebpment � www.cabmphan�odcs,00m ' ,� , f 1 �. �� _� ''� � � ;� � G r : � ��ti �� , ,� � -�- �'� � � ,-- I� � ��.� ,_., �. I ,.� �` � 1� Pervious Pavements SD-�0 able 1 Typical R�ecommended Malntenance Regimes Activity 3chedule Nrnimtze use of salt or�it for de-icirig Reep landscaped areas well mai�ained �ngoing Prevent soil beingwashed orrto pavement Vacuum clean surface using commemially available sweeping machines at the following times: . � - End of wirtter (Aprll) s/g x per }rear - Mid-summer (July/ August) - After Autumn leaf-fall (November) � Inspect outleis �� If routine cleaning does not restore inflltration rates, then . recons�uction of part of the whole of a pervious surface may be required. . - The surface area affected by hydraulic failure should be llfted for . inspection of the irrternal materials to ide�tify the locaiion and � needed (infi�equent) axtent of the blocl�ge. Maximum i6-so years 3�face materials ahould ba lifted and replaced after brush cleaning. C�eotiextiles mayneed completia replac�ment Sub-surface layers may need cleaning and replacing. Remaved silts may need to be diaposed of as controlled wasta Permeable pavements are up bo 25 % cheape;r (a� at least no more egpensivie than the trac�itional forms of pavemeut constructioa�), when all conshv,ction and drainage casts ai e taken into account (Accepting that the porous asghalt itself is a maa�e e$pensive s�mfacing, ti�e extr�a cost of which is a�set by the savings in �mde�grovnd pi.pework etc.) (Niemczpnowic� et al:, r98�) Table i gives US cost estimates faa� capital and. mainte�nance costs of porous paveme� ( I.andPhaa et al., 2 000) Redeveloping�izstingbestaIiations � parious j�isc�ictio�al sbormwater management and mitigation glans (SUSMP, WQMP, etc.) define'�edevelopment" in berms of amotm� of ad�itional im�'vi.ous area, inr.rPAces m gross floor area and/or e;xberior consti�ucti.an, and land di.st�bi.ng activities with stiv.ct�al a� impetvio� sutfaces. The de6.n.ition of " redevelapme.n�' must be co�ulxed tio dete�nP whether a�r not tl�,e rem»*�mPr,t� far new de�velopment apply bo �areas inte�nded for redevelapment If the definitiam ap�lies, the sbeps outlined lmder "designing new installations" above sl�ould be followed. January 2003 Callfomla Storm►Kater BMP HarxJbodc 5 of 10 New Development and Redevelopm�t www,cabmphandbooks. can � v) a ' I t ■ ,_ � SD-2� Per�ious Pa�ements �, . a Additionei Information , , 4 Cast ConsfderatEons ' permeable paveme;n..ts are up to 25 % c�eap�r (or at least no more expen�i.ve than the tr�aditional faa�ms a�f pavement consliuction.}, when aIl co�ctio� and drainage casts are taken mto , acco�mt (Accepting that ths porous asphalti�elf is a more e�n.�i.ve swfacing, the e.�a cost a� which is offse� by i�e savi� in undergr.v�md pipewo�k e�tc. )(Niemczynawicz, e�t aL, i987) -- Table 2 gives US cost estimates faa� capital and ma.i.nt�enance costs of poraus pa.vements ,� (I.an�phair et aL, 2000) . d �-.; ,, 1 ;� ^, F 6 of 10 Callfomla Stormwaber 8MP Haidbook January 2003 i�� New Development end Redevelopment y www, cabmphan�od<s,com I� � - - � - - - � - ' - ' �--- - _, �_ - - - - - �- - - ; , - , �_ � i �- -- - Pervious Pa�ements � SD-2� � Table 2 Engineer's Estimat�e for Porous Pavemerrt Jerw�y 2(303 Callfvrnla S6ormwater BN� Hax�ook 7 of 10 New Davelopment and Redevelopment www, cabrnphan�ooks,can -� ' avem�nts , SD-2Q Per�ious P � ;; Other Resources '� Ahbott C.L. and ComanA-Mateos L. 2orn. In situ perfr�rmcm.oe monitoMng of � infzltrc�ion �� c�rzage system and fieid tesiing of cr�rent desigri procedw�es. Jo�nal CIWEM, i�(3), pp.i98- 202. i�' '� Camstiruction IndUstry Research and Luformatia�. Associatiaas (CIRIA}. 2002. Source Coritroi using Constructed Pert�ious Sur, faces C,582, London, S`i+ViP 3AU. �� C�.struction Industry Research and Informatia� Assoaatiam (CIRIA}. 2000. SustainaIile r,�bcuc �-1 drairtage sr�stems - design manuaI fvr Scottand cutd Northern Ireiand Report C,52Y, Landon, - SbViP 3AU. � ' J Coa�uction Indushy Research and Informatiom. Associatian (CIRIA). 200o C�2a Sust�nabie rv�b� dr�rzage systems - design mcmua2 fr�r EngJand cacd Wales, Londam., SWiP 3AU. � Co�struction Industry Research and Iuformation Associatia� (CTR TAI. RPq�8 Manual of good '- f pradzce fr�r the design, oonstruction cmd m�ntenanoe of infcltration �nage sysi-ems fnr stormwater rrmo.,�`contrql anddisposat, Lond,on, SWiP gAU. �_' Dierkres C., Ki�hlma�ni L.� Kandasamy J. & A�qgelis G. PoIhrtion Rete�.tion Capal�ility and �� Mai.n�nance of Permea.ble Paveme�.ts. Proc gth International Conferenoe on £Trbcui DrcBnage, , Portland Oregon, September 2ooa. -� Hart P{2002) Permeable �aving as a Stormwatier Source Caritrol System. Paper presented c� _ Sc�ttish Hydraulics SYudy Group z4th Amival s�eminar� SUDS. 22 Marc,�. 2002, Glasgow. '' Kob ayashi M., i999. St�ormwater ruiwff ca�tr�ol i.n. Nag�ya Cit�. Froc. 8 th Int Canf. on ,, Urban Stiorm. Drainage, SY�eY� Au.�tr.'alia, PP•825-833• � �' Landplia�, H., McFaIls, J., Thiompson, D., 2000, Des�gn Methods, Selection, and Cost Effectiveness of St�ormwaber Qualiiy Struch�es, Texas'I4�ansportation Insiitate Reseaiic,h Repa�t i � �.8g�-�, College Stalion, Texas. I� � Legret M,�Colandiui V, Effec�s of a paa�ous paveme;at with reservi� strucutre a� ru�wff ;— wat�r:wat�ex quality and tl�e fabe a�f heavy metals. I.aboratioire Central. Des Pants et C�a.ussesss , . • �--� Macdonald K. & Jefferies C. Perfaa�mance Compaiison a� Paa�ous Paved and Traditional C� r Parks. Proc. FfrstN�ional Con�rence on Susicanabte Drcun.age Systems, Co�entry Jrme 2ooY. '_ � Niemczynowirz J, Hogland W, ig8�: Test a�f poraus pavements performed in Limd, Sw�ie,n, in Tapics in. Drai.nage Hydrauli.cs and Hyrirology. BC. Yen (Ed.), pub. Int Assoc. For Hydraulic �� f Researc3s, PP �9-80. � � � I � Pratt C.J. SUSTAINABLE URBAN DR.AINAGE — A Review o� published mat�rrial am the peifor�,Anc� � various SUDS devices prepared for the iTK Environme�t Age�cy. Cav�atry � i Unive�i.ty, LTK December 2ooi. (_ Pratt C.J., �99�. InfiZtr�ation drain�ge — case str�dies of LTK practice. Project Repca�t —i 8 of 10 Callfomla Stormwater BMP Haidbod< January 2003 � ! New Development and Redevelopment ' . . rrww.cabmphancbodcs.com r- '; I� f _ Per�ious Pa�ements 5D-20 ,� 22,Construction Industry Research and Information Association, London, SW�P 3AU; also l�awn as National Rivers Authorit,y R& D Note 48g Pratt C. J., �990. Permeable Paveme�ts for Stnrmwater Quality F.nhancement In: Urban , Stiormwater Qualit,y Enhancement - Saurce Ca�tiiol, re�afitbn,g and combined se�vver tec�inology, Ed H.C. Torno, ASCE, ISB1V o8�z62 7594, pp. �,3�.-i�,5 Raimbault G., igg� F�euch Develapme�ts m Reservoir Struct�es Sustainable watier resoiu�ces I the 2i� ceatiuy. Malmo Sweden Schl.iiter W. � Jefferies C. Momt�ri�g the airtflow from a Porous C� Park Proc. Fcrst National Conf�renae on S`�st�nable Ur�nage S'ystems, Cove.niry Jtme 2ooY. �Nild, T.C., Jeffe:ries, C., and D'Arcy, B.J. SUDS in Scotiand — t3ve Scattish SUDS da.tabase Repc7rt No SR(o2.)09 Scotl�.d cmdNorthern Irelcucd Porurn fr�r Emrironmental Research, ,� Edfrtbw yh. In. preparation A,� t�r 2002. �� I� . 4 , i r I � � I_ J {� � ' . � . I � � � f- -, . I �� ' I J . I �� ' i . 1 � �� I + . I � - Jax�ay 2(103 Callfomla Stormwater BMP Fi�dboo{t 9 of 10 i � Ne�v Devebprnait �d Redevelopm�t www,cabmphan�ooks. com �' �_1 , i , � �, � I �_ I I � _� �D-2Q Per�ious Pa�ements � �, 3 : , t ) .1 ^ Y { � 1 ` • �t . + t � ( 1 . ' y � � j ` .-f..C�.�:�-.;_�,.a.^3-�':� _�r--•.F .,.- �&'oFe�.� . `�, .,.�_, �.`6 ,�,.� ,,«�v � . .� L y,�I U fi �` �.�.-� "� jr�Q ��1�'0^ • t , +: � � ' � � �ot P.*�� +»�,.�.a ��. � L . ` e ' � r � � , ,l , � ` t • 4 ` ` . . . �� 1 ` ` 1 , . , , . _ �:i:. .._.t.zcti vu:'...a::� `�'..5.-.�{' .. ._. . �;� .,.. • r ,, -61� �`-��.-'�',ri F ' w . *'� �'' � �.� 1 ��_�g Y ��..Z.R � OppSC�e � • b�►a�. roa r�� ►�� r�w� Schematic� of a Pervloua Pavemeat System �i �_; 10 of 10 Callfomla Starmweter BNW Handbook ]awary 2QD3 New Developrnent and Redevelo{�ment � www. cabrr�hand�ooks.com Storm Drain Signage SD-13 _ �., ,:�..,... ---�-.-��,_ ..,,,y,.� �--.�.�. v�;. _..� . �_. _.__ .�.� _ � �,�,.n .,�,; > . , �:�.�.s` �.�a-s.�'��'z.i ':;,"�..� � '.;:;«.-�:wc�:`w �, � � ` �' :F:,� � { � �� . � ;� � � �; �� ;�._ �� *�.`_:� ��:��' ?�" K Description �Design Objectives � �LL...� Mawmize InfilUation.� ��_. ._...., Provide Reiention Slow Runoff Minimize Impervious Land Coverage mr Prohibif Dumping of Improper Materials Confain Pollutanfs Collecf and Convey Waste mate�rials dumped into storm drain inlet� can have severe unpacts on receiving and ground waters. Posting notices regarding discharge prohibitions at storm drain inlets can prevent waste dumping. Storm drain signs and stenals are highly visible source conirols that are typically placed directly adjacent to storm draini.nlets. Approach The stencil ar affixed sign contai.ns a brief statement that prohibits dumping of improper materials into the i�ban runoff conveyance system. Storm drain messages have become a popular method of alerting the public about the effects of and the prohibitions against waste disposal. Suitable Applications Stencils and signs alert the public to the destination of pollutants discharged ta the storm drain. Sign.s are appropriate in residential, cammercial, and industr�ial areas, as well as an.y other area where coniributions or dumpin,g to starm drains is likely. Design Considerations Storm drain message markers or placards are recommended at all storm drai.n inlets within the boundary of a development project. The marker should be placed in clear sight facing toward anyone approachi.ng the inlet from either side. All storm drain inlet locations should be identified on the development site map. Designing ilrewlnstailations The followin4g methods should be considered. for inclusion in the proj ect design an.d show on proj ect plans: ■ Provide stencilin,g or labeling of all storm c�ain inlets and catch basins, consh�u.cted or modified, wiiivn the project area with prohibitive language. Examples include "NO DUMPING :--� .�.�� ; )anuary 2003 Callfornla Stormwater BMP Handbook 1 of 2 New Development and Redevelopment www. c�mphandbooks. corn SD-13 Storm �Drain Signage - DRAINS TO OCEAN" and/or other �a.phical icoms b� discaurage �71ega1 dumping. ■_ Post s�g� with pirohibitive la�gi�ge and/or g� aphical icoms, whic�. prohibit illegal dumpin,g at public access pom� ala�,g channels and creeks within the pa�oject area.. �I Notie - Some local agencies have appro�ed sparfic si,gnage and/or sto�-m drain message placards �- I for use. Consvlt local agen.cq stoa�mwater staff tio detexmin.e apecifii.c requirements for placard. types and methods of applicatian. . Rede�eioping Bxis iiaeg InataIta#ioxs Various jwisdictional stormwatier manageme�t emd mitigation plans {SUSMP, WQMP, ebc.} � define "rede�velopmeIIt" in terms a�' amotmts of additional impervious area, increases m gross flo� area and/a�r exterior caa�striLciic�., and land c�i.st�bir�g activities with str�uct�al. or im.pervious surfaces. If the prag ect meets the de�imtion c� "redevelopmen�', thea the requu�emerns statied unde�r " designing new installatiaais" abave s}�ould be included in all pnoject des�gn. Fl�.s• � Add Ftiona I Informaiion MaintenaQece Coxsidera.tiona ' ■ Legibility of markers and si.gns shauldbe ma;,,t�;ned. If requu�ed by the agency with jtn�sdictiam over the pa�aj ect, the owner/agerator �r homeowner's as�ociation should eater '- � into a mA;r,te�anc� agreementwith the agency orrecord a d,eed restriction upon the i � pa�operty title tio mainta�m the leg�.bility of placards a¢� s�gns. Piacerneut ■. Sign�ge aai tap a� curbs teadg to weather �d fade. ■ Sigt�ge cai face a� curbs tm.ds tio be w�n by coo�tact with vehicl.e tires and sweepe� brooms. SupplementelInformation � Excmepiea ■ Most MS4 pa�ograms have sta�m draiu �i.gaage programs. Some MS4 programs will provid,e steuals, o� arrange for vohmteeis tio sben.al sta�m drains as part of the,� outreach pa�og�.�m. Other Resources �� AManual faa� the Standard Urban Stbrmwat�er Mitigation Plan (SUSMP), I.os Angeles Cowrty De�partme�.t af Public Wa�rks, May 2002. �� Model S�ndard Urban Si�orm. Watier 11�'it�ga.tion Plan (SUSMP) for San Diego Cowzty, Port of '-� San I}iego, and Cities in. S� Diego Cow�', FebruarY i4, 2002. �. ,,__, Mod.el Waber Quality M�geme�rt Pl.� (WQMP) for Cow�.�V af �ra�ge, OranSe Cow�y Flood !} Cae�.tr�ol Distric� and the In.corporal�ed C�ties of Orange Colmty, Draft Febivary 2003. Ventt�a Coimt,yw�id,e Tec,hnical Guidan,ce Ma�.al for Stiormwater Quality Control Meas�es, July 2�. ;� �_ 1 ' 2 of 2 Callfixnla Stormwal�r BI� Handbook Jawary 2003 ! � New Development arzd Redevelopment ; ? www.cabmphan�ooks.com ��, Outlet ProtectionNelocity Dissipation Devices :;i�" � k ;,.�>..'-�.. �.�`°. ..-'• �. � , , "",, �,' �` �w,z �--` f,�,� r�' .,� �`.� ; � � ^�.:: : r . ,'� ' '" .•" ,�• � � � � ti :' '� � � r� ��:: �:�. �� , t , '� - , �° �� - �r Standard Symbol SS-10 BMP Objectives • Soil Stabilization • Sediment Control o Tracking Control o Wind Erosion Control o Non-Storm Water Management o Materials and Waste Management Definition and These devices are placed at pipe outlets to prevent scour and reduce the velocity Purpose ��or energy of storm water flows. Appropriate ■ Applications These devices may be used at the following locations: Outlets of pipes, drains, culverts, slope drains, diversion ditches, swales, conduits or channels. Outlets located at the bottom of mild to steep slopes. Discharge outlets that carry continuous flows of water. Outlets subject to short, intense flows of water, such as flash floods. Points where lined conveyances discharge to unlined conveyances. ■ This BMP may be implemented on a project-by-project basis with other BMPs when determined necessary and feasible by the Resident Engineer (�)• Limitations ■ Loose rock may have stones washed away during high flows. ■ Grouted riprap may break up in areas of freeze and thaw. ■ If there is not adequate drainage, and water builds up behind grouted riprap, it may cause the grouted riprap to break up due to the resulting hydrostatic pressure. L�Caltrans Storm Water Quality Handbooks Section 3 Construction Slte Best Management Practices Manual Outlet ProtectionNelocity Dissipation Devices SS-10 � March 1, 2003 1 of 3 Water Conservation Practices NS-1 BMP Objectives o Soil Stabilization o Sediment Control o Tracking Control o Wind Erosion Control • Non-Storm Water Management o Materials and Waste Management Definition and Water conservation practices are activities that use water during the construction of Purpose a project in a manner that avoids causing erosion and/or the transport of pollutants off site. Appropriate ■ Water conservation practices are implemented on all construction sites and Applications wherever water is used. ■ Applies to all construction projects. Limitations ■ None identified. Standards and ■ Keep water equipment in good working condition. Specifications ■ Stabilize water truck filling area. ■ . Repair water leaks promptly. ■ Vehicles and equipment washing on the construction site is discouraged. ■ Avoid using water to clean construction areas. Do not use water to clean pavement. Paved areas shall be swept and vacuumed. ■ Direct construction water runoff to areas where it can infiltrate into the ground. ■ Apply water for dust control in accordance with the Standa.rd Specifications Section 10, and WE-1, "Wind Erosion Control." ■ Report discharges to RE immediately. C�Caltrans Storm Water Quality Handbooks Section 7 Constructton Site Best Management Practices Manual Water Conservation Practices NS-1 �,� March 1, 2003 1 of 2 �_ � Water Conservation Practices NS-1 ; �� ; ; li � � � � �> ;� Maintenance and ■ Inspect water equipment at least weekly. Inspection ■ Repair water equipment as needed. 0 �.i �Caltrans Storm Water Qua�ty Handbooks Conatructlon 31te Beat Managemerrt Practices Manual � March�l, 2003 Sectlan 7 Water Conservatlon Pracaces N3•1 2 of 2 '� f � , � APPENDIX 5 Drainage Study � ;� ,� �� , ;Z ; _. ,__ �_ � �; �; f �; �_ � ;" �- � � i � I, ; , ; i , , I �`�� ; TABLE OF CONTENTS s,�mmaxy ................................................................................................................................ 1 VicinityMap .......................................................................................................................... 2 APPENDICES San Diego County Isopluvial Chart 100-Year, 6-Hour . . . .... . . ... . . .. . . . . . . ... . .. .. . . ... .. . .. .. .. .......A Tables and Charts for run-off coefficients and times of concentration . . . . ... .. . .. . .. .. .. . .. .. .. ... ....B On-site Detention Calculations ...............:..............................................................0 Existing Cond.ition Hydrologic Calculations for the 100-Year Storm Event ......................... ... ...D I Developed Condition Hydrologic Calculations for the 100-Yeaz Storm Event ...................... .....E � �� Hydraulic Calculations .......................�.. .......F .................................................................................. i � 85� Percentile Calculations ................................:..........................................................................G HydrologyMap . ..... . . .. . .. . .. . . . . ... .. . .. . .. . ... ..... .... .......... . . .. . . ..... . . .. .. .. . ... .... .. ... ....Pocket ! HYDROLOGY Summary �i 1 This 1.02-acre project (APN 206-200.0� is located on the south side of Adams Street, east of the intersection with Highland Drive in the City of Carlsbad.. Topographically the site slopes to the '��, south towards the Agua Hed.ionda Lagoon. Very little runoff enters the site from the adjacent ' -� property to the wes� E�stin� Condit�ion , � This project is adjacent and north of the Agua Hedionda Lagoon, which serves a final repository �, � of an enormous �drainage basin that serves parts San Diego North County, includi.ng Carlsbad and San Marcos. The final step after the Agua. Hedionda La.goon is the Pacific Ocean. The cuirent site is approximately 57% impervious. Using table 3-1, in Appendix B, a prorated C value of 0.67 is obtai.ned for soil type D and an impervious percentage of 57%. ;� The current storm waters are partly absorbed onsite and the remai.nder flow southerly towards the Agua. Hedionda Lagoon. There currently exists a,lazge residential structure tha.t serves as the Boat � Club's meeting and administrative facilities. The p�cel is lightly vegetated and a large portion of � the site is paved with very weathered asphal� There are no storm drain facilities on-site and the run-off from storm events sheet flows into the beach at the south end of the property and into the ;� Lagoon. The current site generates approximately 3.94 cfs in a 100-year storm event. _ � - Develoned Condition �-_� The existing residence✓boat club structure is to be removed. In its place will be a new 3 story boat club and time share with under ground parking for vehicles and sma11 boats. Three floors will be � r visible from the Lagoon and only one floor will be visibla from Adams Street. The site will �e �' -i accessed from Adams Street via a driveway, which starts out at 5% and at its steepest point reaches 19%. � . . ;� The proposed site is approxi.mately 63% impervious. Using table 3-1, in Appendix B, a prorated ,- C value of 0.70 is obtained for soil type D and an impervious percentage of 63%. � '' The nuioff generated by a 100-year storm event has .been calculated to be approxi.mately 4.25 cfs, --, an increase of .31 cfs. This runoff will.be collected in an on-site storm drain system and allowed � to infiltrate and to settle debris & hydrocarbons before discharging into the Agua Hedionda � Lagoon. Additionally the project will be detaining the additiona10.31 cfs, generated. by the new ,� development, before treating it and discharging into the Agua Hedionda Lagoon Watershed �_ _; The watersheds were analyzed using the 2003 San Diago County Hydrology Manual. -� � � , t � ? Pre-Development Pre-development Condition, as described in the Hydrology Calculations, is 0:90 acres and contributes 3.94 cfs (100-year) in pre-development conditions. This runoff drains directly to the Agua Hedionda Lagoon . . "� �� Post-Development . � '�, . —¢ Area "A" (Hydrology Map, Pre-development Conditions), as described in the Hydrology Calculations, is 0.13 acres and contributes 0.58 cfs (100-year) in post-developad conditions. This �� runoff drai.ns directly to the proposed curb inlet located on the west side of the driveway. Area `B", as described in the Hydrology Calculations, is .08 acres and contributes 0.38 cfs (100- year) in the post-developed. condition. This runoff drains directly to the proposed. curb inlet located on the east side of the driveway. ?; Area "C" is .11 acres and contributes .35 cfs (100-year) in the post-d.aveloped condition. This 1 - runoff drains directly to the proposed curb inlet located at the end of the driveway. Area "D" is .18 acres and contributes 0.83 cfs (100-year) in the post-developed. condition. This runoff is flow southerly along the east property li.ne and onto and into the Agua. Hedionda Lagoon. This runoff passes through pedestrian concrete walkways and boat raznp area. Subsequently no hydrocar�ons or pollution is picked up in its flow. ,� � ; � Area "E" is .11 acres and contributes 0.48 cfs (100-year) in the post-d.eveloped cond.ition. This � will across the club house patio area and onto the beach. More than 50% of the square footage of area `B" is the bea.ch it's self. This area contn`butes the least to any possible pollution of the ' r Agua Hedionda Lagoon. �� Area "F"' is 0.29 acres and contributes 1:65 cfs (100-year) in the post-developed condition. This runoff will flow to roof drains and to the storm drain system located in the driveway on the west side of the project. This water then confluences with the runoff from areas "A", `B" and "C" and will be processed through a CDS unit before any discharge into the Agua Hedionda. Lagoon. �; All ruuoff from this project will ultima.tely proceed southerly and into the Agua Hedionda �� ' Lagoon. According to the 1998 303d list published by the San Diego Regional Water Quality -��C Conttol Board, the Agua Hedionda Lagoon is an "impaired water bod�'. Pro- and post- ;� construction BMPs are mentioned. in the Water Quality Technical Report for this project and will be detailed in the project's future SWPPP. ( r� ; k VICINITY MAP :1:.��5-!°+-��:� �°.m Ya � , �, i � H E, � � _ �.� � ta. 1 t�� `� �� "'r �' J' � �'� �� ,, �v t i� �' v �. �� -� �;� a �� a s i_ i E Y �'tf, ,��i � �T � !'9n � �Y , ( ~ '�� '� 5 x+ .;�t<' y ti ' � r.�. � . �{-' f� �� ,,u �+i y �� W` ,. Y ., � t�f �Y Y „�. ` •,� � t ?� , . �,, . ti, �� ' •'� �' ��g , , . , .. �,. . 'i� � ,':. a,. . tit i�, . . .." , �S�' v`J, �,r W �, �� i � °�' '° �: �� }�, �i-�� r ��' � � ! ; `� ' `°� � ,�� 4 � � � � �'i� �ay `t r : ` � `�� `� � y`�� c 6+ . 't v� : , �t v � s < � (, �' r, �, �rt � .. � . ,�� , ;, , ; ��1 ��_. � �� : us � < < c ` aF R r�r'c�� ,�,c �, S' , .- � { {.. ".. ! 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J` L t � > m �- �i;� , ,,. 5 f ` "� � %�y �5% � . �� . � � `'� , ."� � I ;�,. �F�c,�n��, ` �� a i � y : �.,� y �di t � � , ,� �� ^• 'r!rf � a : ,�7 �. �'dy i �' i ��. � { ,:_ cr � �v a� -� �1 .r � rt• ,, " 1 � , �y�� "•1�y ,�� Jt r+,1S1'��,i '� � ,' p �" YN� 31i 4 . � � � n� i f� � � � '�' � � _ �'f <%' r � � k �y � �.a 4�, . �r N - t'' �� r'4� � � � i .� 1 E �. l ' X y � . . ^}� , � �, i � {}. t ,i"' ",� a w . R < P,� vi�`!a � 'k � §,-� �Ce"m �. ,'� L7 �. i s�.... " � 1'r' - i' 3 a] ;,- � l (� ' d' . � �f�,J �� a��Y � t,��a� � t � �'a� �� 4: � L' `s , ?�a�I v R 2'D` ``'4 , � �� ' f b4,s'j''" ,'` �',��,d�`A �� :+n � i q; , �,c� .� . �rp I � � 1 � + s`- '"t`j ' ! �'�r ,,• �,�� '� r�y„`�i , qij �� ,, ,�, • y � f � �.� 1 , '�i'S� �,a � � c ,..�` �� ... r �__ � � ' f' . � �S� , w '�„� as ; _ � - , ,� , `tt t'�i : � � � �� a� � •� � ��` � �, � �;� � �� , } �'� ��f'-� � i t �r� �h� � i �� - 1 �s}p,,._ �'Sw�,,.�' � ,� �G .q� �'� t . � 1 � .. �s4 t ,t ; � . � r , e ��g, . ✓^ ^L [ � `.. " '-1.4 1 dv t "� �� ti,cs �', yY. � � i u'��„ x t , -1 +7� a Y; �. . �: 'aS4�' r � i t � �yq o' CY : ` ,_ ( .. , , �. � . `w F � '�ri� �' �"`�Vi �2d ,n,'�ua ,,�"�z\ �, � 4 ,'* �• �a...�' i � : �� O ,� r .;J u�,r2pct.�d _ \ _ pt }�1 w .��1,�, � 1 ir`t � r ry ; �� _ 1� � � ; � , �.' � . -'"a ,�� ` '+``-�y ` �,� �.� . ��, {t�,2�� * SITE `�' �y$f �: � _ r'� . -� _ y f ry3:� `S.ti��,. � � � `Y .. ��I� � k '��.` . i o�o n ' � m - {��C�Ot''�'ahaa!Ens , . , . z . ,t� �C[�20�BN)+�.�TEQ Not to Scale 3 �r �� J__1 ; �� , � � i � I � � � � ( � �� l `, t � �� , r �f �f � .s ;, � _� ,t �� r� �; << �ti r :� �,� APPENDIX A Connty of San Diego 2003 Isopluvials 100-Year RainfaII Event — 6 Honr & 24 Hour 0 0 `-- � l �_ � ,j l` � r '` _ � - ��1 I i � a f— I !, i 4 ' � APPENDIX B Tables and Charts for run-off coefflcients and times of concentration , ti ,- - - -- - �� -r --� - - - - -- - � � , � � , -- �- -- - - -- ; � -- -- � � - , � �'�, , � d ' . , _ -- `a --� . -�_' ,� ._ _ . _- -- - � R�. .__ .___ � ._ - � - --� •- � � � - J - � . � � �- _ ._� � _� ti _ y -�_ SSII D1egQ COimty Hyd101Ogy IViaIIUSI Date: June 2003 Scction: Page: 3 6 of 26 Table 3-1 RUNOFF COEFFICIIIVTS FOR URBAN AREAS Land Use NRCS Elemeuts ' Rnnoff Coefficient "-C" Soil Tvna % II�IPER A - B C D Undisturbed Nahiral Teaain (Natm-a1) pamanent ppen Space . 0* 020 025 0.30 0.35 Low Density Residential (L,DR) Residential, 1.0 DU/A or less 10 027 032 036 � 0.41 Low Density Rssideutial (I.DR) Rcaidential, 2.0 DU/A or less 20 034 03 8 � 0.42 0.46 Low Den�tY Reaidential CI-DR) Residantial, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49 Medium Density Resideniial (MDR) Residential, 43 DU/A or lesa 30 0.41 0.45 0_48 OS2 Medium Density Rcsidcntial (MDR) R,�idential, �,3 DU/A or less 40 0.48 0.51 0.54 0.57 Medium Density Residential (MDR) R,osid�tial, 10.9 DU/A or less 45 0.52 �. 0.54 OS7 0.60 Medium Density Residential (MDR) Resideutial, 14S DU/A ot lasa 50 0.55 0.58 0.60 0.63 �S� D�tS' �s�� (fIDR) Residential, 24.0 DU/A ar loss 65 0.66 0.67 ' 0.69 0.71 High Density Resid�tial (HDR) R�ideatiai, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79 Commercial/rr,�„at,;At (N. �� Neighbo�ood Commercial . 80 0.76 0.77 0.78 0.'19 � '(�. �On°) � ��1 �� ss o.go o.so o.si o.sa CommerciaUlnduslriel (O.P. Com) Office Profe.ssionaUComme,rcial 90 0.83 0.84 0.84 0.85 Commcrcia]/Indnstrial (L'moited I.) Limited Industrial 90 0.83 0.84 0.84 0.85 CO�� L �� 95 0.87 0.87 0.87 0.87 ''The vaIues associab�d with 0% impervions may be used for dircct calculation of the nmoff coeffiaient as descnbed in Section 3.12 (representing the pervious nmo_ff coeffcieat, CP, for the soil tyPe), or for areas that will remain undisturbed in perpetuity. Justificatiom m�st be given that t�e area will remain natural foreve� (e.g., the area is located in Clevelaad National Forest). DU/A = dwelling �its per acx-e NRCS a National Resources Consezvation Seavice � �1 1 � '1 %`il I �' � � �, i ;, ;� T �r San Diego County Hydrology Manual Saction: 3 Data: Juae 2003 Pago: 12 of 26 Note that the Initial Time of Concentration should be reflective of the genesal land-use at the upstream end of a drainage basin. A single lot with an area of two or less acres does not have a significant effect where the drainage basin area is 20 to 600 acres. Table 3-2 providas limits of the length (Maximum Length (I,�) of sheet flow to be used in hydrology studies. Initial T{ values based on average C values for the Land Use Element are also included. These values can be used in planning and dasign applications as descn'bed below. Bxceptions ma.y ba approved by the "Regulating Agenc�' when submitted with a detailed study. Table 3-2 OVERLAND FLOW LENGTH (L� n �� S- J� .;�. ', �f i r -,� � _� i� _„ �i 11V1'1'lAL '1'1M�; UF CONCENTRATION T Element* DU/ .5% 1% 2% 3% 5% 10% Acre LM Ti LM Ti LM Ti I,M 'Ti - L T• I,� Ti Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8:7 100 6.9 - LDR 1 50 12.2 70 11.5. 85 10.0 1(}0 9.5 100 8.0 100 6.4 LDR 2 50 11�.3 70 10.5 85 9.2 100 8.8 100 7.4 100. 5.8 LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 140 7.0 100 5.6 MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 1(10 6.7 100 5.3 MDR 7.3 50 ' 9.2 65 8,4 80 7.4 95 7.0 100 6.0 100 4.8 MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 �100 4.5 MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3 HDR 24 50. 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5 �IDR 43 50 . 5.3 65 4.7 75 4.0 85 3.8 � 95 3.4 100 2.7 N. Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7 C�. Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4 O.PJCom 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 G}encral I. � 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9 "See Ta�le 3-1 for more detailed description 3-12 �� "�� !r E�i�9Fl��i�illiill[ilil�El1��11'1ii13�lf1��l;Illi!Is�liil�il e �Il�liii�il?f E�IiN�l��illll�l�iilii�i9111��f+l�l;ll� �i�p �3�e!dl�1�1��l�111llliill�il��i9llli�6fll�Il�Ifif;fl.,l�ii� ��'`r��I�C��1�I�E�i��l��li��. :, ��,�i�ti#�e�l��j�!!lli�l�ill��l��lll�l�ll��:� ��I�':2�:'1i��;:��':.��I��II1�� - '._., ��C1�`I��E!��li,��ty�'��'��' �� ' G.�i : �� e: �� `��ar��.. f!'IEli:l� �1��i��11111 �a�;��ti.�:�o�+��; +�Ill''�°' � � ■i�i� ■�en r.�ee� ��e�3�e�� I��@ii��,;;�1 ��:��i�l��li�l� I��l�i;��!il�; l��il�lll��lll�� i��l��lll��ll��' ,.:�:..,..:.:::,, ii�i�ii=iu�n�ii IR::6l��lpCE�[Il:i I��G�17;li��R�11111 �er�wa�are�owu ��uue��a�reu[�! �a�w�aireauu�u �r.:o�a�oeR�ci:[�� nu.a�_��oxew» ��":��!��1M��N1�� <<;;;�::i;�� li�:�:�'i��. . lllil�Iliil[illli ��.'��:�� I;�:i��t�� .'I�t��1��1��i I� �� t7 ;1� ..'W� �'nl�� Yw ��' � �..=.r 1�::l�l��i'J57Wa!l�Y11 Ilii!i!!� s�M:Yi.ia'r�N■ �ue��e��e�wrr.�. � 1� !1��>Lf�Z`�P_f �ipw u:c�ia� i a�r� �� e�a�■ ��,t:.�e:.�::a�iwcn�e e�cr.e �G.: @i.fo SCSl: Blir �iQ� i��v�ea �sr.�ns�s nr! s I:�itilrlli��eR��CI 11'1[ShS� 2-FiYGp7Y aEYS FL'S:..T.£r7!�Z97171S�ICGi7� fl�:i�l�7■Aw9�l�iz li�el�l7 ��7�1�!■ �l1E) �: i11�q�i�Il��1��K� I:;ii��ii9i�1��...i i!:`;iEl ��i��5i a�llf l6��1�l��J�I�EE� :1ilili! �IIliil; �:�:�.,� il��!;�ll! �l��t�l.��ll�1'�(li� � n �-. '� ,,, �� n h; t i , ' �+, �� - _� � , �, � �_ _ ,�? i� �� i� e � �� APPENDIX C Detention Facflities Calculations 9 ' � , n I� ��<< � Required Detention: The required retention for the site was determined from the San Diego County Hydrology manual formula for volume `as follows: Volume = C*Ps*A .'� ,; a� ; �� ' � ;� �, ,��`� _�, �� ' _�. :� � �� ;� ,� �� Where: Volume = volume of runoff (acre-inches) P6 = 6-hour precipitation (inches) = 2.8 C= delta of runoff coefficient = 0.03 A= area of watershed = 0.90 Volume = 0.03(2.8)(0.90) = 0.0756 acre-inches Volume = 276 cnbic feet of rec�nired detentfon. Check of 85� Percentile rainfall volume: The 85�' percentile volume (see 85`� percentile calculations) has been calculated as follows: Q=0.64 cfs Duration' of 10 minutes Volume=Q*D Volume=(0.64cfs)*(10 mi.n)(60 sec) V=384 cubic feet Volume = 384 cnbic feet of required detention. Using four 20-foot 1Qng, 30-inch CMP for storage. Area of 30-inch CMP = 4.91 square feet A 20-foot section will yi.eld 98 cubic feet Four 20 foot sections will provide 392 cubic feet, which is more than what is required. We will have 1.02% stora.ge capacity for detention. � � T ; �-n ,� APPENDIX D �; 'j Pre-developed Hydrologfc Calculations for the 100-Year Storm Event Onsfte � �� • ,� r ,� �� " � �1 � � ; � _ �� i � �� f �f� i � � � �� •i � �_ ; � �'_1 ,- � i ;� **************************************************************************** RATIONAL METHOD HYDROLOGY COMPIITER PROGRAM PACKAGE Reference: SAN DIEGO COUNTY E'LOOD CONTROL DISTRICT 2003 HYDROLOGY MANUAL (c) Copyright 1982-2003 Advancad Engineering Software •(aes)� Ver. 1.5A Release Date: O1/O1/04 License ID 1462 ---------------------------------------------------------------------------- '� ' FILE NAME : CBC . DAT � i TIME/DATE OF STUDY: 16:22 5/18/2006 v � '- ----------------------�__-____________-________________�_-___-------------__ : USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION: � � � ��---------------------------------------------------------------------------- l 2003 SAN DIEGO MANUAL CRITERIA �� USER SPECIFIED STORM EVENT(YEAR) � 100.00 r� 6-HOQR DURATION PRECIPITATION (INCHES) m 2.800 , �-� SPECIFIED MINIMUM PIPE SIZE(INCH) m 10.00 SPECIFIED PERCEN� OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE �.95 �� SAN DIEGO HYDROLOGY MANUAL "C"-VALUES IISED a�, � NOTE: ONLY PEAK CONFLLTENCE VALUES CONSIDERED � 1 � � �� 1 �� { � i ' � �� i ! 1 �' � � , ,� �� I � *********************************************************�****************** FLOW PROCESS FROM NODE 1.00 TO NODE 2.00 IS CODE � 22 --------------=------------------------------------------------------------- »»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««< SOIL CLASSIFICATION IS "D" RQRAL DEVELOPMENT RUNOFF COEFFICIENT � .6700 IIRBAN SUBAREA OVERLAND TIME OF EZOW(MINIITES) m 3.230 *CAIITION: SIIBAREA SLOPE EXCEEDS CODNTY NOMOGRAPH DEFINITION. EXTRAPOLATION OF NOMOGRAPH USED. TIME OF CONCENTRATION ASSUMED AS 6-MINUTES 100 YEAR RAINFALL INTENSITY(INCH/HOIIR) � 6.559 SUBA�tEA RIINOFF(CFS) m 4.90 TOTAL AREA(ACRES) a 1.12 TOTAL RIINOFF(CFS) = 4.90 —��-�--- � ��_--�_=��_ _ ��-��_ END OF STIIDY SUMMARY: ' . PEAK FLOW RATE(CFS) = 4.90 Tc(MIN.) � 6.40 TOTAL AREA(ACRES) = 1.12 a�=----�--�-�---�—__�- = _�—=-=_ -- --=--a��--- END OF RATIONAL METHOD ANALYSIS � (0.22 ACRES OF THIS RUN-OFF IS COMIMG FROM OFF-SITE, WHICH AMOIINTS TO A TOTAL OF 0.96 CFS. THEREFORE THE TOTAL RUN-OFF GENERATED FROM 0.90 ACRES IS 3.94 CFB. �:� `I l.� �r APPENDIX E 9; Developed Hydrologic Calculations for the 100-Year Storm Event ,; �� ` =1 � f, , y y, • �,l 1-' l Y f �i � `�1 1 �__+ S I II� 1i i �..' {` 1 . � l� � � _ � Y � � �� ` il � � � �� i' � � ,� , i_ ; , oi � i ,/ � � �� ;�� 1 N f �1 r _\ � f ^ a',, �� i a � �a � **�************************************************************************� RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE Reference: SAN DIEGO COQNTY FLOOD CONTROL DISTRICT 2003 HYDROLOGY MANUAL (c) Copyright 1982-2003 Advanced Engineering Software (aes) Ver. 1.5A Release Date: O1/Ol/04 License ID 1462 FILE NAME: CBCF.DAT . . TIME/DATE OF STUDY: 16:36 5/18/2006 __USER SPECIFIED HYDROLOGY RND HYDRAULIC MODEL INFORMATION: ----------------------------------------------------------------------- 1985 SAN DIEGO MANUAL CRITERIA ' USER SPECIFIED STORM EVENT(YEAR) a 100.00 6-HOIIR DURATION PRECIPITATION (INCHES) � 2.600 SPECIFIED MINIMUM PIPE SIZE(INCH) = 10.00 SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE _.95 SAN DIEGO HYDROLOGY MANUAL "C"-VALUES USED NOTE: ONLY PEAK CONFLDENCE VALUES CONSIDERED ' ********�***************+*************************************************** FLOW PROCESS FROM NODE 1.00 TO NODE 2.00 IS CODE = 21 AR&A "p�n . ---------------------------------------------------------------------------- »»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««< �-- za- �caa��n ac==�s - - SOIL CLASSIFICATION IS "D" COMMERCIAL DEVELOPMENT R[INOFF COEFFICIENT = .7000 INITIAL SUBAREA FLOW—LENGTH = 170.00 UPSTREAM ELEVATION m 55.00 DOWNSTREAM ELEVATION = 19.50 � ELEVATION DIFFERENCE = 35.50 URBAN SIIBAREA OVERLAND TII� OF FLOW(MINUTES) = 2.131 *CAUTION: SUBAREA SLOPE EXCEEDS COUNTY NOMOGRAPH DEFINITION. EXTRAPOLATION OF NOMOGRAPH USED. TIME OF GONCENTRATION ASSUI�D AS 6—MIN�TES 100 YEAR RAINFAi�L INTENSITY(INCH/HOUR) a 6.559 SUBAREA RUNOFF(CFS) � .58 TOTAL AREA(ACRES) � .13 TOTAL RUNOFF(CFS) � .58 ******************************�*************************'****************�*** FLOW PROCESS FROM NODE 2.00 TO NODE 4.00 IS CODE = 4 »»>COMPUTE PIPEFLOW TRAVELTIME THRQ SiJBAREA««< »»>USING.USER-SPECIFIED PIPESIZE««< -- a��e�a��===--- � - _ DEPTH OF ELOW IN 12.0 INCH PIPE IS 1.3 INCHES PIPEFLOW VELOCITY(FEET/SEC.) � 4.8 UPSTREAM NODE ELEVATION = 1:6.00 DOWNSTREAM NODE ELE�IATION = 15.50 FLOWLENGTH(FEET) = 18.00 MANNING'S N — .011 GIVEN PIPE DIAMETER(INCH) � 18.00 NIIMBER OF PIPES = 1 PIPEFLOW THRU SUBAREA(CFS) _ .58 TRAVEL TIME(MIN.) Q .06 TC(MIN.) — 6.06 ;� ti r � � , � **************************�************************�************************ �! FLOW PROCESS FROM NODE 4.00 TO NODE 4.00 IS CODE a 1 FIAW IN PIPE � f I ------------------------------ ---------------------------------------------- r � »»>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE««< � �_ — --- � ��—=�a�—�o��—��—,�_��o�_ _s—o ,_ TOTAL NUMBER OF STREAMS s 3 j �, CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 1 ARE: , TII� OF CONCENTRATION(MIN.) = 6.06 RAINFALL INTENSITY(INCH/HR) = 6.51 ;�� TOTAL STREAM AREA(ACRES) m .13 �� PEAK FLOW RATE(CFS) AT CONFLUENCE m .58 � � � ******************+********************************************************* FLOW PROCESS FROM NODE 3.00 TO NODE 4.00 IS CODE — 21 � � ��grr �-� »»>RATIONAL METHOD INITIAL SDBAREA ANALYSIS««< ; -- o�� —aa ��v __� m — —=�m ---__�—_-- �� SOIL CLASSIFICATION IS "D" COMMERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .7000 �'�,� INITIAL SUBAREA FLOW—LENGTH � 235.00 { � UPSTREAM ELEVATION = 50.00 ' � DOWNSTREAM ELEVATION 9 19.50 ' ELEVATION DIFFERENCE a 30.50 � QRBAN SUBAREA OVERLANp TIME OF FLOW(MINUTES} = 2.936 '�.y *CAIITION: SUBAREA SLOPE EXCEEDS COIINTY NOMOGRAPH DEFINITION. EXTRAPOLATION OF NOMOGRAPH IISED. '"� TIME OF'CONCENTRATION ASSUMED AS 6—MINUTES � 100 YEAR RAINFALL INTENSITY(INCH/HOUR) m 6.559 `y SUSAREA RUNOFF(CFS) a .38 TOTAL AREA(ACRES) _ .08 TOTAL RIINOFF(CFS) _ .38 � �j ****�1c�,F*�/c�,ir�F*�c�k�k**ic�tdr***it�c�IrsFit**�c,F**�k*�lc*irlciF***�rir�r�lr�c*i4*�Ir*iF�k�cir�r�cic�Ic�,F�c�k�,F�kiF**ic*�k,k�k*ir ;'ri FLOW PROCESS FROM NODE 4.00 TO NODE 4.00 IS CODE m 1 - ---------------------------------------------------------------------------- »»>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE««< � ��==��m��a�� m�v — —� ��a — — ,;, TOTAL NUMBER OF STREAMS � 3 � �' CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 2 ARE: TIME OF CONCENTRAT,ION(MIN.) = 6.00 �, RAINFALL INTENSiTY(INCH/HR) = 6.56 TOTAL STREAM AREA(ACRES) _ .08 PEP�K FLOW RATE(CFS) AT CONFLUENCE � .96 � � ac-k****�Ir�r***�k**�F�k**�k*�r*�r�r�lc***ir***�**�lr*�+F*iFilr�F*�lr�ic�r**ik*�k�F�Jr�lr�k�lt*****�k*�1c�1c�F�Fic�F**�k�Ic�F�Jr** � FLOW PROCESS FROM NOD& 5.00 TO NODE 6.00 IS CODE _. 21 AREA "E^ ROOH' AREA � ---------------------------------------------------------------------------- �� »»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««< S/ ��) SOIL CLASSIFICATION IS "D!' � INDUSTRIAL DEVELOPMENT .RIINOFF COEFFICIENT =.8700 (DIIE TO ROOF) `—�" INITIAL SUBAREA FLOW—LENGTH = 140.00 . �l �ta j , �; _ ' ,. , "� � UPSTREAM ELEVATION = 50.00 DOWNSTREAM ELEVATION = 49.00 ELEVATION DIFFERENCE - 1.00 URBAN SUBAREA OVERLAND TIME OF FLOW(MINUTES) = 3.574 TIME OF CONCENTRATION ASSIIMED AS 6-MINUTES 100 YEAR RAINFALL INTENSITY(INCH/HOIIR) � 6.559 � SUBAREI� RUNOFFjCFS) - 1.65 TOTAL AREA(ACRES) _ .29 TOTAL RUNOFF(CFS) = 1.65 � ; ., ` ************************�**,r********,r*************************************** � FLOW PROCESS FROM NODE 6.00 TO NODE' 4.00 IS CODE a 3 � g PIPE &'I�C7W � - `"' ---------------------------------------------------------------------------- »»>COMPUTE PIPEFLOW TRAVELTIME THRU SUBAREA««< ' »»>USING COMPUTER-ESTIMATED PIPESIZE (NON-PRESSURE FLOW) ««< ,� ! �� { 1 J ` � � �� _V �, ' � � 9 '-ti � 4 � `,, ;,� �� 'l �� _` ESTIMATED PIPE DIAMETER(INCH) INCREASED TO 10.000 DEPTH OF FLOW IN 10.0 INCH PIPE IS 1.8 INCHES PIPEFLOW VELOCITY(FEET/SEC.) = 9.2 � UPSTREAM NODE ELEVATION = 16.00 DOWNSTREAM NODE ELEVATION = 15.50 FLOWLENGTH(FEET) � 10.00 MANNING'S N - .011 ESTIMP,TED PIPE DIAMETER(INCH) m 10.00 NQMBER OF PIPES = PIPEFLOW THRQ SUBAREA(CFS) a 1.65 TRAVEL TIME(MIN.) m .02 TC(MIN.) = 6.02 1 ******************************************************�********�************ FLOW PROCESS F'ROM NODE 4.00 TO NODE 4.00 IS CODE = 1 ---------------------------------------------------------------------------- »»>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE««< »»>AND COMPIITE VARIOUS CONFLUENCED STREAM VALIIES««< _�_-��=�a-_____�--��_---��-_.�-�- ��a�n�-=�� TOTAL NUMBER OF STREAMS g 3 CONFLUENCE VALUES USED FOR INDEPENDENT STREAM 3 ARE: TIME OF CONCENTRATION(MIN.) = 6.02 RAINFALL INTENSITY(INCH/HR) � 6.55 TOTAL STREAM AREA(ACRES) � • .29 PEAK FLOW RATE(CFS) AT CONFLUENCE � 1.81 ** CONFLUENCE DATA ** STREAM RUNOFF Tc INTENSITY AREA NUMBER (CFS) (MIN.) (INCH/AODR) (ACRE) 1 .58 6.06 6.515 .13 2 .38 6.00 6.559 .OS 3 1.65 6.02 6.546 .29 RAINFAI,L INTENSITY AND TIME OF CONCENTRATION RATIO CONFLUENCE FORMULA USED FOR 3 STREAMS. ** PEAK FLOW RATE TABLE ** STREAM RUNOFF Tc INTENSITY NUMBER (CFS) (MIN.) (INCH/HOUR} 1 2.56 6.00 6.559 2 2.60 6.02 6.546 3 2.56 6.06 6.515 i _ COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS: �� PEAK FLOW RATE(CFS) s 2.60 Tc(MIN.) � 6.02 " TOTAL AREA(ACRES) _ .50 **************************************************************************** , FLOW PROCESS FROM NODE 4.00 TO NODE B.00 IS CODE = 3 -y PIPE &ZOW ---------------------------------------------------------------------------- ' � »»>COMPUTE PIPEFLOW TRAVELTINiE THRU SUBAREA««< , , »»>USING COMPUTER-ESTIMATED PIPESIZE (NON-PRESSURE FLOW) ««< - - -��_�,,.... Q�� - - �� _��_�� "� ESTiMATED PIPE DIAMETER(INCH) INCREASED TO 12.000 �; " DEPTH OF FLOW IN 12.0 INCH PIPE IS 2.1 INCHES - PIPEFLOW VELOCITY(FEET/SEC.) _� 11.2 UPSTREAM NODE ELEVATION a 15.50 � , DOWNSTREAM NODE ELEVATION = 8.00 '' FLOWLENGTH(FEET) m 90.00 MANNING'S N= .011 � ESTIMATED PIPE DIAMETER(INCH) a 10.00 NQMBER OF PIPES = 1 ,-, PIPEFLOW THRU SUBAREA(CFS) = 2.60 � j TRAVEL TIME (MIN. )_ . 13 TC (MIN. ).g 6. 15 ********************�**************************************************�**** ;�� FLOW PROCESS FROM NODE 8.00 TO NODE 8.00 IS CODE � 1 � r ---------------------------------------------------------------------------- �" »»>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE««< • TOTAL NUMBER OF STREAMS m 2 '_� CONFLIIENCE VALUES USED FOR INDEPENDENT STREAM 1 ARE: TIME OF CONCENTRATION(MIN.) s 6.15 RAINFALL INTENSITY(INCH/HR) � 6.45 � TOTAL STREAM AREA(ACRES) � .50 `� PEAK FLOW RATE(CFS) AT CONFLUENCE m 2.60 � , ******************,r********************************************************* �_� FLOW PROCESS FROM NODE 7.00 TO NODE � 8.00 IS CODE = 21 ARBA �� C �� , -- ---------------------------------------------�------------------------------- �I � �»»>RATIONAL NSETHOD INITIAL SUBAREA ANALYSIS««< ��-� -- _. _�-s��-�-��vm��=- -� ��_ ---- - - SOIL CLASSIFICATION IS "D" ' ' COI�IIrIERCIAL DEVELOPMENT RUNOFF COEFFICIENT = .7000 P INITIAL SIIBAREA FLOW-LENGTH = 195.00 . UPSTREAM ELEVATION m 38.00 --- DOWNSTREAM ELEVATION = 10.25 � ELEVATION DIFFERENCE = 27.75 . URBAN SIIBAREA OVERLAND TIME OF FLOW(MINUTES) - 2.593 *CAUTION: SUBAREA SLOPE EXCEEDB COUNTY NOMOGRAPH '`; DEFINITION. EXTRAPOLATION OF NOMOGRAPH IISED. � TIME OF CONCENTRATION ASSDMED AS 6-MINUTES 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 6.559 , SUBAREA RIINOFF(CFS) - .35 TOTAL AREA(ACRES) a .11 TOTAL RIINOFF(CFS) � .35 _� - **�*****�******************************************************************* ,�--; FLOW PROCESS FROM NODE 8.00 TO NODE 8.00 IS CODE � 1 iI ---------------------------------------------------------------------------- -' »»>DESIGNATE INDEPENDENT STREAM FOR CONFLUENCE««< � 't �, �! »»>AND COMPUTE VARIOUS CONFLUENCED STREAM VALIIES««< ; � -�o=�mamv - - ��Qv- ---� �= e==�=� � - TOTAL NIIMBER OF STREAMS = 2 { CONFLIIENCE VALUES USED FOR INDEPENDENT STREAM 2 ARE: � TIME OF CONCENTRATION(MIN.) = 6.00 _ RAINFALL INTENSITY(INCH/HR) = 6.56 TOTAL STREAM AREA(ACRES) _ .11 . T-- PEAK FLOW RATE(CFS) AT CONFLUENCE _ .59 ** CONFLUENCE DATA ** • STREAM RQNOFF Tc INTENSITY ARFA NLTMBER (CFS) (MIN.) (INCH/HOUR) • (ACRE) 1 2.60 6.15 6.454 .50 2 .35 6.00 6.559 .11 RAINFALL INTENSITY AND TIME OF CONCENTRATION RATIO CONFLUENCE FORMIILA USED FOR 2 STREAMS. , ' ** pEAK FLOW RATE TABLE ** � STREAM RUNOFF Tc INTENSITY " NUMBER (CFS) (MIN.) (INCH/HOIIR) � 1 2.91 6.00 6.559 ! 2 2.94 6.15 6.454 COMPUTED CONFLUENCE ESTIMATES ARE AS FOLLOWS: PEAK FLOW RATE(CFS) � 2.94 Tc(MIN.) m 6.15 TOTAL AREA(ACRES) _ .61 ***************************************+*************+********************** I FLOW PROCESS FROM NODE 8.00 TO NODE 9.00 IS CODE = 3 PIPE FLOW ---------------------------------------------------------------------------- - »»>COMPUTE PIPEFLOW TRAVELTIME THRQ SUBAREA««< y ! »»>USING COMPUTER-ESTIMATED PIPESIZE (NON-PRESSURE FLOW) ««< ESTIMATED PIPE DIAMETER(INCH) INCREASED TO 12.000 . r� DEPTH OF FLOW IN 12.0 INCH PIPE IS 2.1 INCHES � I PIPEFLOW VELOCITY(FEET/SEC.) = 27.4 . UPSTREAM NODE ELEVATION = 7.50 - DOWNSTREAM NODE ELEVATION � 7.00 I' FLOWLENGTH(FEET) = 5.00 MANNING'S N a .011 iJ ESTIMATED PIPE DIAMETER(INCH) - 10.00 NIIMBER OF PIPES � 1 PIPEFLOW THRU SUBAREA(CFS) = 2.94 TRAVEL TIME(MIN.) _ .00 TC(MIN.) = 6.15 I' _-�� -- ---�---��-�os�= _--- �_o�� - END OF STUDY SUI�FtY: PEAK F'LOW RATE(CFS) � 2.94 Tc(MIN.) - 6.15 �, �F TOTAL AREA(ACRES} _ .61 , a�am� �-a��omso �� e�-�- .-.��-� -- �- END OF RATIONAL METHOD ANALYSIS � ,- i ; I **************************************************************************** RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE Reference: SAN DIEGO COUNTY FLOOD CONTROL DISTRICT � 2003 HYDROLOGY MANUAL (c) Copyright 1982-2003 Advanced Engineering Software (aes) Ver. 1.5R Release Date: O1/O1/04 License ID 1462 ---------------------------------------------------------------------------- AREA "D" . FILE NAI�: CBCF2.DAT TIME/DATE OF STUDY:�16:38 5/18/2006 ---------------------------------------------------------------------------- USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION: ---------------------------------------------------------------------------- 1985 SAN DIEGO MANUAL CRITERIA • USER SPECIFIED STORM"EVENT(YEAR) = 100..00 ' 6-HOIIR DIIRATION PRECIPITATION (INCHES) a 2.800 �- SPECIFIED MINIMIIM PIPE SIZE(INCH) � 10.00 SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO USE FOR FRICTION SLOPE _.95 , SAN DIEGO HYDROLOGY.MANUAL "C"-VALUES USED NOTE: ONLY PEAK CONFLUENCE VALIIES CONSIDERED � ****************************************'************************************ '�� FLOW PROCESS FROM NODE 10.00 TO NODE 11.00 IS CODE = 21 --=-----------------=------------------------------------------------------- , »»>RATIONAL METHOD INITIAL SUBAREA ANALYSIS««< � � � � — -_--� - _ -- � SOIL CLASSIFICATION IS "D" • COI�RCIAL DEVELOPI�NT RUNOFF COEFFICIENT = .7000 INITIAL SUBAREA F'LOW-LENGTH a 290.00 . � UPSTREAM ELEVATION = 50.00 DOWNSTREAM ELEVATION = 6.00 - �- ELEVATION DIFFERENCE = 44.00 URBAN SUBAREA OVERLAND TIME OF FLOW(MINUTES) � 3.096 *CAUTION: SUBAREA.SLOPE EXCEEDS COUNTY NOMOGRAPH DEFINITION. EXTRAPOLATION OF NOMOGRAPH USED. TII� OF CONCENTRATION ASSUMED AS 6-MINOTES � 100 YEAR RAINFALL INTENSITY(INCH/HOUR) = 6.559 SUBAREA RUNOFF(CFS) = 0.83 -- TOTAL AREA(ACRES) _ .18 TOTAL RUNOFF(CFS) = 0.83 ', ' e�- - � - o�m��e�� a�� J END OF STUDY SUMMARY: PEAK FLOW RATE(CFS) � 0.83 Tc(MIN.) � 6.00 � TOTAL AREA(ACRES) _ .18 �� END OF RATIONAL METHOD ANALYSIS i -i � ` ********************�******************************************************* RATIONAL METHOD HYDROLOGY COMPUTER PROGRAM PACKAGE Reference: SAN DIEGO COUNTY FLOOD CONTROL DISTRICT 2003 HYDROLOGY MANQAL (c) Copyright 1982-2003 Advanced �ngineering Software (aes) Ver. 1.5A Release Date: O1/O1/04 License ID 1462 �, ---------------------------------------------------------------------------- • p� ��.n . , FILE NAME: CBCF2.DAT � TIME/DATE OF STUDY: 16:38 5/18/2006 I ---------------------------------------------------------------------------- USER SPECIFIED HYDROLOGY AND HYDRAULIC MODEL INFORMATION: � ---------------------------------------------------------------------------- � 1985 SAN DIEGO MANUAL CRITERIA - USER SPECIFIED STORM EVENT(YEAR) � 100.00 �� 6-HOUR DURATION PRECIPITATION (INCHES)�= 2.800 !-_ SPECIFIED MINIMIIM PIPE SIZE(INCH) = 10.00 SPECIFIED PERCENT OF GRADIENTS(DECIMAL) TO QSE FOR FRICTION SLOPE _.95 SAN DIEGO HYDROLOGY MANIIAL "C"-VALUES IISED �; NOTE: ONLY PEAK CONFLUENCE VALUES CONSIDERE'D , ***********+*********************************************************+****** ! FLOW PROCESS FROM NODE 12.00 TO NODE 13.00 IS CODE � 21 , ---------------------------------------------------------------------------- �-, »»>RATIONAL I�THOD INITIAL SUBAREA AAIALYSIS««< � ��m�oa�� _ _ - ��vm� —��_� - SOIL CLASS�IFICATION IS "D" - CO[�fERCIAL DEVELOPMENT RUNOFF COEFFICIENT �.6700 (50� OF AREA I3 SAIID) INITIAL SIIBAREA FLOW-LENGTH � 260.00 UPSTREAM ELEVATION � 11.00 DOWNSTREAM ELEVATION = 6.00 ,- ELEVATION DIFFERENCE � 44.00 '� IIRBAN SIIBAREA OVERLAND TIME OF FLOW{MINIITES) = 3.096 '- *CAUTION: .SUBAREA SLOPE EXCEEDS COUNTY NOMOGRA.PH DEFINITION. EXTRAPOLATION OF IdOMOGRAPH IISED. TIME OF CONCENTRATION ASSUMED AS 6-MINUTES ! 100 YEAR RAINFALL INTENSITY(INCH/HOIIR) = 6.559 SUBAREA RDNOFF(CFS) = 0.48 ,_ TOTAL AREA(ACRES) � .11 TOTAL RUNOFF(CFS) � 0.48 i=- ��_-- m -- �a ��a�=---_._.------��@- - ' END OF STUDY SUMMARY: PEAK FLOW RATE(CFS) - 0.51 Tc(MIN.).� 6.00 � TOTAL AREA(P;CRES) Q .11 ' � �aa�=a�� _�� -- - �a��e �x�� -�� END OF RATIONAL NIETHOD ANA.LYSIS • , I i I � �� A.PPENDIX F Hydraulic Calcnlations ,I Carlsbad Boat Club Onsite Drainage Calculations The purpose of these calculations is to show that the two curb i.nlets along the westerly driveway � are adequately sized and will intercept the run off generated by a 100-year storm even� Below aze the calculations for the curb inlets. The site is drained from the curb i.nlets via 12-inch and 10" SCH-40 PVC at slope that varies , between 2%and 2.6%. The pipe flow table below verifies that the proposed pipes carrying the runoff can convey the flow generated by a 100-yeai event in open channel flow. CURB INLET CALCULATIONS: CHECK INLET LENGTH SEE TABLE ON TI� FOLLOWIlIG PAGE FOR CURB INLET LINGTH CAL,CULATIONS Per figure 7-832.9A (following page) and using a flow of 0.58 cfs & a slope of 19% the required inlat length is 3.5 fee� Use a standard curb inlet with an opening of 4.0 feet PIPE FLOW CALCULATIONS: � CHECK PIPE FLOW CIRCULAR PIPB CAPAGTTY CHECK DIAMETER No.OF MANNING �. ��E u 1.0 1 0.011 1,0 1 0.011 0.83 1 0.011 FLOW � 0.58 2.60 1.65 DEPTH �. 0.21 0.46 0.32 SLOPE i1s� 2.00 2.00 2.60 VELOCTI'Y � 4.83 7.33 7.22 RIP-RAP SIZING CALCULATION5: Per figure 19.7 (followi.ng pages) and using e�t velocity of 7.33 fps the required rip-rap sizing '! should be No. 2 backiug rock approximately 1.0 feet thick with a 1" aggregate base and filter --' fabric •� i' � � � '' i 1 r 0.06 0.05 0.04 Q.03 o.ox l.� o.az� , .� � ,. �s m -� . �v � � o.oic �. 0.00, � } 0.�. � _ �� aoos 0.005 0.00 4 aow � �� Using a gutter depression � and intercepting the entire fiow t1i OTlE S . Frguro 7-832.9A Aapod, 1961 , . : LE.GEND . ^ CAUTION � ' 3oltd Un�s ■ 0.10' qutlsr depruaion �� , ' � Dasb Ltn�s �-- ■023' qvtter d�pn:ctoa applies aalj to stda ap�aira�s� � L■ Lanqth of opanlnq � • �� P�a(IeGnq tha dl�ectioeof theiatueipted tlaw • • If is basadop I.��perceaf pavement crau• ' . sbp� aad thq qutter depnasfaa uoss• slop• os ' • � shawo ia (Fiq.7-832.IOA1.� ' � _�� _��I�� . ��-5�1��_��0�� --■,��__��5��-■�� . ��1��1��►��i�v�� ►��o�►��s��■ . ��\�l�s►��\��1i1��N��s� -■.��.�� ,��■,� . ��e ��t�► , �� s�� 1 1 : . T . ,, � 1 , ��o►a��►i��i��a��■ ��1\�� ■� ■ l� ' i ■■ ��5'�0�� 1. . 1 - 11� ' ��I � � ��■ �� ,i� �l , ��1�l�■ ■.■`�,■■.s..�►..�►■■��.�■ .... �.... �,. ■ �, ��..■.�.■. �.o ■ ►�... � ■ ��►��o��n�r��a�a�■ ��s�l��tl��l�[f��s�l�! �-.■ ■�l._�■ ��. �. ■„�5.� ��1��►�L�t1��1��p -■� — � - , . � � � .� i - . 0.�Z l i �l 0.3 Q4 �.g Q6 0.7 QB 0,9 �.� I.S 2.� LO 3.0 4.� g.� s.� 8.� �0.� �� Capacity — Cubic Feet er Second � ,� ,� �� - _, �. _. . _. . _ . ... - - _ . 1 l_ � I �� _, ' -.•' ' i �. �, i � •� �200-1.6.1 Seleetibn of Riprap and F11ter ,' , • an e a -FRoM� - � SPECIAL PROV151�01V5 � REGtoNAL STD. SPECS_ '( �9d2) 200-1.6 • Stone for Rlprap (p. 69) Add: "Tha Indivlduai classes'of rocic� used fn slope protectlon shall conform to the follrn+ing: PERCFNTA(� IARGER THAN�` Fit�ker Blanket.(3) . Upper Layer(s) opt. t opt. z �el• Rodc Riprap Sec. Sec. l.ower Ft/Sec Class Th(dc- 200 400 Opt. 3 Layer (1) (Z) ness "'f^ .(4) (41 (S) (6) No. 3 � . ' Badc- 6-7 1ng ' .6 3/16" 'C2� D.G. — . No. 2 Back- � 7-8 i.ng; ', 1.0 1/4^ 83 O.G. �- Fac- ' 8-9.5 ing 1.4 3/8" -- D.G. -- , 3Y4", . 1 1 /2" 9.i-19 Llght 2.0 1/Z" -- �P.B. -- • 3/4", � 1/4 1 1/2" 11-#'3 Tart 2.7 3/4^ -- P.B. Sand �• , 1 3/4". ' 1%2 • 1 1/2" 13-15 Ton • 3.4 1" -- P.B. Sand � 15-17 1 Ton 4.3 1 1/Z" -- Type 8 Sand 17-ZO 2 Ton L S.4 2" -- Type B• Sand �- � • f . { i� Practica) usa of thls tabie is lim(ted to sltuatlorts *The arnount of materlal smaller than the smallest where "T" is less tfian D. . • _ size listed ln the table for any class of rock slope ' protectlon shalf not�exceed.the percqntage limit �1) Average yelocity In ptpe or bottom veloclty 1n Ifsted fn the table determl.ned on a�Ight basl�. energy dissipator, whlchever'1a greater. .� . CortQlience wifih the percentage Ilmit shorm in the � i. 'table tor all other slzes of the indlvldual pleces �Z� �f dest�ed rlprap and fi{ter blanket class Ts of arty, class of rodc slope protectlon shall be de- � q�ail,able, use next largei- class. _ -hermined by the retlo of the number of iridtvldual � �� ' �� pleces larger than the smalles't sfze ilsted in the (3) Filter bianket thidcnesa n 1 Focrt «- "T", xhich- table for that class. .• . ' '• ever fa less• ' •� • ' •(4) �tandard Speclflcatlons for Puhllc Morks Cor struction.� . . ' (7,) . D.G. =.Dfslntegrated Granite� 1 M�1 to 10 hT�l ' .•.P.B. n Processed'Miscellaneous Base- • � Type B a Type. 8 bedding materlal, (min Rnum 735� crushed•particlas, 100z passing 2 1/2^ sieve, � ' lOz'paasing 1" sleve) .. � •(6) Sand 79S retalned on /200 sleve. CLASSEI Rock 1/2. 1/4 No. Z No.'3 S1zes 2 Ton T Ton Ton Ton Badcing Bacicing 4 Ton �-5 � . 2 Ton 50-10� 0-5 . ` 1 Ton 93-100 SO-100 . 0-3 �• 1/Z Ton — 50-100 0-3 1/4 Ton 99-100 — 50-100 200 Ib 93-tOd — � 7g Ib 93-iQ0 0-5 25 Ib 25-73 0-5 S Ib 90-1Q0 25-73' 1 Ib 90-100 ,� !� FIGURE__1_9.7 III.304 '� � �_ I I .• � : ' � � .� 2D or 2'W {inin.) E1Af�� i�� r t t 0 � �ip� Ourtnnr � W� Bottom Widti� of Chartnil � � . . , b ' .5T (min.)' No: 4 Bu= r ' ' Flaw • - � B" wida siot � • . • �— .. ;; � q , ,� � � �, �-. ' � ` � `•L! ; •; x ..;. Ftt�r Blan kat : 'r-:;i. � �_ �� , ' .' .�• '��.j:,.i.! r!•�fi . •t. , :� ��•� �� . _. 3� Of � ' . . r . �' � 6" ' 5►71, Clsa 42QE•Z000 Cancrate � • A . � ' . . � SECTION A—A� PLAN. . ► ' � � � � - . . . • �NOTES: � � . . . ' . ' � . '1. Plxu sh�ll sp�dfy; , ' , . • • , • • • . . • . • • • . A) Rocic dsu ond thickneu ('i), � • Conaate ' 81 FiiUr antarial, number of I�yers �nd thicknea, Chartnd 0 or W 2 Rip np sh�ll bs �ith�r quarry smne ar brolan cnnrnn =-� ,�— . Gf shown an th� pl�ns,j Cobhla ue not lcnspta6le. • .\ '�4D mia. .� 3. RIp rap sf�ll b�•plaad mnr � ftlter blu�kst which' mav b� htfur granulu mst�rial or plastic filur clotf�. � "*' � 4. 5n scandard spadal provisioru fnr sal�ction ot �p csp _ 4. • t � CL , � �� 3(min�,) �nd filc.F bhnkat ,. _ ., w: --• .�,��.'�u �� . 5. fiiP r�P eestgy dlsapatars shall b� desgnaud a�ithv Al�u TYP� 1 ar Typ� Z Typi 1 sf�all h■ wittr canaau all; 2D or 2V11 TYpt 2 shsll bt withput siif. SECTION B -9 - � FIGU FzE i 9.� �' �' i • � . �cawc�ota n r� sru oiEaa $�qN DIEGO REG10NAl� STANDARD DRAWII�G� R""�0n By .Aopt� 0a� �� Ecwuu sr�ra►�os ccyw�E . S'iil,'filtar iK;D. iv-tz - l�l1'-�0�...L�O 4�. ins �'"�". "T` � . RIP. 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' � _ .. - , . . . �_1 .\ � , . \��,— i � \._ ;� - �/ ` �` � .��i : ��.. � � '\� i /��`\ \ `-\ ' � _ l 1 N� ft O J� 3 O 1 S�! 3�A� I 8 / . � t - i-i i;, � �\ .• ^=i ` . , . . - . . . }I�e J �1/ �� `.J� \ -� � . v . .i�f , �11 ``. ac° t- _ . . . %. �/ ��`\ `� ,/.c J'.3�? i , •-: .. �_.� `ifl ��' 2 r_ . .. . , : _ - -'-` --' - - -' � ' � .. . ;. _ . _ _ �. �. ..< . � ' - . . , ; a � . _..�._ . �.._._:. ....__...._ ..�. . . :' ' . . • � . � ". i � .: \ � � ~ ._ .� San Diego County Hydrology Manual Date: June 2003 . 3.1.3 RainfallIntensity Section: 3 Page: . 7 of 26 � The rainfall intensity (I) is the rainfall in inches per hour (in/hr) for a dur,ation equal to the T� - for a selected storm frequency. Once a particular storm frequency has been selected for ,, design and a T� calculated for the drainage area, the rainfall intensity can be determined from ��__ the Intensity-Duration Design Chart (Figure 3-1). The 6-hour storm rairifall amount (P6) and the 24-hour storm ra.infall amount (P24) for the selected storm frequency are also needed for � calculation of I. P6 and P24 can be read from the isopluvial maps provided in Appendix B. An Intensity-Duration Design Chart applicable to all a3�eas within San Diego County is i provided as Figure 3-l. Figure 3-2 pr.ovides an example of use of the Intensity-Duration Design Chart. Intensity can also be calculated using the following equation: �� I = 7.44 P6 D-o.6as 'Where: P6 = adjusted 6-hour storm rainfall amount (see discussion �elow) D= duration in minutes (use T�) ote: This equation applies only to the 6-hour storm rainfall amount (i.e., P6 cannot be changed to P24 to calculate a 24-hour intensity using this equation). The Intensity-Dura.tion Design Chart and the equation are for the 6-hour storm rainfall ; amount. In general, P6 for the selected frequency should be between 45% and 65% of P24 for � the selected frequency. If P6 is not within 45% to 65% of P24, P6 should be increased or � decreased as necessary to meet this criteria, The isopluvial lines are based on precipitation gauge data. At the time that the isopluvial lines were created, the majority of precipitation gauges in San Diego County were read daily, and these readings yielded 24-hour � precipita.tion data.. Some 6-hour data were available from the few recording gauges distributed throughout the County at that time; however, some 6-hour data were extrapolated. Therefore, the 24-hour precipitation data for San I7iego County are considered to be more reliable. � 3-7 • �i i � . 85�' PERTENTILE FLOWS � ;� � The chart is i.ncluded in this report, immediately followi.ng this page. The isopluvial for the site has a"P" value of 0.60 inches per hour (in/hr) for a storm. Flow for the 85�' percantile storm � would amount to: , I=7.44(P)(D)^-0645 �, - Where: I=lntansity P=0.60 �� i I�10 mi.nutes �; 1=�.aa��o6.0��10�^-o.�s I=1.01 in/hr ; . Q=C*I*A � � ; Where: C=0.70 � I=1.01 � , A�.90 Q=(o.�o�*�i.oi�*�o.90� �o.6a �� The run-off generated from the 85�' percenti.le storm will be treated by three mechanical methods: 1) Roof drai.ns will be passed t�rough a mechanical cleaning device to remove organics and hydrocarbons. . . 2) The run-off generated on the paved surfaces and landscape areas will pass through a gravel and sand filter before entering the curb i.nlet. 3) Run-off that has been filtered will then proceed t�uough the storm drain system and be allowed to settle and have additional filtration before dischargi.ng into the lagoon. � ;� 'i� � � ,- ,� 0 APPENDIX 6 Drainage Map