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Home My WebLink AboutGPA 09-07; Palomar Commons; General Plan Amendment (GPA) (14)---- INTRODUCTION -1. PROJECT DESCRIPTION 1.1. Topography and Land Use ............................................................................ . 1.2. Hydrologic Unit Contribution ....................................................................... . 2. -WATER QUALITY ENVIRONMENT 2.1 Beneficial Uses .................................................................... .. -2.1.1. Coastal Waters ....................................................................................... . 2.1.2. Ground Water ....................................................................................... .. .. 3. CHARACTERIZATION OF PROJECT RUNOFF .......................................... . -3.1. Pre-Construction and Post-Construction Drainage ...................... .. 3.2. Anticipated & Potential Pollutants .............................................................. .. -3.3. Soil Characteristics ......................................................................................... . 4. MITIGATION MEASURES TO PROTECT WATER QUALITY 4.1. Construction BMPs ........................................................................................ . -4.2. Post-construction BMPs ............................................................................... .. 4.2.1. Low Impact Development BMPs ...................................................... .. 4.2.2. Source Control BMPs ......................................................................... . 4.2.3. Priority Development Project BMPs ................................................ .. -4.2.3.1 Dock Areas ............................................................................... . 4.2.3.2 Vehicle Wash Areas ................................................................ . 4.2.3.3 Surface Parking Areas ........................................................... .. -4.2.3.4 Fueling Areas ........................................................................... . 4.2.3.5 Equipment Wash Areas .......................................................... . 4.2.3.6 Outdoor Processing Areas ..................................................... .. -4.2.3.7 Outdoor Garden Sales Area .................................................. .. 4.2.4. Structural Treatment Control BMPs ............................................... .. 4.2.4.1 Nutrient Separating Baffle Boxes .......................................... . -4.2.4.2 Detention/Infiltration Systems .............................................. .. 4.2.4.3 Biofiltration Systems ............................................................... . 4.2.4.4 UrbanGreenTM Biofilter .......................................................... . 4.2.4.5 Bio Clean Trench Drain Filter .............................................. .. -5. OPERATION AND MAINTENANCE PROGRAM .......................................... . 5.1. Nutrient Separating Dame Boxes ................................................................. . 5.2. Detention/Infiltration Systems ...................................................................... . .. 5.3. Biofiltration Systems ...................................................................................... . 5.4. U rbanGreenTM Biofilter ................................................................................ .. -5.5. Bio Clean Trench Drain Filter ..................................................................... .. .. 6. SUMMARY/CONCLUSIONS .............................................................................. . ATTACHMENTS -A. Location Map -B. Project Map & Proposed Drainage Area Map (DM2) C. BMP/Water Quality Plan D. City of Carlsbad Storm Water Standards Questionnaire E. Educational Material -F. Treatment Control BMP Sizing G. Treatment Control BMP Fact Sheets H. Sample Treatment Control BMP Maintenance Forms & Information - - - - - - - --- - - - - - - - ... • 1.2 Hydrologic Unit Contribution The Palomar Airport Commons project is located within the Carlsbad hydrologic unit (4.40). The project drains southerly from Palomar Airport Road and discharges into the Canyon de las Encinas which runs westerly to the Pacific Ocean. 1.3 Priority Project Category The proposed project is designated as a priority project because it meets or exceeds the criteria set forth in the Storm Water Standards Questionnaire from the City of Carlsbad's Storm Water Standards Manual, revised 06/04/08 for a significant redevelopment. (See Attachment D for a completed copy ofthe project's Storm Water Standards Questionnaire) 2 ---- Table 2.1.2 -Beneficial Uses for Ground Water - Hydrologic Unit 5 Number ~ --4.40 + + = Excepted from MUN X= Existing Beneficial Use 0 =Potential Beneficial Use ---- - - - - - - - -- ... .. 4 .. .. -- - - - - - - - - - - - - • • 3. CHARACTERIZATION OF PROJECT RUNOFF 3.1 Pre-Construction and Post-Construction Drainage A single natural drainage discharge point is currently located within the project at the southwest comer of the site and discharges into the existing natural and man-made drainage way which flows into Encinas Creek. This discharge includes not only runoff generated from within the project site, but the previously discussed three (3) public storm drain outfall pipes which enter and discharge across the project site. The existing project site runoff pattern generally flows from east to west within existing concrete swales and man-made vegetated depressed areas. The proposed project's grading pattern and drainage facilities will maintain the existing discharge point. The design of the storm drainage system will capture the on-site runoff separate from the large flow rates from the off-site drainage areas. The off-site water will be collected within a proposed public storm drain system, combined with the private storm drain discharge locations and ultimately conveyed to the existing discharge location at the southwesterly comer of Parcel A, Portion of Lot G. Many of the drainage areas in storm drain system A will drain through landscaping or biofiltration areas before entering the private, on-site storm drain system. Some drainage areas were not able to drain to landscape or biofiltration areas due to the site's layout and grading design. These areas include the roof drains for the proposed retail anchor on the east side of the project and other areas located along the south side of the proposed retail anchor on the east side. A trench drain in a sump condition in the proposed loading dock for the proposed retail anchor will have an initial pre-treatment for storm water quality through the use of a BioClean Trench Drain Filter (or an approved equal proprietary trench drain insert) before additional storm water quality treatment takes place farther downstream in the system. Storm drain system A, including the loading dock area and those other areas unable to be pre- treated described above, will flow through a proposed Nutrient Separating Baffle Box by Bio Clean Environmental (or an approved equal proprietary water quality inlet), which will serve as a structural treatment control BMP in a BMP treatment train. The Nutrient Separating Baffle Box will remove sediment, total suspended solids (TSS), hydrocarbons, trash and debris, organics and gross solids before the runoff enters the underground detention/infiltration facility. This subsurface system will be comprised of large diameter, perforated HDPE pipe which allow runoff to infiltrate into the soil for the 851h percentile water quality event for a volume based BMP. This facility also provides storm water detention by controlling the outflow rate through the use of an elevated invert ofthe outfall pipe located downstream ofthe system. Many of the drainage areas in storm drain System B/C will drain through landscaping or biofiltration areas before entering the private, on-site storm drain system. Some drainage areas were not able to drain to landscape or biofiltration areas due to the site's layout and grading design. These areas include the roof drains for some of the proposed retail buildings on the west side of the project, the fuel island area and other areas located along the project's drive aisles or parking areas on the west side . 5 ---- • • • .. Ill ------------.. Ill .. • • .. The fuel island area will drain to an UrbanGreen Biofilter unit (or an approved equally proprietary high rate biofilter) prior to entering the storm drain system where the runoff will continue its BMP treatment train by flowing through a proposed Nutrient Separating Baffle Box by Bio Clean Environmental (or an approved equal proprietary water quality inlet) and the subsurface infiltration/detention system . The other uncaptured areas unable to be pre-treated by landscaping or bio-filtration in System B/C described above, will flow through a proposed Nutrient Separating Baffle Box by BioClean Environmental (or an approved equal proprietary water quality inlet), which will serve as a structural treatment control BMP in a BMP treatment train. The Nutrient Separating Baffle Box will remove sediment, total suspended solids (TSS), hydrocarbons, trash and debris, organics and gross solids before the runoff enters the underground detention/infiltration facility. This subsurface system will be comprised of large diameter, perforated HDPE pipe which allow runoff to infiltrate into the soil for the 85th percentile water quality event for a volume based BMP. This facility also provides storm water detention by controlling the outflow rate through the use of an elevated invert of the outfall pipe located downstream of the system. Storm drain system D will use biofiltration for storm water treatment prior to discharging directly into the proposed public storm drain system on-site. In summary, the subsurface detention/infiltration systems enable storm drain systems A and B/C to meet pre-development, peak discharge flow rates for the 100 year, 6 hour rainfall event for the overall project and, in conjunction with the propose biofiltration areas, UrbanGreen Biofilter Unit (or approved equal proprietary biofilter), Bio Clean Trench Drain Filter (or an approved equal trench drain insert) and Nutrient Separating Baffle Boxes by BioClean Environmental (or an approved equal proprietary water quality inlet), provide water quality treatment to the maximum extent practicable. 3.2 Anticipated and Potential Pollutants There is no sampling data available for the existing site. The table on the following page identifies pollutants that are associated with similar types of developments and could affect water quality. 6 • • -• • • • ---- - - - ----• ... • Anticipated and Potential Pollutants Generated by Land Use Type <;,,:":;., ' ·· · · • Geneiai'PoJJutant Ciltegorl• < { ::><~:·~,;: '• .,. , .. ,, ,~,, ~, . : ' . ' ,, '"~,:,!~'-£2U ··:: -:.:: Project Trash Oxygen Bacteria Categories Heavy Organic & Demanding Oil& & Sediments Nutrients Metals Compounds Debris Substances Grease Viruses Pesticides Detached Residential X X X X X X X Development Attached Residential X X X p(1) p(2) p(1) X Development Commercial Development p(1) p(1) p(2) X p(S) X p(3) p(S) >1 00 000 ft2 Heavy industry /industrial X X X X X X development Automotive X x'4)(5) X X Repair Shops Restaurants X X X X Steep Hillside Development X X X X X X >S,OOOW Parking Lots p(1) p(1) X X p(1) X p(1) Retail Gasoline X X X X X Outlets Streets, p(1) x'4) p(5) Highways& X X X X Freeways X = anticipated P = potential (1) A potential pollutant if landscaping exists on-site. (2) A potential pollutant if the project includes uncovered parking areas. (3) A potential pollutant if land use involves food or animal waste products. (4) Including petroleum hydrocarbons. is) Including solvents. Table 3.2.1: Anticipated and Potential Pollutants Generated by Land Use Type (from Table 2 ofthe City of Carlsbad's Storm Water Standards Manual; revised 01/22/10) Palomar Airport Commons: Anticipated Pollutants -Heavy Metals -Organic Compounds -Trash & Debris -Oxygen Demanding Substances -Oil & Grease -Bacteria & Viruses -Sediments -Nutrients Potential Pollutants -Pesticides 7 -- ----- -----... -- - - ----- IIIII 1111 3.3 Soil Characteristics A subsurface investigation was performed on the property to explore and sample the subsurface soils. The excerpted results of the investigation are as follows: "Geologic Setting" "The subject property lies within the Peninsular Ranges geomorphic province. The Peninsular Ranges geomorphic province, one of the largest geomorphic units in western North America, extends from the Transverse Ranges geomorphic province and the Los Angeles Basin, south to Bqja California. It is bound on the west by the Pacific Ocean, on the south by the Gulf of California and on the east by the Colorado Desert Province. The Peninsular Ranges are essentially a series of northeast-southeast oriented fault blocks (CGS, 2002). Major fault zones and subordinate fault zones found in the Peninsular Ranges Province typically trend in a northwest-southeast direction. "During the Pleistocene-age, regional sea levels gradually increased, causing wave-cut platforms, most of which were covered by relatively thin marine and nonmarine terrace deposits, formed as the sea receded from the land. Fluvial erosion caused by periods of heavy rainfall, along with lowering sea levels noted during the Quarternary-age, resulted in the existing rolling hills, mesas, and canyons that characterize the setting of the site vicinity. "The subject property is located within an area of California known to contain a number of active and potentially active faults. The property is not located within a State of California Earthquake Fault Zone (Hart and Bryant, 1997)." "Regional Groundwater" A review of USGS topographic maps of the subject site area indicates regional topographic relief slopes towards the southwest. This information suggests that regional groundwater in the site vicinity can be inferred to flow in the same general topographic direction. Within the subject property, groundwater was encountered in three (3) of the subsurface exploratory excavations recently drilled onsite at approximate depths of 17 to 37 feet below the existing ground surface (bgs) as part of our geotechnical evaluation. A previous subsurface exploration performed on the overall site by Leighton Consulting, Inc. (Leighton, 2006) reported encountered groundwater at depths of 16 to 28 feet bgs at the time of subsurface exploration. EEl reviewed the California Department of Water Resources Water Data Library (VJDL, 2009) Website for information regarding wells and depth to groundwater information. A review indicated that no public water wells are located on or in the immediate vicinity of the subject property. "Fill" "Undocumented artificial fill materials of variable thickness were encountered in our exploratory excavations at various locations and appear to be associated with minor fills that were utilized to create the previous driving range features and utility baclifill. In addition, recently imported fill materials also appear to underlie portions of the easterly edge of the subject site area. In general, the fill materials were observed to be comprised of light brown silty sands with organics consisting of scattered roots and rootlets. These materials were noted to be typically damp to slightly moist and loose at the time of our subsurface exploration and are not considered suitable for the support of additional fills and/or structures in their current condition. 8 -- - ---------- .. -• ------- ... A more detailed description of the encountered soils is provided on the boring logs included as Appendix A. " "Quaternary Alluvium " "Quaternary-aged alluvium deposits were encountered in our exploratory borings to maximum depths of approximately 20 feet below the existing ground suiface. In general, the encountered portions of these deposits were observed to be comprised of brown and orange-brown sandy clays, clayey sands, and lesser amounts silty sands, sandy silts and silty clays. The sandy portions of these materials were noted to be typically slightly moist to very moist and loose to medium dense, while the clayey portions were observed to be moist to wet and medium stiff to stiff at the time of our subsurface exploration. Zones of concentrated organics were observed locally within the alluvium. A more detailed description of the encountered soils is provided on the boring logs included as Appendix A. " "Santiago Formation" 'The sedimentary bedrock unit underlying the undocumented fill and alluvium is the Tertiary- aged Santiago Formation. The Santiago Formation as encountered in all of our exploratory borings and in one of our exploratory test pits to maximum depths of 41% feet below the existing ground surface. In general, the encountered portions of these deposits were observed to be comprised of gray and brown to olive brown silty claystones, siltstones and clayey to silty sandstones. The sandy portions of these materials were noted to be typically slightly moist to very moist and medium dense to dense, while the clayey portions were observed to be moist to very moist and medium stiff to very stiff at the time of our subsurface exploration. A more detailed description of the encountered soils is provided on the boring logs included as Appendix A., "Surface and Ground Water" "No suiface water was evident at the time of our field exploration. Groundwater was encountered in three of our exploratory borings at approximate depths of 17 feet to 3 7 feet below existing grades. However, it should be noted that variations in groundwater may result from fluctuations in the ground surface topography, subsurface stratification, precipitation, irrigation and other factors that may not have been evident at the time of our subsurface exploration. " (Note: The above selected excerpts, regarding general soil characteristics, were obtained from "Geotechnical Investigation, Proposed Retail Development, Palomar Airport Commons, Carlsbad, San Diego County, California" as prepared by EEl Geotechnical & Environmental Services, dated January 13, 2010; EEl Project No. SUD-70986.1) 9 --- ----------.. ---.. -- - - ---.. IIIII .. Ill .. • • IIIII 4. MITIGATION MEASURES TO PROTECT WATER QUALITY To address storm water quality for the project, BMPs will be implemented during construction and post-construction. 4.1 Construction BMPs Construction BMPs will be designed and located on the Grading Plan Construction Documents. Construction BMPs for this project will be selected, installed and maintained to comply with all applicable ordinances and guidance documents. 4.2 Post-construction BMPs Anticipated and potential pollutants, as noted in Section 3.2, will be addressed through three types of BMPs: Low Impact Development (LID) Site Design, Source Control and Structural Treatment Control. Using Table 4.2 on the following page, the project is required to implement LID Site Design BMPs, Source Control BMPs and to select one or more applicable and appropriate Structural Treatment Control BMPs since the proposed project was identified as a priority development project in Section 1.3 of this report. 10 ----- -• --- ---- - - - ----- • .. IIIII 4.2.1 Low Impact Development (LID) Site Design BMPs The proposed use of the project site will be a commercial/retail facility with on-site loading and parking facilities. The following LID Site Design BMPs were utilized to help minimize the introduction of the pollutants of concern. • The impervious surfaces areas have been minimized by reducing the parking lot drive aisle widths to minimum dimensions considering fire department access, pedestrian and vehicular safety standards. Wherever practical, the parking lot drive aisles are double loaded, which is the most efficient parking configuration. • Runoffwill be safely conveyed from the tops of any slopes. • The project's slopes are anticipated to be landscaped with a mix of native and drought tolerant trees, shrubs and groundcovers. • Subsurface reservoir beds of perforated HDPE pipe will be used in the private storm drain design to infiltrate storm water runoff for storm water quality and to mitigate any increase in post development peak flow rates and volumes above pre-development levels. • Amended in-situ soils, amended import soil or imported, engineered soils which promote infiltration, are proposed to be placed into the biofiltration areas. • Compaction of the biofiltration and landscaped areas will be minimized to allow for rainfall interception and infiltration to occur. • Many roof and impervious surface areas have been directed to multiple landscape areas, co-designed as a biofiltration areas, prior to entering the private storm drain system. • Rip rap energy dissipaters will be sited to prevent erosion from occurring where concentrated runoff from public and private storm drain outfalls and where roof drain downspouts discharge into biofiltration areas, primarily for three buildings on the westerly side ofthe project. 4.2.2 Source Control BMPs Source Control BMPs will consist of measures to prevent polluted runoff from occurring on this project. • An educational component will be provided to the owner who will receive a set of brochures developed by various local agencies (see Attachment E for copies of the material). o Be A Clean Water Leader (thinkbluesdorg, City of San Diego) o Storm Water Pollution Prevention Program "Dumpsters & Loading Dock Areas" (thinkbluesdorg, City of San Diego) o Smart Tips for Hiring a Pest Control Service (City of San Diego Storm Water Pollution Program) o Storm Water Pollution Prevention Program "Impervious Surfaces: Cleaning Sidewalks, Pavements, Patios, Parking Lots & Driveways" (thinkbluesdorg, City of San Diego) 12 -- .. • -• ------ - - - ----- • • IIIIi o Storm Water Protection Program "Trash" (City of Carlsbad) o Storm Water Protection Program "Erosion Control" (City of Carlsbad) o Best Management Practices for Businesses "Commercial and Industrial" (City of Carlsbad) o "Hold onto Your Butts Before They Get a Hold on the Environment" (City of Carlsbad) o Fact Sheet 7, "Bioretention Systems" (County of San Diego LID Appendix, 12131/2007) • Storm drain inlets will be stenciled with a message warning citizens not to dump pollutants into the storm drain system. The stenciling should be labeled with prohibitive language, such as "NO DUMPING-I LIVE DOWNSTREAM", and graphical icons to discourage illegal dumping from occurring. The stencil designs should be in accordance with City of Carlsbad designs and satisfactory to the City Engineer. Stamping may also be required in Spanish. • Signs with prohibitive language and/or graphical icons may be posted which prohibit illegal dumping at public access points along channels and creeks within the project area, trailheads, parks and building entrances. • Proposed trash storage areas will be paved with an impervious surface and designed not to allow run-on from adjoining areas. The trash enclosures will be walled and have impervious roofs to prevent off-site transport of trash and contain trash containers with attached lids to exclude rain from entering the containers. • The project will have the fire sprinkler systems designed to enable operational maintenance and testing to be discharged to the sanitary sewer system. • In compliance with the Water Conservation in Landscaping Act, the site will employ rain shutoff devices to prevent irrigation during and after precipitation. The project's irrigation system will be designed to each landscape area's specific water requirements. In addition, the use of flow reducers or shutoff valves triggered by a pressure drop to control water loss in the event of a broken sprinkler head or lines will be used on the project. Lastly, the proposed project's landscape areas will not be excessively fertilized and, when combined with the monitoring of irrigation, will reduce the potential for polluted runoffto be generated from landscaped areas. • Pesticides should be used as a last line of defense against pests and should only be applied by an individual trained and certified in that field. Other measures should implemented first before pesticides are used such as: keeping pests out of buildings using physical barriers, physical pest elimination techniques, modify landscaping design with pest resistant species and relying on natural enemies to control pets before pesticides are used . • The project will have regular scheduled parking lot sweeping and cleaning to help reduce the amount of trash, sediment and debris. 13 - --- --- - ------- - - -- 4.2.3 Priority Development Project BMPs Since the proposed project meets the priority development project criteria because the project is a significant redevelopment which will create, replace or add at least 5,000 s.f. on an existing development. The following BMPs are required for the anticipated individual priority development project categories and are shown on the next page. • DockAreas • Vehicle Wash Areas • Surface Parking Areas • Fueling Areas • Equipment Wash Areas • Outdoor Processing Areas • Outdoor Garden Sales Area The following BMPs for individual priority development project categories are not applicable for this project. • Private Roads • Residential Driveways & Guest Parking • Maintenance Bays • Hillside Landscaping 4.2.3.1 Dock Areas The following dock area BMPs have been incorporated into the project's design: The surrounding areas near the proposed loading dock will be graded to preclude urban run-on. The proposed loading dock is located in a sump condition and will have a Bio Clean Trench Drain Filter by Bio Clean Environmental installed as an as an initial pre-treatment for trash, debris, large suspended solids and hydrocarbons before discharging to the on-site private storm drain system for further water quality treatment through subsurface infiltration. This drainage area will be able to be isolated from the storm drain system by a mechanically operated shut-off valve to isolate spills in the loading dock. The control for the shut-off valve will be on the outside of the building, adjacent to the loading dock area to prevent spills from being discharged to the storm drain system. The trench drain will be always operational and the shut-off valve will be open. The valve will be closed in the event of a spill in the loading area to prevent a discharge. The proposed retail anchor store staff who regularly work in the loading dock area and/or handle deliveries will be trained on the location and use of the shut-off valve. The Bio Clean Trench Drain Filter will be serviced by the developer or their agents, discussed in detail in Section 5 of this report. 14 ----------------- - - - - --- .. 1111 • 4.2.3.2 Vehicle Wash Areas The following vehicle wash area BMPs have been incorporated into the project's design: The proposed vehicle wash facility will be self-contained to preclude run-on and run-off and covered with a roof or overhang. The vehicle wash area will be equipped with a clarifier or other type of pre-treatment facility before being connected to the sanitary sewer system on-site. 4.2.3.3 Surface Parking Areas The following surface parking area BMPs have been incorporated into the project's design: Proposed landscaping areas have been incorporated into the project's drainage design and are co- designed as biofiltration areas for storm water treatment. Parking areas that are not able to drain to biofiltration areas will either be treated by an UrbanGreen™ Biofilter, Nutrient Separating Baffle Boxes by Bio Clean Environmental and/or underground infiltration or a combination thereof. 4.2.3.4 Fueling Areas The following fueling area BMPs have been incorporated into the project's design: The proposed fueling area will be paved with Portland cement concrete and will extend 6.5 feet from the comer of each fuel dispenser. The proposed impervious pavement will be sloped to prevent pending and separated from the rest of the site through a grade break which prevents run-on. The proposed fueling area will drain to a UrbanGreen Biofilter unit prior to entering the on-site storm drain system. Lastly, the overhanging roof structure or canopy will be equal to the area within the fuel area's grade break and will not drain onto or across the fuel dispensing area. 4.2.3.5 Equipment Wash Areas There are no planned or allowed equipment wash areas associated with the project. 4.2.3.6 Outdoor Processing Areas There are no planned or allowed outdoor processing areas associated with the project. 4.2.3. 7 Outdoor Garden Sales Areas The planned outdoor garden sales area associated with the proposed retail anchor store will all drain to a biofiltration cell for initial storm water quality treatment. The captured runoff from this area will then flow through the downstream Nutrient Separating Baffle Box. Then the runoff will flow into the subsurface detention/infiltration system which will infiltrate the water quality volume from this area generated by the 85th percentile rainfall event. 4.2.4 Structural Treatment Control B.MPs The following structural treatment control BMP selection matrix was used to determine the appropriate structural treatment control BMPs for the project. The locations of the Structural Treatment Control BMPs are noted on the BMP/Water Quality Plan included in Attachment C of this report . 15 - --- - - - ---- - - - - -- - .. Table4. Struct ·~• t Control BMP Selecti m Matrilt Bioretention Settling Wet Ponds Infiltration High-rate Trash Racks & Pollutants of Facilities or Media High-rate Hydro Concern Facilities Basins and Practices Filters biofilters media -dynamic (LID) (Dry Ponds) Wetlands (LID) filters Devices Coarse Sediment High High High High High High High High and Trash Pollutants that tend to associate High High High High High Medium Medium Low with fine particles during treatment Pollutants that tend to be dissolved Medium Low Medium High Low Low Low Low following treatment Table 4.2.4: Structural Treatment Control BMP Selection Matrix (from Table 4 of the City of Carlsbad's Storm Water Standards; revised 06/04/08) As discussed in Section 3.2, the proposed project is anticipated to generate the following pollutants: heavy metals, organic compounds, trash and debris, oxygen demanding substances, oil and grease, and bacteria and viruses. The following structural treatment control BMPs will be implemented to address storm water quality: • Biofiltration Areas/ UrbanGreen Biofilters (CASQA TC-32) • Detention/Infiltration Systems -HDPE perforated pipes (Infiltration Basin, CASQA TC- 11) • Nutrient Separating Baffle Boxes (Water Quality Inlet, CASQA TC-50) • Bio Clean Trench Drain Filter (Drain Inlet, CASQA MP-52) 4.2.4.1 Nutrient Separating Baffle Boxes Nutrient Separating Baffle Boxes by Bio Clean Environmental (Water Quality Inlet) were selected because of their removal for trash and debris, sediments, total suspended solids {TSS), oxygen demanding substances, nutrients, metals, oils, and grease (including various hydrocarbons. These structural treatment control BMPs will function in a treatment train with biofiltration areas, UrbanGreen™ Biofilters, Bio Clean Grate Inlet Skimmer Box and a Bio Clean Trench Drain Filter upstream and detention/infiltration perforated HDPE pipes downstream. The initial pre-treatment the Nutrient Separating Baffle Boxes provide will help ensure the infiltration component of the detention/infiltration system continues to function as designed and efficiently as possible. A Nutrient Separating Baffle Box uses a series of baffles, deflectors, patented filtration screen system, skimmer and boom to remove common pollutants found in storm water runoff. The potential polluted runoff enters the unit through the closed, private storm drain system. A filtration screen captures and stores trash, debris, organics and oxygen demanding substances in the screen. The multiple baffles and sediment chambers maximize the TSS removals and eliminate scouring during large flow rates. The unit's deflectors prevent re-suspension of captured pollutants at higher flows. Lastly, the skimmer and boom capture hydrocarbons and control flow velocity, which improves the unit's removal efficiency. The treated flow then leaves the unit and enters the subsurface HDPE perforated pipe detention/infiltration systems 16 -- - - ... --- ---,,. .. -- - - - --.. - -• .. located under parking lot or landscaped areas before ultimately draining to the public storm drain system. Nutrient Separating Baffle Boxes were selected as a structural treatment control BMP because of the many benefits of the unit. Nutrient Separating Baffle Boxes are very effective in capturing and retaining TSS sediment (up to 93.3% per manufacturer's literature). The units have been shown to be able to capture and retain 99% (per manufacturer's literature) of trash and debris. The units have also been shown to have significant removal rates for metals, total nitrogen and total phosphorus as well. The units have no moving parts, relying on hydraulic energy making the unit non-mechanical and non-blocking. The units will be installed below ground and maintenance can be performed with standard equipment. The units have a relatively low cost "per cfs" treated and are considered low maintenance due to their large holding capacities. Lastly, it is important that as much trash and debris be removed from the runoff prior to entering the underground detention/infiltration facilities because the underground detention/infiltration systems are more difficult to access and maintain than other types of structural treatment control BMPs. The units were sized according to the manufacturer provided specifications, calculations are included in Attachment F, and are adequately sized since the units have ultimate inflow capacity rates greater than the proposed peak runoff rates entering the units for their respective contributing drainage areas . 4.2.4.2 Detention/Infiltration System -Perforated HDPE Pipes Perforated HDPE piping will function as detention/infiltration systems, essentially underground infiltration basins. These systems were selected for this proposed project to provide opportunities for storm water quality treatment through infiltration into the in situ soil. The HDPE detention/infiltration systems meet the intent of LID by allowing infiltration of runoff to occur while mitigating peak post development discharge rates and total runoff volumes to levels at or below predevelopment values. In addition, there is no other more effective structural treatment control BMP, according to Table 4.2.4 for pollutants of concern. The underground detention/infiltration systems will be fitted with a 3-inch diameter relief pipe at the invert elevation of the system, controlled by a gate valve. This outfall will provide a means of draining the system(s) if there is standing water in the units for an extended period or time. The underground detention/infiltration systems infiltrates the entire runoff volume from the 851h percentile rainfall event for the contributing drainage areas by having the invert elevations of the systems' respective outfall pipes at the downstream end of the systems elevated above the invert elevation of the systems. This design allows for the water quality volume to pond up to this level without discharging from the system and infiltrate into the in situ soil through the perforated pipes. The detention/infiltration systems are sized to infiltrate the runoff volume from the 85th percentile rainfall event since these structural treatment control BMPs are considered volume based. Calculations for the systems designs are included in Attachment F. 17 ---------------- - - --- -- ... .. .. 4.2.4.3 Biofiltration Systems According to The County of San Diego's LID Appendix, Fact Sheet 7, "Bioretention systems are essentially a surface and sub-surface water filtration system. In function they are similar to sand filters. Bio-retention systems incorporate both plants and underlying filter soils for removal of contaminants. These facilities normally consist of a treatment train approach: filter strip, sand bed, ponding area, organic layer, planting soil, and plants." Biofiltration systems are effective at removing sediments and pollutants which are associated with fine particles by filtration through surface vegetation, ground cover and underlying filtering media. These systems can also delay runoff peaks by providing retention capacity in the media layer and well as increasing the time of concentration due to their infiltration properties as well as reducing runoffvelocities. The addition of vegetation not only increases the aesthetic value of the area, but also enhances the filtration capacity of the system through plant uptake while helping maintain the porosity ofthe media layer. The biofiltration systems can be constructed as either large or small scale devices with in situ or amended soils. Smaller scale units, like the systems designed for this project, collect storm water from impervious areas and route the runoff to the biofiltration areas through curb cuts, zero curb sections or roof drain downspouts in a non- conveyance system design which allows ponding to occur. The biofiltration areas will be sized to allow ponding of runoff from the system's contributing drainage areas to occur. An amended soil layer, gravel layer and underdrain system will be designed to convey the treated runoff to the private on-site storm drain system. The ponded runoff infiltrates down through a mulch layer, amended soil layer and a gravel layer; ultimately discharging to the private storm drain system through the perforated underdrain pipes. The biofiltration areas will be landscaped with a combination of ground covers, plants, shrubs and/or trees selected by the project's landscape architect. The biofiltration systems will provide water quality treatment for the first 0.2" of rainfall since they are considered a flow based BMP. The systems will also convey larger rainfall events due to their integral nature in the project's drainage design. Preliminary cross-sections of the proposed biofiltration systems are included in Attachment F of this report. 4.2.4.4 UrbanGreen™ Biofilter According to The County of San Diego's LID Appendix, Fact Sheet 7, "Bioretention systems are essentially a surface and sub-surface water filtration system. In function they are similar to sand filters. Bio-retention systems incorporate both plants and underlying filter soils for removal of contaminants. These facilities normally consist of a treatment train approach: filter strip, sand bed, ponding area, organic layer, planting soil, and plants." According to the manufacturer: "The UrbanGreen™ BioFilter is an enhanced biofiltration system that combines nature's ability to treat storm water runoff with the proven performance capabilities of cartridge-based media filtration. This combination of biological and engineered media filtration create the perfect balance for the removal of common pollutants found in storm water runoff." 18 -- - - ---- ... ... ---- - - -- ... • .. • "Although the UrbanGreen™ BioFilter will complement any site, it was specifically developed as a component for low impact development (LID) sites. LID is an approach to storm water management, emphasizing the use of small, decentralized management practices to treat rainfall close to its source and facilitate infiltration back into the ground. The goal of LID is to maintain the predevelopment hydrology and to lower the overall environmental impact footprint of the site." "Common LID practices include biotiltration, bioretention and media filtration. The UrbanGreen™ BioFilter incorporates all three of these processes into one system to maximize the pollutant removal capabilities. Furthermore, the UrbanGreen™ BioFilter is specifically designed to treat small catchment areas and can easily be combined with underground infiltration, so runoff can be treated and infiltrated close to where the rain falls. This decentralized approach to managing storm water is a core principle of LID." "The design infiltration rate of the bioretention bay is controlled by the initial media permeability and a flow control orifice. Although the infiltration rate may vary in different jurisdictions, 50 in!hr (approximately 0.5 gpm per square foot) of surface area is the typical design infiltration rate. The surface of the engineered soil mixture is approximately 32 square feet which equates to a treatment capacity of 16 gpm." "Testing has shown that the engineered soil mixture in the bioretention bay can infiltrate at a rate of 360 inlhr at the design driving head of 12 inches, however an outlet flow control limits the rate so significant pollutant loads can accumulate before the media drops below the design infiltration, and maintenance is required. Using an outlet flow control to control infiltration rates rather than the media itself allows soil with a higher void volume to be used. This substantially decreases the frequency of maintenance because there is more storage volume for captured pollutants within the soil media. It also improves performance by reducing velocities in the pore spaces within the media." "The treatment capacity of the media cartridge portion of the UrbanGreen™ BioFilter is based on treating runoff at a rate of 2 gpm per square foot of cartridge surface area and utilizing two 27-in media cartridges. The treatment capacity of each cartridge is 22.5 gpm for a total capacity of 45 gpm for both cartridges. Like the soil mixture, the media cartridges are designed with a flow control, so flow through each cartridge is restricted to the design rate. This feature improves both the performance and longevity of the cartridges." "Local regulations will typically determine how much flow needs to be treated. Many regulatory agencies specify a water quality "design storm" such as a 6-month or 1-year return period storm event. Refer to local guidelines for the calculation of required design storm. Once the treatment flow rate has been determined, simply divide that amount by the total treatment capacity of the UrbanGreen™ BioFilters (61 gpm) to determine the number ofunits needed." Proprietary high-rate biofiltration systems are effective at removing sediments and pollutants which are associated with fine particles by filtration through underlying filtering media and a tree or shrub and its associate root system. The addition of vegetation not only increases the aesthetic 19 - - - -------- - -- - - - - --.. ... • "'Il 1111 • IIIII value of the unit, but also enhances the biofiltration component of the system through plant uptake while helping maintain the porosity of the media layer. The one (1) UrbanGreen™ BioFilter on-site was sized to allow a maximum water quality flow rate of 61 gallons per minute to flow to the unit based upon a "first flush" rainfall event of 0.2", since the units are considered a flow based BMP. A preliminary sizing calculations of the proposed UrbanGreen™ BioFilter unit is included in Attachment F of this report. 4.2.4.5 Bio Clean Trench Drain Filter Trench drain storm drain inserts are devices which can be inserted into new or existing trench drain designs to provide runoff contaminant removal. Pollutants are removed by runoff entering the trench drain and flowing through the filter element(s) which are comprised of hydrocarbon absorbent pouches. These pouches filter the runoff, capturing oil and grease before the runoff leaves the drainage insert and flows to the outlet point of the trench drain. Larger sediment, trash and debris are trapped by the fiberglass walls of the insert unit and which captures larger debris and trash and prevents them from exiting the trench drain. A Bio Clean Trench Drain Filter by Bio Clean Environmental was selected because it provide adequate trash and debris removal in trench drain applications and, with the addition of sorbent filled pouches, effectively treats "first flush" runoff for potential oil and grease pollutants. The unit has a low installation cost and can be installed into traditional storm water infrastructure. Routine regular maintenance is cost effective and can be performed quickly and easily without any special equipment. The storm drain insert in the loading area's trench drain is located in a sump condition and will be used in series, i.e. a treatment control BMP treatment train, as an initial pretreatment for storm water quality before runoff from this area is discharged to the adjacent private, on-site storm drain system where it will flow to the proposed detention/infiltration system for further water quality treatment. In addition, this drainage area will be able to be isolated from the storm drain system by a mechanically operated shut-off valve to isolate spills in the loading dock. The control for the shut-off valve will be on the outside of the building, adjacent to the loading dock area to prevent spills from being discharged to the storm drain system. The drainage insert used for this project was sized using the 0.2 of an inch ofrainfall required for a flow based BMP. A sizing calculation for the trench drain insert is included in Attachment F of this report. 20 - --- -------- • -• -- - --• • • .. • 1111111 Ill • Ill 5. OPERATION AND MAINTENANCE PROGRAM Designated Responsible Party: Sudberry Development, Inc. 5465 Morehouse Drives, Suite 260 San Diego, California 92121 (858) 546-3000 A training program will be administered and implemented by Sudberry Development, Inc. This program will consist of, at a minimum: the disbursement of the brochures and flyers, included in Attachment E, to all operation and maintenance staff and future tenants ofthe project. Sudberry Development, Inc will complete and maintain operation and maintenance forms to adequately document all maintenance performed on the project's structural treatment control BMPs. These records should be kept on file for a minimum of five (5) years and shall be made accessible to the City of Carlsbad for inspection upon request at any time. Sudberry Development, Inc will also provide an annual verification of the effective operation and maintenance of each and every city-approved structural treatment control BMP by the party responsible for the maintenance of the structural treatment control BMP. The annual verification shall be submitted to the enforcement official in a format as approved by the city prior to the start of the rainy season. All waste generated from the project site is ultimately the responsibility of Sudberry Development, Inc. Disposal of sediment, debris, landscape waste, soil, filter media, trash, etc. will comply with applicable local, county, state, and federal waste control programs. Suspected hazardous waste should be analyzed to determine proper disposal methods. The following operation and maintenance plans have been developed for each type of structural treatment control BMP used on this project. These are minimum requirements only. The maintenance frequency and/or scope may be increased, if necessary, in order to meet and/or maintain the level of storm water quality treatment required of this project. All costs associated with the operation and maintenance of the structural treatment control BMPs listed below will be funded by Sudberry Development, Inc. 21 - - ---- ------------ - -- • • IIIII 5.1 Nutrient Separating Baffle Box Operating Schedule: The Nutrient Separating Baffle Boxes will be operational all year long. The units should be inspected and maintained regularly to ensure the adequate performance and function of the unit. Manufacturer's Information: BioClean Environmental Services, Inc. P.O. Box 869 Oceanside, CA 92049 1-760-433-7640 Maintenance Frequency: Sudberry Development, Inc. will contract with the manufacturer or another qualified company for all inspection, maintenance and service for the units. Records will be kept for at least 5 years. Maintenance should be performed 4 times per year on the following schedule: End of September- Mid-November- Mid-February- Mid-May- Pre-Rainy Season Inspection Inspect and clean unit after several rainfall events with accumulated rainfall greater than 0.5''. Inspect and Clean Unit Post Rainy Season Inspection (Inspect, Pump down unit, Clean out, power wash and inspect) Maintenance: Nutrient Separating Baffle Boxes should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The unit is maintained by opening the access hatches or manholes. The gross solids are removed from the screening basket with a vactor truck. The hinged bottom screen panels are opened to provide access to the sediment chambers and the sediment chambers are vacuumed out with a vactor truck. It is easiest to maintain a system when there is no flow entering. For this reason, cleanout/maintenance of the system should be scheduled during dry weather. The maintenance of this system should be coordinated with the maintenance of the CDS™ units to limit the potential for pollutants to be flushed downstream. Safety: Before entering into any storm sewer or underground detention/infiltration system, it is recommended to check to make sure that all OSHA and local safety regulations and guidelines are observed during the maintenance process. Hard hats, steel-toed boots and any other appropriate personal protective equipment shall be worn at all times. Hazardous Waste: All waste generated from the project site is ultimately the responsibility of Sudberry Development, Inc. Disposal of sediment, debris, landscape waste, soil, filter media, trash, etc. will comply with applicable local, county, state, and federal waste control programs . Suspected hazardous waste should be analyzed to determine proper disposal methods. A solid or liquid waste is considered a hazardous waste if it exceeds the criteria listed in the CCR, Title 22, Article 11. 22 ... ------------------ - - - --- .. • Estimated Annual Costs: 5.2 Cleaning & Service: 2 cleanings per unit x 2 units x $1,000/time = $4,000.00 Annual Inspection: Once per year x 2 units x $1,000/time = $2,000.00 Estimated Annual Operating Cost= $6,000.00 Detention/Infiltration System -HDPE Perforated Pipes Safety: Before entering into any storm sewer or underground detention/infiltration system, check to make sure that all OSHA and local safety regulations and guidelines are observed during the maintenance process. Hard hats, steel-toed boots and any other appropriate personal protective equipment shall be worn at all times. Inspection Frequency: Inspections are recommended at a minimum on an annual basis. The first year of operation may require more frequent inspections. Frequency of inspections will vary significantly on the local site weather and site conditions. An inspection schedule should be established for each installation. Inspections: Inspection is the key to effective maintenance and is easily performed. The entire treatment train should be inspected and maintained beginning with the upstream device and continuing downstream to the discharge orifice located immediately downstream of the detention/infiltration chambers. Maintenance: The underground systems are accessed through manholes above each system. Underground storm water detention/infiltration systems should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend heavily on site activities rather than the size or configuration of the system. Silt should be removed if accumulated silt is interfering with the operation of the system (i.e. blocking outlet pipes or significantly reducing the storage capacity). It is easiest to maintain a system when there is no flow entering. For this reason, cleanout/maintenance of the system should be scheduled during dry weather. The maintenance of this system should be coordinated with the maintenance of the Nutrient Separating Baffle Boxes to limit the potential for pollutants to be flushed downstream. A vactor truck or similar device can be used to remove sediment and trash from the treatment train. High pressure water jets can be used to dislodge and remove any accumulated sediment or debris and the vacuum truck will collect and properly dispose of the resulting runoff. Once maintenance is complete, replace all manhole rims and access covers. It is important to document maintenance events of the Inspection and Maintenance Log and records should be kept for a minimum period of five years. Hazardous Waste: All waste generated from the project site is ultimately the responsibility of Sudberry Development, Inc. Disposal of sediment, debris, landscape waste, soil, filter media, trash, etc. will comply with applicable local, county, state, and federal waste control programs. Suspected hazardous waste should be analyzed to determine proper disposal methods. A solid or 23 ----- • • - --- -- - - - - • .. .. liquid waste is considered a hazardous waste if it exceeds the criteria listed in the CCR, Title 22, Article 11. Expected Annual Costs: The expected annual costs are based cost estimates provided by the manufacturer: Jet Truck/Vactor Removal: 2 clean outs per system x $1200/clean out x 2 systems= $4,800.00 Annual Inspection & Service: Once per year per system x 2 systems x $500/time = $1,000.00 Estimated Annual Operating Cost = $5,800.00 5.3 Biofiltration Systems Operating Schedule: The biofiltration systems will be operational year round and should be inspected and maintained as often as needed to ensure adequate hydraulic function and water quality treatment function of the systems are maintained at all times. Inspection Activities Suggested Frequency Inspect soil and repair eroded areas Monthly - Inspect for erosion or damage to vegetation, preferably at the end of the wet season to schedule dry season maintenance and before major wet season Semi-annually runoff to be sure the areas are ready for the wet season. However, additional ~ction after periods of heavy runoff is recom111ended. ___ , __ _ . ~ Inspect to ensure grasses, ground covers, vegetation is well established. If~ not, either prepare soil and reseed or replant with appropriate alternative Semi-annually species. Install erosion control blankets if necessary. Check for debris and litter, areas of sediment accumulation Semi-annually Inspect health of trees and shrubs . Semi-annually_ Inspect system cleanouts and outfall structures _ ~mi-annually Inspect biofiltration systems on a weekly basis during the wet season, after a rainfall event of 0.5'' or more and frequently during extended periods of wet l As specified weather. Maintenance Activities Suggested Frequency . : At project Water plants dmly for 2 weeks . ________ j__~9_mp. letiop_ Rem()ve litter and debris -----~----~--Mo!J:!h!L __ Irrigate biofiltration areas during dry season (April through October) or when • A d d . . . ~· snee e necessary to mamtam vegetatiOn. n ----·· ·- _frovide weed control, if necessary, to control invasiv~species _ _ As 11_eeded Remove sediment I As needed -~-· ---· ~------·----1 Re-mulch void areas, especially prior to the wetseason ... 1 .. As needed Treat diseased trees and shrubs i As needed --·---------- Mow turf areas, if an_y As needed 24 ------.. • .. • .. -.. -- - - - - .. Maintenance Activities (con't) Suggested Freauency Repair erosion at inflow points As needed Repair outflow structures As needed -- Unclog underdrain system As needed Regulate soil pH As needed --· Remove and replace dead and diseased vegetation ·-As needed -- Add mulch Annual ·- Replace tree stakes and wires Annual Mulch should be replaced every 2 to 3 years or when bare spots appear. Every 2-3 years, or as needed Roto-till or cultivate the surface ifthe system does not draw down in 48 hours As needed Expected annual operating costs: The expected annual costs of maintaining and operating the project's biofiltration systems are: 7% of construction cost x $1 0/square foot construction cost x 15,800± square feet of area Estimated Annual Operating Costs = $11,060.00 Note: Estimated O&M costs for biofiltration areas taken from the County of San Diego's Appendix H, "Estimated O&MCostsfor BMP Project", dated 01/23103. 5.4 UrbanGreen™ Biofilter The UrbanGreen™ BioFilter should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit (i.e. unstable soils or heavy winter sanding will cause the system to fill more quickly but regular sweeping will slow accumulation). Maintenance of the UrbanGreen™ Biofilter should be performed by a qualified professional who has experience with maintenance of storm water management systems. CONTECH, the products manufacturer, offers a full service maintenance compliance program that includes inspection, cleaning and compliance reporting at a competitive price. For more information on this service, please contact CONTECH at 800.338.1122 or maintenancecompliance@contech-cpi.com. Inspection and Routine Maintenance Inspection is the key to effective maintenance. Inspect annually unless local regulations or site conditions require more frequent inspection. Routine maintenance, defined as trash and debris removal and general upkeep, should be performed during each inspection if necessary. First record the height, width and condition of the tree. Once these recordings have been taken, the tree grate should be removed to observe the bioretention bay. Any trash and debris that has collected there should be removed and disposed of appropriately. 25 - - --- • ---- ----- - - - - .. • Ill .. • .. • The design infiltration rate of the engineered soil mixture within the bioretention bay is 50 inlhr with 12 inches of driving head. Testing has shown that a fresh batch of the UrbanGreen™ BioFilter engineered soil mixture has an infiltration rate of 360 in/hr with 12 inches of driving head. If captured pollutants have occluded the media and the infiltration rate of the engineered soil mixture is less than the design infiltration rate, then maintenance of the soil is required. Local jurisdictions may recommend a specific infiltration test to determine the infiltration rate of the soil mixture. However, in the absence of such guidance, a simple test can be performed to estimate the infiltration rate. The following items are required: 4-in diameter, thin wall PVC pipe approximately 15-in long; a mallet; filter fabric; and 2 gallons of water. Use the mallet to drive the PVC pipe 3 inches into the engineered soil mixture in a location away from the base of the tree. Cut a 4-in diameter piece of filter fabric and place the fabric in the pipe at the soil surface level. Fill the pipe with 12 inches of water above the filter fabric and record the time it takes for all of the water to drain. If the measured time is greater than fourteen minutes, then a portion of the engineered soil mixture needs to be replaced. Two infiltration tests should be performed at different locations within the bioretention bay for accuracy. If results from the infiltration tests indicate that the infiltration rate of the soil mixture has dropped below the design standard, then the top layer of the engineered soil mixture should be replaced. Studies have shown that the majority of all captured pollutants reside in the top 2-3 inches of soil and therefore it is likely that only this layer needs to be replaced (California Stormwater Quality Association (CASQA), New Development and Redevelopment Handbook, January, 2003). Replacement soil is available from CONTECH or another source as long as the original soil specifications are maintained. Please note that when replacing the engineered soil mixture, the riprap which protects the inlet from scour should be collected and set aside for use with the new soil once the new soil has been installed, the riprap should be placed back at the inlet in a 2' by 2' pattern. Since the bioretention bay has been inspected and maintenance procedures completed, the tree grate should be put securely back in place. Inspection and maintenance of the media cartridge bay are also critical to the overall performance of the system. Inspection should be performed at the same time as the inspection of the bioretention bay. Remove the cover over the media cartridge bay and observe the accumulated pollutants within the chamber. If more than three inches of sediment is found on the chamber floor or on the tops of the cartridges, then cartridge replacement should be performed. Additionally, if standing water resides in the chamber for greater than twenty-four hours after a storm event, then cartridge replacement should be performed . Depending on site and climatic conditions, maintenance frequency of the media cartridges should range from 3 to 5 years. Instructions for cartridge replacement are provided in the Non- Routine Maintenance section below. All observations from inspection of the media cartridge bay should be recorded in the maintenance log . 26 ------------- - - - - - -- .. .. Non-Routine Maintenance Non-routine maintenance is defined as clean-out of the media cartridge bay and replacement of cartridges. Replacement cartridges can be ordered by contacting CONTECH at 800.338.1122 or maintenancecompliance@contech-cpi.com. The first step in the clean-out of the media cartridge bay is to remove the sediment and debris that has collected in this chamber. A vacuum truck or manual operation can be used for this procedure. Once the sediment and debris has been removed, the existing cartridges should be removed from the system. Cartridges are connected to the underdrain manifold by a simple quarter-tum connection and are easily disconnected. Once the cartridges are removed from the vault, any remaining sediment and/or debris should be cleaned out. The final step in the cartridge replacement process is to install the replacement cartridges. Replacement cartridges should be installed securely to the quarter-tum connection system and the cover placed securely back over the media cartridge bay. General Maintenance Notes All OSHA standards for health and safety should be followed at all times when inspecting or maintaining the UrbanGreen™ Biofilter. Furthermore, disposal of pollutants removed from the UrbanGreen™ Biofilter should be performed in accordance with all regulatory requirements. Expected annual operating costs: The expected annual costs of maintaining and operating the project's UrbanGreen Biofilter units are: Annual Inspection & Service: Twice per year per unit x $500/time x 1 units= $1,000.00 Estimated Annual Operating Cost= $1,000.00 5.5 Bio Clean Trench Drain Filter Operating Schedule: The trench drain inlet storm drain insert will be operational all year long and should be maintained to ensure the adequate filtration of the storm water runoff and debris removal. Manufacturer's Information: Bio Clean Environmental Services, Inc. P.O. Box 869 Oceanside, CA 92049 1-760-433-7640 Maintenance Frequency: Sudberry Development, Inc. shall contract with the manufacturer or another qualified company for all inspection, maintenance and service of the insert. Service records will be kept for at least 5 years and maintenance should be performed 3 times per year on the following schedule: End of September-Pre-Rainy Season Maintenance Mid-January -During Rainy Season Maintenance Mid-May-Post Rainy Season Maintenance 27 ---.. - - -- - --- .. • • The inspection of the trench drain inlet insert can be performed with and on the same frequency as the regular maintenance . Routine Service: The sediment and debris should be collected from around the inlet, if present. The trench drain should be inspected for defects or illegal dumping. {If illegal dumping has occurred, the property owner shall be immediately notified.) After the grate has been removed, the filter housing and outlet adaptor are removed. The hydrocarbon booms should be removed and the components of the system should be thoroughly inspected. Repairs should be made immediately, if necessary. The booms should be inspected, cleaned and/or replaced if necessary. Next, a vactor-truck can collect debris trapped in the trench drain. Once all the debris is removed, the unit should be reassembled and the grate replaced. Specific Maintenance: The hydrocarbon booms should be inspected during the three inspections per year. The booms are expected to be replaced once annually and should be replaced more often if necessary or if defects are noticed. When re-installing the booms, they should line the entire length of the BioClean Trench Drain Filter tray and all should be replaced simultaneously. Hazardous Waste: All waste generated from the project site is ultimately the responsibility of Sudberry Development, Inc. Disposal of sediment, debris, landscape waste, soil, filter media, trash, etc. will comply with applicable local, county, state, and federal waste control programs. Suspected hazardous waste should be analyzed to determine proper disposal methods. A solid or liquid waste is considered a hazardous waste if it exceeds the criteria listed in the CCR, Title 22, Article 11. Expected annual operating costs: The expected annual costs of maintaining and operating the project's storm drain inserts are: 1 BioClean Trench Drain Filter x $1,183.40/unit/year = $1,183.40 Estimated Annual Operating Costs = $1,183.40 Note: Estimated O&M costs for the trench drain .filter taken from the County of San Diego's Appendix H, "Estimated O&M Costs for BMP Project", dated 01123/03. Total Estimated Annual Operating Costs for Project = $25.050.00 28 -----• -• • .. 1111 • ---------- -- .. ATTACHMENT A LOCATION MAP ---- --.. -• • .. • .. ----------- • • • • -- ATTACHMENT B PROJECT MAP AND PROPOSED DRAINAGE AREA MAP (DM2} ATTACHMENT C BMP/WATER QUALITY SHEET .. ..... ... - --.. .. .. • .. • .. ----- • • -.. -- .. .. -ATTACHMENT D -CITY OF CARLSBAD -STORM WATER STANDARDS QUESTIONNAIRE - - ·• - - -... .... ... -- • • ... .. - -- ---- - - ----------------- ... IIIII I SECTION 1 NEW DEVELOPMENT PRIORITY PROJECT TYPE YES NO Does you project meet one or more of the following criteria: 1. Home subdivision of 100 units or more. Includes SFD, MFD, Condominium and Apartments 2. Residential development of 10 units or more. Includes SFD, MFD, Condominium and Apartments 3. Commercial and industrial development greater than 100, 000 sguare feet including parking areas. Any development on private land that is not for heavy industrial or residential uses. Example: Hospitals, Hotels, Recreational Facilities, Shopping Malls, etc. 4. Heavy Industrial I lndustrv greater than 1 acre (NEED SIC CODES FOR PERMIT BUSINESS TYPES) SIC codes 5013,5014, 5541, 7532-7534, and 7536-7539 5. Automotive 'repair shop. SIC codes 5013, 5014, 5541, 7532-7534, and 7536-7539 6. A New Restaurant where the land area of development is 5,000 sguare feet or more including parking areas. SIC code 5812 7. Hillside development (1) greater than 5,000 square feet of impervious surface area and (2) development will grade on any natural slope that is 25% or oreater B. EnvironmentallY Sensitive Area fESAJ. Impervious surface of 2,500 square feet or more located within, "directly adjacent"2 to (within 200 feet), or "discharoino directly to"3 receivino water within the ESA 1 9. Parking lot. Area of 5,000 square feet or more, or with 15 or more parking spaces, and potentially exposed to urban runoff 10. Retail Gasoline Outlets-serving more than 100 vehicles per da'i Serving more than 100 vehicles per day and greater than 5,000 square feet 11. Streets. roads, drivewavs, highwavs, and freewa"t.S. Project would create a new paved surface that is 5,000 square feet or greater. 12. Coastal Development Zone. Within 200 feet of the Pacific Ocean and (1) creates more than 2500 square feet of impermeable surface or (2) increases impermeable surface on property by more than 10%. 1 Environmentally Sensitive Areas include but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special Biological Significance by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); water bodies designated with the RARE beneficial use by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); areas designated as preserves or their equivalent under the Multi Species Conservation Program within the Cities and Count of San Diego; and any other equivalent environmentally sensitive areas which have been identified by the Copermittees. 2 "Directly adjacent" means situated within 200 feet of the environmentally sensitive area. 3 "Discharging directly to" means outflow from a drainage conveyance system that is composed entirely of flows from the subject development or redevelopment site, and not commingled with flow from adjacent lands. Section 1 Results: If you answered YES to ANY of the questions above you have a PRIORITY project and PRIORITY project requirements DO apply. A Storm Water Management Plan, prepared in accordance with City Storm Water Standards, must be submitted at time of application. Please check the "MEETS PRIORITY REQUIREMENTS" box in Section 3. If you answered NO to ALL of the questions above, then you are a NON-PRIORITY project and STANDARD requirements apply. Please check the "DOES NOT MEET PRIORITY Requirements" box in Section 3 . SWMP Rev 6/4/08 --.. - ------ .. --------.. • • .. .. • ... .. ... I SECTION2 SIGNIFICANT REDEVELOPMENT: YES NO 1. Is the project redeveloping an existing priority project type? (Priority projects X are defined in Section 1) If you answered YES, please proceed to question 2. If you answered NO, then you ARE NOT a significant redevelopment and you ARE NOT subject to PRIORITY project requirements, only STANDARD requirements. Please check the "DOES NOT MEET PRIORITY Requirements" box in Section 3 below. 2. Is the project solely limited to one of the following: a. Trenchino and resurfacing associated with utility work? X b. Resurfacing and reconfiguring existing surface parking lots? X c. New sidewalk construction, pedestrian ramps, or bike lane on public X and/or private existing roads? d. Replacement of existing damaged pavement? X If you answered NO to ALL of the questions, then proceed to Question 3 . If you answered YES to ONE OR MORE of the questions then you ARE NOT a significant redevelopment and you ARE NOT subject to PRIORITY project requirements, only STANDARD requirements. Please check the "DOES NOT MEET PRIORITY Requirements" box in Section 3 below. 3. Will the development create, replace, or add at least 5,000 square feet of impervious surfaces on an existing development or, be located within 200 X feet of the Pacific Ocean and (1 )create more than 2500 square feet of impermeable surface or (2) increases impermeable surface on property by more than 1 0%? If you answered YES, you ARE a significant redevelopment, and you ARE subject to PRIORITY project requirements. Please check the "MEETS PRIORITY REQUIREMENTS" box in Section 3 below. If you answered NO, you ARE NOT a significant redevelopment, and you ARE NOT subject to PRIORITY project requirements, only STANDARD requirements. Please check the "DOES NOT MEET PRIORITY Requirements" box in Section 3 below. I SECTION 3 Questionnaire Results: MY PROJECT MEETS PRIORITY REQUIREMENTS, MUST COMPLY WITH PRIORITY PROJECT STANDARDS AND MUST PREPARE A STORM WATER MANAGEMENT PLAN FOR SUBMITTAL AT TIME OF APPLICATION. D MY PROJECT DOES NOT MEET PRIORITY REQUIREMENTS AND MUST ONLY COMPLY WITH STANDARD STORM WATER REQUIREMENTS. Applicant Information and Signature Box This Box for City Use Only Address: Assessors Parcel Number(s): City Concurrence: I YES I 6111 El Camino Real 760-221-015 I I Applicant Name: Applicant Title: By: Mark Radelow Vice President Date: Applicant Signature: Date: 11/19/09 Project ID: NO SWMP Rev 6/4/08 -.. ... --ATTACHMENT E -.... EDUCATIONAL MATERIAL -,,. ------- • • -• -• - • • • -.. ·-- -- - ·- -.. - - ... ---.. - • .. • • ... CITY OF SAN DIEGO STORM WATER POLLUTION PROGRAM INTEGRATED PEST MANAGEMENT Smart Tips for Hiring a Pest Control Service If you are thinking of hiring a pest control service there are some important things to consider before you take that step. Here is a checklist to help you hire a service that will adequately research your pest problem and safely apply the appropriate material to control it. Should I hire a Pest Control Service? Determine if the pest problem warrants hiring a pest control professional: • Is the damage or nuisance something you can live with? • Can you safely and effectively treat the problem yourself? • Can you make changes that will control the pest problem over the long term and eliminate the need for any chemical control? Get Recommendations and Facts Obtain recommendations from neighbors, friends or family. Call at least three companies and consider the following: • What types of services does the company offer? For example, do they provide only monthly spray contracts or do they offer an Integrated Pest Management (IPM) approach? • Are least-toxic pesticides or baits used when appropriate? • Is the company operating with the required licenses, certificates and insurance? Pest control companies and individuals making household treatments must operate with a license issued by the Structural Pest Control Board. Verify the status of a pest control company's license online at http://www.pestboard.ca.gov/license.htm. • Individuals operating in landscape maintenance or gardening businesses and performing incidental pest control must possess a Qualified Applicator Certificate or License (QAC or QAL) issued by the California Department of Pesticide Regulation. Verify the status of an individual or business QAC or QAL online at http://www.cdpr.ca.gov/docs/license/currlic.htm. • Most reputable pest control companies carry both general liability insurance and worker's compensation insurance. Ask for an Inspection • Ask the company to inspect the site. The company may charge a fee to do this inspection, but for that fee they should provide you with a diagnosis of the problem or an identification of the pest. They should show you where the pest is causing the problem and discuss how they plan to control it. The company should also provide you with details regarding the course of treatment(s), the frequency of inspections and treatment, and an estimate of the cost of implementing their treatment plan. • Consider long-term solutions to the problem. A company that practices IPM will suggest modification of the habitat or use of baits and monitoring, rather than just a guarantee to spray when and if the pest reappears. • Ask which pesticides will be used, the active ingredients they contain, and their effects on people, pets and the environment. Determine if there are specific label instructions for precautions after application. You may request a copy of the Material Safety Data Sheet from the pest control company for each pesticide used. • Ask how the pesticide will be applied and where. Chemicals sprayed around the home perimeter may be washed away by irrigation or rain, especially if concrete walkways or other impervious materials surround the home. Avoid companies that do this type of spraying . - - --.. -.. - - - ------- • -• - • .. .. .. • Is the company forthcoming with information on the identified pest problem, the reasons behind a chosen treatment, and the application techniques? Monitor the Work Following selection of a pest control company, continue a dialogue with the company to insure that you are getting the service stated in your contract . • Verify that pest populations are being monitored by the company as agreed in the contract. • Communicate to the company the levels of pests that are tolerable as well as intolerable. For example, you may tolerate ants in the landscape, but not inside the home. • Inform the company of any appearance or increase in pest populations that you notice between visits. Keep These Tips in Mind Important considerations to keep in mind when applying pesticides in your garden, landscape or home: • Be aware of weather patterns and do not apply pesticides just prior to rainfall or during windy conditions. • Avoid the use of pesticides such as diazinon and chlorpyrifos that have been detected in streams, rivers and lakes. These specific products are no longer available for purchase, and can be disposed of at a household hazardous waste collection facility. • Avoid the use of "broad-spectrum" insecticides. These products indiscriminately kill many types of insects, including beneficial and desirable species, and damage the balance between pest populations and their natural enemies. Frequent use of broad-spectrum pesticides can also result in the development of resistant strains of pests or secondary outbreaks of other pests. • Under no circumstances should pest control equipment be cleaned in a location where rinse water could flow into gutters, storm drains or open waterways. • Be aware that some pesticides are more easily carried in surface runoff than others and therefore have a greater potential to move off-site during irrigation or rain events. The leaching and runoff risks of specific pesticides can be obtained from UC Riverside's Pesticide Wise web site at http://www.pw.ucr.edu. Just enter the pesticide trade name or active ingredient and the conditions under which the material will be applied, such as type of soil texture, slope, irrigation rate and vegetative cover. Information From: Cheryl Wilen, San Diego area IPM Advisor; Darren Hewer; Mary Louise Flint; Pamela M. Geisel, University of California Cooperative Extension Farm Advisor, Environmental Horticulture, Fresno County; Carolyn L. Unruh, University of California Cooperative Extension Fresno County staff writer. - ----------- ---------... • -• • -• • -• -• The County of San Diego LID Appendix removal efficiencies for a wider range of contaminants due to enhanced filtration/biological processes associated with the surface vegetation. • Best suited to small residential, commercial, and industrial developments with high percentages of impervious areas, including parking lots, high density residential housing, and roadways. • Aesthetic benefits due to the surface vegetation make bioretention systems appealing for incorporation into streetscape and general landscape features. DESIGN • Provide a gentle slope for overland flow and adequate water storage. No water should be allowed to pond in the bioretention system for longer than 72 hours. • Usually designed in conjunction with swales and other devices upstream so as to reduce filter clogging and provide water treatment (treatment train). • Filter media employed is usually the plant growing material, which may comprise soil, sand and peat mixtures. • "Planting box" type systems should be restricted to very small catchment areas. • A subdrain system should be included in urban areas along with associated cleanout to facilitate maintenance. • For more precise design techniques, see: CASQA (2003, January) California Stormwater BMP Handbook: New Development and Redevelopment MAINTENANCE • Generally, only routine periodic maintenance typical of any landscaped area (mulching, plant replacement, pruning, weeding) is necessary. • Regular inspections and maintenance are particularly important during the vegetation establishment period. • Routine maintenance should include a biannual health evaluation of the trees and shrubs and subsequent removal of any dead or diseased vegetation. • Other potential tasks include soil pH regulation, erosion repair at inflow points, mulch replenishment, unclogging the under-drain, and repairing overflow structures . LIMITATIONS • Adequate sunlight is required for vegetation growth. • The use of irrigation may not meet State water conservation goals. Appropriate drought-tolerant plants should be considered. • Placement may be limited by the need for upstream pre-treatment so as to avoid filter clogging (treatment train) . • Contributing drainage area should be less than 1 acre for small-scale, on-lot devices • Bioretention (a BMP with incidental infiltration) is not an appropriate BMP when: o the seasonal high groundwater table is within 6 feet of the ground surface (US EPA 1999) o at locations where or where surrounding soil stratum is unstable • exceptions to the 6 foot separation can be made when: Final o the BMP is designed with an under-drain and approved by a qualified licensed professional, or when: -43-12/31/2007 - -.. --.... .. - -.. - -• -• -----• ... • - The County of San Diego LID Appendix o written approval of a separation in the interval of 4-6 feet has been obtained by the Regional Water Quality Control Board and the Department of Environmental Health. • Site must contain sufficient elevation relief so that subdrain system may discharge to receiving swale, curb or storm drain system . ECONOMICS • Construction cost estimates for a bioretention area are slightly greater than those for the required landscaping for a new development (EPA, 1999). • The operation and maintenance costs for a bioretention facility will be comparable to those of typical landscaping required for a site. (CASQA, 2003) • Maintenance costs are projected at 5-7% ofthe construction cost annually . REFERENCES • California Stormwater Quality Association. (2003, January) California Stormwater BMP Handbook: New Development and Redevelopment. • URS Australia Pty Ltd, (2004, May), Water Sensitive Urban Design: Technical Guidelines for Western Sydney, Upper Parramatta River Catchment Trust. • US EPA (1999, September) BMP Fact Sheet 832-F-99-012. http://www.epa.gov/owm/mtb/biortn.pdf • US EPA (1999, August) Preliminary Studies: Preliminary Data Summary of Urban Stormwater Best Management Practices. EPA-821-R-99-012 Part D. • For additional information pertaining to Bioretention Systems, see the works cited in the San Diego County LID Literature Index. Final -44-12/3112007 - - • • - -.. --- ---.. - -- -• -.. -------------------~--------~ -LANG-. . eng1neer1ng co. Consulting Engineers · Land Planners I I -- Drainage Basin A, con't .. J I I i I i Contributing drainage areas for basin's treatment control, BMT+I . Area A32 = 0.10 acres --· -. Total Basin Area= 10.76 acres c = 0.84 r---T--:r -----· ! i- Size Nutrient Separating Baffle Box (i.e. Water Quality Inlet) :_rrr! 111111111 I -· Project: Palomar Airport Commons Job No.: 090227 Scale: N/A Calc. By: GWL Date: 06/14/10 Checked: RGL Date: 06/14/10 Sheet: I OfZ I I I I I I I -~ - I +--i I -- ----1---- --- Nutrient Separating Baffle Box is sized based upon in-flow pipe diameter and max. flow rate at 6 fps r-I I -~1 I c--Il_J I _ l--l Inflow pipe size = 36 inches I : I I I ··- i ----· i : i I I I I ------~ Maximum flow rate for 36 inch pipe with 6 fps = 42.4 cfs I i ---· ----I--! I I I i p-t Select model from manufacturer provided information (See following pages) ill I ! ' ! -r-'- 1 I i r--· l --- I I Select Model Number NSBB 6-12-84 I r--T I l f------· I --···---- : ' I ' ' i I I I -'--r----- Q100 for System A entering NSBB = 36.8 cfs : ' [T-- I 36.8 cfs s 42.4 cfs i I ----- i I Since Q100 S ~ax Inflow• Nutrient Separating Baffle Box is adequately sized ' -·- ! I f--· -- I I 1 ' 1---I I ' ~ ! I ' I I i I --··-- I I I ---- ! -- I ---_j_j_ __ ! I I --I I I • I -.. .. --... • ... .. ... .. ... .. --- ------.. -.. ---.. .. ... .. • Tecnical Specifications For The Nutrient $epqrqtin9 Bqffle Box Model -Stormwater Treqtment Svstem 7. The stormwoter treatment system shall be capable of inline installation with minimal head loss. Offline installation is not on acceptable oleternotive, unless orginolly deisigned by the engineer. Treatment of gross solids must occur ot flow roles higher than the specified treatment flow. The stormwoler treatment system must provide treatment at all flow rates . 2. For flaws of 74.67 gpm per square foot of settling chamber area a removal efficiency of at least 90% for TSS will be achieved and flows of up to 124.44 gpm per square foot of see/ling chamber area will be able Ia pass through the stormwater treatment system far treatment without causing scouring. This must be proven though full scale testing . J. The starmwater treatment system will be able to store captured solid debris such as leaves and litter in a dry state within the nutrient separating screen syselm between rain events. The volume of dry storage will be equal or greater than that specificed on the drawing . 4. The stormwater treatment system will have the capacity to stare equal to or greater than that specified on the drawing far captured sediment . 5. The stormwater treatment system will hove a skimmer located in front of the outflow opening. The bottom of the skimmer will be located 6" below the static water level. Adjacent to the influent side of the skimmer is a cage containing many hydrocarbon absorption booms that will float at the tap surface of the water in the starmwater treatment structure. This ensures absorption of hydrocarbons though a wide range of operating flows . 6. The nutrient separating screen system shall be positioned approximately 3.5" above the static water level within the baffle box. Adjacent to the inflow, the screen system will have openings on both sides that hove a combined cross sectional area that exceeds the crass sectional area of the pipe. These openings will act as ·an internal bypass far water flaw in the event that the screen system becomes full of debris. 7. The nutrient separating screen system shall hove o mmtmum of 6" of vertical adjustment. The adjustment method shall be a system with brackets that ore attached to the sides of the screen system that will slide vertically along I 1/2" x 7 7/2" aluminum square poles. Two stainless steel balls an each brocket con be tightened to lock the screen system in place, or loosened Ia allow for vertical adjustment of the screen system. The square pales are anchored to the baffle wall by 1/2" minimum diameter stainless steel balls. 8. The nutrient separating screen system shall hove o minimum of J" of horizontal adjustment in the direction of the length of the concrete structure. The brackets that clamp the vertical adjustment poles to the side of the screen system can be repositioned to allow of horizontal adjustment. 9. The nutrient separating screen system shall have a section adjacent to the inflow which is hinged and con be opened for cleaning. This section will function as o screened romp to direct debris into the main body of the screened system. The sides of this section will be mode of stainless steel screen and transition in vertical height from a minimum of 8" toll nearest the inflow to the height of the main body of the screen system. The lower sides along this inflow section will provide bypass for water flaw around the main body of the screen system if necessary. The cross sectional area of the bypass around the screen system will be equal Ia or exceed the cross sectional oreo of the inflow pipe. 10. The nutrient separating screen system shall give access from above grade to the lower sediment collection chambers by the following method. The bottom of the screen system will contain hinged screened doors that can be opened in such o way as to allow adequate access for o vacuum truck to remove everything in all the lower collection chambers. 7 7. The nutrient separating screen will be o welded aluminum framework spanned by stainless steel screen, be rectangular in shape, and be formed to make a bottom, 2 lang sides, and 7 end ; the top and 7 end will remain open. The screen system will consist of panel sections that are held together with stainless steel bolls. When the panel sections ore unbolted and separated from each other they must be able to pass through on access hatch or manhole in the top of the baffle box for removal purposes. The aluminum frame work will be made 7 1/2" x I 1/2" x Jt" aluminum angle beam. The screen used to span the aluminum frame is described as follows: For the body of the screen system, flattened expanded stainless steel sheet 1/2" No. 16 F; Open area = 60%; Grade = 304 Stainless Steel. The screen will be attached to the screen system frame by sandwiching the screen to the aluminum frame between a series of 7" x J/16" aluminum bars and welded in place . 12. A turbulence deflector will be attached near the top of each of the baffles with ~" stainless steel through bolts and stainless fender washers. The turbulence deflectors will be mode from laminated fiberglass and measure a minimum of 1/4" in thickness. turbulence deflectors will form a horizontal ledge that measures 8" from the downstream side of the first baffle and 6" from the downstream side of the second bafflt:, and span the full width of the baffle box. steel The IJ. The stormwater treatment system will be precast concrete. The concrete will be 28 day compressive strength fc = 5,000 psi. Steel reinforcing will be ASTM A -615 Grade 60. Structure will support an H20 loading as indicated by AASHTO. The joint between the concrete sections will ship lop and the joint sealed with Rom-Nek or equal butyl rubber joint sealant. 14. For access into the stormwater treatment system, two to three holes will be cast into the top of the vault. 15. The inflow and outflow pipes will not intrude beyond flush with the inside surface of the Nutrient Separating Baffle Box. The space between the pipe holes in the ends of the stormwater treatment system and the outside surface of the pipe will be filled with non-shrink grout to form a water proof seal. 16. The nutrient separating screen system shall extended more than half way of the internal lenghl of the stormwater treatment system. The nutrient separating screen system shall start at the inflow pipe not more than 4" from the wall of the inflow pipe. I 7. The storm water treatment system must have two separate reports verifying no scouring occurs at flows equal to or greater than the specified treatment flow rate for that particle size distribution. 18. The stormwater treatment system shall have o shallow sump, not more than 48" from invert of outflow pipe to bottom floor of the sump area. 19. The stormwater treatment system must have a mmtumium of two sediment chambers (sump areas) which are separated by a vertical wier that divides the chamber from the bottom of the sump to the invert of the outflow pipe. No openings are allowed at the bottom or coming up vertically along the wier. Or any other method that would connect the two chambers together such as orfices . - -Palomar Airport Commons Page 1 of 1 -Project: Palomar Airport Commons -Date: 06/14/10 -Description: Rational Method Hydrograph Routing Overview System "A" System "A", Volume Based Water Quality 2.75 100 Year P6 , inches 0.65 Pasth, inches 0.84 c 0.84 c -10.78 Area, acres 10.78 Area, acres -Volume to Detain Volume to Retain 24.90 VOL, acre-inches 5.89 VOL, acre-inches 2.08 VOL, acre-feet 0.49 VOL, acre-feet -90,400 VOL, cu.ft. 21,400 VOL, cu.ft. -6 Hour Storm 6 Hour Storm, Assumed -360 Duration, minutes 360 minutes 5.0 Tc, minutes 5.0 Tc, minutes 72 blocks 72 blocks -System "B" System "B", Volume Based Water Quality -2.75 100 Year P6 , inches 0.65 Pasth, inches -0.84 c 0.84 c -4.59 Area, acres 4.59 Area, acres Volume to Detain Volume to Infiltrate -10.60 VOL, acre-inches 2.51 VOL, acre-inches -0.88 VOL, acre-feet 0.21 VOL, acre-feet 38,500 VOL, cu.ft. 9,100 VOL, cu.ft. --6 Hour Storm 6 Hour Storm, Assumed 360 Duration, minutes 360 minutes 9.2 Tc, minutes 9.2 Tc, minutes -39 blocks 39 blocks -.. .. -• 090227-Detention Hydrograph.xlsx LANG ENGINEERING CO. Overview -.. -Palomar Airport Commons Page 2 of 5 Project: Palomar Airport Commons -Date: 02/23/10 -System: Storm System "A", Sorted by Rainfall Blocks in Numerial Order Storm: 85th Percentile, 6 Hour Assumed -N Pr(NJ (inches) Pr(N-ll (inches) PN (inches) QN (cfs) Mid block Tc, min 1 0.14 0.00 0.14 15.5 240 2 0.18 0.14 0.04 4.3 235 -3 0.21 0.18 0.03 3.1 230 4 0.23 0.21 0.02 2.5 245 5 0.25 0.23 0.02 2.1 225 -6 0.27 0.25 0.02 1.8 220 7 0.28 0.27 0.02 1.6 250 8 0.30 0.28 0.01 1.5 215 -9 0.31 0.30 0.01 1.4 210 10 0.32 0.31 0.01 1.3 255 11 0.33 0.32 0.01 1.2 205 -12 0.34 0.33 0.01 1.1 200 -13 0.35 0.34 0.01 1.1 260 14 0.36 0.35 0.01 1.0 195 15 0.37 0.36 0.01 1.0 190 16 0.38 0.37 0.01 0.9 265 17 0.39 0.38 0.01 0.9 185 ... 18 0.40 0.39 0.01 0.9 180 19 0.41 0.40 0.01 0.8 270 20 0.41 0.41 0.01 0.8 175 -21 0.42 0.41 0.01 0.8 170 -22 0.43 0.42 0.01 0.8 275 23 0.43 0.43 0.01 0.7 165 -24 0.44 0.43 0.01 0.7 160 25 0.45 0.44 0.01 0.7 280 26 0.45 0.45 0.01 0.7 155 -27 0.46 0.45 0.01 0.7 150 28 0.47 0.46 0.01 0.6 285 29 0.47 0.47 0.01 0.6 145 -30 0.48 0.47 0.01 0.6 140 -31 0.48 0.48 0.01 0.6 290 32 0.49 0.48 0.01 0.6 135 -33 0.49 0.49 0.01 0.6 130 -34 0.50 0.49 0.01 0.6 295 35 0.50 0.50 0.01 0.6 125 ... 36 0.51 0.50 0.01 0.6 120 -37 0.51 0.51 0.00 0.5 300 38 0.52 0.51 0.00 0.5 115 ... 39 0.52 0.52 0.00 0.5 110 • 40 0.53 0.52 0.00 0.5 305 41 0.53 0.53 0.00 0.5 105 -42 0.54 0.53 0.00 0.5 100 • -090227-Detention Hydrograph.xlsx LANG ENGINEERING CO. System "A"-85th • -Palomar Airport Commons Page 4 of 5 -Project: Palomar Airport Commons -Date: 02/23/10 System: Storm System "A", Sorted by Rainfall Distribution Storm: 85th Percentile, 6 Hour Assumed --N Pr(N) (inches) Pr(N-ll (inches) PN (inches) QN (cfs) Mid block Tc, min 72 0.65 0.65 0.00 0.35 0 71 0.65 0.64 0.00 0.35 5 -69 0.64 0.64 0.00 0.36 10 -68 0.64 0.63 0.00 0.36 15 66 0.63 0.63 0.00 0.37 20 -65 0.63 0.62 0.00 0.37 25 -63 0.62 0.62 0.00 0.38 30 62 0.62 0.61 0.00 0.39 35 -60 0.61 0.61 0.00 0.39 40 -59 0.61 0.60 0.00 0.40 45 57 0.60 0.60 0.00 0.41 50 -56 0.60 0.59 0.00 0.41 55 -54 0.59 0.58 0.00 0.42 60 53 0.58 0.58 0.00 0.43 65 -51 0.58 0.57 0.00 0.44 70 -50 0.57 0.57 0.00 0.44 75 48 0.56 0.56 0.00 0.46 80 -47 0.56 0.56 0.00 0.46 85 -45 0.55 0.55 0.00 0.48 90 44 0.55 0.54 0.00 0.48 95 -42 0.54 0.53 0.00 0.50 100 -41 0.53 0.53 0.00 0.51 105 39 0.52 0.52 0.00 0.52 110 -38 0.52 0.51 0.00 0.53 115 36 0.51 0.50 0.01 0.55 120 35 0.50 0.50 0.01 0.56 125 -33 0.49 0.49 0.01 0.58 130 -32 0.49 0.48 0.01 0.59 135 30 0.48 0.47 0.01 0.62 140 -29 0.47 0.47 0.01 0.63 145 -27 0.46 0.45 0.01 0.66 150 26 0.45 0.45 0.01 0.68 155 -24 0.44 0.43 0.01 0.72 160 -23 0.43 0.43 0.01 0.74 165 21 0.42 0.41 0.01 0.78 170 20 0.41 0.41 0.01 0.81 175 18 0.40 0.39 0.01 0.87 180 17 0.39 0.38 0.01 0.90 185 -15 0.37 0.36 0.01 0.98 190 14 0.36 0.35 0.01 1.03 195 12 0.34 0.33 0.01 1.14 200 -11 0.33 0.32 0.01 1.21 205 .. 090227-Detention Hydrograph.xlsx LANG ENGINEERING CO . System "A"-85th Sorted .. - -Palomar Airport Commons Page 5 of 5 Project: Palomar Airport Commons -Date: 02/23/10 System: Storm System "A", Sorted by Rainfall Distribution Storm: 85th Percentile, 6 Hour Assumed --N Pr(Nl (inches) Pr(N·ll (inches) PN (inches) QN (cfs) Mid block Tc, min -9 0.31 0.30 0.01 1.39 210 8 0.30 0.28 0.01 1.50 215 -6 0.27 0.25 0.02 1.84 220 -5 0.25 0.23 0.02 2.09 225 3 0.21 0.18 0.03 3.07 230 ... 2 0.18 0.14 0.04 4.33 235 1 0.14 0.00 0.14 15.51 240 4 0.23 0.21 0.02 2.46 245 -7 0.28 0.27 0.02 1.65 250 10 0.32 0.31 0.01 1.29 255 13 0.35 0.34 0.01 1.08 260 ... 16 0.38 0.37 0.01 0.94 265 19 0.41 0.40 0.01 0.84 270 22 0.43 0.42 0.01 0.76 275 -25 0.45 0.44 0.01 0.70 280 28 0.47 0.46 0.01 0.65 285 31 0.48 0.48 0.01 0.61 290 34 0.50 0.49 0.01 0.57 295 .. 37 0.51 0.51 0.00 0.54 300 40 0.53 0.52 0.00 0.51 305 -43 0.54 0.54 0.00 0.49 310 -46 0.56 0.55 0.00 0.47 315 49 0.57 0.56 0.00 0.45 320 -52 0.58 0.58 0.00 0.43 325 -55 0.59 0.59 0.00 0.42 330 58 0.60 0.60 0.00 0.40 335 -61 0.61 0.61 0.00 0.39 340 -64 0.62 0.62 0.00 0.38 345 67 0.63 0.63 0.00 0.37 350 -70 0.64 0.64 0.00 0.36 355 73 0.65 0.65 0.00 0.35 360 ---- --090227-Detention Hydrograph.xlsx LANG ENGINEERING CO. System "A" -85th Sorted -.. ----·-------------.. -.. ---.. --... .. ... • -• .. -... - ...,,._,.._~~·-·-----~ Hydrograph Report Hydraflow Hydrographs by lntelisolve v9.23 Hyd. No. 3 Basin A Water Quality -85th Hydrograph type = Manual Storm frequency = 1 yrs Time interval = 5 min Hydrograph Discharge Table Time --Outflow Time --Outflow (min cfs) (min cfs) 5 0.360 230 4.330 10 0.360 235 15.51 « 15 0.370 240 2.460 20 0.370 245 1.650 25 0.380 250 1.290 30 0.390 255 1.080 35 0.390 260 0.940 40 0.400 265 0.840 45 0.410 270 0.760 50 0.410 275 0.700 55 0.420 280 0.650 60 0.430 285 0.610 65 0.440 290 0.570 70 0.440 295 0.540 75 0.460 300 0.510 80 0.460 305 0.490 85 0.480 310 0.470 90 0.480 315 0.450 95 0.500 320 0.430 100 0.510 325 0.420 105 0.520 330 0.400 110 0.530 335 0.390 115 0.550 340 0.380 120 0.560 345 0.370 125 0.580 350 0.360 130 0.590 355 0.350 135 0.620 140 0.630 ... End 145 0.660 150 0.680 155 0.720 160 0.740 165 0.780 170 0.810 175 0.870 180 0.900 185 0.980 190 1.030 195 1.140 200 1.210 205 1.390 210 1.500 215 1.840 220 2.090 225 3.070 Peak discharge Time to peak Hyd. volume Wednesday, Nov 18,2009 = 15.51 cfs = 235 min = 21,120 cuft (Printed values>= 1.00% ofQp.) -.. -Hydrograph Report ------.. ---------- ----- ... Hydraflow Hydrographs by lntelisolve v9.23 Hyd. No. 3 Basin A Water Quality -85th Hydrograph type Storm frequency Time interval Q (cfs) 18.00 15.00 12.00 9.00 6.00 3.00 0.00 0 = = = 60 -HydNo.3 Manual 1 yrs 5 min Peak discharge Time to peak Hyd. volume Basin A Water Quality -85th Hyd. No. 3 --1 Year I _/ ~ 120 180 240 300 VVednesday, Nov18,2009 = = = 15.51 cfs 235 min 21,120 cuft Q (cfs) 18.00 15.00 12.00 9.00 6.00 3.00 ' 0.00 360 Time (min) ·- •• ------- -----------------• ... -... • ... • -• Pond Report Hydraflow Hydrographs by lntelisolve v9.23 Wednesday, Feb 24, 2010 Pond No. 2 -Basin A-Underground Storage Pond Data UG Chambers -Invert elev. = 263.90 ft, Rise x Span= 4.50 x 4.50 ft, Barrel Len= 616.00 ft. No. Barrels= 4, Slope= 0.00%, Headers= Yes Encasement· Invert elev. = 263.40 ft, Width = 6.00 ft, Height = 5.50 ft, Voids = 40.00% Stage I Storage Table Stage (ft) Elevation (ft) Contour area (sqft) lncr. Storage (cuft) Total storage (cuft) 0.00 263.40 n/a 0 0 0.55 263.95 n/a 3,364 3,364 1.10 264.50 n/a 5,172 8,536 1.65 265.05 n/a 6,248 14,785 2.20 265.60 n/a 6,778 21,562 2.75 266.15 n/a 7,011 28,573 3.30 266.70 n/a 7,010 35,583 3.85 267.25 n/a 6,777 42,360 4.40 267.80 nla 6,250 48,610 4.95 268.35 nla 5,167 53,777 5.50 268.90 n/a 3,364 57,141 Culvert I Orifice Structures Weir Structures [A] [B) [C) [PrfRsr] [A) [B) [C) [D) Rise (in) = 30.00 Inactive 0.00 0.00 Crest Len (ft) = 0.00 0.00 0.00 0.00 Span (in) = 30.00 0.00 0.00 0.00 Crest El. (ft) = 0.00 0.00 0.00 0.00 No. Barrels = 1 1 0 0 WeirCoeff. = 3.33 3.33 3.33 3.33 Invert El. (ft) = 265.25 0.00 0.00 0.00 Weir Type Length (ft) = 20.00 0.00 0.00 0.00 Multi-Stage = No No No No Slope(%) = 2.00 0.00 0.00 n/a N-Value = .013 .013 .013 n/a Orifice Coeff. = 0.60 0.60 0.60 0.60 Exfil.(in/hr) = 0.500 (by Wet area) Multi-Stage = n/a Yes No No TW Elev. (ft) = 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). Stage (ft) 6.00 5.00 4.00 3.00 2.00 1.00 0.00 Stage I Storage I/ ·~ v ~ ~ .. ~ ~ ~ ..... ~." ~ / ~ v fl' 0 6,000 12,000 18,000 24,000 30,000 36,000 42,000 48,000 54,000 -Storage ......... Elev (ft) 269.40 268.40 267.40 266.40 265.40 264.40 263.40 60,000 Storage ( cuft) ---~----------~ -.. -Hydrograph Report -------- -• --- --- ----- - --- Hydraflow Hydrographs by lntelisolve v9.23 Hyd. No. 7 Basin A WQ Routing Hydrograph type Storm frequency Time interval Inflow hyd. No. Reservoir name = Reservoir = 1 yrs = 5 min = 3 -Basin A Water Quality -85th = Basin A -Underground Storage Storage Indication method used. Exfiltration extracted from Outflow. Elev (ft) 267.00 266.00 265.00 r ... ~ "'-.... I .. Basin A WQ Routing Hyd. No. 7 --1 Year "' ~ Peak discharge = Time to peak = Hyd. volume = Max. Elevation = Max. Storage = Thursday, Nov 19, 2009 0.000 cfs 15 min 0 cuft 265.19ft 16,496 cuft Elev (ft) 267.00 266.00 265.00 "' ~ ) ~~ 264.00 v v 263.00 0 2 4 6 8 10 12 14 -2. Basin A -Underground Storage "" 16 18 20 -......... "" "" 22 24 26 264.00 263.00 28 Time (hrs) - - --... ------ - ------ --- - • -- -LANG-. . eng1neer1ng co. Project: Palomar Airport Commons Job No.: 090227 Scale: N/A Calc. By: GWL Date: 06/14/10 Checked: RGL Date: 06/14/10 Consulting Engineers · Land Planners Sheet: 1 Of z I I I I II I I ! ~~~~~--~+-~~-+--~+-~·--~+--~'---+----f--+~~--~-+-~-~~~1 ~--- Drainage Basin B/C Contributing drainage areas for basin's treatment control BMPs I ~-------=---~~~~--~~~--~~--,--~--,--~~-4-~--+-~-,k-~-+--~~----~--+-~~ Area B16 = 0.52 acres Total Basin Area = 4.4 acres ' I I c = o.s• i 1 _j_j_LI i ~---+--~ -+- 1) UrbanGreenrM Biofilter unit (High-rate biofiltration unit) (Basin 816) ~-----~-~--~~~--~~ +-~-~--+--- 2) Nutrient Separating Baffle Box by 8io Clean Enviornmental (Water Quality Inlet) (Total Basin B/C) ----3) Detention/Infiltration System -HOPE perforated pipes (Total Basin 8/C) I :_Lj_J 1 I_IJ . TJ I I -J 1 i ----+~--+---+_ ----+~+---~-= Select UrbanGreenrM Biofilter by Contech Construction Products, Inc. for storm water quality treatment !m_Ui II I I II I 1_1 l_l_j I II I i-~ J ~~ :T-=---- na"leen'" ·;·fil~er Is a fl~w based BMP, therefo.-e usr~ of f"T-1 -. -; -t-i + I -i I i . ;u~~xA -I' T I rt 1-+ ! j_::_l i 11__: -I I I I I \ ! . ll --------~ Owu = 0.09 cfs for B16 ' ---W --'r-----t---+-~ I I ! ___ __[_ __ _L____L____l __ _l__~--f--~-+--+---+---+--+--t----t---+-~--f----+---+---+--+----+--+--+---+--f---f------ Owu = 39 gpm for 816 ~---rr-,---,--~--+--+--+-~---t--+--+---~-+--+--t---+---+---f---+--1---t----t---r----------+--+---+---- _~-i I f--_l____L __ j___l____j_ __ _l___j___l ___ ~ __ _j__ _ _L___L ___ L--_l_~ __ _L___j___L __ ~~--'1--~--t ----+---+ --+--1--- Select standard model from manufacturer provided information (See following pages) 'u,.~}~.m~ ! I I I I t-~-T---,i--!,----T"--'--,=-_.r--l+--+--+-, -+--t---1--1 - rr-I -. ' r -=r i ~-+-t-+---+-1----~--- ;]gpm ~ 61 gpm + 1 ± L~-~: 1 '_ -+-!i --+-t---+---r--! ---+++-' --+--J ___ __ J 1,: IIi __l_ I __ Since Owu s QTREAT• UrbanGreenrM Biofilter is adequately sized 1 !, F==r=9===~~===F=9==9===r==r=9===T==r=9===~~=9~--t---r--+--+--t----t--T--r·-+--+---4--+--1 ' i.lllj r-----r--r----+---+--+----t--+--t----l-+--+--t--+--+--+----+-~-~--~-+--t---t--+--1-------t ·--- 1------t----t--+--+--t----ti---~-+--+--t--+---t--+--t----t ---+--+--+---+1--+'---t----t----+-~---i -- ---1---l--c---------+--+--+ 1 --+---t--t-. =I I I --: I tl--+--+--~-'-+ ~ ' - f--· --c-+~-+--_+---+-~·· ~--• _ , -~--c 1~4+ 1---+--+---+--+--+--i--+--+--t--+--+--+--+---t---t----t---t---t----t-i __ --f----H--1---t-- --------..... --- ---.. -.. ... -... ------- - -- Design Process The UrbanGreen BioFilter provides a variety of stormwater management and development benefits including a high level of removal of the primary pollutants of concern, unconstrained placement of the system on the site, improved aesthetics, improved air quality and potential LEED credits. Another benefit is the simple sizing process for this technology. As shown in Table 1, the UrbanGreen BioFilter is available in one standard size and has a total treatment capacity of 61 gallons per minute (gpm). The total treatment capacity is the aggregate of the treatment capacities of the bioretention bay and Storm Filter media cartridges. --- Treatment Capacity'.2 (gpm) 61.0 Footprint' (LXW) (ft) 6x8 1. Combined capacity of bioretention and media cartridges Depth4 (ft) 5.083 2. Maximum conveyance flow through the system is a function of the allowable depth of flow at the curb face as defined by the governing jurisdiction 3. Inside dimensions 4. Distance from tree grate to invert of outlet pipe (or vault floor) Table 1: Treatment Capacity, Bypass Capacity and Dimensions The design infiltration rate of the bioretention bay is controlled by the initial media permeability and a flow control orifice. Although the infiltration rate may vary in different jurisdictions, 50 in/hr (approximately 0.5 gpm per square foot) of surface area is the typical design infiltration rate. The surface of the engineered soil mixture is approximately 32 square feet which equates to a treatment capacity of 16 gpm. Testing has shown that the engineered soil mixture in the bioretention bay can infiltrate at a rate of 360 in/hr at the design driving head of 12 inches, however an outlet flow control limits the rate so significant pollutant loads can accumulate before the media drops below the design infiltration, and maintenance is required. Using an outlet flow control to control infiltration rates rather than the media itself allows soil with a higher void volume to be used. This substantially decreases the frequency of maintenance because there is more storage volume for captured pollutants within the soil media. It also improves performance by reducing velocities in the pore spaces within the media. The treatment capacity of the media cartridge portion of the UrbanGreen BioFilter is based on treating runoff at a rate of 2 gpm per square foot of cartridge surface area and utilizing two 27-in media cartridges. The treatment capacity of each cartridge is 22.5 gpm for a total capacity of 45 gpm for both cartridges. Like the soil mixture, the media cartridges are designed with a flow control, so flow through each cartridge is restricted to the design rate. This feature improves both the performance and longevity of the cartridges. Local regulations will typically determine how much flow needs to be treated. Many regulatory agencies specify a water quality "design storm" such as a 6-month or 1-year return period storm event. Refer to local guidelines for the calculation of required design storm. Once the treatment flow rate has been determined, simply divide that amount by the total treatment capacity of the UrbanGreen BioFilter (61 gpm) to determine the number of units needed. When placing the system on site, there are few constraints on the location of the UrbanGreen BioFilter system (unlike similar systems that cannot be placed at the low point of a parking lot or require unidirectional flow along a curb face in order to function). Once a location for the UrbanGreen BioFilter has been determined, compare the anticipated peak conveyance flow with the bypass capacity to ensure that the system has sufficient capacity to handle these higher flows. Two hydraulic controls impact the bypass capacity of the UrbanGreen BioFilter. The throat opening controls the hydraulic capacity as a function of the opening width, allowable top width, gutter cross slope, manning's "n," and other relative factors. State and local jurisdictions typically provide inlet design guidelines for flow hydraulics. (If this information is not available, refer to the FHWA HEC 12 Drainage of Highway Pavements, 1984. http://www.fhwa.dot.gov/engineering/hydraulics/pubs/hee/ hec12.pdf) The second hydraulic control is the internal bypass weir. The crest elevation is 4 inches below the grade break point of the curb opening inlet at the face of curb and has a weir length of 2-ft by 4-in. It is a sharp crested weir. Calculate the capacity of the bypass weir using the discharge equation, Q = cLH's . For example, with 4 inches of driving head and a discharge coefficient of 3.3, the design discharge is 1.48 cfs. At a discharge of 2 cfs, the head on the weir is 4.9 inches giving a depth of flow at the curb face of approximately 1-in. This is given the conservative assumption that there is no flow through the treatment system itself . The UrbanGreen BioFilter has been hydraulically tested and evaluated for scour at flows up to 2 cfs with results showing that no scour was present in the system. These observations indicate that the system could handle higher flows without compromising performance. The maximum bypass capacity of the UrbanGreen BioFilter is therefore a function of the maximum allowable depth of flow at the curb face as defined by the governing jurisdiction. This substantial internal bypass capacity is a key advantage of the UrbanGreen BioFilter as it eliminates the need for additional external structures. However, if the bypass capacity of the UrbanGreen BioFilter is less than the anticipated peak conveyance flow rate, then an external bypass may be used. -- - -- - - -- -------------.. --.. -.. --- -LANG-. . eng1neer1ng co. Project: Palomar Airport Commons Job No.: 090227 Scale: N/A Calc. By: GWL Date: 06/14/10 Checked: RGL Date: 06/14/10 Consulting Engineers · Land Planners Sheet: .§ Of 1 Drainage Basin B/C, con't I I '---· Contributing drainage areas for basin's treatment control BMPs - Area B16 = 0.52 acres --- Total Basin Area = 4.59 acres I I --~- c = 0.84 I L_ Detention/Infiltration system is a volume based BMP, therefore use the 85'" percentile rainfall event ~H65i:nc+ I I I • I I I I • n ---------~ - I -- ' I I I ' I _L__ ----- Assumed infiltration rate of 0.5 inches per hour for in situ and/or import material ±t+----~ ---l _ 1 ~r --- -~ Design outfall from detention/infiltration system to have invert out elevation higher than the maximum water surface elevation produced by the 85th percentile rainfall event. Therefore, 85th percentile rainfall event will not produce any discharge from the underground detention/infilration system and the entire volume from the 85th percentile event will infiltrate into the soil. -- Invert of perforated pipe system= 255.29 : ---- System to be encased in gravel backfill, 6 inches above and below pipe and one foot around the footprint -~---r-~ Gravel backfill void ratio assumed to be 40% i ! I I ! ' I I I a~--··+-· i i i i -r--- Invert of 24" HDPE pipe out= 258.70 (Elevation set so no discharge would occur from 85th percentile event) --1----r----l ---__ _ VOLssth Req = 7, 700 cubicfeet (cu. ft.) maximum storage required (See following printouts) ! : I l I I I I I I I I I I I I i I I • i i _l_ 1---- Maximum 85th Percentile W.S.E. = 258.67 based on Vssth (See following printouts) ' I T i --------·--1---- VOLsvstem = 7,750± cu.ft. to maximum elevation of 258.70 (invert of 24" HDPE pipe out) 0:1 I I I I I I I 1-1 I I L _ _l I I I I I - -+-i Since VOLssth S VOLsvstem and Max. 85"' W.S.E. S 24" I.E. out, system is adequately sized I I -----~ ___ Ll __ L_ J I ! ~ I Estimated draw down time for water quality event= 50 hours (See following prinouts) i I I I I --"" I I I --- 1 i -Palomar Airport Commons Page 1 of 1 Project: Palomar Airport Commons -Date: 06/14/10 -System: Storm System "B", Sorted by Rainfall Distribution Storm: 100 Year, 6 Hour ·-N Pr(NJ (inches) Pr(N-ll (inches) PN (inches) QN (cfs) Mid block Tc, min 1 0.75 0.00 0.75 18.81 240 2 0.96 0.75 0.21 5.25 231 -3 1.11 0.96 0.15 3.72 222 -4 1.23 1.11 0.12 2.99 249 5 1.33 1.23 0.10 2.54 212 -6 1.42 1.33 0.09 2.23 203 -7 1.50 1.42 0.08 2.00 258 8 1.57 1.50 0.07 1.82 194 -9 1.64 1.57 0.07 1.68 185 10 1.70 1.64 0.06 1.56 268 11 1.76 1.70 0.06 1.47 175 -12 1.81 1.76 0.06 1.38 166 13 1.87 1.81 0.05 1.31 277 14 1.92 1.87 0.05 1.25 157 15 1.96 1.92 0.05 1.19 148 -16 2.01 1.96 0.05 1.14 286 17 2.05 2.01 0.04 1.10 138 ..... 18 2.09 2.05 0.04 1.05 129 -19 2.13 2.09 0.04 1.02 295 20 2.17 2.13 0.04 0.98 120 21 2.21 2.17 0.04 0.95 111 -22 2.25 2.21 0.04 0.92 305 23 2.28 2.25 0.04 0.90 102 -24 2.32 2.28 0.03 0.87 92 -25 2.35 2.32 0.03 0.85 314 26 2.39 2.35 0.03 0.83 83 -27 2.42 2.39 0.03 0.81 74 -28 2.45 2.42 0.03 0.79 323 29 2.48 2.45 0.03 0.77 65 -30 2.51 2.48 0.03 0.75 55 -31 2.54 2.51 0.03 0.74 332 32 2.57 2.54 0.03 0.72 46 -33 2.60 2.57 0.03 0.71 37 34 2.62 2.60 0.03 0.69 342 35 2.65 2.62 0.03 0.68 28 36 2.68 2.65 0.03 0.67 18 -37 2.70 2.68 0.03 0.66 351 38 2.73 2.70 0.03 0.64 9 39 2.76 2.73 0.03 0.63 0 • 40 2.78 2.76 0.02 0.62 360 -090227-Detention Hydrograph.xlsx LANG ENGINEERING CO. System "B" -100 Year - --Palomar Airport Commons Page 1 of 1 Project: Palomar Airport Commons -Date: 06/14/10 System: Storm System "B", Sorted by Rainfall Blocks in Numerial Order Storm: 85th Percentile, 6 Hour Assumed --N Pr(N) (inches) Pr(N-ll (inches) PN (inches) QN (cfs) Mid block Tc, min 1 0.18 0.00 0.18 4.45 240 2 0.23 0.18 0.05 1.24 231 -3 0.26 0.23 0.04 0.88 222 4 0.29 0.26 0.03 0.71 249 5 0.31 0.29 0.02 0.60 212 6 0.34 0.31 0.02 0.53 203 -7 0.35 0.34 0.02 0.47 258 8 0.37 0.35 0.02 0.43 194 9 0.39 0.37 0.02 0.40 185 -10 0.40 0.39 0.01 0.37 268 11 0.42 0.40 0.01 0.35 175 -12 0.43 0.42 0.01 0.33 166 -13 0.44 0.43 0.01 0.31 277 14 0.45 0.44 0.01 0.29 157 -15 0.46 0.45 0.01 0.28 148 -16 0.47 0.46 0.01 0.27 286 17 0.49 0.47 0.01 0.26 138 18 0.50 0.49 0.01 0.25 129 -19 0.50 0.50 0.01 0.24 295 20 0.51 0.50 0.01 0.23 120 21 0.52 0.51 0.01 0.23 111 -22 0.53 0.52 0.01 0.22 305 23 0.54 0.53 0.01 0.21 102 24 0.55 0.54 0.01 0.21 92 25 0.56 0.55 0.01 0.20 314 26 0.56 0.56 0.01 0.20 83 -27 0.57 0.56 0.01 0.19 74 -28 0.58 0.57 0.01 0.19 323 29 0.59 0.58 0.01 0.18 65 -30 0.59 0.59 0.01 0.18 55 -31 0.60 0.59 0.01 0.17 332 32 0.61 0.60 0.01 0.17 46 33 0.61 0.61 0.01 0.17 37 • 34 0.62 0.61 0.01 0.16 342 35 0.63 0.62 0.01 0.16 28 -36 0.63 0.63 0.01 0.16 18 • 37 0.64 0.63 0.01 0.16 351 38 0.65 0.64 0.01 0.15 9 -39 0.65 0.65 0.01 0.15 0 • 40 0.66 0.65 0.01 0.15 360 -.. -090227-Detention Hydrograph.xlsx LANG ENGINEERING CO. System "B"-85th • .. Palomar Airport Commons Page 1 of 1 -Project: Palomar Airport Commons Date: 06/14/10 System: Storm System "B", Sorted by Rainfall Blocks in Numerial Order Storm: 851h Percentile, 6 Hour Assumed --N Pr(Nl (inches) Pr(N·ll (inches) PN (inches) QN (cfs) Mid block Tc, min 39 0.65 0.65 0.01 0.15 0 38 0.65 0.64 0.01 0.15 9 36 0.63 0.63 0.01 0.16 18 -35 0.63 0.62 0.01 0.16 28 33 0.61 0.61 0.01 0.17 37 -32 0.61 0.60 0.01 0.17 46 -30 0.59 0.59 0.01 0.18 55 29 0.59 0.58 0.01 0.18 65 27 0.57 0.56 0.01 0.19 74 26 0.56 0.56 0.01 0.20 83 24 0.55 0.54 0.01 0.21 92 -23 0.54 0.53 0.01 0.21 102 -21 0.52 0.51 0.01 0.23 111 20 0.51 0.50 0.01 0.23 120 -18 0.50 0.49 0.01 0.25 129 -17 0.49 0.47 0.01 0.26 138 15 0.46 0.45 0.01 0.28 148 14 0.45 0.44 0.01 0.29 157 -12 0.43 0.42 0.01 0.33 166 11 0.42 0.40 0.01 0.35 175 9 0.39 0.37 0.02 0.40 185 -8 0.37 0.35 0.02 0.43 194 6 0.34 0.31 0.02 0.53 203 5 0.31 0.29 0.02 0.60 212 3 0.26 0.23 0.04 0.88 222 2 0.23 0.18 0.05 1.24 231 ... 1 0.18 0.00 0.18 4.45 240 4 0.29 0.26 0.03 0.71 249 7 0.35 0.34 0.02 0.47 258 -10 0.40 0.39 0.01 0.37 268 -13 0.44 0.43 0.01 0.31 277 16 0.47 0.46 0.01 0.27 286 .. 19 0.50 0.50 0.01 0.24 295 • 22 0.53 0.52 0.01 0.22 305 25 0.56 0.55 0.01 0.20 314 -28 0.58 0.57 0.01 0.19 323 -31 0.60 0.59 0.01 0.17 332 34 0.62 0.61 0.01 0.16 342 37 0.64 0.63 0.01 0.16 351 .. 40 0.66 0.65 0.01 0.15 360 -090227-Detention Hydrograph.xlsx LANG ENGINEERING CO . System "B" -85th Sorted .. -Hydrograph Report Hydraflow Hydrographs by lntelisolve v9.23 Monday, Jun 14, 2010 -Hyd. No. 1 Basin B Water Quality -85th -Hydrograph type = Manual Peak discharge = 4.450 cfs -Storm frequency = 1 yrs Time to peak = 216 min Time interval = 9 min Hyd. volume = 8,662 cuft --Hydrograph Discharge Table (Printed values>= 1.00% of Qp.) Time --Outflow .. (min cfs) -9 0.160 .. 18 0.170 27 0.170 -36 0.180 45 0.180 -54 0.190 63 0.200 -72 0.210 81 0.210 .111 90 0.230 99 0.230 -108 0.250 117 0.260 .111 126 0.280 135 0.290 -144 0.330 153 0.350 -162 0.400 171 0.430 -180 0.530 -189 0.600 198 0.880 207 1.240 -216 4.450 « .. 225 0.710 234 0.470 -243 0.370 252 0.310 -261 0.270 270 0.240 -279 0.220 288 0.200 • 297 0.190 306 0.170 ... 315 0.160 324 0.160 • 333 0.150 ... . . .End • -• -- - -Hydrograph Report -Hydraflow Hydrographs by lntelisolve v9.23 -Hyd. No. 1 -Basin B Water Quality -85th -Hydrograph type = Manual -Storm frequency = 1 yrs Time interval = 9 min IIIII ---• --Q (cfs) -5.00 .. -.. 4.00 -.. -.. 3.00 . . ... .. -2.00 • ... • 1.00 .. .. ... 0.00 v 0 81 .. ... -HydNo.1 • "" • Peak discharge Time to peak Hyd. volume Basin B Water Quality -85th Hyd. No. 1 --1 Year I __..,.,. ~ "' I'-- " 162 243 324 Monday, Jun 14, 2010 = 4.450 cfs = 216 min = 8,662 cuft Q (cfs) 5.00 4.00 3.00 2.00 1.00 0.00 405 Time (min) - -- ----.. -.. -.. - - ----- ---• ----- -• -- Pond Report Hydraflow Hydrographs by lntelisolve v9.23 Monday, Jun 14, 2010 Pond No. 1 -Basin B-Underground Storage Pond Data UG Chambers. Invert elev. = 255.29 ft, Rise x Span= 4.50 x 4.50 ft, Barrel Len= 90.00 ft, No. Barrels= 4, Slope= 0.00%, Headers= Yes Encasement -Invert elev. = 254.79 ft, Width= 7.00 ft, Height= 6.00 ft, Voids= 40.00% Stage I Storage Table Stage (ft) Elevation (ft) 0.00 254.79 0.60 255.39 1.20 255.99 1.80 256.59 2.40 257.19 3.00 257.79 3.60 258.39 4.20 258.99 4.80 259.59 5.40 260.19 6.00 260.79 Culvert I Orifice Structures Rise (In) Span (In) No. Barrels Invert El. (ft) Length (ft) Slope(%) N-Value Orifice Coeff. Multi.Stage Stage (ft) 6.00 5.00 4.00 [A] = 24.00 = 24.00 = 1 = 258.70 = 61.00 = 4.52 = .013 = 0.60 = n/a Contour area (sqft) lncr. Storage (cuft) Total storage (cuft) n/a 0 0 n/a 721 721 n/a 1,071 1,792 n/a 1,256 3,048 n/a 1,343 4,391 n/a 1,371 5,761 n/a 1,350 7,111 n/a 1,275 8,387 n/a 1 '114 9,500 n/a 761 10,261 n/a 699 10,960 Weir Structures [B] [C] [PrfRsr] [A] [B] [C] [D] Inactive 0.00 0.00 Crest Len (ft) = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Crest El. (ft) = 0.00 0.00 0.00 0.00 1 0 0 WelrCoeff. = 3.33 3.33 3.33 3.33 0.00 0.00 0.00 Weir Type 0.00 0.00 0.00 Multi.Stage = No No No No 0.00 0.00 n/a .013 .013 n/a 0.60 0.60 0.60 Exfll.(lnlhr) = 0.500 (by Wet area) Yes No No TW Elev. (ft) = 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). Stage I Storage _,~ ~ v v ./ ""' v v v Elev (ft) 260.79 259.79 258.79 257.79 256.79 v .,..,. / / ~ 1.00 0.00 0 1,000 2,000 3,000 4,000 -Storage 5,000 6,000 7,000 8,000 9,000 10,000 255.79 254.79 11,000 Storage ( cuft) ... -... ---... --- ... ... .. -.. - ------ --... ----- -LANG-. . eng1neer1ng co. Project: Palomar Airport Commons Job No.: 090227 Scale: N/A Calc. By: GWL Date: 06/14/10 Checked: RGL Date: 06/14/10 Consulting Engineers · Land Planners Sheet: 1 Of 1 i I ! ' I I I i I i I i I I I Drainage Basins A, B/C & D I I i I I I I I I I -- c = 0.84 I I -___ _L_ I ! ' I +----1-------------1------; These drainage basins contain sub-basins which will have ---r I r---r- I ! _j____J_ __ ------ Drainage Basin A & D's biocell designs will be per Figure A (see attached sample detail) I 1 TT[ 1 ~---r-T---r-·-r 1 I l_Ll_l __ l_L __ r----------t--1-------r---- Drainge Basin B/C biofiltration designs will be per Figure B (see attached sample detail) I --T T-1·--r~: -r--r-T-T I ------------ All biofiltration areas will be sized using 0.2" of rainfall for a flow based BMP I I f1 I < I < I I i I i : : I ! I I The biofiltration areas will have an assumed soil infiltration rate of 5 inches per hour_t_ ---·~ ---~ -T--T-TIT I I I I I I I ~---~-J-----~----------- ---<««------------'------ These two design parameters allow the biofiltration area's footprint to be calculated by 4% times the contributing drainage area. (Per draft Countywide Model SUSMP, dated January 2, 2009) ___ T_T_ : ----------~ m I I I -----t---- -- i ! I -- I I ------t----t---------- --- -----------------------·1-------- -···------------t--------·· ------ I ------------ i I I I ·-·---I --~---------- i I I ------- ----- I i i I ·t-I -----t----. ---r------- I I I ---------------1------------[---- I i i I I 1--I t---i I I I I -----ATTACHMENT G ---TREATMENTCONTROLBMPFACTSHEETS ----·-... --.... -... - - -• - --- - -.. -- -... ----- - - - - - --- ·-----.. - - - TC-32 Bioretention be required since clogging may result, particularly if the BMP receives runoff with high sedimentloads (EPA. 1999). • Bioretention is not a suitable BMP at locations where the water table is within 6 feet of the ground surface and where the surrounding soil stratum is unstable. • By design, bioretention BMPs have the potential to create very attractive habitats for mosquitoes and other vectors because of highly organic, often heavily vegetated areas mixed with shallow water. • In cold climates the soil may freeze, preventing runoff from infiltrating into the planting soil. Design and Sizing Guidelines • The bioretention area should be sized to capture the design storm runoff. • In areas where the native soil permeability is less than 0.5 in/hr an underdrain should be provided. • Recommended minimum dimensions are 15 feet by 40 feet, although the preferred width is 25 feet. Excavated depth should be 4 feet. • Area should drain completely within 72 hours. • Approximately 1 tree or shrub per 50 ft2 of bioretention area should be included. • Cover area with about 3 inches of mulch. Construction/Inspection Considerations Bioretention area should not be established until contributing watershed is stabilized. Performance Bioretention removes stormwater pollutants through physical and biological processes, including adsorption, filtration, plant uptake, microbial activity, decomposition, sedimentation and volatilization (EPA, 1999). Adsorption is the process whereby particulate pollutants attach to soil (e.g., clay) or vegetation surfaces. Adequate contact time between the surface and pollutant must be provided for in the design of the system for this removal process to occur. Thus, the infiltration rate of the soils must not exceed those specified in the design criteria or pollutant removal may decrease. Pollutants removed by adsorption include metals, phosphorus, and hydrocarbons. Filtration occurs as runoff passes through the bioretention area media, such as the sand bed, ground cover, and planting soil. Common particulates removed from stormwater include particulate organic matter, phosphorus, and suspended solids. Biological processes that occur in wetlands result in pollutant uptake by plants and microorganisms in the soil. Plant growth is sustained by the uptake of nutrients from the soils, with woody plants locking up these nutrients through the seasons. Microbial activity within the soil also contributes to the removal of nitrogen and organic matter. Nitrogen is removed by nitrifying and denitrifying bacteria, while aerobic bacteria are responsible for the decomposition of the organic matter. Microbial processes require oxygen and can result in depleted oxygen levels if the bioretention area is not adequately 2 of8 California Storrnwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com January 2003 - -.. -,. - - - -- ------ ---... - - - - Bioretention TC-32 aerated. Sedimentation occurs in the swale or ponding area as the velocity slows and solids fall out of suspension. The removal effectiveness of bioretention has been studied during field and laboratory studies conducted by the University of Maryland (Davis et al, 1998). During these experiments, synthetic stormwater runoff was pumped through several laboratory and field bioretention areas to simulate typical storm events in Prince George's County, MD. Removal rates for heavy metals and nutrients are shown in Table 1. Table 1 Laboratory and Estimated Bioretention Davis et al. (1998); PGDER (1993) Pollutant Removal Rate Total Phosphorus 70-83% Metals (Cu. Zn, Ph) 93-98% TKN 68-80% Total Suspended Solids 90% Organics 90% Bacteria 90% Results for both the laboratory and field experiments were similar for each of the pollutants analyzed. Doubling or halving the influent pollutant levels had little effect on the effluent pollutants concentrations (Davis et al, 1998). The microbial activity and plant uptake occurring in the bioretention area will likely result in higher removal rates than those determined for inf:Utration BMPs. Siting Criteria Bioretention BMPs are generally used to treat stormwater from impervious surfaces at commercial, residential, and industrial areas (EPA, 1999). Implementation of bioretention for stormwater management is ideal for median strips, parking lot islands, and swales. Moreover, the runoff in these areas can be designed to either divert directly into the bioretention area or convey into the bioretention area by a curb and gutter collection system . The best location for bioretention areas is upland from inlets that receive sheet flow from graded areas and at areas that will be excavated (EPA, 1999). In order to maximize treatment effectiveness, the site must be graded in such a way that minimizes erosive conditions as sheet flow is conveyed to the treatment area. Locations where a bioretention area can be readily incorporated into the site plan without further environmental damage are preferred. Furthermore, to effectively minimize sediment loading in the treatment area, bioretention only should be used in stabilized drainage areas. January 2003 California Storrnwater BMP Handbook New Development and Redevelopment wvwv .cabmphandbooks.com 3 of 8 ------- ----- ------ --... -.. ... • ... - TC-32 Bioretention Additional Design Guidelines The layout of the bioretention area is determined after site constraints such as location of utilities, underlying soils, existing vegetation, and drainage are considered (EPA, 1999). Sites with loamy sand soils are especially appropriate for bioretention because the excavated soil can be backfilled and used as the planting soil, thus eliminating the cost of importing planting soil. The use of bioretention may not be feasible given an unstable surrounding soil stratum, soils with clay content greater than 25 percent, a site with slopes greater than 20 percent, and/or a site with mature trees that would be removed during construction of the BMP. Bioretention can be designed to be off-line or on-line of the existing drainage system (EPA, 1999). The drainage area for a bioretention area should be between 0.1 and 0. 4 hectares (0.25 and 1.0 acres). Larger drainage areas may require multiple bioretention areas. Furthermore, the maximum drainage area for a bioretention area is determined by the expected rainfall intensity and runoff rate. Stabilized areas may erode when velocities are greater than 5 feet per second (1.5 meter per second). The designer should determine the potential for erosive conditions at the site. The size of the bioretention area, which is a function of the drainage area and the runoff generated from the area is sized to capture the water quality volume. The recommended minimum dimensions of the bioretention area are 15 feet (4.6 meters) wide by 40 feet (12.2 meters) long, where the minimum width allows enough space for a dense, randomly-distributed area of trees and shrubs to become established. Thus replicating a natural forest and creating a microdimate, thereby enabling the bioretention area to tolerate the effects of heat stress, acid rain, runoff pollutants, and insect and disease infestations which landscaped areas in urban settings typically are unable to tolerate. The preferred width is 25 feet (7.6 meters), with a length of twice the width. Essentially, any facilities wider than 20 feet (6.1 meters) should be twice as long as they are wide, which promotes the distribution of flow and decreases the chances of concentrated flow. In order to provide adequate storage and prevent water from standing for excessive periods of time the ponding depth of the bioretention area should not exceed 6 inches (15 centimeters). Water should not be left to stand for more than 72 hours. A restriction on the type of plants that can be used may be necessary due to some plants' water intolerance. Furthermore, if water is left standing for longer than 72 hours mosquitoes and other insects may start to breed . The appropriate planting soil should be backfilled into the excavated bioretention area. Planting soils should be sandy loam, loamy sand, or loam texture with a clay content ranging from 10 to 25 percent. Generally the soil should have infiltration rates greater than 0.5 inches (1.25 centimeters) per hour, which is typical of sandy loams, loamy sands, or loams. The pH of the soil should range between 5.5 and 6.5, where pollutants such as organic nitrogen and phosphorus can be adsorbed by the soil and microbial activity can flourish. Additional requirements for the planting soil ind ude a 1.5 to 3 percent organic content and a maximum 500 ppm concentration of soluble salts . 4 of 8 California Stormwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com January 2003 -------------- ·- ------ IIIII - IIIII ... - IIIII -- Bioretention TC-32 Soil tests should be performed for every 500 cubic yards (382 cubic meters) of planting soil, with the exception of pH and organic content tests, which are required only once per bioretention area (EPA, 1999). Planting soil should be 4 inches (10.1 centimeters) deeper than the bottom of the largest root ball and 4 feet (1.2 meters) altogether. This depth will provide adequate soil for the plants' root systems to become established, prevent plant damage due to severe wind, and provide adequate moisture capacity. Most sites will require excavation in order to obtain the recommended depth. Planting soil depths of greater than 4 feet (1.2 meters) may require additional construction practices such as shoring measures (EPA, 1999). Planting soil should be placed in 18 inches or greater lifts and lightly compacted until the desired depth is reached. Since high canopy trees may be destroyed during maintenance the bioretention area should be vegetated to resemble a terrestrial forest community ecosystem that is dominated by understory trees. Three species each of both trees and shrubs are recommended to be planted at a rate of 2500 trees and shrubs per hectare (1000 per acre). For instance, a 15 foot (4.6 meter) by 40 foot (12.2 meter) bioretention area (600 square feet or 55.75 square meters) would require 14 trees and shrubs. The shrub-to-tree ratio should be 2:1 to 3:1. Trees and shrubs should be planted when conditions are favorable. Vegetation should be watered at the end of each day for fourteen days following its planting. Plant species tolerant of pollutant loads and varying wet and dry conditions should be used in the bioretention area. The designer should assess aesthetics, site layout, and maintenance requirements when selecting plant species. Adjacent non-native invasive species should be identifted and the designer should take measures, such as providing a soil breach to eliminate the threat of these species invading the bioretention area. Regional landscaping manuals should be consulted to ensure that the planting of the bioretention area meets the landscaping requirements established by the local authorities. The designers should evaluate the best placement of vegetation within the bioretention area. Plants should be placed at irregular intervals to replicate a natural forest. Trees should be placed on the perimeter of the area to provide shade and shelter from the wind. Trees and shrubs can be sheltered from damaging flows if they are placed away from the path of the incoming runoff. In cold climates, species that are more tolerant to cold winds, such as evergreens, should be placed in windier areas of the site. Following placement of the trees and shrubs, the ground cover and/ or mulch should be established. Ground cover such as grasses or legumes can be planted at the beginning of the growing season. Mulch should be placed immediately after trees and shrubs are planted. Two to 3 inches (5 to 7.6 em) of commercially-available fine shredded hardwood mulch or shredded hardwood chips should be applied to the bioretention area to protect from erosion. Maintenance The primary maintenance requirement for bioretention areas is that of inspection and repair or replacement of the treatment area's components. Generally, this involves nothing more than the routine periodic maintenance that is required of any landscaped area. Plants that are appropriate for the site, climatic, and watering conditions should be selected for use in the bioretention cell. Appropriately selected plants will aide in reducing fertilizer, pesticide, water, and overall maintenance requirements. Bioretention system components should blend over time through plant and root growth, organic decomposition, and the development of a natural January 2003 California Stormwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com 5 of 8 .. --- -.. ------------ ---------.. -• - ---- TC-32 Bioretention soil horizon. These biologic and physical processes over time will lengthen the facility's life span and reduce the need for extensive maintenance. Routine maintenance should include a biannual health evaluation of the trees and shrubs and subsequent removal of any dead or diseased vegetation (EPA, 1999). Diseased vegetation should be treated as needed using preventative and low-toxic measures to the extent possible. BMPs have the potential to create very attractive habitats for mosquitoes and other vectors because of highly organic, often heavily vegetated areas mixed with shallow water. Routine inspections for areas of standing water within the BMP and corrective measures to restore proper inf:t.ltration rates are necessary to prevent creating mosquito and other vector habitat. In addition, bioretention BMPs are susceptible to invasion by aggressive plant species such as cattails, which increase the chances of water standing and subsequent vector production if not routinely maintained. In order to maintain the treatment area's appearance it may be necessary to prune and weed. Furthermore, mulch replacement is suggested when erosion is evident or when the site begins to look unattractive. Specifically, the entire area may require mulch replacement every two to three years, although spot mulching may be sufficient when there are random void areas. Mulch replacement should be done prior to the start of the wet season. New Jersey's Department of Environmental Protection states in their bioretention systems standards that accumulated sediment and debris removal (especially at the inflow point) will normally be the primary maintenance function. Other potential tasks include replacement of dead vegetation, soil pH regulation, erosion repair at inflow points, mulch replenishment, unclogging the underdrain, and repairing overflow structures. There is also the possibility that the cation exchange capacity of the soils in the cell will be significantly reduced over time. Depending on pollutant loads, soils may need to be replaced within 5-10 years of construction (LID, 2000). Cost Construction Cost Construction cost estimates for a bioretention area are slightly greater than those for the required landscaping for a new development (EPA, 1999). A general rule of thumb (Coffman, 1999) is that residential bioretention areas average about $3 to $4 per square foot, depending on soil conditions and the density and types of plants used. Commercial, industrial and institutional site costs can range between $10 to $40 per square foot, based on the need for control structures, curbing, storm drains and underdrains. Retrofitting a site typically costs more, averaging $6,500 per bioretention area. The higher costs are attributed to the demolition of existing concrete, asphalt, and existing structures and the replacement of fill material with planting soil. The costs of retrofitting a commercial site in Maryland, Kettering Development, with 15 bioretention areas were estimated at $111,600. In any bioretention area design, the cost of plants varies substantially and can account for a significant portion of the expenditures. While these cost estimates are slightly greater than those of typical landscaping treatment (due to the increased number of plantings, additional soil excavation, backfill material, use of underdrains etc.), those landscaping expenses that would be required regardless of the bioretention installation should be subtracted when determining the net cost. 6of8 California Storrnwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com January 2003 -- ---- ... - -- --------- - -.. - ---- Bioretention TC-32 Perhaps of most importance, however, the cost savings compared to the use of traditional structural stormwater conveyance systems makes bioretention areas quite attractive financially. For example, the use of bioretention can decrease the cost required for constructing storm water conveyance systems at a site. A medical offtce building in Maryland was able to reduce the amount of storm drain pipe that was needed from 800 to 230 feet-a cost savings of $24,000 (PGDER. 1993). And a new residential development spent a total of approximately $100,000 using bioretention cells on each lot instead of nearly $400,000 for the traditional stormwater ponds that were originally planned (Rappahanock, ). Also, in residential areas, stormwater management controls become a part of each property owner's landscape, reducing the public burden to maintain large centralized facilities. Maintenance Cost The operation and maintenance costs for a bioretention facility will be comparable to those of typical landscaping required for a site. Costs beyond the normal landscaping fees will include the cost for testing the soils and may include costs for a sand bed and planting soil. References and Sources of Additional I nformatlon Coffman, L.S., R. Goo and R. Frederick, 1999: Low impact development: an innovative alternative approach to stormwater management. Proceedings of the 26th Annual Water Resources Planning and Management Conference ASCE, June 6-9, Tempe, Arizona. Davis, A.P., Shokouhian, M., Sharma, H. and Minami, C., "Laboratory Study of Biological Retention (Bioretention) for Urban Stormwater Management," Water Environ. Res., 73(1), 5-14 (2001). Davis, A.P., Shokouhian, M., Sharma, H., Minami, C., and Winogradoff, D. "Water Quality Improvement through Bioretention: Lead, Copper, and Zinc," Water Environ. Res., accepted for publication, August 2002. Kim, H., Seagren, E.A., and Davis, A.P., "Engineered Bioretention for Removal of Nitrate from Stormwater Runoff," WEFTEC 2000 Conference Proceedings on CD ROM Research Symposium, Nitrogen Removal, Session 19, Anaheim CA, October 2000. Hsieh, C.-h. and Davis, A.P. "Engineering Bioretention for Treatment of Urban Stormwater Runoff,· Watersheds 2002, Proceedings on CD ROM Research Symposium, Session 15, Ft. Lauderdale, FL, Feb. 2002. Prince George's County Department of Environmental Resources (PGDER), 1993. Design Manual for Use of Bioretention in Stormwater Management. Division of Environmental Management, Watershed Protection Branch. Landover, MD. U.S. EPA Offke of Water, 1999. Stormwater Technology Fact Sheet: Bioretention. EPA 832-F- 99-012. Weinstein, N. Davis, A.P. and Veeramachaneni, R. "Low Impact Development (LID) Stormwater Management Approach for the Control of Diffuse Pollution from Urban Roadways," 5th International Conference Diffuse/Non point Pollution and Watershed Management Proceedings, C.S. Melching and Emre Alp, Eds. 2001 International Water Association January 2003 California Stormwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com 7 of 8 --- - -------·---- ------- - .. • .. • -• TC-11 Infiltration Basin signiflcant portion of the average annual rainfall runoff is inf:U trated and evaporated rather than flushed directly to creeks. • If the water quality val ume is adequately sized, infiltration basins can be useful for providing control of channel forming (erosion) and high frequency (generally less than the 2-year) flood events. Limitations • May not be appropriate for industrial sites or locations where spills may occur. • Infiltration basins require a minimum soil inf:t.ltration rate of0.5 inches/hour, not appropriate at sites with Hydrologic Soil Types C and D. • If inf:tltration rates exceed 2.4 inches/hour, then the runoff should be fully treated prior to infiltration to protect groundwater quality. • Not suitable on f:t.ll sites or steep slopes. • Risk of groundwater contamination in very coarse soils. • Upstream drainage area must be completely stabilized before construction. • Difficult to restore functioning of inf:t.ltration basins once clogged. Design and Sizing Guidelines • Water quality volume determined by local requirements or sized so that 85% of the annual runoff volume is captured. • Basin sized so that the entire water quality volume is infiltrated within 48 hours. • Vegetation establishment on the basin floor may help reduce the clogging rate. Construction/Inspection Considerations • Before construction begins, stabilize the entire area draining to the facility. If impossible, place a diversion berm around the perimeter of the infiltration site to prevent sediment entrance during construction or remove the top 2 inches of soil after the site is stabililized. Stabilize the entire contributing drainage area, including the side slopes, before allowing any runoff to enter once construction is complete. • Place excavated material such that it can not be washed back into the basin if a storm occurs during construction of the facility. • Build the basin without driving heavy equipment over the infiltration surface. Any equipment driven on the surface should have extra-wide ("low pressure") tires. Prior to any construction, rope off the inf:tltration area to stop entrance by unwanted equipment. • After flnal grading, till the infiltration surface deeply . • Use appropriate erosion control seed mix for the specific project and location . 2 of 8 California Stormwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com January 2003 - ----- ------- - -- --------- ... -.. - TC-11 Infiltration Basin • Base flow should not be present in the tributary watershed. Secondary Screening Based on Site Geotechnical Investigation • At least three in-hole conductivity tests shall be performed using USBR 7300-89 or Bouwer- Rice procedures (the latter if groundwater is encountered within the boring), two tests at different locations within the proposed basin and the third down gradient by no more than approximately 10 m. The tests shall measure permeability in the side slopes and the bed within a depth of 3 m of the invert. • The minimum acceptable hydraulic conductivity as measured in any of the three required test holes is 13 mm/hr. If any test hole shows less than the minimum value, the site should be disqualified from further consideration. • Exclude from consideration sites constructed in f:tll or partially in f:tll unless no silts or clays are present in the soil boring. Fill tends to be compacted, with clays in a dispersed rather than flocculated state, greatly reducing permeability. • The geotechnical investigation should be such that a good understanding is gained as to how the stormwater runoff will move in the soil (horizontally or vertically) and if there are any geological conditions that could inhibit the movement of water. Additional Design Guidelines (1) Basin Sizing -The required water quality volume is determined by local regulations or sufncient to capture 85% of the annual runoff. (2) (3) (4) (5) 4 of 8 Provide pretreatment if sediment loading is a maintenance concern for the basin. Include energy dissipation in the inlet design for the basins. Avoid designs that include a permanent pool to reduce opportunity for standing water and associated vector problems. Basin invert area should be determined by the equation: where A= A=WQV kt Basin invert area (m2) WQV =water quality volume (m3) k = 0.5 times the lowest f:teld-measured hydraulic conductivity (m/hr) t = drawdown time ( 48 hr) The use of vertical piping, either for distribution or inf:tltration enhancement shall not be allowed to avoid device classification as a Class V injection well per 40 CFR146.5(e) (4). California Stormwater BMP Handooak New Development and Redevelopment www .cabmphandbooks.com January 2003 -- - ----- ... --- --------- -- ---- Infiltration Basin TC-11 Maintenance Regular maintenance is critical to the successful operation of infiltration basins. Recommended operation and maintenance guidelines include: • Inspections and maintenance to ensure that water infiltrates into the subsurface completely (recommended inf:Lltration rate of 72 hours or less) and that vegetation is carefully managed to prevent creating mosquito and other vector habitats. • Observe drain time for the design storm after completion or modification of the facility to confirm that the desired drain time has been obtained. • Schedule semiannual inspections for beginning and end of the wet season to identify potential problems such as erosion of the basin side slopes and invert, standing water, trash and debris, and sediment accumulation . • Remove accumulated trash and debris in the basin at the start and end of the wet season. • Inspect for standing water at the end of the wet season. • Trim vegetation at the beginning and end of the wet season to prevent establishment of woody vegetation and for aesthetic and vector reasons. • Remove accumulated sediment and regrade when the accumulated sediment volume exceeds 10% of the basin. • If erosion is occurring within the basin, revegetate immediately and stabilize with an erosion control mulch or mat until vegetation cover is established. • To avoid reversing soil development, scarif1cation or other disturbance should only be performed when there are actual signs of clogging, rather than on a routine basis. Always remove deposited sediments before scarif1cation, and use a hand-guided rotary tiller, if possible, or a disc harrow pulled by a very light tractor. Cost Infiltration basins are relatively cost-effective practices because little infrastructure is needed when constructing them. One study estimated the total construction cost at about $2 per ft (adjusted for inflation) of storage for a 0.25-acre basin (SWRPC, 1991). As with other BMPs, these published cost estimates may deviate greatly from what might be incurred at a specific site. For instance, Caltrans spent about $18/ft3 for the two infiltration basins constructed in southern California, each of which had a water quality volume of about 0. 34 ac.-ft. Much of the higher cost can be attributed to changes in the storm drain system necessary to route the runoff to the basin locations. Infiltration basins typically consume about 2 to 3% of the site draining to them, which is relatively small. Additional space may be required for buffer, landscaping, access road, and fencing. Maintenance costs are estimated at 5 to 10% of construction costs. One cost concern associated with inf:Lltration practices is the maintenance burden and longevity. If improperly maintained, inf:Lltration basins have a high failure rate. Thus, it may be necessary to replace the basin with a different technology after a relatively short period of time. January 2003 California Stormwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com 5 of 8 -- - - .. ---------------- ----- TC-11 Infiltration Basin References and Sources of Additional I nformatlon Cal trans, 2002, BMP Retrofit Pilot Program Proposed Final Report, Rpt. CTSW-RT-01-050, California Dept. of Transportation, Sacramento, CA. Galli, J. 1992. Analysis of Urban BMP Perfonnance and Longevity in Prince George's County, Maryland Metropolitan Washington Council of Governments, Washington, DC. Hilding, K. 1996. Longevity of infiltration basins assessed in Puget Sound. Water:shed Protection Techniques 1(3):124-125. Maryland Department of the Environment (MD E). 2000. Maryland Stonnwater Design Manual http:/ /WNW.mde.state.md.us/environment/wma/stormwatermanual. Accessed May 22,2002. Metzger, M. E., D. F. Messer, C. L. Beitia, C. M. Myers, and V. L. Kramer. 2002. The Dark Side OfStormwater Runoff Management: Disease Vectors Associated With Structural BMPs. Stormwater 3(2): 24-39. Nightingale, H.l., 1975, "Lead, Zinc, and Copper in Soils of Urban Storm-Runoff Retention Basins," American Water Works Assoc. Journal. Vol. 67, p. 443-446. Nightingale, H.l., 1987a, "Water Quality beneath Urban Runoff Water Management Basins," Water Resources Bulletin, Vol. 23, p. 197-205. Nightingale, H.l., 1987b, "Accumulation of As, Ni, Cu, and Pb in Retention and Recharge Basin Soils from Urban Runoff," Water Resources Bulletin, Vol. 23, p. 663-672. Nightingale, H.l., 1987c, "Organic Pollutants in Soils of Retention/Recharge Basins Receiving Urban RunoffWater," Soil Science Vol. 148, pp. 39-45. Nightingale, H.I., Harrison, D., and Salo, J.E., 1985, "An Evaluation Technique for Ground- water Quality Beneath Urban Runoff Retention and Percolation Basins," Ground Water Monitoring Review, Vol. 5, No.1, pp. 43-50. Oberts, G. 1994. Performance ofStormwater Ponds and Wetlands in Winter. Water:shed Protection Techniques 1 (2): 64-68. Pitt, R., et al. 1994, Potential Groundwater Contamination from Intentional and Nonintentional Stormwater Infiltration, EPA/600/R-94/051, Risk Reduction Engineering Laboratory, U.S. EPA, Cincinnati, OH. Schueler, T. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban BMPs. Metropolitan Washington Council of Governments, Washington, DC. Schroeder, R.A., 1995, Potential For Chemical Transport Beneath a Storm-Runoff Recharge (Retention) Basin for an Industrial Catchment in Fresno, CA, USGS Water-Resource Investigations Report 93-4140. 6of8 California Stormwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com January 2003 -- ---- - ------ --.. ·---------• ------ Infiltration Basin TC-11 Southeastern Wisconsin Regional Planning Commission (SWRPC).1991. CostsofUrban Nonpoint Source Water Pollution Control Measures. Southeastern Wisconsin Regional Planning Commission, Waukesha, WI. U.S. EPA, 1983, Results of the Nationwide Urban Runoff Program: Volume 1-Final Report, WH-554, Water Planning Division, Washington, DC. Watershed Management Institute (WMI). 1997. Operation, Maintenance, and Management of Storm water Management Systems. Prepared for U.S. Environmental Protection Agency Office of Water, Washington, DC. Information Resources Center for Watershed Protection (CWP). 1997. Stormwater BMP Design Supplement for Cold Climates. Prepared for U.S. Environmental Protection Agency Office of Wetlands, Oceans and Watersheds. Washington, DC. Ferguson, B.K., 1994. Stormwater Infiltration. CRC Press, Ann Arbor, MI. US EPA. 1993. Guidance to Specify Management Measures for Sources of Nonpoint Pollution in Coastal Waters. EPA-840-B-92-002. U.S. Environmental Protection Agency, Office of Water, Washington, DC. January 2003 California Storrnwater BMP Handbook New Development and Redevelopmert WWN .cabmphandbooks.com 7 of 8 ·- -... -- --------- ------ --.. - - - -- TC-50 Water Quality Inlet • Designs that utilize covered sedimentation and filtration basins should be accessible to vector control personnel via access doors to facilitate vector surveillance and controlling the basins if needed. Performance WQis are primarily utilized to remove sediment from stormwater runoff. Grit and sediment are partially removed by gravity settling within the first two chambers. A WQI with a detention time of 1 hour may expect to have 20 to 40 percent removal of sediments. Hydrocarbons associated with the accumulated sediments are also often removed from the runoff through this process. The WQI achieves slight, if any, removal of nutrients, metals and organic pollutants other than free petroleum products (Schueler, 1992). A 1993 MWCOG study found that an average of less than 5 centimeters (2 inches) of sediments (mostly coarse-grained grit and organic matter) were trapped in the WQis. Hydrocarbon and total organic carbon (fOC) concentrations of the sediments averaged 8,150 and 53,900 milligrams per kilogram, respectively. The mean hydrocarbon concentration in the WQI water column was 10 milligrams per liter. The study also indicated that sediment accumulation did not increase over time, suggesting that the sediments become re-suspended during storm events. The authors concluded that although the WQI effectively separates oil and grease from water, re-suspension of the settled matter appears to limit removal efficiencies. Actual removal only occurs when the residuals are removed from the WQI (Schueler 1992). A 1990 report by API found that the efficiency of oil and water separation in a WQI is inversely proportional to the ratio of the discharge rate to the unit's surface area. Due to the small capacity of the WQI, the discharge rate is typically very high and the detention time is very short. For example, the MWCOG study found that the average detention time in a WQI is less than 0.5 hour. This can result in minimal pollutant settling (API, 1990). However, the addition of coalescing units in many current WQI units may increase oil/water separation efficiency. Most coalescing units are designed to achieve a specific outlet concentration of oil and grease (for example, 10-15m/L oil and grease). Pollutant removal in stormwater inlets can be somewhat improved using inserts, which are promoted for removal of oil and grease, trash, debris, and sediment. Some inserts are designed to drop directly into existing catch basins, while others may require extensive retrofit construction. Siting Criteria Oil/water separation units are often utilized in specific industrial areas, such as airport aprons, equipment washdown areas, or vehicle storage areas. In these instances, runoff from the area of concern will usually be diverted directly into the unit, while all other runoff is sent to the storm drain downstream from the oil/water separator. Oil/water separation tanks are often fitted with diffusion baffles at the inlets to prevent turbulent flow from entering the unit and resuspending settled pollutants. Additional Design Guidelines Prior to WQI design, the site should be evaluated to determine if another BMP would be more cost-effective in removing the pollutants of concern. WQis should be used when no other BMP is feasible. The WQI should be constructed near a storm drain network so that flow can be easily diverted to the WQI for treatment (NVPDC, 1992). Any construction activities within the 2 of 6 California Storrnwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com January 2003 - --------- ----------------- ----- Water Quality Inlet TC-50 drainage area should be completed before installation ofthe WQI, and the drainage area should be revegetated so that the sediment loading to the WQI is minimized. WQis are most effective for small drainage areas. Drainage areas of0.4 hectares (1 acre) or less are often recommended. WQis are typically used in an off-line configuration (i.e., portions of runoff are diverted to the WQI), but they can be used as on-line units (i.e., receive all runoff). Generally, off-line units are designed to handle the first 1.3 centimeters (0.5 inches) of runoff from the drainage areas. Upstream isolation/diversion structures can be used to divert the water to the off-line structure (Schueler, 1992). On-line units receive higher flows that will likely cause increased turbulence and resuspension of settled material, thereby reducing WQI performance. Oil/water separation tanks are often fitted with diffusion baffles at the inlets to prevent turbulent flow from entering the unit and resuspending settled pollutants. WQis are available as pre-manufactured units or can be cast in place. Reinforced concrete should be used to construct below-grade WQis. The WQis should be water tight to prevent possible ground water contamination. Maintenance Typical maintenance ofWQis includes trash removal if a screen or other debris capturing device is used, and removal of sediment using a vactor truck. Operators need to be properly trained in WQI maintenance. Maintenance should include keeping a log ofthe amount of sediment collected and the date of removal. Some cities have incorporated the use of GIS systems to track sediment collection and to optimize future catch basin cleaning efforts. One study (Pitt, 1985) concluded that WQis can capture sediments up to approximately 60 percent of the sump volume. When sediment fills greater than 60 percent of their volume, catch basins reach steady state. Storm flows can then resuspend sediments trapped in the catch basin, and will bypass treatment. Frequent clean-out can retain the volume in the catch basin sump available for treatment of stormwater flows. At a minimum, these inlets should be cleaned at least twice during the wet season. Two studies suggest that increasing the frequency of maintenance can improve the performance of catch basins, particularly in industrial or commercial areas. One study of 60 catch basins in Alameda County, California, found that increasing the maintenance frequency from once per year to twice per year could increase the total sediment removed by catch basins on an annual basis (Mineart and Singh, 1994). Annual sediment removed per inlet was 54 pounds for annual cleaning, 70 pounds for semi-annual and quarterly cleaning, and 160 pounds for monthly cleaning. For catch basins draining industrial uses, monthly cleaning increased total annual sediment collected to six times the amount collected by annual cleaning (180 pounds versus 30 pounds). These results suggest that, at least for industrial uses, more frequent cleaning of catch basins may improve efficiency._ BMPs designed with permanent water sumps, vaults, and/or catch basins (frequently installed below-ground) can become a nuisance due to mosquito and other vector breeding. Preventing mosquito access to standing water sources in BMPs (particularly below-ground) is the best prevention plan, but can prove challenging due to multiple entrances and the need to maintain the hydraulic integrity of the system. BMPs that maintain permanent standing water may require routine inspections and treatments by local mosquito and vector control agencies to January 2003 California Stormwater BMP Handbook New Development and Redevelopment www .ca bmpha ndbooks.com 3 of 6 - --------------------- ----- - - TC-50 Water Quality Inlet suppress mosquito production. Standing water in oil/water separators may contain sufficient floating hydrocarbons to prevent mosquito breeding, but this is not a reliable control alternative to vector exclusion or chemical treatment. Cost A typical pre-cast catch basin costs between $2,000 and $3,000; however, oil/water separators can be much more expensive. The true pollutant removal cost associated with catch basins, however, is the long-term maintenance cost. A vactor truck, the most common method of catch basin cleaning, costs between $125,000 and $150,000. This initial cost may be high for smaller Phase II communities. However, it may be possible to share a vactor truck with another community. Typical vactor trucks can store between 10 and 15 cubic yards of material, which is enough storage for three to five catch basins. Assuming semi-annual cleaning, and that the vactor truck could be filled and material disposed of twice in one day, one truck would be sufficient to clean between 750 and 1,000 catch basins. Another maintenance cost is the staff time needed to operate the truck. Depending on the regulations within a community, disposal costs of the sediment captured in catch basins may be significant. References and Sources of Additional Information American Petroleum Institute (API) ,1990. Monographs on Refinery Environmental Control- Management of Water Discharges (Design and Operation of Oil-Water Separators). Publication 421, First Edition. Aronson, G., D. Watson, and W. Pisaro. Evaluation of Catch Basin Performance for Urban Stormwater Pollution Control. U.S. Environmental Protection Agency, Washington, DC. Berg, V.H, 1991. Water Quality Inlets (Oil/Grit Separators). Maryland Department of the Environment, Sediment and Stormwater Administration. Lager, J., W. Smith, R. Finn, and E. Finnemore.1977. Urban Stormwater Management and Technology: Update and Users' Guide. Prepared for U.S. Environmental Protection Agency. EPA-600/8-77-014. 313 pp. Metropolitan Washington Council of Governments (MWCOG), 1993. The Quality of Trapped Sediments and Pool Water Within Oil Grit Separators in Suburban Maryland. Interim Report. Metzger, M. E., D. F. Messer, C. L. Beitia, C. M. Myers, and V. L. Kramer. 2002. The Dark Side Of Stormwater Runoff Management: Disease Vectors Associated With Structural Bmps. Stormwater 3(2): 24-39. Metzger, M. E., and S. Kluh. 2003. Surface Hydrocarbons Vs. Mosquito Breeding. Stormwater 4(1): 10. Mineart, P., and S. Singh.1994. Storm Inlet Pilot Study. Alameda County Urban Runoff Clean Water Program, Oakland, CA. Northern Virginia Planning District Commission (NVPDC) and Engineers and Surveyors Institute, 1992. Northern Virginia BMP Handbook. Pitt, R., and P. Bissonnette.1984. Bellevue Urban Runoff Program Summary Report U.S. Environmental Protection Agency, Water Planning Division, Washington, DC. 4 of 6 California Stormwater BMP Handbook New Development and Redevelopment www .cabmpha ndbooks.com January 2003 - --------- - -- ---" ------------------ Water Quality Inlet TC-50 Pitt, R., M. Lilburn, S. Nix, S.R. Durrans, S. Burian, J. Voorhees, and J. Martinson. 2000. Guidance Manual for Integrated Wet Weather Flow (Wt1P) Collection and Treatment Systems for Newly Urbanized Areas (New WWF Systems). U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, OH. Schueler, T.R., 1992. A Current Assessment of Urban Best Management Practices. Metropolitan Washington Council of Governments. U.S. EPA, 1999, Stormwater Technology Fact Sheet: Water Quality Inlets, EPA 832-F-99-029, Office of Water, Washington DC. January 2003 California Stormwater BMP Handbook New Development and Redevelopment www .ca bmpha ndbooks.com 5 of 6 --- ------------------------ ------- MP-52 Drain Inserts one box; that is, the setting area and filtration through media occurs in the same box. One manufacturer has a double-box. Storm water enters the first box where setting occurs. The stormwater flows into the second box where the filter media is located. Some products consist of one or more trays or mesh grates. The trays can hold different types of media. Filtration media vary with the manufacturer: types include polypropylene, porous polymer, treated cellulose, and activated carbon. Construction/Inspection Considerations Be certain that installation is done in a manner that makes certain that the stormwater enters the unit and does not leak around the perimeter. Leakage between the frame of the insert and the frame of the drain inlet can easily occur with vertical (drop) inlets. Performance Few products have performance data collected under field conditions. Siting Criteria It is recommended that inserts be used only for retrofit situations or as pretreatment where other treatment BMPs presented in this section area used. Additional Design Guidelines Follow guidelines provided by individual manufacturers. Maintenance Likely require frequent maintenance, on the order of several times per year. Cost • The initial cost of individual inserts ranges from less than $100 to about $2,000. The cost of using multiple units in curb inlet drains varies with the size of the inlet. • The low cost of inserts may tend to favor the use of these systems over other, more effective treatment BMPs. However, the low cost of each unit may be offset by the number of units that are required, more frequent maintenance, and the shorter structural life (and therefore replacement). References and Sources of Additional I nformatlon Hrachovec, R., and G. Minton, 2001, Field testing of a sock-type catch basin insert, Planet CPR, Seattle, Washington Interagency Catch Basin Insert Committee, Evaluation of Commercially-Available Catch Basin Inserts for the Treatment of Stormwater Runoff from Developed Sites, 1995 Larry Walker Associates, June 1998, NDMP Inlet/In-Line Control Measure Study Report Manufacturers literature Santa Monica (City), Santa Monica Bay Municipal Stormwater/Urban Runoff Project- Evaluation of Potential Catch basin Retrofits, Woodward Clyde, September 24, 1998 2 of 3 California Stormwater BMP Handbook New Development and Redevelopment www .cabmphandbooks.com January 2003 - ----- ----- ------ '----------- ---- ATTACHMENT H SAMPLETREATMENTCONTROLBMP MAINTENANCE FORMS & INFORMATION - ---- ------ - ------------- - -- UrbanGreen Biofilter™ Inspection and Maintenance The UrbanGreen '" BioFilter should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit (i.e. unstable soils or heavy winter sanding will cause the system to fill more quickly but regular sweeping will slow accumulation). Maintenance of the UrbanGreen BioFilter should be performed by a qualified professional who has experience with maintenance of stormwater management systems. CONTECH offers a full service maintenance compliance program that includes inspection, cleaning and compliance reporting at a competitive price. For more information on this service, please contact CONTECH at 800.338.1122 or maintenancecompliance@contech-cpi.com. Inspection and Routine Maintenance Inspection is the key to effective maintenance. Inspect annually unless local regulations or site conditions require more frequent inspection. Routine maintenance, defined as trash and debris removal and general upkeep, should be performed during each inspection if necessary. First record the height, width and condition of the tree. A sample log is provided. Once these recordings have been taken, the tree grate should be removed to observe the bioretention bay. Any trash and debris that has collected here should be removed and disposed of appropriately. The design infiltration rate of the engineered soil mixture within the bioretention bay is 50 in/hour with 12 inches of driving head. Testing has shown that a fresh batch of the Urban Green BioFilter engineered soil mixture has an infiltration rate of 360 in/hr with 12 inches of driving head. If captured pollutants have occluded the media and infiltration rate of the engineered soil mixture is less than the design infiltration rate, then maintenance of the soil is required. Local jurisdictions may recommend a specific infiltration test to determine the infiltration rate of the soil mixture. However, in the absence of such guidance, a simple test can be performed to estimate the infiltration rate. The following items are required: 4-in diameter, thin wall PVC pipe approximately 1 5-in long; a mallet; filter fabric; and 2 gallons of water. Use the mallet to drive the PVC pipe 3 inches into the engineered soil mixture in a location away from the base of the tree. Cut a 4-in diameter piece of filter fabric and place the fabric in the pipe at soil surface level. Fill the pipe with 12 inches of water above the filter fabric and record the time it takes for all the water to drain. If the measured time is greater than fourteen minutes, then a portion of the engineered soil mixture needs to be replaced. Two infiltration tests should be performed at different locations within the bioretention bay for accuracy. A sample log is provided for observations from the infiltration tests to be recorded. If results from the infiltration tests indicate that the infiltration rate of the soil mixture has dropped below the design standard, then the top layer of the engineered soil mixture should be replaced. Studies have shown that the majority of all captured -2 - pollutants reside in the top 2-3 inches of soil and therefore it is likely that only this layer needs to be replaced. (California Stormwater Quality Association (CASQA), New Development and Redevelopment Handbook, January 2003). Replacement soil is available from CONTECH or other source as long as the original soil specifications are maintained. Please note that when replacing the engineered soil mixture, the riprap which protects the inlet from scour should be collected and set aside for use with the new soil. Once the new soil has been installed, the riprap should be placed back at the inlet in a 2' by 2' pattern. Once the bioretention bay has been inspected and maintenance procedures completed, the tree grate placed should be put securely back in place. Inspection and maintenance of the media cartridge bay are also critical to the overall performance of the system. Inspection should be performed at the same time as inspection of the bioretention bay. Remove the cover over the media cartridge bay and observe the accumulated pollutants within the chamber. If more than three inches of sediment is found on the chamber floor or on the tops of the cartridges, then cartridge replacement should be performed. Additionally, if standing water resides in the chamber for greater than twenty-four hours after a storm event, then cartridge replacement should be performed. Depending on site and climatic conditions, maintenance frequency of the media cartridges should range from 3 to 5 years. Instructions for cartridge replacement are provided in the Non-Routine Maintenance section below. All observations from inspection of the media cartridge bay should be recorded in the maintenance log. Non-Routine Maintenance Non-routine maintenance is defined as clean-out of the media cartridge bay and replacement of cartridges. Replacement cartridges can be ordered by contacting CONTECH at 800.338.1122 or maintenancecompliance@contech-cpi.com. The first step in the clean-out of the media cartridge bay is to remove the sediment and debris that has collected in this chamber. A vacuum truck or manual operation can be used for this procedure. Once the sediment and debris has been removed, the existing cartridges should be removed from the system. Cartridges are connected to the underdrain manifold by a simple quarter-turn connection and are easily disconnected. Once the cartridges are removed from the vault, any remaining sediment and/or debris should be cleaned out. The final step in the cartridge replacement process is to install the replacement cartridges. Replacement cartridges should be installed securely to the quarter- turn connection system and the cover placed securely back over the media cartridge bay. General Maintenance Notes All OSHA standards for health and safety should be followed at all times when inspecting or maintaining the UrbanGreen BioFilter. Furthermore, disposal of pollutants removed from the UrbanGreen BioFilter should be performed in accordance with all regulatory requirements.