Loading...
HomeMy WebLinkAboutCT 06-12; La Palmas Drive Office Condominiums; Storm Water Quality; 2007-05-18STORM WATER MANAGEMENT PLAN For LAS PALMAS DRIVE OFFICE CONDOMINIUMS Prepared: May 18, 2007 JN 06-1177 Prepared By: O'DAY CONSULTANTS 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92010 Uk4 Timothy O. Carroll, Jr. RCE 55381 Date 12/31/08 1 G:\06n77\SWMP\Storm Water Management Plan-Las Palmas.doc 4 TABLE OF CONTENTS 1.0 PROJECT DESCRIPTION 3 1.1 Hydrologic Unit Contribution 3 1.2 Beneficial Uses 3 2.0 CHARACTERIZATION OF PROJECT RUNOFF 4 2.1 Soil Characteristics 4 2.2 Potential Discharges 4 3.0 MITIGATION MEASURES TO PROTECT WATER QUALITY 5 3.1 Site Design BMP's 5 3.2 Source Control BMP's 5 3.3 Individual Priority Project Categories 6 3.4 Treatment Control BMP's 6 3.5 Construction BMPs 7 4.0 MONITORING, INSPECTION, AND REPORTING 7 Attachments: 1. Vicinity map 2. Beneficial uses for the hydrologic unit 3. 303(D) list for impaired water bodies 4. Table 2: Anticipated and potential pollutants 5. Table 1: Storm Water BMP Requirements Matrix 6. Table 3: Numeric Sizing Treatment Standards 7. Table 4: Structural Treatment Control BMP Selection Matrix 8. Project site plan & BMP map 9. Source Control BMPs 10. Treatment Control BMPs 11. Bioclean Inlet Filter Information 2 G:\061177\SWMP\Storm Water Management Plan-Las Palmas.doc STORM WATER MANAGEMENT PLAN Federal, state and local agencies have established goals and objectives for storm water quality in the region. The proposed project, prior to the start of construction activities, will comply with all federal, state and local permits including the Stormwater Management Plan (SWMP) required under the County of San Diego Watershed Protection, Stormwater Management, and Discharge Control Ordinance (WPO) (section 67.871), the City of Carlsbad's Standard Urban Storm Water Mitigation Plan, and the National Pollution Discharge Elimination System (NPDES) from the Regional Water Quality Control Board (RWQCB). The purpose of this SWMP is to address the water quality impacts from the proposed improvements as shown on the Tentative Parcel Map. This project will provide guidehnes in developing and implementing Best Management Practices (BMPs) for storm water quality during construction and post construction. Since the site is not more than 1 acre, a Storm Water Pollution Prevention Plan (SWPPP) will not be required. 1.0 PROJECT DESCRIPTION The Las Palmas Drive Office Condominiums are proposed in the City of Carlsbad along Las Palmas Drive off of the intersection of Camino Via Roble and Las Palmas Drive (see Vicinity Map, attachment 1). Lot 6 of Carlsbad Tract 79-1 will be split from one office/warehouse building into ten condominiums. The site will include 35,947 S.F. building, landscaped area, and one outdoor employee eating area. 1.1 Hydrologic Unit Contribution The project is located in the Aqua Hedionda Hydrologic Subarea (904.31) of the San Marcos Watershed in the Carlsbad Hydrologic Unit in the San Diego Region. Under existing conditions, storm water runoff enters a drainage system and conveyed northeriy into Agua Hedionda creek. This subarea has a low priority impairment for bacteria and sediment. The proposed project will not alter the drainage discharge patterns on site. Since the proposed improvements consist of only a building conversion, the flows for the existing and the proposed conditions are the same. 1.2 Beneficial Uses The beneficial uses for the hydrologic unit are included in attachment 2, and the definitions are listed below. This information comes from the Water Quality Control Plan for the San Diego Basin. REC 1 -Contract Recreation: Includes uses of water for recreational activities involving body contact with water, where ingestion of water is reasonably possible. These uses include, but are 3 G:\061177\SWMP\Storm Water Management Plan-Las Palmas.doc not limited to, swimming, wading, water-skiing, skin and SCUBA diving, surfing, white water activities, fishing, or use of natural hot springs. REC 2 -Non-Contact Recreation: Includes the uses of water for recreational activities involving proximity to water, but not normally involving body contact with water, where ingestion of water is reasonably possible. These include, but are not limited to, picnicking, sunbathing, hiking, camping, boating, tide pool and marine life study, hunting, sightseeing, or aesthetic enjoyment in conjunction with the above activities. EST - Estuarine Habitat: Includes the uses of water that support estuarine ecosystems including, but not limited to, preservation or enhancement of estuarine habitats, vegetation, fish, or wildUfe (e.g., estuarine mammals, waterfowl, shorebirds). MAR -Marine Habitat: Includes uses of water that support marine ecosystems including, but not limited to, preservation or enhancement or marine habitats, vegetation such as kelp, fish, shellfish, or wildlife (e.g., marine mammals, shorebirds). WILD -Wildlife Habitat: Includes uses of water that support terrestrial ecosystems including but not limited to, preservation and enhancement of terrestrial habitats, vegetation, wildlife, (e.g., mammals, birds, reptiles, amphibians, invertebrates), or wildlife water food and sources. RARE - Rare, Threatened, or Endangered Species: Includes uses of water that support habitats necessary, at least in part, for the survival and successful maintenance of plant or animal species established under state or federal law as rare, threatened or endangered. MIGR -Migration of Aquatic Organisms: Includes uses of water that support habitats necessary for migration, acclimatization between fresh and salt water, or other temporary activities by aquatic organisms, such as anadromous fish. BIOL - Preservation of Biological Habitats of Special Significance: Includes uses of water that support designated areas or habitats, such as established refuges, parks, sanctuaries, ecological reserves, or Areas of Special Biological Significance (ASBS), where the preservation or enhancement of natural resources requires special protection. 2.0 CHARACTERIZATION OF PROJECT RUNOFF According to the California 2002 303(d) list published by the RWQCB (attachment 3), San Marcos Creek HA is an impaired water body associated with the direct stormwater discharge from this project. San Marcos Creek HA has low priority impairment for Bacteria indicators and sedimentation. 2.1 Soil Characteristics The project area consists entirely of soil group D. 2.2 Potential Discharges There is no sampling data available for the existing site condition. The project will contain some pollutants commonly found on similar developments that could affect water quality. The following list is taken from Table 2 of the City of Carlsbad's Storm Water Standards Manual (attachment 4). It includes anticipated pollutants for streets & parking lots. 4 G:\061177\SWMP\Storm Water Management Plan-Las Palmas.doc streets Nutrients from fertilizers Heavy metals Organic compounds Trash and debris Oxygen demanding substances Oil and grease from paved areas Pesticides from landscaping Parking Lots Nutrients from fertilizers Heavy metals Trash and debris Oxygen demanding substances Oil and grease from paved areas Pesticides from landscaping 3.0 MITIGATION MEASURES TO PROTECT WATER QUALITY To address water quality for the project, BMPs will be implemented during construction and post construction. Required BMPs are selected from Table 1: Storm Water BMP requirements Matrix along with Table 4: Structural Treatment Control BMP Selection Matrix, of the City of Carlsbad's Storm Water Standards Manual (attachments 5 & 7). 3.1 Site Design BMP's Control of post-development peak storm water runoff discharge rates and velocities is desirable in order to maintain or reduce pre-development downstream erosion by applying the following concepts (see attachment 6 for details): Development Clustering: Establishing planning areas in clusters accomplishes several desirable effects. Drainage systems service only developed areas reducing the amount of debris, siltation, and sedimentation associated with natural drainage courses. Natural drainage courses are preserved maintaining existing hydrologic regimes. Smaller basins are established with multiple distributed outlets minimizing flow concentrations Minimize Directly Connected Impervious Areas: To the maximum extent practicable, parking lots, sidewalks, patios, roof top drains, rain gutters, and other impervious surfaces shall drain into adjacent landscaping prior to discharging to the storm water conveyance system. Protect Slopes and Channels: All runoff will be safely conveyed away from the tops of slopes. 3.2 Source Control BMP's Source Control BMPs help minimize the introduction of pollutants into storm water in order to maintain or reduce pre-development levels of pollutants by applying the following concepts (see attachment 8 for details): G:\061177\SWMP\Storm Water Management Plan-Las Palmas.doc street Sweeping: Private parking lots and city maintained streets will be swept routinely in order to reduce introduction of trash, debris, sediment and siltation into drainage systems. Trash Storage Areas to Reduce Pollution Introduction: The areas will be paved with an impervious surface, graded to drain away from the enclosure, screened and walled to prevent off-site transport of trash. All trash containers shall contain attached lids that exclude rain or contain a roof or awning to minimize direct precipitation Use Efficient Irrigation Systems & Landscape Design: Irrigation systems shall employ rain shutoff devices to prevent irrigation during precipitation and be designed to each landscape area's specific water requirements consistent with the Carlsbad Landscape Manual Provide Storm Water Conveyance System Stenciling and Signage: All storm water conveyance inlets and catch basins shall provide concrete stamping, porcelain tile, inset permanent marking or equivalent as approved by the City of Carlsbad within the project area with prohibitive language satisfactory to the City Engineer. 3.3 Individual Priority Project Categories Surface Parking Areas: Where landscaping is proposed in surface parking areas (both covered and uncovered), incorporate landscape areas into the drainage design. 3.4 Treatment Control BMP's As identified in Table 1 (Attachment 5), a combination of treatment control BMP's shall be incorporated into this project in order to minimize pollutants of concern from entering the storm drain system. The project has been designed so that runoff is treated by Site Design BMP's prior to Structural Treatment BMP's. Treatment control BMP's were selected by comparing a list of pollutants for which the receiving water bodies are impaired to a list of expected pollutants for each basin. A combination of Landscaped Areas and Inlet Filters were chosen and will provide maximum pollutant removal efficiency for anticipated pollutants. The Treatment BMPs selected are shown on Attachment 9. Though all types of Treatment Control BMPs were considered for this project, the choices were very limited due to the fact that the site lies in an existing commercial lot with a set drainage pattern. Since the drainage pattern is already set, it would be very difficult to include detention or infiltration basins. With all of the interior usable lot already paved and being used as either parking or driveway space (with the exception of the small landscaped areas between the buildings), biofiltration would not be possible to install without committing some of the already used land as landscaped area. The surrounding area does not support placing a wet pond or wetlands on site. Hydrodynamic separator systems were not used because of their minimal gain compared to the high cost of installing the system. With the existing drainage pattern and the 6 G:\061 !77\SWMP\Storm Water Management Plan-Las Palmas.doc restrictions caused by the existing lot, retaining the existing landscaped areas and installing inlet filters are the best treatment control BMPs for this project. 3.5 Construction BMPs The following is a list of potential construction phase BMPs to be used. 1. Silt fence, fiber rolls, or gravel bag berms 2. Check dams 3. Street sweeping and vacuuming 4. Storm drain inlet protection 5. Stabilized construction entrance/exit 6. Vehicle and equipment maintenance, cleaning, and fueling 7. Hydroseed, soil binders, or straw mulch 8. Material delivery and storage 9. Stockpile management 10. Spill prevention and control 11. Waste management for solid, liquid, hazardous and sanitary waste, contaminated soil. 12. Concrete waste management 4.0 MONITORING, INSPECTION, AND REPORTING During construction, the BMPs will be monitored on a weekly basis, and observations recorded on the included checklists (see next page). The following will be responsible for the monitoring and maintenance of the BMPs: Ponto Associates 2221 Las Palmas Drive, Suite F Carlsbad, Ca 92011 Phone #: (760) 685-1700 7 G:\061177\SWMP\Storm Water Management Plan-Las Palmas.doc Attachment 1 CITY OF OCEANSfDE an OF VISTA NOT TO SCALE CITYa" SAN MARCOS PACIFIC OCEAN CITY CF ENCINITAS VICINITY MAP NOT TO SCALE Attachment 2 J02 CWA SECTION 303(d) LIST OF WAi R QUALITY LIMITED SEGMENT SAN DIEGO REGIONAL WATER QUALITY CONTROL BOARD July 2003 R£G10N TYPE NAM£ CALWATER WATERSHED POLLUTANT/STRESSOR FOTEimAL SOURCES TMDL PRIORITY ESTIMATED SIZE AFFECTED PROPOSED TMDL COMPLETION 9 R Agua Hedioada Creek 9 E Agua Hedionda Lagooo 9 R Aliso Creek 9 E Aliso Creek (mouth) 9 E Bueoa Vista Lagoon 90431000 90431000 90113000 90113000 90421000 Total Dissolved Solids Bacteria Indicators Sedimentatioa/SUtation Urban Runoff/Stonn Sewers Unknown Nonpoint Source Unknown point source Nonpoint/Point Source Nonp(Hnt/Point Source Bacteria Indicators Urban RunoffiStorm Sewers Unknown point source Nonpoint/Point Source Phosphorus Impairment located at lower 4 miles. Urban RunofS^Storm Sewers Unknown Nonpoint Source Unknown point source Toxicity Bacteria Indicators Bacteria Indicators Uriian RunofiyStonn Sewers Unknown Nonpoint Source Unknown point source Nonpoint/Point Source Low Low Low Medium Low Low Medium Low Nonpoint/Point Source Nutrient Low Estimated size of impairment is 150 acres located in upper portion of lagoon. Nonpoint/Point Source Sedimentation/Siltation Medium Nonpoint/Point Source 7 Miles 6.8 Acres 6.8 Acres 19 Miles 19 Miles 19 Miles 0.29 Acres 202 Acres 202 Acres 202 Acres Page 1 of 16 Attachment 3 1 Table 2-2. BENEFICIAL USES OF INLAND SURFACE WATERS BENEFICIAL USE Inland Surface Waters Hydrologic Unit Basin Number M U N A G R 1 N D P R 0 C G W R F R S H P 0 W R E C 1 R E C 2 B 1 0 L W A R M C 0 L D W 1 L D R A R E S P W N San Diego County Coastal Streams - continued Buena Vista Lagoon 4.21 See Coastal Waters-Table 2-3 Buena Vista Creek 4.22 + • • • • • • Buena Vista Creek 4.21 + • • • • • • • Agua Hedionda 4.31 See Coastal Waters-Table 2-3 Agua Hedionda Creek 4.32 • • • • m • • Buena Creek 4.32 • • • • m • • Agua IHedlonda Creek 4.31 • • • • • • • Letterbox canyon 4.31 • • • • • • • Canyon de las Encinas 4.40 + 0 • • • San Marcos Creek Watershed Batiquitos Lagoon 4.51 See Coastal Waters-Table 2-3 San Marcos Creek 4.52 + • • • • • unnamed Intermittent streams 4.53 + • • • • • San Marcos Creek Watershed San Marcos Creek 4.51 + • • • • • Enclnitas Creek 4.51 + • • • • • V Existing Beneficial Use O Potential Beneficial Use -f Excepted From MUN (See Text) Waterbodies are listed multiple times if they cross hydrologic area or sub area boundaries. Beneficial use designations apply to all tributaries to the indicated waterbody, if not listed separately. Table 2-2 BENEFICIAL USES 2-27 September 8, 1994 Attachment 4 storm Water Standards 4/03/03 III. PERMANENT BEST MANAGEMENT PRACTICES SELECTION PROCEDURE When referred to this Section, by Step 2 of Section II, complete the analysis required for your project in the subsections of Section III.1 below. 1. IDENTIFY POLLUTANTS & CONDITIONS OF CONCERN A. Identify Pollutants from the Project Area Using Table 1, identify the project's anticipated pollutants. Pollutants associated with any hazardous material sites that have been remediated or are not threatened by the proposed project are not considered a pollutant of concern. Projects meeting the definition of more than one project category shall identify all general pollutant categones that apply. Table 2. Anticipated and Potential Pollutants Generated by Land Use Type. Project Catsgories General Pollutant Categories Sediments Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Substances Oil& Grease Bacteria & Viruses Pesticides Detached Residential Development X X Attached Residential Development po) P(2) P(1) Commercial Development >100,000 ft2 po) pii) P(2} P(5) PO) P(5) Automotive Repair X('')(5) Restaurants Hillside Development >5,000 ft^ Parking Lots p(i) p(i) Streets, Highways & Freeways p(1)X X(^) p(i) P(5) PID X = anticipated P = potential (1) A potential pollutant if landscaping exists on-site. (2) A potential pollutant if the project includes uncovered paridng areas. (3) A potential pollutant if land use involves food or animal waste products. (4) Including petroleum hydrocarbons. (5) Including solvents. ^ . 12 Attachment 5 Storm Water Standards 4/03/03 Table 1. Standard Development Project & Priority Project Storm Water BMP Requirements Matrix standard Projects Site Design BMPsf^i R Source Control BMPs(2> R 0 BMPs Applicable to Individual Priority Project Categories'^ v> >^ m I Q g •a wj w a> 0) =3 cc: CD 0 0 0 O) 0 0 0 < cn Q_ -2 CD 0 0 Tfeafment Contro/ SMPsf^) 0 Priority Projects: Detached Residential Development Attached Residential Development Commercial Development >100,000 ft2 Automotive Repair Shop Restaurants Hillside Development >5,000 ^ Parking Lots Streets, Highways & Freeways R R R R R R R(5) R R = Required; select one or more applicable and appropriate BMPs from the applicable steps in Section III.2.A-D, or equivalent as identified in Appendix C. 0 = Optional/ or may be required by City staff. As appropriate, applicants are encouraged to incorporate treatment control BMPs and BMPs applicable to individual priority project categories into the project design. City staff may require one or more of these BMPs, where appropriate. S = Select one or more applicable and appropriate treatment control BMPs from Appendix C. (1) Refer to Section II1.2.A. (2) Refer to Section III.2.B. .. u. n • • * (3) Priority project categories must apply specific storm water BMP requirements, where applicable. Pnonty projects are subject to the requirements of all priority project categories that apply. (4) Refer to Section III.2.D. ^. u « (si Applies if the paved area totals >5.00Q square feet or with >15 parking spaces and is potentially exposed to urban runoff. 8 Attachment 6 storm Water Standards 4/03/03 Table 3. Numeric Sizing Treatment Standards. Volume 1 Volume-based SMPs shall be designed to mitigate (infiltrate, filter, or treat) the volume of runoff produced from a 24-hour 85'^ percentile storm event, as determined from isopluvtal maps contained in the County of San Diego Hydrology Manual. OR Flow 2 Flow-based BMPs shall be designed to mitigate (infiltrate, filter, or treat) the maximum flow rate of runoff produced from a rainfall intensity of 0.2 inch of rainfall per hour for each hour of a storm event. /. Structural Treatment BMP Selection Procedure Priority projects shall select a single or combination of treatment BMPs from the cateqories in Table 4 that maximize pollutant removal for the particular pollutant(s) of concern. Any pollutants the project is expected to generate that are also causing a Clean Water Act section 303(d) impairment of the downstream receiving waters of the project should be given top priority in selecting treatment BMPs. To select a structural treatment BMP using the Structural Treatment Control BMP Selection Matrix (Table 4). each priority project shall compare the list of Pflutants for which the downstream receiving waters are impaired (if any). According o the I9y« 303(d) listing, the Agua Hedionda Lagoon is impaired for sediment and siltation Buena Vista Lagoon also has impaired beneficial uses (aquatic life) due to high sedimentation/siltation. Portions of Carlsbad where construction sites have the potential to discharge into a tributary of a 303(d) or directly into a 303(d) water body or sites located within 200 feet of an ESA require additional BMP implementation These water bodies Include the Pacific Ocean, Buena Vista Lagoon. Encinas Creek, Agua Hedionda Lagoon, and Batiquitos Lagoon. Priority projects that are not anticipated to generate a pollutant for which the receiving water is Clean Water Act Section 303(d) Impaired shall select a single or combination of structural treatment BMPs from Table 4 that are effective for pollutant removal of the identified pollutants of concern determined to be most significant for the project. Selected BMPs must be effective for the widest range of pollutants of concern anticipated to be generated by a priority project (as identified in Table 1). Alternative storm water BMPs not identified in Table 4 may be approved at the discretion of the City Engineer, provided the alternative BMP is as effective in removal of pollutants of concern as other feasible BMPs listed in Table 4. 20 Attachment 7 storm Water Standards 4/03/03 Table 4. Structural Treatment Control BMP Selection Matrix. Pollutant of Concern Sediment Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Substances Bacteria Oil & Grease Pesticides Treafmenf Control BMP Categories Biofilters M M M U Detention Basins M M U Infiltration Basinst!) H M M U U Wet Ponds or Wetlands H M U U Drainage Inserts M Filtration M M M H U Hydrodynamic Separator Systems!^) M M (1) Including trenches and porous pavement. (2) Also known as hydrodynamic devices and baffle boxes. L: Low removal efficiency M: Medium removal efficiency H: High removal efficiency U: Unknown removal efficiency Sources: Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters (1993), National Stonnwater Best Management Practices Database (2001), and Guide for BMP Selection in Urban Developed Areas (2001). //. Restrictions on the Use of Infiltration Treatment BMPs 31 Treatment control BMPs that are designed to primarily function as infiltration devices shall meet the following conditions (these conditions do not apply to treatment BMPs which allow incidental infiltration and are not designed to pnmanly function as infiltration devices, such as grassy swales, detention basins, vegetated buffer strips, constructed wetlands, etc.): (1) urban runoff from commercia developments shall undergo pretreatment to remove both physical and chemical contaminants, such as sedimentation or filtration, prior to infiltration; (2) all dry weather flows shall be diverted from infiltration devices except for those non-storm water discharges authorized pursuant to 40 CFR 122.26(d)(2)(iv)(B)(1): diverted stream flows rising ground waters, uncontaminated ground water infiltration [as defined at 40 CFR 35.2005(20)] to storm water conveyance systems, uncontaminated pumped ground water, foundation drains, springs, water from crawl space pumps, footing drains, air conditioning condensation, flow from riparian habitats and wetlands, water line flushing, landscape irrigation, discharges from potable water sources other than water main breaks, irngation water, individual residential car washing, and dechlorinated swimming pool discharges; (3) pollution prevention and source control BMPs shall be implemented at a leve appropriate to protect groundwater quality at sites where infiltration structural treatment BMPs are to be used; (4) the vertical distance from the base of any infiltration structural treatment BMP to the seasonal high groundwater mark shall be at least 10 feet. Where groundwater does not support beneficial uses, this vertical distance criterion may be reduced, provided groundwater quality is maintained- (5) the soil through which infiltration is to occur shall have physical and 21 Attachment 8 Attachment 9 Site Design & Landscape Planning SD-10 Design Objectives Maximize Infiltration Provide Retention Slow Runoff Minimize Impervious Land Coverage Prohibit Dumping of Improper Materials Contain Pollutants Collect and Convey Description Each project site possesses unique topographic, hydrologic, and vegetative features, some of which are more suitable for development than others. Integrating and incorporating appropriate landscape planning methodologies into the project design is the most effective action that can be done to minimize surface and groundwater contamination from stormwater. Approach Landscape planning should couple consideration of land suitability for urban uses with consideration of community goals and projected grovrth. Project plan designs should conserve natural areas to the extent possible, maximize natural water storage and infiltration opportunities, and protect slopes and channels. Suitable Applications Appropriate apphcations include residential, commercial and industrial areas planned for development or redevelopment. Design Considerations Design requirements for site design and landscapes planning should conform to applicable standards and specifications of agencies with jurisdiction and be consistent with applicable General Plan and Local Area Plan policies. Ute. ^ - LC ASQA California Stormwater Quality Association January 2003 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com 1 of 4 SD-10 Site Design & Landscape Planning Begin the development of a plan for the landscape unit with attention to the following general principles: . Formulate the plan on the basis of clearly articulated community goals. CarefuUy identify conflicts and choices between retaining and protecting desired resources and community growth. , Map and assess land suitability for urban uses^ Include the f''<'^-f'^^2l!^r " the assessment- wooded land, open unwooded land, steep slopes, eros on-prone soils, Sat oTsuUabm^^ soil suiiabilify for waste disposal, aquifers, aquifer recharge areas, rtlanis! flSlains surface waters, agricultural lands, and various categories of urban Tand use When appropriate, the assessment can highlight outstanding local or regional resources that the community determines should be protected (e.g., a scenic area, rrc"nal area, threatenedspecies habitat, farmland, fish run). Mapping and assessment TouTd recognize not only these resources but also additional areas needed for their sustenance. Proiect plan designs should conserve natural areas to the extent possible, maximize natural water storage and infiltration opportunities, and protect slopes and channels. Conserve Natural Areas during Landscape Planning Tf annUcable the following items are required and must be implemented in the site layout W dulg SMMI defign and approval process, consistent with applicable General Plan and Local Area Plan policies: . Cluster development on least-sensitive portions of a site while leaving the remaining land in a natural undisturbed condition. . Limit clearing and grading of native vegetation at a site to the minimum amount needed to build lots, allow access, and provide fire protection. . Maximize trees and other vegetation at each site by planting additional vegetation, clustering tree areas, and promoting the use of native and/or drought tolerant plants. . Promote natural vegetation by using parking lot islands and other landscaped areas. • Preserve riparian areas and wetlands. Maximize Natural Water Storage and Infiltration Opportunities Within the Landscape Unit . Promote the conservation of forest cover. Building on land that is already deforested affects bal hydrolorfo a lesser extent than converting forested land. Loss of forest cover reduces interception storage, detention in the organic forest floor layer, and water losses by evapranspiration, resulting in large peak runoff increases and either their negative effects or the expense of countering them with structural solutions. . Maintain natural storage reservoirs and drainage corridors, including depressions, areas of ,^ "able soils, swa^ Develop and implement policies and Site Design & Landscape Planning SD-10 regulations to discourage the clearing, filling, and channelization of these features. Utilize them in drainage networks in preference to pipes, culverts, and engineered ditches. • Evaluating infiltration opportunities by referring to the stormwater management manual for the jurisdiction and pay particular attention to the selection criteria for avoiding groundwater contamination, poor soils, and hydrogeological conditions that cause these facilities to fail. If necessary, locate developments vdth large amounts of impervious surfaces or a potential to produce relatively contaminated runoff away from groundwater recharge areas. Protection of Slopes and Channels during Landscape Design • Convey runoff safely from the tops of slopes. • Avoid disturbing steep or unstable slopes. • Avoid disturbing natural channels. • Stabilize disturbed slopes as quickly as possible. • Vegetate slopes with native or drought tolerant vegetation. • Control and treat flows in landscaping and/or other controls prior to reaching existing natural drainage systems. I V • Stabilize temporary and permanent channel crossings as quickly as possible, and ensure that increases in run-off velocity and frequency caused by the project do not erode the channel. • Install energy dissipaters, such as riprap, at the outlets of new storm drains, culverts, conduits, or channels that enter unlined channels in accordance with applicable specifications to minimize erosion. Energy dissipaters shall be installed in such a way as to minimize impacts to receiving waters. • Line on-site conveyance channels where appropriate, to reduce erosion caused by increased flow velocity due to increases in tributary impervious area. The first choice for linings should be grass or some other vegetative surface, since these materials not only reduce runoff velocities, but also provide water quality benefits from filtration and infiltration. If velocities in the channel are high enough to erode grass or other vegetative linings, riprap, concrete, soil cement, or geo-grid stabilization are other alternatives. • Consider other design principles that are comparable and equally effective. Redeveloping Existing Installations Various jurisdictional stonnwater management and mitigation plans (SUSMP, WQMP, etc.) define "redevelopment" in terms of amounts of additional impervious area, increases in gross floor area and/or exterior construction, and land disturbing activities with structural or impervious surfaces. The definition of " redevelopment" must be consulted to determine whether or not the requirements for new development apply to areas intended for redevelopment. If the definition applies, the steps outiined under "designing new installations" above should be followed. January 2003 California Stormwater BMP Handbook 3 of 4 New Development and Redevelopment www.cabmphandbooks.com SD-10 Site Design & Landscape Planning slow ZoffTed^ce i^^^^^^ a;eas: disconnect directly connected impervious areas. fMrnu^rtrs^dardUrban Stormwater Miti^^^^^^ Department of Public Works, May 2002. Stormwater Management Manual for Western Washington, Washington State Department of Ecology, August 2001. Model Standard Urban Storm Water Mitigation Plan (SUSMP) for San Diego County, Port of San Diego, and Cities in San Diego County, February 14, 2002. Ventura Countywide Technical Guidance Manual for Stonnwater Quality Control Measures, July 2002. 4 of 4 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com January 2003 Efficient Irrigation SD-12 Design Objectives Maximize Infiltration Provide Retention Slow Runoff Minimize Impervious Land Coverage Prohibit Dumping of Improper Materials Contain Pollutants Collect and Convey Description Irrigation water provided to landscaped areas may result in excess irrigation water being conveyed into stormwater drainage systems. Approach Project plan designs for development and redevelopment should include application methods of irrigation water that minimize runoff of excess irrigation water into the stormwater conveyance system. Suitable Applications Appropriate applications include residential, commercial and industrial areas planned for development or redevelopment. (Detached residential single-family homes are typically excluded from this requirement.) Design Considerations Designing New Installations The following methods to reduce excessive irrigation runoff should be considered, and incorporated and implemented where determined apphcable and feasible by the Permittee; • Employ rain-triggered shutoff devices to prevent irrigation after precipitation. • Design irrigation systems to each landscape area's specific water requirements. • Include design featuring flow reducers or shutoff valves triggered by a pressure drop to control 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. ^HkC A S Q A California Stormwater Quality Association January 2003 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandb00k5.com 1 of 2 SD-12 Efficient Irrigation Design timing and apphcation methods of irrigation water to minimize the runoff of excess irrigation water into the storm water drainage system. . Group plants with similar water requirements in order to reduce excess irrigation runoff and promote surface filtration. Choose plants with low irrigation requirements (for example, native or drought tolerant species). Consider design features such as: - Using mulches (such as wood chips or bar) in planter areas without ground cover to minimize sediment in runoff - Installing appropriate plant materials for the location, in accordance with amount of sunlight and climate, and use native plant materials where possible and/or as recommended by the landscape architect - Leaving a vegetative barrier along the property boundary and interior watercourses, to act as a pollutant filter, where appropriate and feasible - Choosing plants that minimize or eliminate the use of fertihzer or pesticides to sustain growth . Employ other comparable, equally effective methods to reduce irrigation water runoff. Redeveloping Existing Installations Various jurisdictional stormwater management and mitigation plans (SUSMP, WQMP, etc.) w define "redevelopment" in terms of amounts of additional impervious area, increases m gross floor area and/or exterior construction, and land disturbing activities with structural or impervious surfaces. The definition of " redevelopment" must be consulted to determine whether or not the requirements for new development apply to areas intended tor ^ redevelopment. If the definition applies, the steps outhned under "designmg new mstallations above should be followed. Other Resources . , ^ A Manual for the Standard Urban Stormwater Mitigation Plan (SUSMP), Los Angeles County Department of Pubhc Works, May 2002. Model Standard Urban Storm Water Mitigation Plan (SUSMP) for San Diego County, Port of San Diego, and Cities in San Diego County, February 14, 2002. Model Water Quality Management Plan (WQMP) for County of Orange, Orange County Flood Control District, and the Incorporated Cities of Orange County, Draft February 2003. Ventura Countywide Technical Guidance Manual for Stormwater Quality Control Measures, July 2002. storm Drain Signage SD-13 Design Objectives Maximize Infiltration Provide Retention Stow Runoff Minimize Impervious Land Coverage ^ Prohibit Dumping of Improper Materials Contain Pollutants Coilect and Convey Description Waste materials dumped into storm drain inlets can have severe impacts on receiving and ground waters. Posting notices regarding discharge prohibitions at storm drain inlets can prevent waste dumping. Storm drain signs and stencils are highly visible source controls that are typically placed directly adjacent to storm drain inlets. Approach The stencil or affixed sign contains a brief statement that prohibits dumping of improper materials into the urban 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 to the storm drain. Signs are appropriate in residential, commercial, and industrial areas, as well as any other area where contributions or dumping to storm drains is likely. Design Considerations Storm drain message markers or placards are recommended at all storm drain inlets within the boundary of a development project. The marker should be placed in clear sight facing toward anyone approaching the inlet from either side. All storm drain inlet locations should be identified on the development site map. Designing New Installations The following methods should be considered for inclusion in the project design and show on project plans: Provide stenciling or labehng of all storm drain inlets and catch basins, constructed or modified, within the project area with prohibitive language. Examples include "NO DUMPING - € ASOA California Stormwater Quality Association January 2003 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com 1 of 2 SD-13 Storm Drain Signage DRAINS TO OCEAN" and/or other graphical icons to discourage illegal dumping. . Post signs with prohibitive language and/or graphical icons, which prohibit illegal dumping at pubhc access points along channels and creeks within the project area. Note - Some local agencies have approved specific signage and/or storm drain message placards for use. Consult local agency stormwater staff to determine specific requirements for placard types and methods of application. Redeveloping Existing Installations Various jurisdictional stormwater management and mitigation plans (SUSMP, WQMP, etc.) define "redevelopment" in terms of amounts of additional impervious area, increases m gross floor area and/or exterior construction, and land disturbing activities with structural or impervious surfaces. Ifthe project meets the definition of "redevelopment .then the requirements stated under " designing new installations" above should be included m all project design plans. Additional Information Maintenance Considerations m Legibility of markers and signs should be maintained. If required by the agency with iurisdiction over the project, the owner/operator or homeowner's association should enter into a maintenance agreement with the agency or record a deed restriction upon the property title to maintain the legibility of placards or signs. Placement • Signage on top of curbs tends to weather and fade. . Signage on face of curbs tends to be worn by contact with vehicle tires and sweeper brooms. Supplemental Information Examples m Most MS4 programs have storm drain signage programs. Some MS4 programs will provide stencils, or arrange for volunteers to stencil storm drains as part of their outreach program. Other Resources A Manual for the Standard Urban Stormwater Mitigation Plan (SUSMP), Los Angeles County Department of Public Works, May 2002. Model Standard Urban Storm Water Mitigation Plan (SUSMP) for San Diego County, Port of San Diego, and Cities in San Diego County, February 14, 2002. Model Water Quality Management Plan (WQMP) for County of Orange, Orange County Flood Control District, and the Incorporated Cities of Orange County, Draft February 2003. Ventura Countywide Technical Guidance Manual for Stormwater Quality Control Measures, July 2002. Trash Storage Areas SD-32 Description Trash storage areas are areas where a trash receptacle (s) are located for use as a repository for solid wastes. Stormwater runoff fi-om areas where trash is stored or disposed of can be polluted. In addition, loose trash and debris can be easily transported by water or wind into nearby storm drain inlets, channels, and/or creeks. Waste handling operations that may be sources of stonnwater pollution include dumpsters, litter control, and waste piles. Approach This fact sheet contains details on the specific measures required to prevent or reduce pollutants in stormwater runoff associated with trash storage and handling. Preventative measures including enclosures, containment structures, and impervious pavements to mitigate spills, should be used to reduce the likelihood of contamination. Design Objectives Maximize Infiltration Provide Retention Slow Runoff Minimize Impervious Land Coverage Prohibit Dumping of Improper Materials y Contain Pollutants Collect and Convey Suitable Applications Appropriate applications include residential, commercial and industrial areas planned for development or redevelopment. (Detached residential single-family homes are typically excluded from this requirement.) Design Considerations Design requirements for waste handling areas are governed by Building and Fire Codes, and by current local agency ordinances and zoning requirements. The design criteria described in this tact sheet are meant to enhance and be consistent with these code and ordinance requirements Hazardous waste should be handled in accordance with legal requirements estabhshed in Title 22, California Code of Regulation. Wastes from commercial and industrial sites are typically hauled by either public or commercial carriers that may have design or access requirements for waste storage areas. The design catena in this fact sheet are recommendations 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 trash collection areas. Conflicts or issues should be discussed with the local agency. Designing New Installations Trash storage areas should be designed to consider the following structural or treatment control BMPs: • Design trash 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 run-on of ^CASQA • Make sure trash container areas are screened or walled to ^ prevent off-site transport of trash. ^^k" QuX" ^^^^ Association January 2003 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com 1 of 2 SD-32 Trash Storage Areas • Use lined bins or dumpsters to reduce leaking of liquid waste. • Provide roofs, awnings, or attached lids on all trash containers to minimize direct precipitation and prevent rainfall from entering containers. • Pave trash storage areas with an impervious surface to mitigate spills. • Do not locate storm drains in immediate vicinity of the trash storage area. • Post signs on all dumpsters informing users that hazardous materials are not to be disposed of therein. Redeveloping Existing Installations Various jurisdictional stormwater management and mitigation plans (SUSMP, WQMP, etc.) define "redevelopment" in terms of amounts of additional impervious area, increases in gross floor area and/or exterior construction, and land disturbing activities with structural or impervious surfaces. The definition of" redevelopment" must be consulted to determine whether or not the requirements for new development apply to areas intended for redevelopment. If the definition applies, the steps outlined under "designing new installations" above should be followed. Additional Information Maintenance Considerations The integrity of structural elements that are subject to damage (i.e., screens, covers, and signs) must be maintained by the owner/operator. Maintenance agreements between the local agency and the owner/operator may be required. Some agencies will require maintenance deed restrictions to be recorded of the property title. If required by the local agency, maintenance agreements or deed restrictions must be executed by the owner/operator before improvement plans are approved. Other Resources A Manual for the Standard Urban Stormwater Mitigation Plan (SUSMP), Los Angeles County Department of Public Works, May 2002. Model Standard Urban Storm Water Mitigation Plan (SUSMP) for San Diego County, Port of San Diego, and Cities in San Diego County, February 14, 2002. Model Water Quality Management Plan (WQMP) for County of Orange, Orange County Flood Control District, and the Incorporated Cities of Orange County, Draft February 2003. Ventura Countywide Technical Guidance Manual for Stormwater Quality Control Measures, July 2002. 2 of 2 California Stormwater BMP Handbook January 2003 New Development and Redevelopment www.cabmphandbooks.com Parking/Storage Area Maintenance SC-43 Objectives Cover Contain Educate Reduce/Minimize Product Substitution Description Parking lots and storage areas can contribute a number of substances, such as trash, suspended solids, hydrocarbons, oil and grease, and heavy metals that can enter receiving waters through stormwater runoff or non-stormwater discharges. The protocols in this fact sheet are intended to prevent or reduce the discharge of pollutants from parking/storage areas and include using good housekeeping practices, following appropriate cleaning BMPs, and training employees. Approach The goal of this program is to ensure stormwater pollution prevention practices are considered when conducting activities on or around parking areas and storage areas to reduce potential for pollutant discharge to receiving waters. Successful implementation depends on effective training of employees on applicable BMPs and general pollution prevention strategies and objectives. Pollution Prevention • Encourage alternative designs and maintenance strategies for impervious parking lots. (See New Development and Redevelopment BMP Handbook) • Keep accurate maintenance logs to evaluate BMP implementation. Targeted Constituents Sediment y Nutrients Trash ^ Metals / Bacteria Oil and Grease ^ Organics y ASQA lallfornfa Stormwater QualHy Association January 2003 Caiifornia Stormwater BMP Handbook Industrial and Commercial www.cabmphandbooks.com 1 of 4 SC-43 Parking/Storage Area l^aintenance Suggested Protocols General • Keep the parking and storage areas clean and orderly. Remove debris in a timely fashion. • Allow sheet runoff to flow into biofilters (vegetated strip and swale) and/or infiltration devices. • Utilize sand filters or oleophilic collectors for oily waste in low quantities. • Arrange rooftop drains to prevent drainage directiy onto paved surfaces. • Design lot to include semi-permeable hardscape. • Discharge soapy water remaining in mop or wash buckets to the sanitary sewer through a sink, toilet, clean-out, or wash area with drain. Controlling Litter • Post "No Littering" signs and enforce anti-litter laws. • Provide an adequate number of litter receptacles. • Clean out and cover litter receptacles frequently to prevent spillage. • Provide trash receptacles in parking lots to discourage litter. • Routinely sweep, shovel, and dispose of litter in the trash. Surface Cleaning m Use dry cleaning methods (e.g., sweeping, vacuuming) to prevent the discharge of pollutants into the stormwater conveyance system if possible. • Establish fi-equency of public parking lot sweeping based on usage and field observations of waste accumulation. • Sweep all parking lots at least once before the onset of the wet season. • Follow the procedures below if water is used to clean surfaces: - Block the storm drain or contain runoff. - Collect and pump wash water to the sanitary sewer or discharge to a pervious surface. Do not allow wash water to enter storm drains. - Dispose of parking lot sweeping debris and dirt at a landfill. • Follow the procedures below when cleaning heavy oily deposits: - Clean oily spots with absorbent materials. Use a screen or filter fabric over inlet, then wash surfaces. 2 of 4 California Stormwater BMP Handbook January 2003 Industrial and Commercial www.cabmphandbooks.com Parking/Storage Area Maintenance SC-43 (- Do not allow discharges to the storm drain. - Vacuum/pump discharges to a tank or discharge to sanitary sewer. - Appropriately dispose of spilled materials and absorbents. Surface Repair m Preheat, transfer or load hot bituminous material away from storm drain inlets. • Apply concrete, asphalt, and seal coat during dry weather to prevent contamination from contacting stormwater runoff. • Cover and seal nearby storm drain inlets where applicable (with waterproof material or mesh) and manholes before applying seal coat, slurry seal, etc. Leave covers in place until job is complete and all water from emulsified oil sealants has drained or evaporated. Clean any debris from these covered manholes and drains for proper disposal. • Use only as much water as necessary for dust control, to avoid runoff. • Catch drips from paving equipment that is not in use with pans or absorbent material placed under the machines. Dispose of collected material and absorbents properly. Inspection m Have designated personnel conduct inspections of parking facilities and stormwater ^ •W^ conveyance systems associated with parking facilities on a regular basis. • Inspect cleaning equipment/sweepers for leaks on a regular basis. Training • Provide regular training to field employees and/or contractors regarding cleaning of paved areas and proper operation of equipment. • Train employees and contractors in proper techniques for spill containment and cleanup. 5pi/{ Jiesponse and Prevention • Keep your Spill Prevention Control and Countermeasure (SPCC) Plan up-to-date. • Place a stockpile of spill cleanup materials where it will be readily accessible or at a central location. • Clean up fluid spills immediately with absorbent rags or material. • Dispose of spilled material and absorbents properly. Other Considerations Limitations related to sweeping activities at large parking facilities may include high equipment costs, the need for sweeper operator training, and the inability of current sweeper technology to remove oil and grease. January 2003 California Stormwater BMP Handbook 3 of 4 Industrial and Commercial www.cabmphandbooks.com SC-43 Parking/Storage Area Maintenance Requirements Costs Cleaning/sweeping costs can be quite large. Construction and maintenance of stormwater structural controls can be quite expensive as well. Maintenance • Sweep parking lot regularly to minimize cleaning with water. • Clean out oil/water/sand separators regularly, especially after heavy storms. • Clean parking facilities regularly to prevent accumulated wastes and pollutants from being discharged into conveyance systems during rainy conditions. Supplemental Information Further Detail of the BMP Surface Repair Apply concrete, asphalt, and seal coat during dry weather to prevent contamination from contacting stormwater runoff. Where apphcable, cover and seal nearby storm drain inlets (with waterproof material or mesh) and manholes before applying seal coat, slurry seal, etc. Leave covers in place until job is complete and all water from emulsified oil sealants has drained or evaporated. Clean any debris from these covered manholes and drains for proper disposal. Only use only as much water as is necessary for dust control to avoid runoff. ^ References and Resources California's Nonpoint Source Program Plan http://www.swrcb.ca.gov/nps/index.html Clark County Storm Water Pollution Control Manual http://www.co.clark.wa.us/pubworks/bmpman.pdf King County Storm Water Pollution Control Manual http://dnr.metrokc.gov/wlr/dss/spcm.htm Pollution from Surface Cleaning Folder. 1996. Bay Area Stormwater Management Agencies Association (BASMAA). http://www.basmaa.org/ Oregon Association of Clean Water Agencies. Oregon Municipal Stormwater Toolbox for Maintenance Practices. June 1998. Santa Clara Valley Urban Runoff Pollution Prevention Program http: / /www, scvurppp.org The Storm Water Managers Resource Center http://www.stormwatercenter.net/ 4 of 4 California Stormwater BMP Handbook January 2003 Industrial and Commercial www.cabmphandbooks.com Drainage System Maintenance SC-44 Objectives Cover Contain Educate Reduce/Minimize Description As a consequence of its function, the stormwater conveyance system collects and transports urban runoff and stormwater that may contain certain pollutants. The protocols in this fact sheet are intended to reduce pollutants reaching receiving waters through proper conveyance system operation and maintenance. Approach Pollution Prevention Maintain catch basins, stormwater inlets, and other stormwater conveyance structures on a regular basis to remove pollutants, reduce high pollutant concentrations during the first flush of storms, prevent clogging of the downstream conveyance system, restore catch basins' sediment trapping capacity, and ensure the system functions properly hydraulically to avoid flooding. Suggested Protocols Catch Basins/Inlet Structures m Staff should regularly inspect facilities to ensure compliance with the following: Immediate repair of any deterioration threatening structural integrity. - Cleaning before the sump is 40% full. Catch basins should be cleaned as frequently as needed to meet this standard. - Stenciling of catch basins and inlets (see SC34 Waste Handling and Disposal). Targeted Constituents Sediment Nutrients Trash Metals Bacteria Oil and Grease Organics ASOA illfornia Stormwater Quality Association January 2003 California Stormwater BMP Handbook Industrial and Commercial www.cabmphandbooks.com 1 of 6 SC-44 Drainage System Maintenance • Clean catch basins, storm drain inlets, and other conveyance structures before the wet season to remove sediments and debris accumulated during the summer. • Conduct inspections more frequentiy during the wet season for problem areas where sediment or trash accumulates more often. Clean and repair as needed. • Keep accurate logs of the number of catch basins cleaned. • Store wastes collected from cleaning activities of the drainage system in appropriate containers or temporary storage sites in a manner that prevents discharge to the storm drain. • Dewater the wastes if necessary with outflow into the sanitary sewer if permitted. Water should be treated with an appropriate filtering device prior to discharge to the sanitary sewer. If discharge to the sanitary sewer is not allowed, water should be pumped or vacuumed to a tank and properly disposed. Do not dewater near a storm drain or stream. Storm Drain Conveyance System • Locate reaches of storm drain with deposit problems and develop a flushing schedule that keeps the pipe clear of excessive buildup. • Collect and pump flushed effluent to the sanitary sewer for treatment whenever possible. Pump Stations m Clean all storm drain pump stations prior to the wet season to remove silt and trash. • Do not allow discharge to reach the storm drain system when cleaning a storm drain pump station or other facility. • Conduct routine maintenance at each pump station. • Inspect, clean, and repair as necessary all outlet structures prior to the wet season. Open Channel • Modify storm channel characteristics to improve channel hydraulics, increase pollutant removals, and enhance channel/creek aesthetic and habitat value. • Conduct channel modification/improvement in accordance with existing laws. Any person, government agency, or public utility proposing an activity that vrill change the natural (emphasis added) state of any river, stream, or lake in California, must enter into a Steam or Lake Alteration Agreement with the Department of Fish and Game. The developer-applicant should also contact local governments (city, county, special districts), other state agencies (SWRCB, RWQCB, Department of Forestry, Department of Water Resources), and Federal Corps of Engineers and USFWS. Illicit Connections and Discharges • Look for evidence of illegal discharges or illicit connections during routine maintenance of conveyance system and drainage structures: Is there evidence of spills such as paints, discoloring, etc? 2 of 6 California Stormwater BMP Handbook January 2003 Industrial and Commercial www.cabmphandbooks.com Drainage System Maintenance SC-44 - Are there any odors associated with the drainage system? - Record locations of apparent illegal discharges/ilhcit connections? - Track flows back to potential dischargers and conduct aboveground inspections. This can be done through visual inspection of upgradient manholes or alternate techniques including zinc chloride smoke testing, fluorometric dye testing, physical inspection testing, or television camera inspection. - Eliminate the discharge once the origin of flow is established, • Stencil or demarcate storm drains, where applicable, to prevent illegal disposal of pollutants. Storm drain inlets should have messages such as "Dump No Waste Drains to Stream" stenciled next to them to warn against ignorant or intentional dumping of pollutants into the storm drainage system. • Refer to fact sheet SC-io Non-Stormwater Discharges. Illegal Dumping m Inspect and clean up hot spots and other storm drainage areas regularly where illegal dumping and disposal occurs. • EstabHsh a system for tracking incidents. The system should be designed to identify the following: - Illegal dumping hot spots - Types and quantities (in some cases) of wastes - Patterns in time of occurrence (time of day/night, month, or year) - Mode of dumping (abandoned containers, "midnight dumping" from moving vehicles, direct dumping of materials, accidents/spills) Responsible parties • Post "No Dumping" signs in problem areas with a phone number for reporting dumping and disposal. Signs should also indicate fines and penalties for illegal dumping. • Refer to fact sheet SC-io Non-Stormwater Discharges. Training • Train crews in proper maintenance activities, including record keeping and disposal. • Allow only properly trained individuals to handle hazardous materials/wastes. • Have staff involved in detection and removal of illicit connections trained in the following: - OSHA-required Health and Safety Training (29 CFR 1910.120) plus annual refresher training (as needed). January 2003 California Stormwater BMP Handbook 3 of 6 Industrial and Commercial www.cabmphandbooks.com SC-44 Drainage System Maintenance - OSHA Confined Space Entry training (Cal-OSHA Confined Space, Title 8 and Federal OSHA 29 CFR 1910.146). - Procedural training (field screening, samphng, smoke/dye testing, TV inspection). .Spitz Response and Prevention • Investigate all reports of spills, leaks, and/or illegal dumping promptly. • Clean up all spills and leaks using "dry" methods (with absorbent materials and/or rags) or dig up, remove, and properly dispose of contaminated soil. • Refer to fact sheet SC-11 Spill Prevention, Control, and Cleanup. Other Considerations (Limitations and Regulations) u Clean-up activities may create a shght disturbance for local aquatic species. Access to items and material on private property may be limited. Trade-offs may exist between channel hydraulics and water quality/riparian habitat. If storm channels or basins are recognized as wetlands, many activities, including maintenance, may be subject to regulation and permitting. • Storm drain flushing is most effective in small diameter pipes (36-inch diameter pipe or less, depending on water supply and sediment collection capacity). Other considerations associated with storm drain flushing may include the avaflability of a water source, finding a downstream area to collect sediments, liquid/sediment disposal, and prohibition against disposal of flushed effluent to sanitary sewer in some areas. • Regulations may include adoption of substantial penalties for illegal dumping and disposal. • Local municipal codes may include sections prohibiting discharge of soil, debris, refuse, hazardous wastes, and other pollutants into the storm drain system. Requirements Costs • An aggressive catch basin cleaning program could require a significant capital and O&M budget. • The elimination of illegal dumping is dependent on the availability, convenience, and cost of alternative means of disposal. The primary cost is for staff time. Cost depends on how aggressively a program is implemented. Other cost considerations for an illegal dumping program include: - Purchase and installation of signs. - Rental of vehicle(s) to haul illegally-disposed items and material to landfills. - Rental of heavy equipment to remove larger items (e.g., car bodies) from channels. - Purchase of landfill space to dispose of illegally-dumped items and material. 4 of 6 California Stormwater BMP Handbook January 2003 Industrial and Commercial www.cabmphandbooks.com Drainage System Maintenance SC-44 • Methods used for illicit connection detection (smoke testing, dye testing, visual inspection, and flow monitoring) can be costiy and time-consuming. Site-specific factors, such as the level of impervious area, the density and ages of buildings, and type of land use wiU determine the level of investigation necessary. Maintenance • Two-person teams may be required to clean catch basins with vactor trucks. • Teams of at least two people plus administrative personnel are required to identify iUicit discharges, depending on the complexity of the storm sewer system. • Arrangements must be made for proper disposal of collected wastes. • Technical staff are required to detect and investigate illegal dumping violations. Supplemental Information Further Detail of the BMP Storm Drain Flushing Flushing is a common maintenance activity used to improve pipe hydraulics and to remove pollutants in storm drainage systems. Flushing may be designed to hydraulically convey accumulated material to strategic locations, such as an open channel, another point where flushing wiU be initiated, or the sanitary sewer and the treatment facilities, thus preventing resuspension and overflow of a portion of the solids during storm events. Flushing prevents "plug flow" discharges of concentrated pollutant loadings and sediments. Deposits can hinder the designed conveyance capacity of the storm drain system and potentially cause backwater conditions in severe cases of clogging. Storm drain flushing usually takes place along segments of pipe with grades that are too flat to maintain adequate velocity to keep particles in suspension. An upstream manhole is selected to place an inflatable device that temporarily plugs the pipe. Further upstream, water is pumped into the line to create a flushing wave. When the upstream reach of pipe is sufficiently fiall to cause a flushing wave, the inflated device is rapidly deflated with the assistance of a vacuum pump, thereby releasing the backed up water and resulting in the cleaning of the storm drain segment. To further reduce impacts of stormwater pollution, a second inflatable device placed well downstream may be used to recollect the water after the force of the flushing wave has dissipated. A pump may then be used to transfer the water and accumulated material to the sanitary sewer for treatment. In some cases, an interceptor structure may be more practical or required to recollect the flushed waters. It has been found that cleansing efficiency of periodic flush waves is dependent upon flush volume, flush discharge rate, sewer slope, sewer length, sewer flow rate, sewer diameter, and population density. As a rule of thumb, the length of line to be flushed should not exceed 700 feet. At this maximum recommended length, the percent removal efficiency ranges between 65- 75% for organics and 55-65% for dry weather grit/inorganic material. The percent removal efficiency drops rapidly beyond that. Water is commonly supplied by a water track, but fire hydrants can also supply water. To make the best use of water, it is recommended that reclaimed water be used or that fire hydrant line flushing coincide with storm sewer flushing. January 2003 California Stormwater BMP Handbook 5 of 6 Industrial and Commercial www.cabmphandbooks.com SC-44 Drainage System Maintenance References and Resources California's Nonpoint Source Program Plan http://www.swrcb.ca.gov/nps/index.html Clark County Storm Water Pollution Control Manual http://www.co.clark.wa.us/puhworks/bmpman.pdf Ferguson, B.K. 1991. Urban Stream Reclamation, p. 324-322, Journal of Soil and Water Conservation. King County Storm Water Pollution Control Manual http://dnr.metrokc.gov/wlr/dss/spcm.htm Oregon Association of Clean Water Agencies. Oregon Municipal Stormwater Toolbox for Maintenance Practices. June 1998. Santa Clara Valley Urban Runoff Pollution Prevention Program http://www.scvurppp.org The Storm Water Managers Resource Center http://www.stormwatercenter.net United States Environmental Protection Agency (USEPA). 2002. Pollution Prevention/Good Housekeeping for Municipal Operations Storm Drain System Cleaning. On line: http://www.epa.gQv/npdes/menuofbmps/poll i6.htm 6 of 6 California Stormwater BMP Handbook Industrial and Commercial www.cabmphandbooks.com January 2003 Landscape Malntena«^^ DwcriptkMi Targatad Conatltuantg Sedfanenl ' ' 7" Nutrtend / Tmh / Metali Sacterii OlandGreaM SSSSnS£?hSir'*^r*^ AH of the* ?"? dnUn system by Approach i>iolfutfon JVeventfon , and chemical tools. ' SzhS,';;f properly timed January 2003 landscape Maint-Pnan^^a Suggested Protocoh Mowing, Tirbnmbm, and Weeding TaasMuiddirab.. ^^"**«="^^"^«''P»»«ngustaglo;i maintenance ^ ^^°''"'*~"™('"'«««»managemantsecaonrfthb&ct PtanHng " Jl^'^SSSS^fa^^ fimcHon. importance) presenrtng vegetation a^^lSStentS^ betv*- irrigatloa. fertllfeer) than planting .^^Ja^a^ ''^ ' ^ ««ai„tenance (e.g., - ConsiderusinglowwaterusegroundcoverswhenpUntingorreplanting. WastB Management 2 of 5 .T^^-.-.-j,,,„^_.^. California SCormwater BMP Handbnnk Landscape Maintananra Jrrfgatfon • Whewpractical,useautomattetImerstomiiiiniizemnoff. . Appbr»r«eratrate.thatdonotexceedth.inflltrattonratoofthe8oa. FertlHxer and Psfricida Afanaoement sho.dbedla.afect^J?aX"t'^^^^^^^ - «-»---Ua„db.rdscanbee.cludedusi„gfence..„ettin,t.et.™kguard^^ 3pider.thatpr;;rSrS;J^^^^^^^^^ January 2003 California Scormwatar aMP H;inHh,ini- ^'^3 Landscape Naintananca • Use pesticidefl only if there is an actual pest problem (not on a regular preventative schedule). 9 Do not use pesticides if raia is expected. Apply pesticides onty when wind speeds are low Gess than 5 mph). • Do not mix or prepare pesticides for application near storm drains. • PrepaieflieminJmumamourtofpestiddeneededforthejobandusetheteweatratefe^ win «^»ctivi^ oontral tlie pest > EnylgrtechnicmestoailnimiMoff-ta^ indndlng conridaratlon of alternative appHgnHnn h^lin<«pi«^ m FatdUzersshouUbaworiorflntothesottraflw * Calibrate fertilizer and pesticide appUcatioa equipment to avoid excess^ • Periodically test soila for determining proper fertilizer use. wweep pavement and ddewalk if fertilizer is spitted on these aur^ xrlgatlon water. vtfj^m - P«rehj«onlyttoanaount^^ (montii or year depending on liie product). • ^^J^^l^^^' ^ ^ ^ product Dispose of unused pesticide as » Dispose of empty pesticide containers according to the Instructions on the container label. Inspection a Inspe^ irrigation system periodical^ to ensure that tiie riglit amount of water ia beina appUed and *at recessive runoff to not occurring. Minimize excess watering, and repair leaks in tbe irrigation system as soon as they are observed. a Inspect pesticide/fertilizer equipment and transportation vehicles daily. Training a Educate and train employees on use of pesticides and in pesticide application techniques to WHcatlon muat be under the supervi^on of a California qualified pesticide applicator. * av-aiiiunua a Train/encourage municipal maintenance crews to use IPM techniques for manaeine oublic §reen areas. ^ * *^ ^\nnuaUy train employees within departments responsible for pesticide application on the appropnate poitions of the agency's IPM Policy, SOPs, and BMPs, and the latest IPM techniques. •^ofd California Stai-mwatar BMP HandhrtnU "'-'^^ Landscape Maintenance SC'73 • Employees who are not authorized and trained to apply pesticides should be periodically (at least annually) informed tiiat tliey cannot use over-tiie-counter pesticides in or around tiie workplace. • Use a training log or similar method tn document training. SpUi Reaponse and Prwentton • Refer to SC-u» Spill Prevention* Control k Cleanup • Have spin deanup materials readily available and in a know in location • Cleanup spills hnmedlately and use dry methods if possible. • Proper!tfdi^oa«afspin deanup material Otfter Conilileratldiu m lha Federal Pesticide^ Fungicide, and Rodsntidde Act and CaUfor^ Pestiddes and Peat Control Operattona place strict contrds over pestldde aiqilkation and handHng and sped^ training, annual refinsher, and teatfaigrequfeementa. Itie regulations gsnerdlf coven a list of approved pestiddea and selected u8ea» updated regnlazly; gen^ ^pU^doa intanation; equ^ment uae and maintenance procedores; and record keeping. The CaHfernia Department of Pestidde ReguUtiona and OieGoanty Agricultural Commisskm ooordixute and maintain the Uoenslng and certification programs. All public ag^y Mttployeea who apply peatfddes and herbiddea in "agricultural use" areas such as pana, gav Gooraes, rifl^ta-^^ aooordanca witii state regulations. Contracts for landscape maintenance ahouW indude similar roquirementa. a All enyk^ywa who handfe pesticides should be familiar with the most re^ data sheet (MSDS) tiles. a Munic^tiea do not have tiiie autiiority to regulate the use of pesticides by schod dUtricts. however tbe CaUfornU Healtiiy SchooU Act of 2000 (AB 2260) has imposed requirements on CaUfornia schod dutricts regarding pesticide use in achooU. Posting of notification prior to tiie application of pestiddes is now required, and IPM is stated as tiie preferred approach to peat management in schoola. Stdqulrements Coata Additional training of municipal employees will be required to address IPM techniques and BMPs. IPM methods will likely increase labor coat for pest control which may be offset by lower chemical costs. ^ Miafntenance Mot applicable January 2003 California Starmwatar 3M(> Handbook 5 of 6* Supptemantal Information Further Detail <^tha BMP Waste Manc^ement Landscape Maintenance Comp^ng ia one of the bettw dispowl alternatives if locaUy available. Moat munidpaUties privat«»onn»wio«ldpH)bablyh«compatibbwlthmostoompo8^ »™n.a8weua» Contractors and Other Pesticide Users mnridprf5aea4oii»ieqpil»oontractonto(^^ pwvld. doomMrtrtipn or pestldde uae on \_^«nc«s and lUsourcca uCtD!//dnr.nielrnfce.«HrAdr/dM/«,^,],lni ^^ent% Woo*«ud-C»yde. Central Coaat Regional Water Quality ContKrf^. Orange County Stonnwater Program "r" - ^ ^ California Stdrmwatar BMP Manrthr,n\^ Attachment 10 •*(Si»^ Section 5 Treatment Control BMPs 5.1 Introduction This section describes treatment control Best Management Practices (BMPs) to be considered for mcoiT,oration into newly developed public and private infrastructure, as well as retrofit into existmg facilities to meet stormwater management objectives. BMP fact sheets are divided into two groups: pubhc domain BMPs and manufactured (proprietary) BMPs. In some cases, the same BMP may e^ast m each group, for example, media filtration. However, treatment BMPs are typically very different between the two groups. Brand names of manufactured BMPs are not stated. Descriptions of manufactured BMPs in this document should not be inferred as endorsement by the authors. 5.2 Treatment Control BMPs Public domain and manufactured BMP controls are listed in Table 5-1. Table 5-1 Treatment Control BMPs Public Domain Manufactured (Proprietary) Infiltration Infiltration TC-10 Infiltration Trench TC-11 Infiltration Basin TC-12 Retention/Irrigation Detention and Settling Detention and Settling TC-20 Wet Pond TC-21 Constructed Wetland TC-22 Extended Detention Basin MP-20 Wetland Biofiltration Biofiltration TC-30 Vegetated Swale TC-31 Vegetated Buffer Strip TC-32 Bioretention Filtration Filtration TC-40 Media FUter MP-40 Media Filter Flow Through Separation Flow Through Separation TC-50 Water Quality Inlet MP-50 Wet Vault MP-51 Vortex Separator MP-52 Drain Inserts Other Other TC-60 Multiple Systems Section 5 Treatment Control BMPs 5.3 Fact Sheet Format A BMP fact sheet is a short document that gives all the information about a particular BMP. Typically each pubUc domain and manufactured BMP fact sheet contains the information outlined in Figure 5-1. The fact sheets also contain side bar presentations with information on BMP design considerations, targeted constituents, and removal effectiveness (if known). Treatment BMP performance, design criteria, and other selection factors are discussed in 5.4 - 5.6 below. BMP Fact sheets are included in 5.7. TCxx/MPxx Example Fact Sheet Description California Experience Advantages Limitations Design and Sizing Guidelines Performance Siting Criteria Design Guidelines Maintenance Cost References and Sources of Additional Information Figure 5-1 Example Fact Sheet 5.4 Comparing Performance of Treatment BMPs With a myriad of stormwater treatment BMPs from which to choose, a question commonly asked is "which one is best". Particularly when considering a manufactured treatment system, the engineer wants to know if it provides performance that is reasonably comparable to the " typical public-domain BMPs like wet ponds or grass swales. With so many BMPs, it is not likely that they perform equally for all pollutants. Thus, the question that each local jurisdiction faces is which treatment BMPs will it allow, and under what circumstances. What level of treatment is desired or reasonable, given the cost? Which BMPs are the most cost-effective? Current municipal stormwater permits specify the volume or rate of stormwater that must be treated, but not the specific level or efficiency of treatment: These permits usually require performance to the specific maximum extent practicable (MEP), but this does not translate to an easy to apply specific design criteria. Methodology for comparing BMP performance may need to be expanded to include more than removal effectiveness. Many studies have been conducted on the performance of stormwater treatment BMPs. Several publications have provided summaries of performance (ASCE, 1998; ASCE, 2001; Brown and Schueler, 1997; Shoemaker et al., 2000; Winter, 2001). These summaries indicate a wide variation in the performance of each type of BMP, making effectiveness comparisons between BMPs problematic. 5.4.1 Variation in Performance There are several reasons for the observed variation. The Variability of Stormwater Quality Stormwater quality is highly variable during a storm, from storm to storm at a site, and between sites even of the same land use. For pollutants of interest, maximum observed concentrations commonly exceed the average concentration by a factor of 100. The average concentration of a w storm, known as the event mean concentration (EMC) commonly varies at a site by a factor of 5. One aspect of stormwater quality that is highly variable is the particle size distribution (PSD) of 5-2 California Stormwater BMP Handbool< New Development and Redevelopment ufuiuf rahmnhanrihnrtlfs.com January 2003 Section 5 Treatment Control BMPs the suspended sediments. This results in variation in the settle ability of these sediments and the pollutants that are attached. For example, several performance studies of manufactured BMPs have been conducted in the upper Midwest and Northeast where deicing sand is commonly used. The sand, washed off during spring and summer storms, skews the PSD to larger sizes not commonly found in stormwater from California sites except in mountainous areas. Consequently, a lower level efficiency may be observed if the same treatment system is used in California. Most Field Studies Monitor Too Few Storms High variability of stormwater quality requires that a large number of storms be sampled to discern if there is a significant different in performance among BMPs. The smaller the actual difference in performance between BMPs, the greater the number of storms that must be sampled to statistically discern the difference between them. For example, a researcher attempting to determine a difference in performance between two BMPs of 10% must monitor many more storms than if the interest is to define the difference within 50%. Given the expense and difficulty, few studies have monitored enough storms to determine the actual performance with a high level of precision. Different Design Criteria Performance of different systems within the same group (e.g., wet ponds) differs significantly in part because of differing design criteria for each system. This in turn can make it problematic to compare different groups of treatment BMPs to each other (e.g., wet ponds to vortex separators). Differing Influent Concentrations and Analytical Variability With most treatment BMPs, efficiency decreases with decreasing influent concentration. This is illustrated in Figure 5-2. Tims, a low removal efficiency may be observed during a study not because the device is inherently a poorer performer, but possibly because the influent concentrations for the site were unusually low. Also, as the concentration of a particular constituent such as TSS approaches its analytical detection limit, the effect of the variability of the laboratory technique becomes more significant. This factor also accounts for the wide variability of obseivations on the left of Figure 5-2. The variability of the laboratory results as the TSS approaches its analytical detection limit may also account for negative efliciencies at vev)^ low influent concentrations (e.g., TSS less than 10 mg/L). However, some negative efficiencies observed at higher concentrations may not necessarily be an artifact of laboratory analysis. The cause varies to some extent with the type of treatment BMP. Negative efficiencies maybe due to the resuspension of previously deposited pollutants, a change in pH that dissolves precipitated or sorbed pollutants, discharge of algae in the case of BMPs with open wet pools, erosion of unprotected basin side or bottom, and the degradation of leaves that entered the system the previous fall. January 2003 California Stormwater BMP Handbook 5-3 New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs Different Methods of Calculating Efficiency Researchers (l) have used different methods to calculate efficiency, (2) do not always indicate which method they have used, and (3) often do not provide sufficient information in their report to allow others to recalculate the efficiency using a common method. • SWALE • STRIP EDB X SF X WET BASIN Influent Concentration Figure 5-2 Removal Efficiency Versus Influent Concentration One approach to quantifying BMP efficiency is to determine first if the BMP is providing treatment (that the influent and effluent mean event mean concentrations are statistically different from one another) and then examine either a cumulative distribution function of influent and effluent quality or a standard parallel probability plot. This approach is called the Effluent Probability Method. While this approach has been used in the past by EPA and ASCE, some researchers have experienced problems with the general applicability of this method. A discussion of these issues is included in Appendix B. A second approach to comparing performance among BMPs is to compare . effluent concentrations, using a box-whisker plot, the basic form of which is illustrated in Figure 5-3. The plot represents all of the data points, of one study, several studies, or of individual storms. The plots provide insight into the variability of performance within each BMP type, and possible differences in performance among the types. To explain the plot: 50% of the data points as well as the median value of all the data points is represented by the box. That is, the median falls within the 75th and 25th percentile of data (top and bottom of the box). The whisker extends to the highest point within a range of 1.5 times the difference between the first and third quartiles. Individual points beyond this range are shown as asterisks. Whisker extends to the highest value of data points Third Quartile First Quartile Median Whisker extends to ( the lowest value ! of data points ) A line is drawn across the box at ttie median. Ttie bottom of ttie \ box is at ttie 25tti percentile and the top is at the 75th percentile. j The whiskers are the lines that extend from the top and bottom \ ofthe box. I Figure 5-3 Box-Whisker Plot 5-4 California Stormwater BMP Handbook New Development and Redevelopment www.cabmptiandbooks.com January 2003 Section 5 Treatment Control BMPs Recognizing the possible effect of influent concentration on efficiency, an alternative is to compare effluent concentrations. The reasoning is that regardless of the influent concentration a particular BMP will generate a narrower range of effluent concentrations. Figure 5-4 shows ' observed effluent concentrations for several different types of BMPs. These data were generated m an extensive field program conducted by the California Department of Transportation (Caltrans). As this program is the most extensive effort to-date in the entire United States the observations about performance in this Handbook rely heavily on these data The Caltrans study IS unique in that many of the BMPs were tested under reasonably similar conditions (climate, storms, freeway stormwater quality), with each type of BMP sized with the same design criteria. ° An additional factor to consider when comparing BMPs is the effect of infiltration. BMPs with concrete or metal structures will have no infiltration, whereas the infiltration in earthen BMPs will vary fi:om none to substantial. For example, in the Caltrans study, infiltration in vegetated swales averaged nearly 50%. This point is illustrated with Figure 5-4 where effluent quality of several BMPs are compared. As seen in Figure 5-4, effluent concentration for grass swales is higher than either filters or wet basins (30 vs. 10 to 15 mg/L), suggesting that swales in comparison are not particularly effective. However, surface water entering swales may infiltrate into the ground, resulting in a loading reduction (flow times concentration) that is similar to those BMPs with minimal or no infiltration. 200 TC-40 Media Filler (Austin Sand Filter) TC-40 Media TC-40 Media Filter Filter (Multl- (Delaware chamber Lineal Sand Treatment Filter) Train) Observed Effluent Concentrations for Several Different Public DomLln'^BMPs California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com S-5 Section 5 Treatment Control BMPs With equation shown below, it is possible using the data fi-om Figure 5-4 to estimate different levels of loading reduction as a function of the fraction of stormwater that is infiltrated. EEC = (l-I)(EC) + (I)(GC) Where: EEC = the effective effluent concentration I = fraction of stormwater discharged by infiltration EC = the median concentration observed in the effluent GC = expected concentration of stormwater when it reaches the groundwater To illustrate the use of the equation above, the effect of infiltration is considered on the effective effluent concentration of TSS from swales. From Figure S'4, the median effluent concentration for swales is about 30 mg/L. Infiltration of 50% is assumed with an expected concentration of 5 mg/L when the stormwater reaches the groundwater. This gives: EEC = (i-o.5)(3o) + (o.5)(5) = 17-5 mg/L. The above value can be compared to other BMPs that may directly produce a lower effluent concentration, but do not exhibit infiltration, such as concrete wet vaults. 5-4.2 Other Issues Related to Performance Comparisons A further consideration related to performance comparisons is whether or not the treatment BMP removes dissolved pollutants. Receiving water standards for most metals are based on the dissolved fraction; the form of nitrogen or phosphorus of most concern as a nutrient is the dissolved fraction. The common practice of comparing the performance of BMPs using TSS may not be considered sufficient by local governments and regulatory agencies as there is not always a strong, consistent relationship between TSS and the pollutants of interest, particularly those identified in the 303d list for specific water bodies in California. These pollutants frequently include metals, nitrogen, nutrients (but often nutrients without specifying nitrogen or phosphorus), indicator bacteria (i.e., fecal coliform), pesticides, and trash. Less commonly cited pollutants include sediment, PAHs, PCBs, and dioxin. With respect to metals, typically, only the general term is used. In some cases, a specific metal is identified. The most commonly listed metals are mercury, copper, lead, selenium, zinc, and nickel. Less frequently listed metals are cadmium, arsenic, silver, chromium, molybdenum, and thallium. Commonly, only the general term "metals" is indicated for a water body without reference to a particular metal. It is desirable to know how each of the treatment BMPs performs with respect to the removal of the above pollutants. Unfortunately, the performance data are non-existent or very limited for many of the cited pollutants, particularly trash, PAHs, PCBs, dioxin, mercury, selenium, and pesticides. Furthermore, the concentrations of these constituents are very low, often below the 5.6 California Stormwater BMP Handbook January 2003 New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs detection limit. This prevents the determination of which BMPs are most effective. However with the exception of trash and possibly dioxin, these pollutants readily sorb to sediments in ' stormwater and therefore, absent data at this time, can be considered to be removed in proportion to the removal of TSS (i.e.. sediment). Therefore, in general, those treatment systems that are most effective at removing TSS will be most effective at removing pollutants noted above. While there are little data on the removal of trash, those treatment BMPs that include a basin such as a wet pond or vault, or extended detention basin should be similarly effective at removing trash as long as the design incorporates a means of retaining the floating trash in the BMP. Whether or not manufactured products that are configured as a basin (e.g., round vaults or vortex separators) are as effective as pubhc domain BMPs is unknown. However their ability to retain floating debris may be Umited by the fact that many of these products are relatively small and therefore may have limited storage capacity. Only one manufactured BMP is specifically designed to remove floating debris. There are considerable amounts of performance data for zinc, copper, and lead, with a less substantial database for nickel, cadmium, and chromium. An exception is high-use freeways where metals in general are at higher concentrations than residential and commercial properties. Lead sorbs easily to the sediments in stormwater, with typically only 10% in the dissolved phase. Hence, its removal is generally in direct proportion to the removal of TSS. In ase. contrast, zmc, copper, and cadmium are highly soluble with 50% or more in the dissolved ph„.. ^ Hence, two treatment BMPs may remove TSS at the same level, but if one is capable of removing dissolved metals, it provides better treatment overall for the more soluble metals. 5.4,3 Comparisons of Treatment BMPs for Nitrogen, Zinc Bacteria, and TSS ' Presented in Figures 5-5 through 5-8 are comparisons of the effluent concentrations produced by several types of treatment BMPs for nitrogen, zinc, and fecal coliform, respectively (TSS is represented in Figure 5-4)- Graphs for other metals are provided in Appendix C These data are from the Caltrans study previously cited. Total and the dissolved effluent concentrations are shown for zinc. (Note that while box-whisker plots are used here to compare BMPs other methodologies, such as effluent cumulative probability distribution plots, are used by others ) California Stormwater BMP Handbook 5.7 New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs 12 10 D> c £ UJ c .O 4 * + t f * ^ TC-aOWelPond TC-22 Exiondod TC-30 VaaBtated TO-31 Vegetated TC-40Madla TC-40 Madia TC-40Madis Dslantlon Baain Swale Buffer Filler (Austin Filter (Delatrara Fllt«r(M ultl- Sand Filter) LJnaal Sand chamber Filter) Treatment Train) Figure 5-5 Total Nitrogen in Effluent 300 Figure 5-6 Total Dissolved Zinc in Effluent 5-8 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com January 2003 Section 5 Treatment Control BMPs 500 =d 400 3- c Ui N 200 100 TC-20 Wet Pond TC-22 Extended Detention Basin TC-30 Vegetated Swala TC-31 Vegetated Buffer TC-40 Media Filter (Austin Sand Filter) TC-40 Media Filter (Delaware Lineal Sand Filter) TC-40 Media Filter (Multi- chamber Treatment Train) Figure 5-7 Total Zinc in Effluent 1,000,000 c o UJ _c V) i i o o "io o dl 100,000 •2- 10,000 1.000 100 10 9 X TC-20 Wet Pond TC-22 Extended Detention Basin TC-30 Vegetated Swale TC-31 Vegetated Buffer TC-4C Media TC-40 Media TC-40 Media Filter Filter Filter (IVI ultl- (Austin Sand (Delaware ctiamber Filter) Lineal Sand Treatment Filter) Train) Figure 5-8 Total Fecal Conforms in Effluent California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com 5-9 Section 5 Treatment Control BMPs While a figure is provided for fecal coliform, it is important to stress that the performance comparisons between BMPs is problemat- Some California BMP studies have shown excellent removal of fecal coliform through constniCLed wetlands and other BMPs. However, BMP comparisons are complicated by the fact that several BMPs attract wildlife and pets, thereby elevating bacteria levels. As bacteria sorb to the suspended sediments, a significant fraction may be removed by settling or filtration. A cautionary note regarding nitrogen: when comparing nitrogen removal between treatment systems it is best to use the parameter total nitrogen. It consists of Total Kjeldahl Nitrogen - TKN(organic nitrogen plus ammonia) plus nitrate. Comparing TKN removal rates is misleading in that in some treatment systems the ammonia is changed to nitrate but not removed. Examination of the performance data of many systems shows that while TKN may decrease dramatically, the nitrate concentration increases correspondingly. Hence, the overall removal of nitrogen is considerably lower than implied from looking only at Kjeldahl Nitrogen. 5.4.4 General Performance of Manufactured BMPs An important question is how the performance of manufactured treatment BMPs compares to those in the public domain, illustrated previously in Figures 5-4 through 5-8. Figure 5-9 (and Figure 5-10 in log format) presents box-whisker plots of the removal of TSS for the manufactured systems. Data are presented for five general types of manufactured BMPs: wet vaults, drain inserts, constructed wetlands, media filters, and vortex separators. The figures indicate wide ranges in effluent concentrations, reflecting in part the different products and design criteria within each type. Comparing Figures 5-4 and 5-9 suggests that manufactured products may perform as well as the less effective public-domain BMPs such as swales and extended detention basins (excluding the additional benefits of infiltration with the latter). Manufactured wetlands may perform as well as the most effective public-domain BMPs; however, the plot presented in Figure 5-9 for the manufactured wetlands represents only five data points. It should be noted that each type of BMP illustrated in Figure 5-9 contains data from more than one product. Performance of particular products within that grouping may not perform as well as even the least effective public-domain BMPs. This observation is implied by the greater spread within some boxes in Figure 5-9, for example, manufactured wet vaults and vortex separators. Product performance within each grouping of manufactured BMPs vary as follows: • Filters - TSS effluent concentrations range from 2 to 280 mg/L, with a median value of 29 mg/L • Inserts - TSS effluent concentrations range from 4 to 248 mg/L with a median value of 27 mg/L • Wetlands - TSS effluent concentrations vary little, and have a median value of 1.2 mg/L • Vaults - TSS effluent concentrations range from 1 to 467 mg/L, with a median value of 36 mg/L • Vortex - TSS effluent concentrations range from 13 to 359 mg/L, with a median value of 32 mg/L 5-10 California Stormwater BMP Handbook January 2003 New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs 800 J 700 O) E. ^ 600 » m UJ 500 c w •o =: 400 o CO •a 300 c a <o 3 200 CO (2 100 MP-20 Wetland MP.40 Media Filter MP-SO Wet Vault MP-SI Vortex MP-52 Drain inlal Separator Figure 5-9 Total Suspended Solids in Effluent 1.000.0 M P-20 Wetland MP-40 Media M P-50 Wet Vault MP-51 Vortex M P-52 D ratn Inlet Separator ^ . , „ Figure 5-10 Total Suspended Solids in Effluent (log-format) California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com 5-11 Section 5 Treatment Control BMPs As noted earlier, performance of particular products in a grouping may be due to different design criteria within the group. For example, wet vault products differ with respect to the volume of the permanent wet pool to the design event volume; filter products differ with respect to the type of media. 5.4.5 Technology Certification This Handbook does not endorse proprietary products, although many are described. It is left to each community to determine which proprietary products may be used, and under what circumstances. When considering a proprietary product, it is strongly advised that the community consider performance data, but only performance data that have been collected following a widely accepted protocol. Protocols have been developed by the American Society of Civil Engineeing (ASCE BMP Data Base Program), and by the U.S. Environmental Protection Agency (Enviromental Technology Certification Program). The local jurisdiction should ask the manufacturer of the product to submit a report that describes the product and protocol that was followed to produce the performance data. It can be expected that subsequent to the publishing of this Handbook, new public-domain technologies will be proposed (or design criteria for existing technologies will be altered) by development engineers. As with proprietary products, it is advised that new public-domain technologies be considered only if performance data are available and have been collected following a widely accepted protocol. 5.5 BMP Design Criteria for Flow and Volume Many municipal stormwater discharge permits in California contain provisions such as Standard Urban Stormwater Mitigation Plans, Stormwater Quality Urban Impact Mitigation Plans, or Provision C.3 New and Redevelopment Performance Standards, commonly referred to as SUSMPs, SQUIMPs, or C.3 Provisions, respectively. What these and similar provisions have in common is that they require many new development and redevelopment projects to capture and then infiltrate or treat runoff from the project site prior to being discharged to storm drains. These provisions include minimum standards for sizing these treatment control BMPs. Sizing standards are prescribed for both volume-based and flow-based BMPs. A key point to consider when developing, reviewing, or complying with requirements for the sizing of treatment control BMPs for stormwater quality enhancement is that BMPs are most efficient and economical when they target small, frequent storm events that over time produce more total runoff than the larger, infrequent storms targeted for design of flood control facilities. The reason for this can be seen by examination of Figure 5-11 and Figure 5-12. Figure 5-11 shows the distribution of storm events at San Jose, California where most storms produce less than O.50 in. of total rainfall. Figure 5-12 shows the distribution of rainfall intensities at San Jose, California, where most storms have intensities of less than 0.25 in/hr. The patterns at San Jose, California are typical of other locations throughout the state. Figures 5-11 and 5-12 show that as storm sizes increase, the number of events decrease. Therefore, when BMPs are designed for increasingly larger storms (for example, storms up to 1 in. versus storms of up to 0.5 in.), the BMP size and cost increase dramatically, while the number of additional 5-12 California Stormwater BMP Handbook January 2003 New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs treated storm events are small. Table 5-2 shows that doubling the design storm depth from 0.50 in. to 1.00 in. only increases the number of events captured by 23%. Similarly, doubhng the design rainfall intensity fi-om 0.25 in/hr to 0.50 in/hr only increases the number of events captured by 7%. Rain Storms at San Jose, CA 1948-2000 1200 1000 > 111 800 0 600 i-0 Si 400 B 3 z 200 0 US 42 30 5 K.'^^ N- V ">• ti' M ^ \- V 'b- W fe- Storm Depth, Inches Figure 5-11 Rain Storms at San Jose, CA 2963 Rain Intensity at San Jose, CA 1948-2000 9,335 hourly readings less than 0.10 In/hr are not shown 207 10 Rainfall Intensity, Inches per Hour Figure 5-12 Rain Intensity at San Jose, CA January 2003 California Stormwater BMP Handbook 5-13 Section 5 Treatment Control BMPs ^fahiP s-l Incremental Design Criteria VS Storms Treated £ It San Jose, CA Proposed BMP Design Target Number of Historical Events in Range Incremental Increase in Design Criteria Incremental Increase in Storms Treated Storm Depth 0.00 to 0.50 in. 1,067 +100% +23% Storm Depth 0.51 to 1.00 in. 242 +100% +23% Rainfall Intensity 0.10 to 0.25 in/hr 2,963 +100% +7% Rainfall Intensity 0.26 to 0.50 in/hr 207 +100% +7% Due to economies of scale, doubhng the capture and treatment requirements for a BMP are not likely to double the cost of many BMPs, but the incremental cost per event will increase, making increases beyond a certain point generally unattractive. Typically, design criteria for water quality control BMPs are set to coincide with the "knee of the curve," that is, the pomt of inflection where the magnitude of the event increases more rapidly than number of events captured. Figure 5-13 shows that the "knee of the curve" or point of diminishing returns for San Jose, California is in the range of 0.75 to 1.00 in. of rainfall. In other words, targeting design storms larger than this will produce gains at considerable incremental cost. Similar curves can be developed for rainfall intensity and runoff volume. Rain Storms at San Jose, CA 1948-2000 1600 1400 0 1200 0) .0 E 1000 3 </) z +j c 0 800 > > UJ 600 re E 400 3 0 200 "Knee of the Curve' is in this vicinity / V -f <f ^^ storm Depth, Inches Figure 5-13 Rain Storms at San Jose, CA 5-14 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com January 2003 Section 5 Treatment Control BMPs It is important to note that arbitrarily targeting large, infrequent storm events can actually reduce the pollutant removal capabilities of some BMPs. This occurs when outlet structures, detention times, and drain down times are designed to accommodate unusually large volumes and high flows. When BMPs are over-designed, the more frequent, small storms that produce the most annual runoff pass quickly through the over-sized BMPs and therefore receive inadequate treatment. For example, a detention basin might normally be designed to capture 0.5 in. of runoff and to release that runoff over 48 hrs, providing a high level of sediment removal. If the basin were to be oversized to capture 1.0 in. of runoff and to release that runoff over 48 hrs, a more common 0.5 inch runoff event entering basin would drain in approximately 24 hrs, meaning the smaller, more frequent storm that is responsible for more total runoff would receive less treatment than if the basin were designed for the smaller event. Therefore, efficient and economical BMP sizing criteria are usually based on design criteria that correspond to the "knee of the curve" or point of diminishing returns. 5.5.1 Volume-Based BMP Design Volume-based BMP design standards apply to BMPs whose primary mode of pollutant removal depends on the volumetric capacity of the BMP. Examples of BMPs in this category includes detention basins, retention basins, and infiltration. Typically, a volume-based BMP design criteria calls for the capture and infiltration or treatment of a certain percentage of the runoff from the project site, usually in the range of the 75th to 85th percentile average annual runoff volume. The 75th to 85th percentile capture range corresponds to the "knee of the curve" for many sites in California for sites whose composite runoff coefficient is in the 0.50 to 0.95 range. The following are examples of volume-based BMP design standards from current municipal stormwater permits. The permits require that volume-based BMPs be designed to capture and then to infiltrate or treat stormwater runoff equal to one of the following; • Eighty (80)% of the volume of annual runoff, determined in accordance with the methodology set forth in Appendix D of the California Storm Water Best Management Practices Handbook (Stormwater Quahty Task Force, 1993), using local rainfall data. • The maximized stormwater quaHty capture volume for the area, based on historical rainfall records, determined using the formula and volume capture coefficients set forth in Urban Runoff Quality Management (WEF Manual of Practice No. 23/ASCE Manual of Practice No. 87, C1998), pages 175-178). The reader is referred to the municipal stormwater program manager for the jurisdiction processing the new development or redevelopment project application to determine the specific requirements applicable to a proposed project. California Stormwater BMP Handbook Approach The volume-based BMP sizing methodology included in the first edition of the CaUfornia Storm Water Best Management Practice Handbook (Stormwater Quality Task Force, 1993) has been included in this second edition of the handbook and is the method recommended for use. January 2003 California Stormwater BMP Handbook 5-15 New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs The California Stormwater BMP Handbook approach is based on results of a continuous simulation model, the STORM model, de- sloped by the Hydrologic Engineering Center of the U.S. Army Corps of Engineers (COE-HEC .977). The Storage, Treatment, Overflow, Runoff Model (STORM) was applied to long-term hourly rainfall data at numerous sites throughout CaUfornia, with sites selected throughout the state representing a wide range of municipal stormwater permit areas, climatic areas, geography, and topography. STORM translates ramfall into runoff, then routes the runoff through detention storage. The volume-based BMP sizing curves resulting from the STORM model provide a range of options for choosing a BMP sizing curve appropriate to sites in most areas of the state. The volume-based BMP sizing curves are included in Appendix D. Key model assumptions are also documented in Appendix D. San Jose (7821) - Santa Clara County, California ilysis 90 80 f 60 ^ 50 O a Runoff Coafficient = 0.25 Runoff Coefficient = 0.50 Runoff Coefficient = 0.75 Runoff Coefficient = 1.00 0 3 0.4 0.5 0.6 0.7 Unit Basin Storage Volume (inches) Figure 5-14 Capture/Treatment Analysis at San Jose, CA The California Stormwater BMP Handbook approach is simple to apply, and relies largely on commonly available information about a project. The foUowing steps describe the use of the BMP sizing curves contained in Appendix D. 1. Identify the "BMP Drainage Area" that drains to the proposed BMP. This includes afl areas that will contribute runoff to the proposed BMP, including pervious areas, impervious areas, and off-site areas, whether or not they are directly or indirectly connected to the BMP. 2. Calculate the composite runoff coefficient "C" for the area identified in Step i. 3. Select a capture curve representative of the site and the desired drain down time using. See Appendix D. Curves are presented for 24 hour and 48 hour draw down times. The 48 hour curve should be used in most areas of California. Use of the 24 hour curve should be limited 5-16 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com January 2003 Section 5 Treatment Control BMPs to drainage areas with coarse soils that readily settle and to watersheds where warming may be detrimental to downstream fisheries. Draw down times in excess of 48 hours should be used with caution as vector breeding can be a problem after water has stood in excess of 72 hours. 4. Determine the applicable requirement for capture of runoff (Capture, % of Runoff). 5. Enter the capture curve selected in Step 3 on the vertical axis at the "Capture, % Runoff" value identified in Step 4. Move horizontally to the right across capture curve until the curve corresponding to the drainage area's composite runoff coefficient "C" determined in Step 2 is intercepted. Interpolation between curves may be necessary. Move vertically down the from for this point until the horizontal axis is intercepted. Read the "Unit Basin Storage Volume" along the horizontal axis. If a local requirement for capture of runoff is not specified, enter the vertical axis at the "knee of the curve" for the curve representing composite runoff coefficient "C." The "knee of the curve" is typically in the range of 75 to 85% capture. 6. Calculate the required capture volume of the BMP by multiplying the "BMP Drainage Area" ft-om Step 1 by the "Unit Basin Storage Volume" from Step 5 to give the BMP volume. Due to the mixed units that resuff (e.g., ac-in., ac-ft) it is recommended that the resulting volume be converted to cubic feet for use during design. Urban Runoff Quality Management Approach The volume-based BMP sizing methodology described in Urban Runo^Quality Management (WEF Manual of Practice No. 23/ASCE Manual of Practice No. 87, (1998), pages 175-178) has been mcluded in this edition of the handbook as an alternative to the California Stormwater BMP Handbook approach described above. The Urban Runoff Quality Management Approach IS suitable for planning level estimates of the size of volume-based BMPs (WEF/ASCE IQQ8 page 175)- The Urban Runoff Quality Management approach is simflar to the California Stormwater BMP Handbook approach in that it is based on the translation of rainfafl to runoff. The Urban Runoff Quality Management approach is based on two regression equations. The first regression equation that relates rainfafl to runoff The rainfafl to runoff regression equation was developed using 2 years of data from more than 60 urban watersheds nationwide. The second regression equation relates mean annual runoff-producing rainfafl depths to the "Maximized Water Quality Capture Volume" which corresponds to the "knee of the cumulative probability curve" This second regression was based on analysis of long-term rainfall data ft-om seven rain gages representing chmatic zones across the country. The Maximized Water Quality Capture Volume corresponds to approximately the 85th percentfle runoff event, and ranges from 82 to 88%. The two regression equations that form the Urban Runoff Quality Management approach are as follows: C = 0.858Z3 - 0.78/2 + 0.7741 + 0.04 Po = (a • C) • Pft Januai7 2003 California Stormwater BMP Handbook 5.17 New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs Where C = runoff coefficient i = watershed imperviousness ratio which is equal to the percent total imperviousness divided by lOO Po = Maximized Detention Volume, in watershed inches a = regression constant, 3=1.582 and a-1.963 for 24 and 48 hour draw down, respectively P6 - mean annual runoff-producing rainfafl depths, in watershed inches, Table #-1. See Appendix D. The Urban Runoff Quality Management Approach is simple to apply. The following steps describe the use of the approach. 1 Identify the "BMP Drainage Area" that drains to the proposed BMP. This includes afl areas that wifl contribute runoff to the proposed BMP, including pervious areas, impervious areas, and off-site areas, whether or not they are directly or indirectly connected to the BMP. 2. Calculate the "Watershed Imperviousness Ratio" (i), which is equal to the percent of total impervious area in the "BMP Drainage Area" divided by 100. 3. Calculate the "Runoff Coefficient" (C) using the following equation: C = 0.85813 - 0.7812 + 0.7741 + 0-04 4. Determine the "Mean Annual Runoff' (P6)for the "BMP Drainage Area" using Table #-1 in Appendix D. 5. Determine the "Regression Constant" (a) for the desired BMP drain down time. Use a-1.582 for 24 hrs and 3=1.963 for 48 br draw down. 6. Calculate the "Maximized Detention Volume" (Po) using the following equation: P„ = (a . C) • P6 7 Calculate the required capture volume of the BMP by multiplying the "BMP Drainage Area" from Step 1 by the "Maximized Detention Volume" from Step 6 to give the BMP volume. Due to the mixed units that resufl (e.g., ac-in., ac-ft) it is recommended that the resulting volume be converted to ft3 for use during design. 5.5.2 Flow-Based BMP Design Flow-based BMP design standards apply to BMPs whose primary mode of poflutant removal depends on the rate of flow of runoff through the BMP. Examples of BMPs in this category g_^g CaUfornia Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com Section 5 Treatment Control BMPs includes swales, sand filters, screening devices, and many proprietary products. Typically, a flow-based BMP design criteria cafls for the capture and infiltration or treatment of the flow runoff produced by rain events of a specified magnitude. The foflowing are examples of flow-based BMP design standards from current municipal stormwater permits. The permits require that flow-based BMPs be designed to capture and then to infiltrate or treat stormwater runoff equal to one of the foflowing: • 10% of the 50-yr peak flow rate (Factored Flood Flow Approach) • The flow of runoff produced by a rain event equal to at least two times the 85th percentile hourly rainfall intensity for the applicable area, based on historical records of hourly rainfall depths (California Stormwater BMP Handbook Approach) • The flow of runoff resulting from a rain event equal to at least 0.2 in/hr intensity (Uniform Intensity Approach) The reader is referred to the municipal stormwater program manager for the jurisdiction processing the new development or redevelopment project application to determine the specific requirements applicable to a proposed project. The three typical requirements shown above all have in common a rainfafl intensity element. That is, each criteria is based treating a flow of runoff produced by a rain event of specified rainfall intensity. In the first example, the Factored Flood Flow Approach, the design rainfafl intensity is a function of the location and time of concentration of the area discharging to the BMP. The intensity in this case is determined using Intensity-Duration-Frequency curves published by the flood control agency with jurisdiction over the project or available from climatic data centers. This approach is simple to apply when the 50-yr peak flow has already been determined for either drainage system design or flood control calculations. In the second example, the California Stormwater BMP Handbook Approach (so called because it is recommended in this handbook), the rainfafl intensity is a function of the location of the area discharging to the BMP. The intensity in this case can be determined using the rain intensity cumulative frequency curves developed for this Handbook based on analysis of long- term hourly rainfafl data at numerous sites throughout California, with sites selected throughout the state representing a wide range of municipal stormwater permit areas, climatic areas, geography, and topography. These rain intensity cumulative frequency curves are included in Appendix D. This approach is recommended as it reflects local conditions throughout the state. The flow-based design criteria in some municipal permits require design based on two times the 85^ percentfle hourly rainfall intensity. The factor of two included in these permits appears to be provided as a factor of safety: therefore, caution should be exercised when applying additional factors of safety during the design process so that over design can be avoided. January 2003 California Stormwater BMP Handbook 5-19 New Development and Redevelopment Section 5 Treatment Control BMPs In the third example, the Uniform Intensity Approach, the rainfafl intensity is specified directly, and is not a function of the location or time of concentration of the area draining to the BMP. This approach is very simple to apply, but it is not reflective of local conditions. The three example flow-based BMP design criteria are easy to apply and can be used in conjunction with the Rational Formula, a simplified, easy to apply formula that predicts flow rates based on rainfafl intensity and drainage area characteristics. The Rational Formula is as follows: where Q = CiA Q= flowinft3/s i - rain intensity in in/hr A = C = drainage area in acres runoff coefficient The Rational Formula is widely used for hydrologic calculations, but it does have a number of limitations. For stormwater BMP design, a key limitation is the ability of the Rational Formula to predict runoff from undeveloped areas where runoff coefficients are highly variable with storm intensity and antecedent moisture conditions. This limitation is accentuated when predicting runoff from frequent, small storms used in stormwater quality BMP design because many of the runoff coefficients in common use were developed for predicting runoff for drainage design where larger, infrequent storms are of interest. Table 5-3 provides some general guidelines on use of the Rational Equation. Table 5-3 Use of Rational Formula for Stormwater BMP Design Composite Runoff Coefficient, "C BMP Drainage Area (Acres) 0.00 to 0.25 0.26 to 0.50 0.51 to 0.75 0.76 to 1.00 0 to 25 Caution Yes Yes Yes 26 to 50 High Caution Caution Yes Yes 51 to 75 Not Recommended High Caution Caution Yes 76 to 100 Not Recommended High Caution Caution Yes In summary, the Rational Formula, when used with commonly tabulated runoff coefficients in undeveloped drainage areas, wifl likely result in predictions higher than wifl be experienced under actual field conditions. However, given the simplicity of the equation, its use remains 5-20 California Stormwater BMP Handbook New Development and Redevelopment Danuary 2003 Section 5 Treatment Control BMPs practical and is ol^en the standard metliod specified by local agencies. In general use of The following steps describe the approach for application of the flow-based BMP design criteria: 1. Identify the "BMP Drainage Area" that drains to the proposed BMP. This includes all areas nd off ir Tf'' "'^'-'"''•"S pe.^ous areas/^e" areas and off-site areas, whether or not they are directly or indirectly connected to the BMP 2. Determine rainfall intensify criteria to appfy and the corresponding design rainfall intensify. ^"tr/f""'"""'^^^''''""'^ Determine the time of concentration for "BMP TuZ^^T i"""^ P^'^f approved by the local flood control agency or using standard hydrology methods. Identify an Intensify-Duration-Frequency Curve representahve of the drainage area (usuaUy available from the local flood com ol agency or chmatic data center). Enter the Intensity-Duration-Frequency Curve with the time of aSrnT*^ ™T corresponding'theTo-yr returl per o7 ramfall event. This mtensify is the "Design Rainfall Intensify." ^' freltnt" Stormwater BMP Har^dbook Approach: Select a rain intensify cumulative 1 rZerr^"'"*'^'" °™"^Se Area." See Appendix D. Rea^the usuaS 8.7 M '"Tr^'"' 'P^'^^'' *e criteria .TSf "D^et^SSg^ --^^^'^--"^ S'™tS:S^r;5kf ^ *e intensify specified 3. Calculate the composite runoff coefficient" "C" for the "BMP Drainage Area" identified in 4. Apply the Rational Formula to calculate the "BMP Design Flow" a. Factored Flood Flow Approach: Using the "BMP Drainage Area" from Step i the Design Rainfall Intensify" from Step 2a, and "C" from Step 3, apply the Ra?ional Formula and multiply the result by 0.1. The result is the "BMP Sn Flow.- b, California Stormwater BMP Handbook Approach: Using the "BMP Drainage Area" from Step 1, the "Design Rainfall Intensify" from Step 2b and "C" frnn, sTnf ? Rational Formula. The result is the "BMP Design Flow " ^ U^lZn/T'"''S fPP'""""- *e "BMP Drainage Area" from Step 1, the "Design California Stormwater BMP Handbook New Development and Redevelopment '^^ Section 5 Treatment Control BMPs 5,5-3 Combined Volume-Based and Flow-Based BMP Design Volume-based BMPs and flow-based BMPs do not necessarily treat precisely the same stormwater runoff. For example, an on-line volume-based BMP such as a detention basin wifl treat the design runoff volume and is essentially unaffected by runoff entering the basin at an extremely high rate, say from a very short, but intense storm that produces the design volume of runoff. However, a flow-based BMP might be overwhelmed by the same short, but intense storm if the storm intensity results in runoff rates that exceed the flow-based BMP design flow rate. By contrast, a flow-based BMP such as a swale wifl treat the design flow rate of runoff and is essentially unaffected by the duration of the design flow, say from a long, low intensity storm. However, a volume-based detention basin subjected to this same rainfall and runoff event will begin to provide less treatment or will go into bypass or overflow mode after the design runoff volume is delivered. Therefore, there may be some situations where designers need to consider both volume-based and flow-based BMP design criteria. An example of where both types of criteria might apply is an off-line detention basin. For an off-line detention basin, the capacity of the diversion structure could be designed to comply with the flow-based BMP design criteria while the detention basin itself could be designed to comply with the volume-based criteria. When both volume-based and flow based criteria apply, the designer should determine which of the criteria apply to each element of the BMP system, and then size the elements accordingly. 5.6 Other BMP Selection Factors other factors that influence the selection of BMPs include cost, vector control issues, and endangered species issues. Each of these is discussed briefly below. 5.6.1 Costs The relative costs for implementing various public domain and manufactured BMPs based on flow and volume parameters are shown in Tables 5-4 and 5-5 below: Table 5-4 Economic Comparison Matrix - Flow BMP Cost/cfs Strip $$ Swale $$ Wet Vault Not available Media Filter $$$$ Vortex Not available Drain Insert Not available Table 5-5 Economic Comparison Matrix - Volume BMP Cost/acre-ft Austin Sand Filter Basin $$$$ Delaware Lineal Sand Filter $$$$ Extended Detention Basin (EDB) $$ Multi Chamber Treatment Train (MCTT) $$$$ Wet Basin $$$$ Manufactured Wetland Not available Infiltration Basin $ Wet Pond and Constructed Wetland $$$$ 5-22 California Stormwater BMP Handbook New Development and Redevelopment January 2003 Section 5 Treatment Control BMPs 5.6.2 Vector Breeding Considerations The potential of a BMP to create vector breeding habitat and/or harborage should be considered when selecting BMPs. Mosquito and other vector production is a nuisance and public health threat. Mosquitoes can breed in standing water almost immediately following a BMP instaflation and may persist at unnaturally high levels and for longer seasonal periods in created habitats. BMP siting, design, construction, and maintenance must be considered in order to select a BMP that is least conducive to providing habitat for vectors. Tips for minimizing vector breeding problems in the design and maintenance of BMPs are presented in the BMP fact sheets. Certain BMPs, including ponds and wetlands and those designed with permanent water sumps, vauhs, and/or catch basins (including below-ground installations), may require routine inspections and treatments by local mosquito and vector control agencies to suppress vector production. 5-6.3 Threatened and Endangered Species Considerations The presence or potential presence of threatened and endangered species should also be considered when selecting BMPs. Although preservation of threatened endangered species is crucial, treatment BMPs are not intended to supplement or replace species habitat except under special circumstances. The presence of threatened or endangered species can hinder timely and routine maintenance, which in turn can result in reduced BMP performance and an increase in vector production. In extreme cases, jurisdictional rights to the treatment BMP and surrounding land may be lost if threatened or endangered species utilize or become established in the BMP. When considering BMPs where there is a presence or potential presence of threatened or endangered species, early coordination with the California Department of Fish and Game and the U.S. Fish and Wfldlife service is essential. During this coordination, the purpose and the long-term operation and maintenance requirements of the BMPs need to be clearly established through written agreements or memorandums of understanding. Absent firm agreements or understandings, proceeding with BMPs under these circumstances is not recommended. 5.7 BMP Fact Sheets BMP fact sheets for public domain and manufactured BMPs foflow. The BMP fact sheets are individually page numbered and are suitable for photocopying and inclusion in stormwater quality management plans. Fresh copies of the fact sheets can be individually downloaded from the Cahrans Stormwater BMP Handbook website at www.cabmphandbooks.cnm. January 2003 Caiifornia Stormwater BI^IP Handbool< 5.23 New Development and Redevelopment www,cabmphandbool<s.com Attachment 11 GRATE INLET SKIMMER BOX Catch Basin Filter Insert - Grate Type Available in Custom Sizes - 5 Year Warranty BIO CLEAN ^ LNVI BON MENTAL SERVICES. INC,^^^ P O Box 869, Oceanside, CA 92049 (760) 433-7640 • Fax (760) 433-3176 www.blocleanenvironmental.net "The stormwater Standard" GRATE INLET S K I M M E R BOX Screens of Different Sieve Sizes Optimize Filtration and Water Flow . Bypass Opening Coarse Sieve Size Screen Medium Sieve Size Screen Fine Sieve Size Screen ( Fine sieve size screen also on bottom) Interior Components are Easily Removed to Allow Easy Access to Lower Filtration Chamber Storm Boom Skimmer Tray Deflection Shield Flange is Reinforced with Knitted 1808+45° biaxial fiberglass Features f -^ 37 CGRAtt INLET iSI|)MMllif'^Ox j Grate Inlet Skimmer Box—Functional Description Stage I: As Stormwater enters the inlet through the grate it comes in contact with and passes through a Storm Boom located around the top perimeter of the Grate Inlet Skimmer Box. After making contact with the Strom Boom> the stromwater flows down into the lower filtration chamber which is equipped with 3 different sieve size filtration screens and bypass openings. Stage 1 As Stormwater Enters The Inlet Stage 2: Throughout the entire storm event, stormwater continues to come in contact with the Storm Boom and then flow into the lower filtration chamber, adjacent to the fine sieve size screens.The fines sieve size screens are sized to be able to capture sedi- ments such as sand, clay, phosphates, etc.A sand filter quickly forms across the bottom which has the potential to capture the finest of particles. Stage 3; As the storm event increases in inten- sity the water level in the Grate Inlet Skimmer Box rises to a level adjacent to the medium sieve size screens and the turbulence deflector. The medium screen provides additional flow with less chance of obstruction than the fine screen.The turbulence deflector dramatically re- duces the turbulence in the lower filtration chamber, which allows sediment to continue to settle, without re-suspending sediment that has "eviously been captured Stage 3 Typical Medium Flow Storm Event BIO CLEAN ^ ENVIRONMENTAt SERVICES. INC.P^Pl 38 Stage 4: As the storm event increases in intensity to that of high flow storm event, the water level in the Grate Inlet Skimmer Box rises to a level adjacent to the coarse sieve size screen Stage 4 Typical High Row Storm Event The coarse screen provides additional filtered flow with less chance for obstruction than either the medium or fine screen.The coarse screen is sized to capture floatables like foliage and litter. At this stage water is flowing through all the different sieve size screens, the turbulence deflector continues to dramatically reduce the turbulence in the lower filtration chamber, and sediments continues to settle and collect towards the bottom. Stage 5; If the storm event creates an extremely high flow rate into the inlet which ^exceeds the flow through all screens, the water flow can bypass filtration screens through skimmer protected bypass opening near the top of the Grate Inlet Skimmer Box, As water flows through the bypass openings, it also continues to flow through all the other screens. Storm events that produce such high flow rates are rare and typically don't last very long. Stage 5 Typical Super High Flow Storm Event After The Storm Event Can Hold Hundreds of Pounds of Debris After The Storm Event: The stormwa- ter drains completely out of the Grate Inlet Skimmer Box after the storm event. The debris collected in the unit is stored in a dry state which helps to contain the nu- trient pollutant load, prevents mosquitoes from breeding in the unitAfter each storm event more debris is collected, which can ultimately weigh many hundreds of pounds. BIO CLEAN M r- ENVIRONMENTAL SERVICES, INC-H^^ I— — 39 Grate Inlet SUmmer Box - Sizing and Flow Rates Fitter Openings Stonn Boom* Bypa»\ /BypoM -Thiort -CoarM Screen- r" Mlow for wslttT flow untfwfWvr, The maxinnum flow rate of a Grate Inlet Skimmer Box is determined by the amount of flow that can pass through the throat, the exception is found only in very large units. To determine the minimunn flow rate of a Grate Inlet Skimmer Box, consider only the potential flow through the throat and bypass. If the potential flow through the throat is less than the potential flow through the by- pass, then the throat determines the minimum flow. If the potential water flow through the bypass is less than that of the throat then the bypass determines the minimum flow. Filtered Flow represents the potential flow PSte through all screens, and does not include the potential flow through the bypass.Water bypass happens only when the flow rate through the grate exceeds the flow all the screens. Flow Rate Table For 8 dHferent Models DImeneione of the llenge eround the top of the Grate Inlet Skimmer Box Flow Rale (cubic feet per eecond) Model Number Width (inchee) Length (Inchee) Depth (Inchee) Throat Filtered Flow Bypaee Flow GISB-l-24-24-25 24 24 25 4A 14.9 6.7 GiSB-A-24-37-2S 24 37 25 10.2 21.1 G1SB-C-2U7-25 28 37 25 12.2 19.4 rA GISB-J-24^1-25 24 41 25 12 24.6 If GISII-NK-3M2-25 32 32 25 123 19.1 GISB-36-36-25 36 36 25 l&S 23.4 iM. GIS]M>-36-48-18 36 48 18 33.2 263 G1SB-G-52-58-1S 52 58 18 893 40.1 • The yellow Irfocke rapreeem the minimum flow ratee. • FHterad flow la baaed on unobatructed acraena. BIO CLEAN M r ENVIRONMENTAL SERVICES, INC.iiPJ, | | Grate Inlet Skimmer Box - Removal Efficiencies Numeric Reductions (mg/L) Total SusperKied Solids mg/L Total Phosphorus mg/L Total Nitrogen mg/L Location Inlet Outlet Removal Efficiency Inlet Outlet Renwval Efficiency Inlet Outlet Removal Efficiency site Evaluation - Reedy Creek 74% 57% 24.3 10^ 57% Creech Engineering Report 73%, 79% 79% WMman's Pond 978 66% 18.6 0.452 98% 48.08 9.86 79% UC Irvine 53% Zinc mg/L Lead mg/L Copper mg/L Location Inlet Outlet Removal Efficiency Inlet Outlet Removal EffidMicy Inlet Outlet Removal Efficiency UChvlne 11% Longo Toyota «.7 0.73 95% 1.6 02 87% 1.9 0.1 95% Ammonia, Sallcylata mg/L Fecal Coliform CFU/100 mL Cadmium Location Inlet Outlet Removal Efficiency Inlet Outlet Removal Efficiency Inlet Outlet Removal Efficiency site Evaluation - Reedy Creek 0.38 0.23 39% UC Irvine 33% 94% HydrocartMns mg/L COD (mg/L) Location Inlet Outlet Renwval Efficiency Inlet Outlet Removal EfflciencY Site Evaluation - Reedy Cre«k 54% 2670 1490 44% Vntman't Pond 110 60 55% UC Irvine 90% Longo Toyota 199 1043 95% Reedy Creek - Site Evaluatim of a Grate Inlet Skimmer Box for Debris, Sediment, and OH 8> Grease Removal -1999 - Independent Test Creech Engineering Report • PoRutant Removal Testing for a Grate Inlet Skimmer Box - 2001 Wftman's Pond - Restoratfon Protect - Massaciiusetts Dept of Environmwrtal Management -1998 - Independent Test L{C Irvine - OpUmizatton of Stormwater Filtratton at the Urban/Waterehod Interface - Dept of Environmental Health - 2006 - Independent Test go Toyota - Field Test - City of El Monte - 2002 - Independent Test • •! Part / 6/58-12-12-12 TOP VIEW FLOW SCHEMATIC STORM BOOM SKIMMER THROAT TURBULENCE DEFLECTOR Flow Specifications Description of filter opening Percent Open SoMtf on ScnM ObMMlPM Total Square Inches per Unit Square Inches of Total Unobstructed Openings Flow Rate (Cubic Feet per Second) Skimmer protected 0y—Paaa 100X 28.0 28.0 1.0 cfs cooraa Hcraen 3/-*- X 1-3/4' statnleaa ataal ftaitanad axpandad 62X 28.0 17.3 .8 cfs Madlum Scraan lOxlO maah atatnlaam ataal 56X 28.0 15.8 .7 cfs FIna aeraan 14 X 18 maah atalnlaaa ataal 68X 16.0 10.8 .6 cfs THROAT FLOW RATE Total:0.5cfa TREATED FLOW RATE Total: 2,1 cfs FLOW RATES BASED ON UNOBSTRUCTED OPENINGS GRATE SIDE VIEW SKIMMER PROTECTED BYPASS COARSE SCREEN FINE SCREEN BOX MANUFACTURED FROM MARINE GRADE FIBERGLASS & GEL COATED FOR UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED FILTER SCREENS ARE STAINLESS STEEL CONCRETE STRUCTURE REMOVE GRATE INSERT GISB REINSTALL GRATE ErXCLL/S/VE CAUrOHNIA DISTRIBUTOR: BIO OL-EAN ENy/IRONMENTAL. SER\/ICE P.O. BOX BOO. OCEANSIDE. CA. 0ZO4-0 TEL. rOO—*3J—70-*0 rAX:7CO—433—31 76 Email: lrift>9bloolmanmn-><lronmmr»tal.nmt S»m£ QlJfm Pimm m BIMJ FOR EAST (WHHG AM ME DESlim TO BE Pmmm tfBmtJCfm AND SHOUD lASTFOR OECfUES. NOTE- mAi mwm msTo i 79a CLEARLAKE RD. SUITE 02 COCOA FL. 32022 TEL. 32T-gJy—yga2 FAX 32 T —037— 7594- GRATE INLET SKIMMER BOX GISB— 12—IS—12 DATE: OA-/t 2/OA- SCALE:SF' — 7S Part / GISB-18-18-18 TOP VIEW FLOW SCHEMATIC STORM BOOM SKIMMER THROAT TURBULENCE DEFLECTOR SIDE VIEW Flow Specifications Description of finer opening Percent Open Bottd an Scrttit Total Square Inches per Unit Square Inches of Total Unot>structed Openings Flow Rate (Cubic Feet per Second) Skimmer protactmd By—Paaa 100X 50.3 50.3 1.8 cfs Coaraa Screen 3/4' X 1-3/4' atalnlaaa ataal flattened expanded 62X 50.3 31.2 1.4 cfs Madlum Scraan 10x10 maah atalnlaaa ataal 56X 50.3 28.2 1.4 cfs FIna aeraan 14 X 18 maah atalnlaaa ataal 68X 49.0 33.3 1.8cfs THROAT FLOW RATE Total: 0.8 cfs TREATED FLOW RATE Total: 4.6cfs FLOW RATES BASED ON UNOBSTRUCTED OPENINGS GRATE SKIMMER PROTECTED BYPASS COARSE SCREEN MEDIUM SCREEN FINE SCREEN CONCRETE STRUCTURE BOX MANUFACTURED FROM MARINE GRADE FIBERGLASS & GEL COATED FOR UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED FILTER SCREENS ARE STAINLESS STEEL REMOVE GRATE INSERT GISB REINSTALL GRATE EXCLUSI\/E CALIFORNIA DISTRIBUTOR: BIO CLEAN ENy^lRONMENTAL SER\/ICE R. O. BOX aSO. OCEANSIDE. CA. 0204-0 TEL. 7«0—*.3J—70*0 FAX:7eO—4-33—31 76 Email: tnf&^btoalmanmnyftronmmntal.nmt SUHHiEE QUfm PimxnS m BUir fOi EAST aOMNS A« ijESKXB m Be pom&r MmmicnK AMD SHOUU) usrnx DEOVXS. SLJNTFfEE T£CMt\IC2L.OCSI£S 70S CLEARLAKE RD. SUITE 02 COCOA FL. 32022 TEL. 331—337— 7SS2 FAX 321 —037—7S54- GRATE INLET SKIMMER BOX GISB—IB X IS X IB DATE: OA-/'\ 2/OA- SCALE:SF — IS Part / GISB-24-24'24 TOP VIEW FLOW SCHEMATIC STORM BOOM SKIMMER ^ ^— THROAT Flow Specifications Description of filter opening Percent Open flbMrf on SCTNn Total Square Inches per Unit Square Inches of Total Unobstructed Openings Flow Rote (Cubic Feet per Second) Skimmer protactad By-Pass lOOX 162.3 162.3 6.7 cfs Coarse Scraan 3/4' X 1-3/4' stoinlaaa steal flattanad axpandad 62X 143.5 89.0 4.3cfs Medium Screen lOxlO mash atainlass steal 56X 143.5 80.4 4.3cfs Fina aeraan 14 X 18 mash stainless steal 68X 156.1 106.1 6.3cfs THROAT FLOW RATE Totol:4.4 cfs TREATED FLO Total: J4.9cf W RATE s FLOW RATES BASED ON UNOBSTRUCTED OPENINGS GRATE TURBULENCE DEFLECTOR SKIMMER PROTECTED BYPASS COARSE SCREEN MEDIUM SCREEN FINE SCREEN SIDE VIEW BOX MANUFACTURED PROM MARINE GRADE FIBERGLASS & GEL COATED FOR UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED ML FILTER SCREENS ARE STAINLESS STEEL j END VIEW I : CONCRETE STRUCTURE REMOVE GRATE INSERT GISB REINSTALL CRATE <^^LIF-ORNIA DISTRIBUTOR: BIO CLEAN EN^/IRONMENTAL. SER\/ICE ^£r?' f?*' OCEANSIDE. CA. SS04.S TEL. 700-4-33—704.0 rAX:7eO —433—31 70 StWWf OUAUTY PRODUaS AK BOLT FOR EASY UEAMNG AND ARC OESKXD TO BE PERmm HnUSIRUCWRE AND SHOULD FOR DECADES. 708 CLEARLAKE RD. SUITE S3 COCOA FL. 32022 TEL. 32T-e37-7S52 FAX 32I-637-7SS* 708 CLEARLAKE RD. SUITE S3 COCOA FL. 32022 TEL. 32T-e37-7S52 FAX 32I-637-7SS* GRATE INLET SKIMMER BOX GISB—24—S4—24 GRATE INLET SKIMMER BOX GISB—24—S4—24 iwiniau BatCi DATE: 05/20/04. SCALE:Sr mm is iwiniau BatCi DATE: 05/20/04. SCALE:Sr mm is "SSW ORAFTEF^: N.R.B. UNITS —itsiCMES Port / GISB-A-24-37-25 FLOW SCHEMATIC STORM BOOM SKIMMER Flow Specifications Description of filter opening Percent Open Scnmt Total Square Inches per Unit Square Inches of Total Unoljstrueted Openings Flow Rate (Cubic Feet per Second) Skimmer protected By^Pamm wax 211.4 211.4 8.7 cfs Coarse Hereon 3/4' X 1-3/4" atalnlaam atami flattanad axpandad 62X 187.2 116.1 5.6 cfs Medium Scraan lOxlO maah atainlaaa ataal sex 187.2 104.9 5.7 cfs FIna aeraan 14 X 18 maah atalnlaaa ataal 68X 239.8 163.1 9.8 cfs THROAT FLOW RATE Total: 10.2 cfs TREATED FLOW RATE Total: 21.1 cfs FLOW RATES BASED ON UNOBSTRUCTED OPENINGS GRATE SKIMMER PROTECTED BYPASS COARSE SCREEN MEDIUM SCREEN FINE SCREEN SIDE VIEW BOX MANUFACTURED FROM MARINE GRADE FIBERGLASS & GEL COATED FOR UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED ILTER SCREENS ARE STAINLESS STEEL MOUNT TO WALL BELOW GRATE WITH MOUmiNG KIT CONSISTING OF ALUMINUM ANGLES. TAPCONS, AND DRIU. BITS MOUNTING KIT SOLD SEPARATELY (mJIY PRODfJCIS ARE BtALT FOR EXSr CWVmC AM ARE oeasm n X PERiimR Mwismucim AM SHotMD tAST FOR DECADES. EXCLUSI\/E CALIFORNIA DISTRIBUTOR: BIO CLEAN EN\/I RON MENTAL SER\/ICE R. O. BOX BOO. OCEANSIDE. CA. 9204-0 TEL. 700—433—704-0 FAX:700—433—31 70 Email: /nfoObroc/«on«nWrof-ttn«nta/.n«t •• 'i 1 ^! 70a CLEARLAKE- RD. SUITE #2 TEL. COCOA FL. 32T—»37—70a2 32022 FAX 32 T —©37— 733* GFiATE INLET SKIMMER BOX FOR FLORIDA DOT TTPE A INLET STRUCTURES. DATE: OA-/MZ/OA- SCALE:Sr — 7 S Part / GISB-36-36-25 SIDE VIEW Flow Specificotions Description of filter opening Percent Open Bamd en SMMR Total Square Inches per Unit Square Inches of Total Unobstructed Openings Flow Rate (Cubic Feet per Stiffind) Skimmer protactad By—Paaa 100X 381.5 381.5 13.4 cfs Coaraa Scraan 3/4' X 1-3/4' atalnlaaa ataal flattanad axpandad 62X 231.0 143.2 6.2 cfs Madlum Scraan 10x10 mash atainlaaa ataal 56X 231.0 129.3 6.4 cfs Fina scraan 14 X IB maah atalnlaaa ataal 68X 283.5 192.8 10.8 MAXIMUM THROAT FLOW RATE Total: 18.8 cfs SCREEN TREATED F Total: 23.4 c MW RATE fs GRATE FLOW RATES BASED ON UNOBSTRUCTED SCREEN OPENINGS SKIMMER PROTECTED BYPASS COARSE SCREEN MEDIUM SCREEN FINE SCREEN BOX MANUFACTURED PROM MARINE GRADE PIBERGLASS & GEL COATED FOR UV PROTECT/ON 5 YEAR MANUFACTURERS WARRANTY PATENTED P/LTER SCREENS ARE STAINLESS STEEL CONCRETE STRUCTURF REMOVE GRATE INSERT GISB REINSTALL GRATE O^SIGHED W X PERmm mASmJCnjRE AMD sHom lAST FOR OBCADESL 70S CL^RLAKE RD. SUITE dtf COCOA FL. 320%2 *^ TEL. 32 T-337-7332 F^X_J31-a3Z-7aS4 GRATE INLET SKIMMER BOX FOR FLORIDA DOT INLET STRUCTURes. OATE:O4./1Z/04. SCALE:Sr — IS Part / GISB-B~46-51~18 FLOW SCHEMATIC STORM BOOM SKIMMER THROAT TURBULENCE • DEFLECTOR SIDE VIEW RNE SCREEN Flow Specifications Description of filter opening Percent Open Total Square Inches per Unit Square Inches of Total Unobstructed (^enings Flow Rate (Cubic Feet per Second) Skimmer protactad By—Paaa 100X 389.5 389.5 16.6cfs Coaraa Scraan J/4' X 1-3/4' atalnlaaa ataal flattanad axpandad 62X 343.8 213.8 10.6cfs Madlum Scraan lOxlO maah atalnlaaa ataal 56X 343.8 192.5 10.6 cfs Fine screen 14 X IB maah atalnlaaa ataal 68X 249.4 169.6 9.7 cfs THROAT FLOW RATE Total:54.4 cfs TREATED FLOW RATE Total: 30.9 cfs FLOW RATES BASED ON UNOBSTRUCTED OPENINGS GRATE MEDIUM SCREEN COARSE SCREEN SKIMMER PROTECTED BYPASS BOX MANUFACTURED FROM MARINE GRADE FIBERGLASS & GEL COATED FOR UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED ^WL/. PILTER SCREENS ARE STAINLESS STEEL END VIEW MOUNT TO WiL BELOW CRA1E WITH MOUNTING KIT CONStSmNG OF ALUMINUM ANGLES. TAPCONS. WD DRILL OTS MOUNTING KIT SOLD SEPARATELY EXCLusiyye CALIFORNIA DISTRIBUTOR: BIO CLEAN EN\/I RON MENTAL SERVICE P.O. BOX 009, OCEANSIDE. CA. 9X049 TEL. 700—433—7040 FAX:700—433—31 76 Email: /r>^o0b/oc/«an*nWronm*r)ter/.r>«t SmiEE Omirr PRODim ARE BOLT FOR EAST asm! AND ARE DESXim m X PBOmm INFRAmxmRE AM SHOUU) UST FDR DECADES. 70a CLEARLAKE RO. SUITE SZ COCCM FL. 32S22 TEL. 321-037-7-332 FAX 32T-a37-73B-» ORATE INLET SKIMMER BOX FOR FLOHIDA DOT TYRE B INLET STRUCTURES. DATEi 0A./'\a/04 SCALE:SF — SO FLOW SPECIFICATIONS Descf^idon of liter opanfing Pereant Open BoBod on Scresn Dimensions Total Square Inchee per Unit SqutfB Inchss ofTotd Unobamjcted Openings Flow Rats (Qubic Feat per SeooncQ Medkjm Screen lOKlOntmh stainless steal 56% 292 163.5 5.9 cfs THROAT FLOW RATC Total: 3.5 cfs TREATED FLOW RATE Total: 5.9 cfs FLCWRATtS BASED ON UNOBSTRUCTED OPENINGS FLOW SCHEMATIC GRATE SIDEVIBV MBHUM SCREEN m 17i END VIEW CONCRETE SmUCTURE d BOX MANUFACTURED FROM MARINE GRADE FIBERGLASS & GEL COATED FOR UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED AU FILTER SCREENS ARE STAINLESS STEEL REMOVE GRATE INSERT GISB REINSTALL GRATE BIO CLEAN M ENVIRONMENTAL SERVICES. INC.I^^ BIO CLEAN PC Box 868 Oceanside, CA 82048 Office: (TOCQ 433-7640 FcDC (760) 433^176 gkent@bl(x:)ear>enlronrnerital.nst www.biocleanenvlronmen1aI.net PERIMETER GRATE INLET SKIMMER BOX Part#BG-GIS&57-28-11 All Dimensions are in inches, unless otherwise noted. BIO CLEAN PC Box 868 Oceanside, CA 82048 Office: (TOCQ 433-7640 FcDC (760) 433^176 gkent@bl(x:)ear>enlronrnerital.nst www.biocleanenvlronmen1aI.net PERIMETER GRATE INLET SKIMMER BOX Part#BG-GIS&57-28-11 Scale: NONE BIO CLEAN PC Box 868 Oceanside, CA 82048 Office: (TOCQ 433-7640 FcDC (760) 433^176 gkent@bl(x:)ear>enlronrnerital.nst www.biocleanenvlronmen1aI.net CURB INLET BASKET WITHSHELF SYSTEM Catch Basin Filter Insert - Curb Type Available In Custom Sizes C 5 Year Warrant BIO CLEAN ^ ENVIRONMENTAL SERVtCES. INC li^F P O Box 869, Oceanside, CA 92049 (760)433-7640 • Fax (760) 433-3176 www.biodeanenvironmental.net "The Storn.water Standard" CURB INLET BASKET WITHSHELF SYSTEM .<OUNDCURB INLET BASKET WITHSHELF SYSTEM mum lifM/fl Screens of Different Sieve Sizes Optimize Filtration And Water Floe Storm Boom Coarse Sieve Size Screen Medium Sieve Size Screen Fine Sieve Size Screen (Fine Sieve Size Screen Also on Bottom) Installation Schematic Manbote II^JI For use in inlet where the only access is through a manhole. A shelf system directs water flow into the filtration basket and positions the basket directly under the manhole for easy access. If necessary, the water flows can bypass the entire filtration system simply by flowing past the filter into the catch basin. BIO CLEAN ^ ENVIRONMENTAL SERVICES, INcI^^ Manubctured by Sumree Technologies HAWAII REPORT: The Efficier of Storm Drain FUters in Removing Pollutants iiom Urban Road Runoff Turtoidity during short term test Performance matrix for field tested Dll systems Parameter AbTech Hydrocompliance KJiStar Bioclean initial device cost (10 ft drain inlet) Initial installation requirements Flow capadly Short term RDS retention Short term organics retention Long term RDS retention Long term PAH retention Cmg) Long term O/G retained (mg> Longtenn overall rubbish retention Suitabililv for Vector Conirol Unit durability Media replacement Costs Suitability for Type B basin Servicing Requirements TOTAL SCORE 10 10 10 10 2 5 10 r_5 2 5 18 110.5 2 5 10 10 10 10 2 5 2.5 10 2 5 15 7.5 2.5 7.5 7.5 7.5 7.5 7.5 2.5 10 7.5 7.5 15 75 15 91.5 127.5 20 75 2.5 2.5 7.5 10 10 10 20 to 22 1-12 erfom^ance of Dll rs ranked from one to four, with increasing scores assigned to Increasir^g perTonnance of the device Ranks for each category are scaled to 10 except initial costs and media replacement costs which are scaled to 20 iservicmg requirementeare^based on a score of 25 as determined in Appendix A. Maximum total possible score .s 185 l abk 17: DII Sen icing Time Table Site DII System Required Servicing Time (tioun;) 15 Hydmc^mpliancL' 1.75 17 KriSliir 1.0 IX -•\brech 0.5 I') Bioclean 0.25 lENVWOWMEWrAL SERVICES. INcl^Pf I Table 19: Total Servicing Box-Score Suniniar>' ! Site DII System Total Scores l5 Hydrocompliance 17 KriStar 15 IK AbTech tK 19 Bioclean -11 54 „ BES^^M^ Bio Clean Cost: $120 per foot, $1,200 total for a typical Type A catch basin. Maintenance Time: 15 minuteS At a cost of $1,200 per unit >t would cost $2.52 million to inataU 2,100 BioClm systems, nils is less than but compa^^ KnS^ system. Assuming tbiA a work crm units a day, it would talce about two and one-third nionths to service all localionSi This system is the simplest to senrice and access. The hardy oonstniction of the system is a definite advantage and it is antic^iated dmt replacement of the BioClean system and/or its parts would be very infrequent. Recommendation: Potentially feasible system for large scale BMP implementation. Cost: $3,900 per initial catch basin (assuming six subunits in a standard Type A catch basin). Replacement cost of pillows: $150 (x amount of units in catch basin) Maintenance Time: 105 minutes per catdi basin Assuming a median of $3,900 per catch basin, it would cost $8.19 miUion to install the Hysdi^QtPS^^ system in 2,100 catch basin. This figure does not include the replacement cost of pillows. It would take a crew 26 months to service each location. Recommendation: This system is not recommended for large scale BMP Impl^nentation. IJiljech Ultra-Urban Cost: $250 per 13 inches, $2^250 total for a typical Type A catch basin. Maintenance Time: 30 minutes At a cost of $2,250 per catch basin, it would cost $4.2 million to mataU llOO^Uaiacb systems. Assuming that a work crew ooukf service 21 catch basins each day after initial insteiHa*ion, it would take a crew less than five montiis to service each locatkm. This system, however is the most effective for capbuteg oil and grease, ft performs reWively poorly for PAH capture, and is the worst performer for sediment. Recommendation: This system is not recommended for large scae BMP ImpiementatkNi. KciStar ElogardH- Plus Cost: $165 per linear foot; or $1,650 pw* catch basin. Replaeemeitt costs: potymer liners $60-100 and pillows $50M (prices for both are soe dependent) (x amount of units in cstch l>asin) Maintenance Time: 60 minutes per catch basin At a cost of $1,650 per catdi basin, it wouM cost $3.65 million to bistall llOOiCnStu:^rstMns. Once instatted, assuming that a work crew couU servios 14 catch basins a day, it would take a wofk crew just over seven months to service all bcatioRs. Regular replacement of plHows represents the m^ior cost sjoMdantira beyond installatkm. Recommendation: Potentially feasible system for laige | seele BMP implementation. 55 CALIFORNIA CURB SHELF BASKET WATER CLEANSING SYSTEM SAN DIEGO REGIONAL STANDARD CURB INLET CATCH BASIN mi SHELf WW FW RGURE 2 DETAIL OF INSTAUATJON FIGURE 1 DETAIL OF PARTS REMOVABLE BASKET CATCHES EVERYTHING Am MAY BE REMOm> THROUGH MANHOLE WITHOUT ENTRY, FLOW RATES par 3 FT. BaaM SO h (ft) Coaraa Scraan .62 .84 0.146 1.06 Mad Scraan .56 1.36 0.75 3.53 FIna Scraan .68 1.02 1.167 4.01 TOTAL 8.6 FIGURE J DETAIL OF PROCESS BOX MANUPACTURED PROM MARINE GRADE FIBERGLASS & GEL COATED POP UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED ALL PILTER SCREENS ARE STAINLESS STEEL Tha abova flow ratas ora baaad on unobatrvciad acraana. NOTES: 1.SHELF SfSTEM PROVIDES FOR ENTIRE COVERAGE OF INLET OPENING SO TO DtVERT ALL FLOW TO BASKET. 2.SHELF SYSTEM MANUFACTURED FROM MARINE GRADE nBBKLASS.GO. COATED FOR UV PROTECTION. 3.SHELE SYSTEM ATTACHED TO THE CATCH BASIN WITH NON-CORROSIVE HAROmRE. 4. nLTRATI0N BASKET STRUCTURE MANUFACTURED OF MARINE GMDE nBERGtASS,GEL COATED FOR UV PROTECTION. 5. FH.TRAT10N BASKET FINE SCREEN AND COARSE CONTAINMENT SCREEN MANUFACTURED FROM STAINLESS STEEL 6. FILTRAT10N BASKET HOLDS BOOM OF ABSORBENT MEDIA TO CAPTURE HYDROCARBONS. BOOM IS EASn.Y REPLACED WITHOUT REMOVWG MOUNTING HARDWARE 7. FH.TRATK)N BASKET LOCATION IS DIRECTLY UNDER MANHOLE FOR EASY MAINTENANCE EXCLUSIVE CAUFORNIA DISTRIBUTOR: BIO CLEAN EN\/I RON MENTAL SERVICE P.O. BOX BOO, OCEANSIDE. CA. 9204-0 TEL.. 700—433—704-0 FAX:700— 4SS~31 70 Email: tnfo^bfodmonmr^vlronm»ntal.n»t SUNim QUAtm PROOUI^ ARE BUILT FDR EASf OEAMHS MO ARE DESGia m BE ivmm tmsmcivRE MD stms lAST FOR DBCMES. SUNTF^ETE: TE:cit-fMOI-OC3IES 7Sa CLEARLJ^KE RD. SUITE COCOA FL. TEL. 321—037—7032 FAX 321—037—7034 CURB INLETT BASKETF SYSTEM DATE: OA/1 2/0-4- DRAFTER: N.R.B. SCAI-E:Sr — IS UNITS — INCHES ENVIRO-SAPE HIGH CAPACITY GRATE INLET SKIMMER CALIFORNIA CURB SHELF BASKET WATER CLEANSING SYSTEM SAN DIEGO REGIONAL STANDARD CURB INLET CATCH BASIN HSU. SHOF DRfi/E PIN FIGURE 2 DETAIL OF INSTAUATJON HGURE 1 DETAIL OF PARTS 1 REMOVABLE BASKET CATCHES EVERYTHING AND MAY BE REMOVED THROUGH MANHOLE WITHOUT ENTRY. GRATE PLOW DIVERTER FLOW RATES par 3 FT. Baakat 0-S0*ca*A^2*g*h Crf- <«!*«^ .67 SO h (ft) Q(^ Coaraa Scraan .62 .84 0.146 1.06 Mad Scraan .56 1.36 0.75 3.53 FIna Scraan .68 1.02 1.167 4.01 TOTAL 8.6 FIGURE J DETAIL OF PROCESS BOX MANUPACTURED FROM MARINE GRADE FIBERGLASS Sc GEL COATED FOR UV PROTECTION 5 YEAR MANUFACTURERS WARRANTY PATENTED ALL PILTER SCREENS ARE STAINLESS STEEL Tha abova flow rates ora baaad on unobatrvciad acraana. NOTES: 1.SHELF SYSTEM PROVIDES FOR ENTIRE COVERAGE OF INLET OPENING SO TO DIVERT ALL FLOW TO BASKET. 2.SHELF SYSTEM MANUFACTURED FR<M MAKNE G»40E nBERGlASS.GEL COATED FOR UV PROTECTON. 3.SHELF SYSTEM ATTACHED TO THE CATCH BASIN WTTH NON-CORROSIVE HARDWARE. 4. nLTRAV0N BASKET STRUCTURE MANUFACTURED OF MARINE GRADE nBERGLASS.GEL COATED FOR UV PROTECTiON. 5. FH.TRATION BASKET HNE SCREEN AND COARSE CONTAINMENT SCREEN MANUFACTURED FROM STAINLESS STEEL 6. nLTRATION BASKET HOLDS BOOM OF ABSORBENT MEDIA TO CAPTURE HYDROCARBONS. BOOM IS EASILY REPLACED WITHOUT REMOVMS MOUNTING HARDWARE. 7. FJLTRAT10N BASKET LOCATION IS DIRECTLY UNDER MANHOLE FOR EASY MAINTENANCE EXCLUSI\/E CAUFORNIA DISTRIBUTOR: BIO CLEAN EN\/IRONMENTAL SER>^ICE P.O. BOX BOO, OCEANSIDE, CA. 0204-0 TEL. 700—4-3S—704-0 FAX:700—4-33—31 70 Email: lrtfo^blotslman»nvtronrr»mntal.rtmt SUimE imilY PROOUCIS ARE BULT FOR BGT OEAmiB AM ARE DESiem 10 BE Fmyma NFRASIRUCWRE AHD SHOIMD lAST FDR DECADES. SLJFslTIRErE TEC: M MOL-OGIEIS 70B CLEARLAKE RD. SUITE 02 COCOA FL. 32922 TEL. 321—037—7332 FAX 321—037—7304 CURB INLET BASKET SYSTEM DATE: 04-/1 Z/04- DRAFTER: N.R.B. SCALE:SF — 7» UNITS —INCHES 57 ENVIRO-SAPE HIGH CAPACITY ROUND GRATE INLET SKIMMER THE CURB SHELP BASKET WATER CLEANSING SYSTEM HIGH CAPACITY CURB INLET BASKET ROUND GISB POR MOUNTING UNDER MANHOLE DIMENSIONS WIU VARY DETAIL OF PARTS ENSURE 1 WIDTH OF INLET W&l VARY ROUND CANISTER IN CYUNDRICAL BASIN MANHOLE [•^••^•j^ ^ flow FIGURE 2 DETAIL OF INSTAUATKJN FIDW RATES oar 3 FT. Baakat SO A(»^f i> <fO TOP SIDE 1 i35ja 5.50 3.42 CENTER SIDE .62 130.36 11.5 295 BOTTOM sax .56 125.30 17.50 3.17 BOTTOM .68 83.14 20.81 211 TOTAL 11.65 HGURE 3 DETAIL OF PROCESS REMOVABLE BASKET CATCHES EVERYTt^NG AND MAY BE REMOVED 1WOUGH MANHOLE WITHOUT ENTRY. 5 YEAR MANUFACTURERS WARRANTY PATENTED ALL PILTER SCREENS ARE STAINLESS STEEL NOTES: 1.SHELF SYSTEM PROVIDES FOR ENTVTE COVERAGE ^•^S£J^S!^ W«UR1C7W?£D FROM MARINE GRADE FIBERGLASS.GEL COATED FOR UV PROTECTION. ^•^&^J^!P' ^™CMED TO THE CATCH BASIN WTTH NON-CORROSIVE HARDWARE. 4. FJLTRAT10N BASKET STRUCTURE MANUFACTURED OF MARINE GRADE FJBERGtASS.GEL COATED FOR UV FWTECnON. 5. FILTRATK)N BASKET FINE SCREEN AND COARSE CONTAINMENT SCREEN MANUFACTURED FROM STAINLESS STEEL 6. FU.TRATI0N BASKET HOLDS BOOM OF ABSORBENT MEDM 70 CAPTURE HYDROCARBONS. BOOM IS EASILY W>LACED WTTHOUT REMOVING MOUNTING HARDWARE. 7. nLTRATI0N BASKET LOCATION IS DIRECTIY UNDER MANHOLE FOR EASY MAmENANCE. E^'-J^^.^J-Yf. O^L/TORN/ZA DISTRIBUTOR: BIO CLEAN EN\/IRONMENTAL SERVICE ^^9' 5S*' OCEAys/S/Oe, CA. OSO40 7^00 — 433—7B4-0 FAX:700—4-3S—3170 En-iQll: lnfo9broalmanmn\flronmmntcil.nmt SUmEE QUAUIY PRODUm ARE BUIT FOR OlSr aOMND AND ARE DESKm m BE PEimeiT Nnvmxim AM SHouiD lASr FDR DBCaCSi 738 CLEARLAKE RD. SUITE 4A2 COCOA FL. 32022 TEL. 321-837- 7352 FAX 321—037—733^ CURB INLETT BASKET SYSTEM DATE: 04-/1 Z/04-SCALE:SF — 7 S