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CT 14-01; State Mixed Use 30; Tentative Map (CT) (2)
K&S ENGINEERING, INC. Planning Engineenng Surveying STORM WATER MANAGEMENT PLAN SWMP FOR STATE AND OAK 3069 STATE STREET CARLSBAD, CA 92008 PREPARED FOR 3068 STATE STREET, LLC. 539 CARLSBAD VILLAGE DRIVE CARLSBAD, CA 92008 PREPARED BY: K&S ENGINEERING, INC. 7801 MISSION CENTER COURT, SUITE 100 SAN DIEGO, CA 92108 JN 13-038 December 19,2013 7801 Mission Center Court, Suite 100 . San Diego, Califomia 92108 . (619)296-5565 . Fax (619)296-5564 TABLE OF CONTENTS Section Page 1.0 INTRODUCTION l 2J0 PROJECT DESCRIPTION 2 Figure 1 - Location Map _ _ ^ _ 2 3.0 HYDROLOGICJJNIT CONTRIBUTION 3 Figure 2 - Carlsbad Watershed Hydrologic Unit 3 3.1 BENEFICIAL USE 4 Table 1 - Beneficial Uses 4 4.0 CHARACTERIZATION OF PROJECT RUNOFF 5 Figure 3 - Topographic Vicinity Map „ ^ ^ 5 4,1 POLLUTANTS OF CONCERN AND SOURCES _ 6 JTable 2 - Anticipated and Potential Pollutants Generated by LandTUse Type 6 4.1.A GENERAL POLLUTANT CATEGORIES 6 4J^ SOIL CHARACTERISTICS 8 FIGURE 4 SOIL HYDROLOGIC GROUP MAP 8 43 SITE HYDROLOGY 9 MITIGATION MEASURES TO PROTECT WATER QUALITY 10 5.1 Low IMPACT DEVELOPMENT (LID) SITE DESIGN BMPs 10 5.1.1 PRIORITY DEVELOPMENT PROJECT LID BMP REQUIREMENTS lo[ 5.2 ^OURCE CONTROL BMPs 11 5.3 TREATMENT CONTROL BMPS 12 TABLE 4 TREATMENT CONTROL BMP CATEGORIES A3 Figure 5 - Construction BMP and Post Construction BMPS Site Map 14 5.5 SUMMARY 15 6.0 STORMWATER BMP MAINTENANCE 16 6.1 MAINTENANCE MECHANISM 16 Table 5 - Permanent Treatment BMP Maintenance Schedule J17 7.0 FISCAL RESOURCES IS Table 6 Permanent Treatment BMP Estimated Operation & Maintenance Costs 19 8.0 CONCLUSION 20 9.0 CERTIFICATION 21 ATTACHMENTS C D HYDROLOGY STUDY REFERENCE PERMANENT TREATMENT ^IP INFORMATION BIORETENTION FACILITIES NUMERIC SIZING CITY SUSMP FORMS 1.0 INTRODUCTION The Califomia State Water Quality Control Board approved Order Number 2007-01 (Order) on January 24; 2007.The Order outlines the stormwater discharge requirements for municipal stormwater systems, which drain "development" areas from watersheds within; 1. ) The County of San Diego, 2. ) Incorporated cities of San Diego County, and 3. ) San Diego Unified Port District. The City of Carisbad is one of the municipal co-permittees identified in the order and, therefore, subject to its requirements. In general, the order requires that Best IVIanagement Practices (BMPs): • Control the post-development peak storm water storm discharge rates and velocities to maintain or reduce pre-development downstream erosion • Minimize storm water pollutants of concem in urban runoff from new development through implementation of source control BMPs • Remove pollutants of concem from urban runoff through implementation of structural treatment BMPs • Include proof of a mechanism, to be provided by the project proposal, which will ensure ongoing long- term structural BMP maintenance. In addition, structural BMPs shall be located to infiltrate, filter, or treat the required runoff volume or flow (numeric sizing criteria) prior to discharge to any receiving water body supporting beneficial uses. The "numeric sizing criteria" is either volume or flow based. Specifically, volume based BMPs must be designed to infiltrate, filter, or treat the volume of runoff produced from a 24-hour - 85"" percentile storm event. This is approximately 0.6 inches of runoff for San Diego County. Similarly, flow based BMPs must be designed to infiltrate, filter or treat a flow rate of 0.2 inches of rainfall per hour. Note that the above "numeric sizing criteria" allows the option of infiltration, filtering or treatment of this volume/flow and relates only to water quantity. Retention or detention of water volume/flow is not a requirement of the "numeric sizing criteria." This Water Quality Technical Report (WQTR) proposes to address the possible water quality impacts from the proposed grading and private improvements of State and Oak. It will define the potential BMP options that satisfy the requirements, identified in the following documents: 1. ) City of Carlsbad SUSMP January 14, 2011. 2. ) County of San Diego Municipal NPDES Storm Water Pemiit (Order Number 2007-01). The goal of this WQTR is to develop and implement the best available procedure policies of the Standards to insure to the maximum extent practicable that development does not increase pollutant loads from the project site and considers urban run-off flow rates, potential pollutants, and velocities. The WQTR also intends to insure the effectiveness of the Best Management Practices (BMPs) through proper maintenance that is based on long-term fiscal planning. This SWMP is subject to revisions by the engineer as needed due to site revisions or as directed by the City Engineer. Proposed project is within the hydromodification exempt area , per " Hydromodification Exemption Analyses for selected Carlsbad Watersheds" prepared by Wayne Chang dated June 10,2013 According to the Storm Water Standards Questionnaire E-34 (see Appendix C of this report), the Project is subject to; • Priority Development Project (PDP) 2.0 PROJECT DESCRIPTION The Project is located on North East comer of State Street and Oak Avenue in the City Of Carlsbad, County of San Diego, Figure 1 indicates the Project location. Currently there are six small residential buildings, with their corresponding driveways and landscaping. The proposed project consists of 33 Residential Condominiums and 5 commerciai retail units, with landscape, hardscape, enclosed trash enclosure and parking areas. The total disturbed area will be 0.45acres, being 100% of the site. In general, approximately 54% of the site will drain to State Street, and 46% to Oak Avenue drainage systems. The northerly portion is drained to underground storm drain system at corner of Carlsbad Village drive and State which; eventually discharge to Buena Vista Lagoon. The southerly portion is drain to underground storm drain system on Oak Avenue; which eventually discharge to Agua Hedionda Lagoon. On-site mnoff will be treated with the use of flow thru planters "bio-retention" BMP's to reduce or eliminate any pollutant generated by the project. FIGURE 1 LOCATION MAP NTS Page 3 Missing Site splits into two water bodies, the northerly portion discharges to the Buena Vista Lagoon (904.21) located approximately 3,]00feet upstream and the southerly portion to Agua Hedionda Lagoon (904.31) located approximately 5,900 feet downstream. The project will not significantly alter the overall drainage pattern from the existing condition. 3.1 BENEFICIAL USE The beneficial uses of inland surface water, coastal waters and groundwater for this hydrologic sub-area and those downstream of the Project are identified in Table I. The data contained in this table is extracted from Project Clean Water. TABLE 1 Beneficial water uses within the Carlsbad Watershed as designated in the State Water Resources Control Board's San Diego Region Basin Plan. Beneficial Uses Inland Surface Water Coastal Waters Reservoirs and Lakes Ground Water AAunicipal and Domestic Supply X X X Asricultural Supply X X X Industrial Service Supply X X X X Navigation X Contact Water Recreation X X X Non-Contact Water Recreation X X X Commercial and Sport Fishing X Warm Freshwater Habitat X X X Cold Freshwater Habitat X X Estuarine Habitat X Wildlife Habitat X X X Biological Habitats X Rare, Threatened, or End. X X Marine Habitat X Migration of Aquatic Organisms X Aquaculture X Shellfish Harvesting X Spawning, Reprod. and/or Early Develop. X Hydropower Generation 4.0 CHARACTERIZATION OF PROJECT RUN-OFF According to the Califomia 2006 303(d) list published by the San Diego Regional Water Quality Control Board, the Buena Vista Lagoon (904.2) and Agua hedionda (904.31) and Pacific Ocean shoreline within the City Carlsbad beach are impaired water bodies. Figure 3 shows the approximate location of the Project and the surrounding topography. FIGURE 3 PACIFIC OCEAN TopograDhic Vicinity Map 4.1 POLLUTANTS OF CONCERN AND SOURCES There are no sampling data available for the existing site condition. In addition, the project is not expected to generate significant amounts of non-visible pollutants. However, the constituents iisted in Table 2, which could affect water quality, commonly generate from similar developments. The nature of the project development can produce secondary pollutants of concem. Consider the pollutants identified in Table 2 that aren't listed as pollutant stressors on the 303(d) List as being the secondary pollutants of concem. Implementation of source and treatment controls during and after construction limits or eliminates these pollutants to the maximum practicable extent. The sources and affects of the primary and secondary pollutants of concem and other potential pollutants occurring on the project are identified below Table 2. TABLE 2 Priority Project Categories General Pollutant Categories Priority Project Categories Sediments Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Substances Oil& Grease Bacteria &. Viruses Pesticides Commercial Development >l 00,000 ft^ pd) pd) X p(2) X p(5) X p(3) p(5) Attached Residential Development X X X pd) pd) P X Restaurants X X X X pd) 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 (5) Including solvents Anticipated and Potential Pollutants Generated bv Land Use Type 4.1.A General Pollutant Categories The potential sources for the constituents of concem for the project could be, but are not limited to those listed below: o Sediments - Sediments are soils or other surficial materials eroded and then transported or deposited by the action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills, reduce spawning habitat, lower young aquatic organisms survival rates, smother bottom dwelling organisms, and suppress aquatic vegetation growth. o Nutrients - Nutrients are inorganic substances, such as nitrogen and phosphoms. They commonly exist in the form of mineral salts that are either dissolved or suspended in water. Primary sources of nutrients in urban run-off are fertilizers and eroded soils. Excessive discharge of nutrients to water bodies and streams can cause excessive aquatic algae and plant growth. Such excessive production, referred to as cultural eutrophication, may lead to excessive decay of organic matter in the water body, loss of oxygen in the water, release of toxins in sediment, and the eventual death of aquatic organisms. o Metals - Metals are raw material components in non-metal products such as fuels, adhesives, paints, and other coatings. Primary source of metal pollution in storm water are typically commercially available metals and metal products. Metals of concem include cadmium, chromium, copper, lead, mercury, and zinc. Lead and chromium have been used as corrosion inhibitors in primer coatings and cooling tower systems. At low concentrations naturally occurring in soil, metals are not toxic. However, at higher concentrations, certain metals can be toxic to aquatic life. Humans can be impacted from contaminated groundwater resources, and bioaccumulation of metals in fish and shellfish. Environmental concerns, regarding the potential for release of metals to the environment, have already led to restricted metal usage in certain applications. o Organic Compounds - Organic compounds are carbon-based. Commercially available or naturally occurring organic compounds are found in pesticides, solvents, and hydrocarbons. Organic compounds can, at certain concentrations, indirectly or directly constitute a hazard to life or health. When rinsing off objects, toxic levels of solvents and cleaning compounds can be discharged to storm drains. Dirt, grease, and grime retained in the cleaning fluid or rinse water may also adsorb levels of organic compounds that are harmful or hazardous to aquatic life. o Trash & Debris - Trash (such as paper, plastic, polystyrene packing foam, and aluminum materials) and biodegradable organic matter (such as leaves, grass cuttings, and food waste) are general waste products on the landscape. The presence of trash & debris may have a significant impact on the recreational value of a water body and aquatic habitat. Excess organic matter can create a high biochemical oxygen demand in a stream and thereby lower its water quality. Also, in areas where stagnant water exists, the presence of excess organic matter can promote septic conditions resulting in the growth of undesirable organisms and the release of odorous and hazardous compounds such as hydrogen sulfide. o Oxygen-Demanding Substances - This category includes biodegradable organic material as well as chemicals that react with dissolved oxygen in water to form other compounds. Proteins, carbohydrates, and fats are examples of biodegradable organic compounds. Compounds such as ammonia and hydrogen sulfide are examples of oxygen-demanding compounds. The oxygen demand of a substance can lead to depletion of dissolved oxygen in a water body and possibly the development of septic conditions. o Oil and Grease - Oil and grease are characterized as high-molecular weight organic compounds. Primary sources of oil and grease are petroleum hydrocarbon products, motor products from leaking vehicles, esters, oils, fats, waxes, and high molecular-weight fatty acids. Introduction of these pollutants to the water bodies are very possible due to the wide uses and applications of some of these products in municipal, residential, commercial, industrial, and construction areas. Elevated oil and grease content can decrease the aesthetic value of the water body, as well as the water quality. o Bacteria and Viruses - Bacteria and viruses are ubiquitous microorganisms that thrive under certain environmental conditions. Their proliferation is typically caused by the transport of animal or human fecal wastes from the watershed. Water, containing excessive bacteria and viruses can alter the aquatic habitat and create a harmful environment for humans and aquatic life. Also, the decomposition of excess organic waste causes increased growth of undesirable organisms in the water. 0 Pesticides - Pesticides (including herbicides) are chemical compounds commonly used to control nuisance growth or prevalence of organisms. Excessive application of a pesticide may result in run-off containing toxic levels of its active component. 4.2 SOIL CHARACTERISTICS. Per the San Diego Hydrology Manual, Soil Hydrologic Groups map figure 4, the project area consists of soil group B. Soil group B soils have moderate infiltration rates when thoroughly wetted. They consist chiefly of soils that are moderately-deep to deep, moderately-well drained to well drained and moderately-coarse textured. Rate of water transmission is moderate. Group B is classified as having a moderate infiltration rate. The USDA Web Soil Survey corroborates this hydrologic soils group classification. FIGURE 4 County of San Diego Hydrology Manual *wf ^ ''> Legend Soil Groups Group A Group B Group C Group D Undetermined Data Unavailat>le Soil Hydrologic Groups 4.3 SITE HYDROLOGY Based on the most recent San Diego County Hydrology Manual, the Project's runoff coefficient ('C factor) for the existing site value is C=0.41 and the value for the proposed site is C=0.77 There will be no diversion of flow for the development. The Project Hydrology Study contains detailed information as to the methodology used in obtaining these results. 5.0 MITIGATION MEASURES TO PROTECT WATER QUALITY To address water quality for the project, BMP's will be implemented. As a Priority Project, these categories require appropriate BMPs from the applicable categories below : • Low Impact Develpment BMPs • Source Control BMPs • Treatment Control BMPs In addition, incorporated into the Project are appropriate site design and source control BMPs for Standard Projects. 5.1 LOW IMPACT DEVELOPMENT (LID) SITE DESIGN BMPS Low Impact Development (LID) site design denotes a stormwater management and land development strategy that emphasizes conservation and the use of on-site natural features integrated with engineered, small-scale hydrologic controls that closely reflect pre-development hydrologic functions. Projects address SUSMP objectives through the creation of a hydrologically functional project design that attempts to mimic the natural hydrologic regime. 5.1.1 Priority Development Project LID BMP Requirements Optimize Site Layout. The project site is previously developed, thereby negating the presence of natural areas. The site contains no natural resources or areas for conserving. There are no existing trees of major consequence within the Project site's disturbed footprint. Minimize impervious Footprint. - Not applicable. Disperse Runoff to adjacent Landscaping and IMP's. The project directs runoff from impervious surfaces towards landscaped areas. These measures disconnect the paved surfaces and roof areas from direct connection to MS-4. Minimize Soil Compaction in Landscape Areas.- Not applicable Convey Runoff safely from the tops of slopes.- The proposed project does not have existing, nor proposed slopes. Vegetated Disturbed soils with Native or drought tolerat vegetation.- Not applicable 10 5.2 SOURCE CONTROL BMPS Source control BMPs, are selected, constructed, and maintained to comply with all applicable ordinances and guidance documents. The proposed Development will have the following category requirements: Specific Land Use Category BMPs a) Use Efficient Irrigation Systems & Landscape Design.- Landscape irrigation systems shall be of an efficient design with respect to each landscaped area's plantings specific water requirements. Maintenance of system installations on a regular and timely basis prevents over-watering and the transport of silts, sediments, fertilizers and pesticides into the storm drain system. Rain shut-off devices or moisture sensors shall be integral to the operation of the irrigation system to avoid unnecessary irrigation during wet weather conditions. Installing flow reducers or shut-off valves control loss of water due to unexpected pressure drops or other type of system compromise. Pest resistant, drought tolerant or native plants (per landscape architect plans) are used throughout the Project. b) Design Trash Storage Areas to reduce Pollution Contribution.- Trash storage areas shall: be paved with an impervious surface designed to prevent run-on from adjoining areas. Trash containers shall contain attached lids to prevent rainfall intrusion, lids wili remain closed when not in use. c) Employ Integrated Pest Management Principles.- An integrated pest management (IPM) strategy is an ecosystem based pollution prevention strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant plant varieties. Use of pesticides occurs only afler monitoring indicates other IPM methods have failed. Pest control materiais selected and applied in a manner that minimize risks. Obtain more information on IPM principles from the UC Davis website (http://www.ipm.ucdavis.edu/water/u/index.htnil). If fertilizers and pesticides are necessary, they are applied per manufacturer's minimum rates and guidelines to reduce the potential of pollutant transporting to the environment and the risk to human health or beneficial non-target organisms. The owner/developer/association will provide information on IPM practices, at the minimum relating to: the prevention of pests intrusion to buildings and landscaping using barriers, screens, and caulking; physical pest elimination techniques, such as, weeding, squashing, trapping, washing, or pruning out pests; relying on natural enemies to eat insect pests and the proper use of pesticides as a last line of defense. d) Provide Storm Water Conveyance System Stamping and Signage.- Any existing storm drain inlets affected by the project drainage (if not already signed), as well as all on-site private inlets, will be posted with signage, stamped or stenciled (as appropriate to location) to provide notice against illegal dumping of pollutants with prohibitive language or graphics to the satisfaction of the City Engineer. These warnings shall be maintained for legibility throughout the development's existence. The owner will provide information to increase knowledge of tenants/employs/future owners regarding impacts of pollutants and urban mnoff on receiving waters. 11 5.3 TREATMENT CONTROL BMPS The primary pollutants of concem, bacteria, sediment, eutrophic conditions (nutrients) are considered pollutants that tend to associate with fine particles during treatment. Additionally, nutrients are classified as pollutants that tend to be dissolved following treatment (per Table 3). TABLE 3 Pollutant Coarse Sediment and Trash Pollutants That Tend to Associate with Fine Particles During Treatment Pollutants That Tend to be Dissolved Following Treatment Sediment X X Nutrients X X Heavy Metals X Organic Conipounds X Trash & Debris X Oxygen Demanding X Bacteria X Oil & Grease X Pesticides X Table extracted fi-om the City of Escondido Stonnwater Management Requirements. January 14, 2011. Description of Pollutants of Concern Selected, treatment BMPs for this Project at this time is bioretention areas. The Post Construction BMP Site Map exhibit. Figure 5, contains locations, details and contribution areas, attachment C shows the numeric sizing for each basin of the project. Per the selection matrix, Table 4, Bioretention facilities (LID) category offers a "High" treatment to the primary pollutants. 12 TABLE 4 Pollutants of Concern Treatnent Control BMP Categories Pollutants of Concern Bioretention Facilities (LID) Settling Basins (Dry Ponds) Wet Ponds and Wetlands Infiltration Facilities or Practices(LID)* Media Filters High- rate blofilters High- rate media filters Trash Racks & Hydrodynamic Devices Coarse Sediment and Trash High High High High High High High High Pollutants that tend to associate with fine particles during treatment High High High High High Medium Medium High Pollutants that tend to be dissolved following treatment Medium Low Medium High Low Low Low Low Table extracted from the City of Carlsbad SUSMP, January 14, 2011. Treatment Control BMP Selection Matrix 13 14 TENTATIVE MAP - STATE k OAK >- LU SCALE: r=10' OAK AVENUE EXT9A STRENGTH FILTER FABRIC NJEEDEO WITHOUT WIRE UESH SUPPORT SET POSTS AND EXCAVATE A 4 3Y 4 1^ [10 BY 50 CM) TRENCH UP5L0PE FROU AND ALONG THE LINE OF POSTS. 2. STAPLE WIRE FENCING TO THE POSTS. -BERMED CONTAINMENT JiREA EXCESS AND WASTE CONCRETE SHALL NOT BE WASHED INTO THE STREET OR INTO A DRAINAGE SYSTEM. FOR WASHOUT OF CONCRETE AND MORTAR PRODUCTS. A DESIGNATED CONTAINMENT FACILITY OF SUFFICIENT CAPACITY TO RETAIN LIOUID AND SOLID WASTE SHALL BE PROVIDED ON SITE. SLURRY FROM CONCRETE AND ASPHALT SAW CUTTING SHALL BE VACUUMED OR CONTAINED. DRIED, PICKED UP AND DISPOSED OF PROPERLY. CONCRETE WASTE MANAGEMENT (CASQA WM-8) LEGEND SYMBOL SYMBOL WM DESCRIPTION SILT FENCE PER CASOA SE-1 GRAVEL BAG BARRIER PER CASQA SE-8 GRAVEL BAG STORM DRAIN/CURB INLET PROTECTION VO™^^- PER CASOA SE-4. SE-10. CALIFORNIA STORMWATER BMP HANDBOOK CONSTRUCTION. DESCRIPTTON MAT DEUVERY AND STORAGE SOLID WASTE MANAGEMENT STREET SWEEPING CALIFORNIA STORMWATER BMP HANDBOOK CONSTRUCTION LANDSCAPE (PROPOSED) BIORETENTION (PROPOSED) STABILIZED CONSTRUCTION ENTRANCE PER CASOA TC-1 WM-B- \\\\\\\] CONCRETE WASTE MANAGEMENT CALIFORNIA STORMWATER BMP HANDBOOK CONSTRUCTION SANITARY / SEPTIC WASTE MANAGEMENT DRAINAGE STRUCTURE FLOW SURFACE FLOW EROSION CONTROL NOTES 1. IN CASE EMERGENCY WORK IS REOUIRED.CONTACT AT (PHONE NUMBER) 2. EQUIPMENT AND WORKERS FOR EMERGENCY WORK SHALL BE MADE AVAILABLE AT ALL TIMES DURING THE RAINY SEASON. ALL NECESSARY MATERIALS SHALL BE STOCKPILED ON SITE A.T CONVENIENT LOCATIONS TO FACILITATE RAPID CONSTRUCTION OF TEMPORARY DEVICES WHEN RAIN IS EMINENT. 3. DfWCtS SHOl*N ON PLANS SHALL NOT BE MOVED OR MODIFIED WITHOUT THE APPROVAL OF THE ENGINEERING INSPECTOR. 4. THE CONTRACTOR SHALL RESTORE ALL EROSION CONTROL DEVICES TO WORKING ORDER TO THE SATISFACTION OF THE OTY ENGINEER AFTER EACH RUN-OFF PRODUCING RAINFALL 5. THE CONTRACTOR SHALL INSTALL ADDITIONAL EROSION CONTROL MEASURES AS MAY BE REOUIRED BY THE CITY ENGINEER DUE TO UNCOMPLETED GRADING OPERATIONS OR UNFORESEEN CIRCUMSTANCES WHICH MAY ARISE. 6. THE CONTRACTOR SHALL BE RESPONSIBLE AND SHALL TAKE NECESSARY PRECAUTIONS TO PT?EVENT PUBLIC TRESPASS ONTO AREAS WHERE IMPOUNDED WATERS CREATE A HAZARDOUS CONDITION 7 ALL EROSION CONTROL MEASURES PROVIDED PER THE APPROVED GRADING PLAN SHALL BE INCORPORATED HEREON. 8. GRADED AREAS AROUND THE PROJECT PERIMETER MUST DRAIN AWAY FROM THE FACE OF SLOPE AT THE CONCLUSION OF EACH WORKING DAY. 9. ALL REMOVABLE PROTECTIVE DEVICES SHOWN SHALL BE IN PLACE AT THE END OF EACH WORKING DAY WHEN THE FIVE (5) DAY RAIN PROBABILITY FORECAST EXCEEDS FORTY PERCENT (407.) SILT AND OTHER DEBRIS SHALL BE REUOVED AFTER EACH RAINFALL. 10. ALL GRAVEL BAGS SHALL BF BURLAP TYPE WITH 5/4 INCH MINIMUM AGGREGRATE. 11. SHOULD GERMINATION OF HYDROSEEDED SLOPES FAIL TO PROVIDE EFFECTIVE COVERACE OF GRADED SLOPES (907. COVERAGE) PRIOR TO NOVEMBER 15, THE SLOPES SHALL BE STABILIZED BY PUNCH STRAW INSTALLED IN ACCORDANCE WITH SECTION 35.025 OF THE EROSION AND SEDIMENT CONTROL HANDBOOK OF THE DEPARTMENT OF CONSERVATION, STATE OF CALIFORNIA. PONDING HEIGHT NOTES: 1. GRAVEL BAGS, OF EITHER BURLAP OR WOVEN GEOTEXTILE GEOTEXTILE FABRIC, ARE FILLED WITH GRAVEL. LAYERED AND PACKED TIGHTLY. 2. LEAVE ONE GRAVEL BAGS GAP IN THE TOP ROW TO PROVIDE A SPILLWAY FOR OVERFLOW. 3. INSPECT BARRIERS AND REMOVE SEDIMENT AFTER EACH STORM EVENT, SEDIMENT AND GRAVEL MUST BE REMOVED FROM THE TRAVELED WAY IMMEDIATELY PVC RISER PER PLAN- SECTION A-A -ATTACH FILTER FABRIC SECURELY TO UPSTREAM SIDE OF POST CATCH BASIN °ER GRADING PLANS GRAVEL FILLED GRAVEL BAGS-ARE STACKED TIGHTLY GRAVEL SAG CHECK DAM SPACING TABLE STREET GRADE INTERVAL HEIGHT LESS THAN 2% 200' 1,0' (MIN) 2% TO 4% 100' 1 0' (MIN) 4% TO 5% SO' 1.0' (MIN) 67. TO 8% 35' 1.5' (MIN) 8% TO 10% 25' 1.5' (MIN) 3. ATTACH THE FILTER FABRIC TO THE WIRE FENCE AND EXTEND IT INTO THE TRENCH. 4 BACKFILL AND COMPACT THE EXCAVATED SOIL. ;iiBiausiii=iii=iiF 0' (3m) MAXIMUM SPACING WITH WIRE SUPPORT FENCE 6' (1,8m) MAXIMUM SPACING WITHOUT WIRE SUPPORT FENCE, NOTE 1,-THE CONTRACTOR SHALL INSPECT AND REPAIR FENCE AFTER EACH STORM EVENT AND REMOVE SEDIMENT 2-REMOVED SEDIMENT SHALL BE DEPOSITED TO AN AREA THAT WILL NOT CONTRIBUTE TO SEDIMENT OFF-SITE AND CAN BE PERMANENTLY STABILIZED 3,-SILT FENCE SHALL BE PLACED ON SLOPE CONTOURS TO FACILITATE MAXIMUM PONDING EFFICENCY 8" THICK-4"T0 8" COARSE AGREEGATE OVER GEOTEXTILE FABRIC PLAN VIEW GAP BETWEEN BAGS ACTS AS SPILLWAY THREE LAYERS OF GRAVEL BAGS WITH ENDS OVERLAPPED GRAVEL BAG CHECK DAM STORM DRAIN INLET PROTECTION (CASQA SE-10) N.T.S. SLT FENCE (CASQA SE-1) N.TS. STABILIZED CONSTRUCTION ENTRANCE (CASOA TC-1) N.T.S. CITY OF CARLSBAD PROJECT NAME: STATE & OA CONSTRUCTION BMP K FIGURE 5-A STATE k OAK FLOW THROUGH PLANTER (TYP) FLOW THROUGH PLANTER (TYP) DA7- , , , -DA4 OAK AVENUE DA3+DA6 (168SF) FLOW THROUGH PLANTER* (TYP) ROOF DRAINAGE/BMP EXHIBIT W {VARiES} CLEANOUT STAN PIPE PERFORATED PIPE^ DOWNSPOUT/INLET VAULT FABRICATED FROM GALVANIZED STEEL BOLTED TO THE PLANTER INTERIOR (SEE FLOW-THROUGH PLANTER OUTLET OETAIL) - EMERGENCY OVERFLOW DISCHARGE TO AN APPROVED LOCATION A QUIT ALL PIPE \ =£> PLAN NOT TO SCALE - CONCRETE OR OTHER STRUCTURAL PLANTER WALL WITH WATERPROOFING -PLANTER OUTLET DISCHARGE TO AN IRRIGATION APPROVED LOCATION SYSTEM PERFORATED PIPE (UNDERDRAIN) MIN, SL0Pt=0.5% SECTION NOT TO SCALE FORM A 1.5' GROOVE IN CONCRETE AND PROVIDE A CONTINUOS WATERTIGHT CONNECTION. USING AN APPROVED SEALANT CITY OF CARLSBAD PROJECT NAME: STATE & OA POST CONSTRUCTION BMP K FIGURE 5-B 5.5 SUMMARY By implementing the LID site design BMPs, source control BMPs and treatment BMPs , the production of the pollutants of concem will be limited. An effective Integrated Pest Management program preventing access of animal pests to trash receptacles and desirable environments limits the production of bacteria. Limited use of fertilizers and pesticides in landscaping keeps the introduction of nutrients to a minimum. With adequately established ground plantings prevents soil erosion there is a limited possibility for dissolved solids and sediments production from eroded soils. The limited use of fertilizers and the soil stabilization of permanent plantings and mulches covering erodible soil surfaces also limit the introduction of nutrient production leading to eutrophic conditions. Metals introduction to storm water flows are only potentially present during the construction phase of the Project as the usage of the materials most commonly containing this pollutant are most prevalent then. All landscaped areas offer biofiltration for irrigation waters. Mulching, seeding and planting of these areas provide biofiltration of any necessary pesticide and fertilizer applications. Following manufacturer guidelines to avoid over-treatment of landscaping with pesticide & fertilizers will provide a limited occurrence of pollution from these products in the planted areas of the Project. The selected treatment BMPs in conjunction with the LID and source control BMPs provide limiting factors in the production of the pollutants of concem. Moreover, the proper use and adequate maintenance of the bio- retention areas, allow these effective treatment BMPs to work to their ultimate capabilities. 15 6.0 STORMWATER BMP MAINTENANCE The Project developer is financially responsible for the implementation of the erosion control measures during the construction phase in addition to the construction/installation of the post-development BMPs. The developer is responsible for the performance of the maintenance of the permanent BMPs. The applicant must ensure implementation and maintenance of the BMPs through the maintenance mechanism identified below. This mechanism must be acceptable to the City. The City Engineer will not consider structural BMPs "effective," and therefore will not accept stormwater BMPs as meeting the MEP standard, unless a mechanism is in place that will ensure ongoing long-term maintenance of all structural BMPs. Most of the permanent BMPs accrue minimal maintenance costs. Mulching, seeding and plantings are part of a continuing landscape maintenance program and can include the maintenance of the vegetated biofilter swale or bio-retention areas. Landscaping maintenance for permanent stabilization of graded areas and BMP maintenance will be the responsibility of the developer. Development of an Operation & Maintenance (O&M) Plan for the Project BMPs is the responsibility of the developer. The O&M Plan follows approval of this SWMP and prior to the issuance of any grading and/or building permits. The O&M Plan identifies the party responsible for management of the storm water BMPs, implementing a training program and duties, outlines maintenance frequency, routine service schedule, specific maintenance activities, specific costs encountered with operation & maintenance and any other necessary activities. Table 5 (next page) provides an outline of the BMP maintenance necessary for the permanent treatment BMPs. 6.1 MAINTENANCE MECHANISMS Installation and maintenance of the post-development BMPs is the responsibility of the developer under a Storm Water Maintenance Agreement (SWMA). A security will be required (of a form suitable to the City's determination) to back-up the SWMA in an amount determined by the City Engineer based upon costs contained in the O&M Plan. The SWMA remains in effect for the duration of the Project usage of the treatment BMPs identified therein. 16 17 TABLE 5 Permanent Treatment BMP Maintenance Program A schedule of periodic maintenance should be implemented and modified, as needed, to insure effective operation of the indicated BMP's. As a guideline, a tentative schedule of maintenance frequency follows The schedule is based on certain indicators outlined for a particular BMP. BMP ROUTINE ACTIONS MAINTENANCE INDICATORS FIELD MEASUREMENT FREOUENCY MAINTENANCE ACnVITY Bioretention Facility Height of vegetation. Average height of vegetation (grass) exceeds 4". Visual inspection of vegetation. Inspect weekly and after rainy periods. Cut vegetation as required. Assess adequate cover. Bare spots appear in planted/mulched areas or less than 70% coverage over entire area. Visual inspection of lack of vegetative/mulch cover. Record locations to identify persistent probtem areas. Assess growth on a monthly basis. Assess mulch coverage on a monthly basis. Reseed vegetated areas as required. No later than November. Scarify area for reseeding. Reapply mulching as required to cover bare spots. Inspect for debris accumulation. Debris or litter accumulation. Visual inspection for trash. During routine site landscape maintenance. Remove and properly dispose of trash, litter and debris. Inspect for accumulation of sediment or erosion of soil. Sediment is at or near vegetation height. Rills or gullies in topsoil Visual inspection for sediment depth. Visual inspection for rills and soil erosion. Inspect monthly and aftpr each significant rainfall. Remove accumulated sediment when interfering with drainage flows. 7.0 FISCAL RESOURCES The owner/developer ofthe project will be financially responsible for the construction and installation of the post- development BMPs and implementation of the LID site design and source control BMPs. Installation and maintenance of the post-development BMPs will be the responsibility of the property owner as designated in the Storm Water Maintenance Agreement and the O&M Plan. The permanent responsibility of the post-development BMPs will remain with the owner or a designated association. The following table outlines the anticipated maintenance costs of permanent treatment BMPs. 18 ITlifeD© ® 19 TABLE 6 PER-MANENT TREATMENT BMP ESTIMATED OPERATION; AND MAINTENANCE (O&M^ COSTS Pemianent BMPs constructed and installed for this project will necessitate continuous operation and maintenance when the project is complete. O&M costs are based upon Cahfomia Department of Transportation estimated costs for pilot BMP project utilizing prevailing wage rates Below are the itemized costs, based on prevailing wage rates, of the project BMPs as shown on thc Site Map. As identified in SWMP Section 7.0, Fiscal Resources, the source for funding of BMP operation and iraintenance is the responsibility of the property owner(s)/developer Post construction permanent BMP operation and maintenance costs include, but are not limited to the following: BMP OPERATION & MAINTENANCE ITEM LABOR EQUIPMENT MATERIALS TOTAL COST Per Hrs. Bals £ss! Tvoe Davs Rale Item Trimmer Rake. Fork. Shovel. Safetv Eauloment. Baas. Cost TOTAL COST BIORETENTION FACILITY 12.0 43.63 $523.56 1 Ton Truck. Hvdroseeder 198,75 $99.38 Item Trimmer Rake. Fork. Shovel. Safetv Eauloment. Baas. S450 $1.073 12.0 43.63 1 Ton Truck. Hvdroseeder Seed. Testlna & DiSDOsal S450 O&M TOTAL $1,073 8.0 CONCLUSION This SWMP has shown LID site design, source control and treatment BMPs that should satisfy the requirements identified in the Order and Standards. This report insures, to the maximum extent practicable, that the development of the Project does not increase pollutant loads from the site. The effectiveness of these BMPs depends upon the proper operation procedure and effective maintenance on a definitive schedule identified within the O&M Plan. Long-term fiscal resources are necessary to provide the appropriate operation and maintenance activities to prolong the effectiveness of the identified BMPs. The developer is responsible for providing maintenance as outlined in the O&M Plan and agreed to in the PBMPMA. The provision of maintenance to BMPs is enforceable in accordance with the currently applicable City of Carlsbad ordinances, policies and regulations. It is shown that this project can meet the water quality objectives as outlined in Order R9-2007-01 with the BMPs identified on the single sheet BMP exhibit. An analysis has been performed to ensure that the site can accommodate the water quality BMPS. Therefore, it is anticipated that the downstream waters will not be affected by the implementation of these BMPS. 20 9.0 CERTIFICATION By affixing my seal and signature to the front of this report, 1, Hossein Zomorrodi, certify the following: This Storm Water Management Plan has been prepared in accordance with a system designed to assure that qualified personnel properly gather and evaluate the infomiation within. To the best of my knowledge and belief, the information submitted is true, accurate, and complete. Furthermore, the data upon which recommendations, conclusions and decisions are based were derived from accepted engineering practices. This Stormwater Management Plan has been prepared under my direction and supervision to comply with the requirements of the City of Carlsbad "Storm Water Standards Manual," issued January 14, 2011 and the SWRCB Order R9-2007-01. Hossein Zomorrodi 21 I ATTACHMENTS 22 ATTACHMENT A HYDROLOGY STUDY REFERENCE 1^ K&S ENGINEERING, INC. Planning Engineering Surveying HYDROLOGY STUDY FOR STATE AND OAK 3069 STATE STREET CARLSBAD, CA 92008 IN CITY OF CARLSBAD JN 13-038 December 19,2013 Hossein ZamolTOSi RCE 43235 Date 7801 Mission Center Court, Suite 100 . San Diego, California 92108 . (619)296-5565 . Fax (619)296-5564 TABLE OF CONTENTS l.SITE DESCRIPTION 2. HYDROLOGY DESIGN MODELS 3. HYDROLOGIC CALCULATIONS APPENDIX A 4. TABLES AND CHARTS APPENDIX B 5. HYDROLOGY MAPS APPENDIX C SITE DESCRIPTION EXISTING CONDITION EXISTING 0.45 AC PROPERTY CONSIST OF 3 LOTS WITH 7 BUILDINGS AND LANDSCAPING. LOCATED AT THE NE CORNER OF STATE STREET AND OAK AVENUE. THERE IS A HIGH POINT AT THE SOUTHERLY END OF STATE STREET AND DRAINAGE IS NORTH ON STATE AND WEST ON OAK AVENUE. APPROXIMATELY 57% OF THE SITE DRAINS TO STATE STREET AND 43% TO OAK AVENUE DRAINAGE SYSTEM. THE NORTHERLY PORTION DRAINS TO UNDERGROUND STORM DRAIN SYSTEM AT CORNER OF CARLSBAD VILLAGE DRIVE AND STATE STREET WHICH EVENTUALLY DISCHARGE TO BUENA VISTA LAGOON. THE SOUTHERLY PORTION DRAINS TO UNDERGROUND STORM DRAIN SYSTEM ON OAK AVENUE WHICH EVENTUALLY DISCHARGES TO AGUA HEDIONDA LAGOON. THIS PROJECT IS EXEMPT FROM HYDROMODIFICATION ACCORDING TO THE ANALYSIS FOR SELECTED CARLSBAD WATERSHEDS PREPARED BY CHANG CONSULTANTS DATED JUNE 10, 2013. PROPOSED CONDITION PROPOSED PROJECT CONSIST OF ONE BUILDING FOR COMMERCIAL RETAIL AND RESIDENTIAL CONDOMINIUM USE COVERING 80% OF THE SITE. THE RUNOFF FROM THIS PROJECT IS CONTROLLED THROUGH ROOF GUTTER AND DOWNSPOUT LOCATIONS IN ORDER TO TREAT STORM WATER AND TO MAINTAIN THE PRE AND POST DRAINAGE PATTERN AS CLOSE AS POSSIBLE. APPROXIMATELY 54% OF THE SITE WILL DRAIN TO STATE STREET AND 46% TO OAK AVENUE WITH THE USE OF FLOW THROUGH PLANTERS AND SIDEWALK UNDERDRAINS. 2. HYDROLOGY DESIGN MODELS A. DESIGN METHODS THE RATIONAL METHOD IS USED IN THIS HYDROLOGY STUDY; THE RATIONAL FORMULA IS AS FOLLOWS: Q = CIA, WHERE : Q= PEAK DISCHARGE IN CUBIC FEET/SECOND * C = RUNOFF COEFFICIENT (DIMENSIONLESS) I = RAINFALL INTENSITY IN INCHES/HOUR (PER APPENDIX XI-A) A == TRIBUTARY DRAINAGE AREA IN ACRES *1 ACRE INCHES/HOUR = 1.008 CUBIC FEET/SEC THE NATURAL WATERSHED METHOD IS ALSO USED IN THIS HYDROLOGY STUDY; THE NATURAL WATERSHED FLOW FORMULA IS AS FOLLOWS: Tc=1.8 (1.1-C) (L) •V[S(100) ] L = OVERLAND TRAVEL DISTANCE IN FEET S = SLOPE IN FT./FT. « Tc= TIME IN MINUTES B. DESIGN CRITERIA - FREQUENCY, 100 YEAR STORM. - LAND USE PER SPECIFIC PLAN. - RAIN FALL INTENSITY PER COUNTY OF SAN DIEGO 2003 HYDROLOGY DESIGN MANUAL. C. REFERENCES - COUNTY OF SAN DIEGO 2003, HYDROLOGY MANUAL. - COUNTY OF SAN DIEGO 1992 REGIONAL STANDARD DRAWING. - HAND BOOK OF HYDRAULICS BY BRATER & KING, SIXTH EDITION. APPENDIX A (3. HYDROLOGIC CALCULATIONS] EXISTING CONDITION STATE AND OAK San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software, (c)1991-2012 Version 7.9 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 12/19/13 ********* Hydrology Study Control Information ********** Program License Serial Number 6303 Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.600 24 hour precipitation{inches) = 4.400 P6/P24 = 59.1% San Diego hydrology manual 'C values used ++++++++++++++++++++++++++++++++++4+++++++++++++++++++++++++++++++++++ Process from Point/Station 1.000 to Point/Station 2.000 **** INITIAL AREA EVALUATION **** Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (2.9 DU/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.410 Initial subarea total flow distance = 85.000(Ft.) Highest elevation = 47.750(Ft.) Lowest elevation = 46.250(Ft.) Elevation difference = 1.500(Ft.) Slope = 1.765 % USER ENTRY OF INITIAL AREA TIME OF CONCENTRATION Time of Concentration = 5.00 minutes Rainfall intensity (I) = 6,e50(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.410 Subarea runoff = 0.289(CFS) Total initial stream area = 0.103(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.000 to Point/Station 3.000 **** IMPROVED CHANNEL TRAVEL TIME **** Upstream point elevation = 4 6.250(Ft.) Downstream point elevation = 44.590(Ft.) Channel length thru subarea = 80.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 80.000 Slope or 'Z' of right channel bank = 80.000 Estimated mean flow rate at midpoint of channel = 0.503(CFS) Manning's "N" = 0.023 EXISTING CONDITION STATE AND OAK Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.503(CFS) Depth of flow = 0.077(Ft.), Average velocity = 1.061(Ft/s) Channel flow top width = 12.315(Ft.) Flow Velocity = 1.06(Ft/s) Travel time = 1.2 6 min. Time of concentration = 6.26 min. Critical depth = 0.076(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.928 (In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (2.9 DU/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.410 Rainfall intensity = 5.928(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.410 CA = 0.105 Subarea runoff = 0.330(CFS) for 0.152{Ac.) Total runoff = 0.620(CFS) Total area = 0.255(Ac.) Depth of flow = 0.083(Ft.), Average velocity = 1.118(Ft/s) Critical depth = 0.082(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 4.000 to Point/Station 5.000 •*** INITIAL AREA EVALUATION **** Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (2.9 DU/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.410 Initial subarea total flow distance = 70.000(Ft.) Highest elevation = 47.700(Ft.) Lowest elevation = 4 6.300(Ft.) Elevation difference = 1.400(Ft.) Slope = 2.000 % USER ENTRY OF INITIAL AREA TIME OF CONCENTRATION Time of Concentration = 5.00 minutes Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.410 Subarea runoff = 0.261(CFS) Total initial stream area = 0.093(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.000 to Point/Station 6.000 **** IMPROVED CHANNEL TRAVEL TIME **** Upstream point elevation = 47.280(Ft.) Downstream point elevation = 44.690(Ft.) Channel length thru subarea = 107.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank - 80.000 Slope or 'Z' of right channel bank = 80.000 Estimated mean flow rate at midpoint of channel = 0.403(CFS) EXISTING CONDITION STATE AND OAK for a 100.0 year storm Manning's 'N' = 0.023 Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.403(CFS) Depth of flow = 0.069(Ft.), Average velocity = 1.063(Ft/s) Channel flow top width = 11.013(Ft.) Flow Velocity = 1.06(Ft/s) Travel time = 1.68 min. Time of concentration =^ 6.68 min. Critical depth = 0.069(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.685(In/Hr) Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [LOW DENSITY RESIDENTIAL ] (2.9 DD/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.410 Rainfall intensity = 5.685(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.410 CA = 0.080 Subarea runoff = 0.191(CFS) for 0.101(Ac.) Total runoff = 0.452(CFS) Total area - 0.194(Ac.) Depth of flow = 0.072(Ft.), Average velocity = 1.094(Ft/s) Critical depth = 0.072(Ft.) End of computations, total study area = 0.44 9 (Ac.) PROPOSED CONDITION STATE AND OAK San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2012 Version 7.9 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 12/19/13 ********* Hydrology Study Control Infonnation ********** Program License Serial Number 6303 Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.600 24 hour precipitation(inches) = 4.400 P6/P24 = 59.1% San Diego hydrology manual 'C values used ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.000 to Point/Station 2.000 **** INITIAL AREA EVALUATION **** Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [COMMERCIAL area type ) (Neighborhod Commercial ) Impervious value, Ai = 0.800 Sub-Area C Value = 0.770 Initial subarea total flow distance = 50.000(Ft.) Highest elevation = 45.550(Ft.) Lowest elevation = 45.300(Ft.) Elevation difference = 0.250(Ft.) Slope = 0.500 % USER ENTRY OF INITIAL AREA TIME OF CONCENTRATION Time of Concentration = 5.00 minutes Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q^KCIA) is C = 0.770 Subarea runoff = 0.190(CFS) Total initial stream area = 0.036(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 2.000 to Point/Station 3.000 **** IMPROVED CHANNEL TRAVEL TIME **** Upstream point elevation = 45.300(Ft.) Downstream point elevation = 44.730(Ft.) Channel length thru subarea = 100.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 80.000 Slope or 'Z' of right channel bank = 80.000 Estimated mean flow rate at midpoint of channel = 0.648(CFS) Manning's 'N' = 0.015 PROPOSED CONDITION STATE AND OAK Maximum depth of channel = 0.500(Ft.) Flow(q) thru subarea = 0.64 8(CFS) Depth of flow = 0.092(Ft.), Average velocity = 0.959(Ft/s) Channel flow top width = 14.704(Ft.) Flow Velocity = 0.96(Ft/s) Travel time = 1.74 min. Time of concentration = 6.74 min. Critical depth = 0.083(Ft.) Adding area flow to channel Rainfall intensity (I) = 5.652(In/Hr) for a 100.0 year storm Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [COMMERCIAL area type ] (Neighborhod Commercial ) Impervious value, Ai = 0.800 Sub-Area C Value = 0.770 Rainfall intensity = 5.652(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.770 CA = 0.186 Subarea runoff = 0.859(CFS) for 0.205{Ac.) Total runoff = 1.049(CFS) Total area = 0.241(Ac.) Depth of flow = 0.110(Ft.), Average velocity = 1.082(Ft/s) Critical depth = 0.102(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.000 to Point/Station 4.000 **** INITIAL AREA EVALUATION **** Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 1.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 0.000 [COMMERCIAL area type ] (Neighborhod Commercial ) Impervious value, Ai = 0.800 Sub-Area C Value = 0.770 Initial subarea total flow distance = 50.000(Ft.) Highest elevation = 45.550(Ft.) Lowest elevation = 45.300(Ft.) Elevation difference = 0.250(Ft.) Slope = 0.500 % USER ENTRY OF INITIAL AREA TIME OF CONCENTRATION Time of Concentration = 5.00 minutes Rainfall intensity (I) = 6.850(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area {Q=KCIA) is C = 0.770 Subarea runoff = 0.116(CFS) Total initial stream area = 0.022(Ac.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 4.000 to Point/Station 5.000 **** IMPROVED CHANNEL TRAVEL TIME **** Upstream point elevation = 45.300(Ft.) Downstream point elevation = 44.690(Ft.) Channel length thru subarea = 200.000(Ft.) Channel base width = 0.000(Ft.) Slope or 'Z' of left channel bank = 80.000 Slope or 'Z' of right channel bank = 80.000 Estimated mean flow rate at midpoint of channel = 0.4 28(CFS) PROPOSED CONDITION STATE AND OAK 0.500(Ft.) .428(CFS) Average velocity = .151(Ft.) 0.684(Ft/s) 100.0 year storm Manning's 'N' = 0.015 Maximum depth of channel = Flow(q) thru subarea = 0. Depth of flow = 0.088(Ft.), Channel flow top width = 14. Flow Velocity = 0.68(Ft/s) Travel time = 4.87 min. Time of concentration = 9.87 min. Critical depth = 0.071(Ft.) Adding area flow to channel Rainfall intensity (I) = Decimal fraction soil group A Decimal fraction soil group B Decimal fraction soil group C Decimal fraction soil group D [COMMERCIAL area type ] (Neighborhod Commercial ) Impervious value, Ai = 0.800 Sub-Area C Value = 0.770 Rainfall intensity = 4.417(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.770 CA = 0.156 Subarea runoff = 0.571(CFS) for 0.180(Ac.) Total runoff = 0.687(CFS) Total area = 0.202(Ac.) Depth of flow = 0.106(Ft.), Average velocity = 0.770(Ft/s) Critical depth = 0.085(Ft.) End of computations, total study area = 0.443 (Ac.) 4.417(In/Hr) for a 0.000 1.000 0.000 0.000 APPENDIX B (4. TABLES AND CHARTS) Emast F. Bratar ind Horace Williams King HANDBOOK OF Tabic 7-H. X'alucs.of A'' for ('ircular Channrls in the Formul.fJ- K' Q D « depth of wateii- d «= diaiucU't o{ chacnei u .01 1 .00 .01 ,02 .03 .04 .05 .00 .07 .08 .09 .0 .00007 .00031 .00074 .00138 .00222 .00328 .00455 .00004 .00775 .1 .OODf.7 .0118 .0142 .0107 .0105 .0225 .0257 .0291 .0327 .0300 2 .04,00 .0448 .0402 .0537 .03 8.^ .0034 .0G8C .0738 .07U3 .0849 .3 .0907 .OOOfi .1027 .losy .1153 .1218 .1284 .1352 .1420 .1490 .4 .15C1 .1033 .1705 .177'J .1854 .1929 .2005 .2082 .2100 .2238 .5 .232 .239 .247 .255 .203 .271 .279 .287 .295 .303 .6 .311 .319 .327 ,335 .343 .350 .358 .300 .373 .380 .7 .388 .395 .402 .401) .416 .422 .429 .435 .441 .447 .6 .458 .463 .408 .473 .477 .481 .485 .488 .491 .9 .494 .496 .497 .498 .408 .498 ,49C-"' .494 .489 .483 LO .463 Average Values of Roughness Coefficient (Manning's n) Roughness Type of Waterway Coefficient Cn) 1. Closed Conduits (1} Stelel (not lined) Q QJ^ Cast Ixon oldS AluninuB Sand Concrete .021 Corrugated Metal (not lined? 0.024 Corrugated Metal (2) (saooth a*ph»lt quarterlining) 0.021 Comifated Metal (2) (ssootK a«i*»it half lining) 0.018 Corrugated Metal (smooth a^halt full lining) 0.012 Concrete RCP Q Clay (fewer) Q'Q^^ Asbestos Ceaent-^ Pv*:- 0.011 Drain Tile (terra cotta) 0 O'S Cast-in-place Pipe 0 OlS Reinforced Concrete Bex o'oK 2. Open Channels (1) u.. Unlined Clay Loaa 0 023 D.020 b. Revetted Gravel 0,050 0.040 Pipe- and Wire 0.025 Sacked Concrete 0.02S c. Lined Coi^rete (poured) 0.0'l4 Air^Blown Mortar (5) 0.016 Aspbaltic Concrete or Bituainous Plant Mix o.OlB d. Veg.etated (5) Grass lined, Maintained .OSS 6ra;s and Weeds .045 Grass lined with concrete low flow channel .032 5. Pavenent and Gutters (1) 0.015 Bituainous (plant-Bixed) o!oi6 Type of Waterway i*. Depressed Medians (10:1 slopesd) Earth (without growth) , Earth (with growth) iGravel 5. Natural Streams " ^S"''F:r;rrJ'r::"!.r!_^!^" ^'-^^ «age < ,00 ft) Roughness Coefficient fr) (a) (b) (c) id) M Fajrly regular section Some grass and weeds, little or no brush Dense growth of weeds, depth of flow materially greater than weed height Some weeds, light brush on banks Some weeds, heavy brush on banks for trees within channel with branches submerged at high stage, Increase all above values by 0.015 rle'a'^der" ^'^^ ^^'^^^ » Channels (a) to (e) above. Increase all values by 0.015 Mountain stream; no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stage U Bottom, gravel, cobbles' and few boulders (b) fiottom. cobbles with large boulders o'r'^P"-^!--'f""* ^° natural streams) (2) (3) (2) (3) W (5) (6) (7) Pasture, no brush (s) Short grass (b) High grass Cultivated, areas (a) No crop (b) Mature row crops (c) Mature field crops Heavy weds, scattered brush Light brush and trees Medium to dense brush Dense willows Cleared land with tree stumps, 100-150 per acre Heavy stand of timber, little undergrowth KB) Flood deoth below branches W Flood depth reaches branches COifO 0.050 0.055 0.030 O.OUO 0.060 0.050 0.060 0.030 0.040 0.0^40 0.040 0,050 0.050 0.060 0.090 0.170 0.060 o.no 0. l4o APPENDIX XVI 3 3 4 5 6 Hours Directions for Application: (1) From precipitation maps determine 6 hr and 24 hr amounts fbr the selected frequency. These maps are Included in the County Hydrolcgy Manual (10,50, and 100 yr maps induded in the Design and Procedure Manual). (2) Adjust 6 hr precipitation (if necessary) so that it is within the range of 45% to 65% of the 24 hr precipitation (not applicaple to Desert). (3) Plot 6 hr precipitation on the right side ofthe chart. (4) Draw a line through the point parallel to the ptotted lines. (5) This line is the intensity-duration curve for the location being analyzed. Application Form: (a) Selected frequency. year ^, (b)P6 = in., P 24 = LS.= '24" %P) in. (c) Adjusted PgP) = (d) tjj= min. (e) I = in./hr. Note: This chart replaces the Intensity-Duration-Frequency curves used since 1965. P6 DufAdon', Jl 15 30 jn so 120 ISO IM 240 300 I 3 it I • 4.5 2.63 3.8S S.27 6.SS 7.80 9.22 1034 M<Mij8[7^' 8.48 • IJO 3]2<n3j»l4J«' 5.19 2.12 l3L18i4J24 1.0B oJo 11.86 584 1.24 1.03 0.90 0.53 a4i 0.34 029 0.26 OM 0.51 0.44 0.39 0^2 :0.33 0.43 ai9 i0.28!0.38 1.88 1.62:2.15 Zra; 3.23:377U.3V' 4j5 i4jorilfflJBT£i6|3J7i 3.73 •2.b7!2.«i2ioj 132 1.«T2.or|2:41i l76 t.-wTi.Tg^iisl iM 1.33:Tiffl i.<BTiJa' S S3 6 13.17j 14.49 15.81 m80hlJBB'l2.ra ^42 I 9i7 jail 6.49:7.13 7.3TB 1.19* 1.06 Oi2 0S9 i932 ai7 0.25! 0.33 ojsiioe 0.731 oia 133 i.Mn.i8 oil' 4.20 3.73 310 2.39 1^2^ 1.18 5.39 4.67' 4.15^ l4S 2.98 2.65 '•• 2.04 ! iTO 1.31 ! 0.76i037^ 6.47jo.5er6.«i6r oTs: 0J«! 085j O.TO 593 6^46 513'5.W 4.56 ] 4.98 3,79 4.13 338' 338 2.92^3.18 2i5 '2.45 1.87 !t04 1 62 ; 1,76 1.44 i 1.57 1.08 i (>.M 1.1? 1.30 iM', 1.13 034 0,«2 1.00 FIGURE Intensity-Duration Design Chart - Template San Diego County Hydrology Manual Date: June 2003 Section: Page: 3 6 of 26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use Runoff Coefficient "C" Soil Type NRCS Elements County Elements % IMPER. A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 0.35 Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 0.36 0.41 Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 0.42 0.46 Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 MJ. 0.45 0.49 Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 0.48 0.52 Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57 Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 0.57 0.60 Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0,55 0.58 0.60 0.63 High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71 High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0,78 0.79 Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0,78 0.79 Commercial/Industrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82 Commercial/Industrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (General 1.) General Industrial 95 0.87 0.87 0.87 0.87 *The values associated with 0% impervious may be used for direct calculation ofthe ranoff coefficient as described in Section 3.1.2 (representing the pervious runoff coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area is located in Cleveland National Forest). DU/A = dwelling units per acre NRCS = National Resources Conservation Service 3-6 EXAMPLE: Given: Watercourse Distance (D) = 70 Feet Stope(s)=1.3% Runoff Coefficient (C) = 0.41 Overland Flow Ttme (T) = 9.5 Minutes SOURCE: Airport Drainage, Federal Aviation Administration, 1965 j_'i.6 (1.1-C) VD FIGURE Rational Formula - Overland Time of Flow Nomograph San Diego County Hydrology Manual Date: June 2003 Section: Page: 3 12 of 26 Note that the Initial Time of Concentration should be reflective of the general land-use at the upstream end of a drainage basin. A single lot with an area of two or less acres does not have a significant effect where the drainage basin area is 20 to 600 acres. Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in hydrology studies. Initial Tj values based on average C values for the Land Use Element are also included. These values can be used in planning and design applications as described below. Exceptions may be approved by the "Regulating Agency" when submitted with a detailed study. Table 3-2 MAXIMUM OVERLAND FLOW LENGTH (LM) Element* DU/ Acre .5% 1% 2% 3% 5% 10% Element* DU/ Acre LM Ti LM Ti LM Ti LM T, LM Ti LM Ti Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9 LDR I 50 12.2 70 11.5 85 10.0 100 9.5 100 8.0 100 6.4 LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8 LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6 MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3 MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8 MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5 MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3 HDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5 HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4 100 2.7 N.Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7 G. Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4 O.P./Com 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 Limited I. 50 4.2 60 3.7 70 3.] 80 2.9 90 2.6 100 2.2 General I. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9 *See Table 3-1 for more detailed description 3-12 AE Feet Tc ^ii.9L9y EQUATION 385 • 5000 .4000 • 3000 •2000 -1000 -900 ^ BOO -TOO -500"^. • 300 '200 -100 — 50 — 40 — 30 — 20 — 10 Tc = Time of concentration (houn) L • Watercourse Distance (miias) AE = Change in elevation along effective slope line (See Figure 3-5)(fe»t) Tc Hours S Mile* Feet o.s> 4000 — 3000 .2000 I—1800 leoo — 1400 — 1200 .1000 900 H-BOO 700 — GOO -SOO 400 — 300 — 200 S Minutes — 240 •180 120 — 100 M —to 1-70 -60 -50 •40 — 30 -20 (—18 16 — 14 12 -10 9 — 8 — 7 — 6 — 4 —3 AE SOURCE: California Division of Highways (1941) and Kirpich (1940) Tc FIGURE Nomograph for Determination of Time of Concentration (Tc) or Travel Time (Tt) for Natural Watersheds Watershed Divide, Watershed Divide Area "A" = Area "B" SOURCE: Califomia Division of Highways (1941) and Kirpich (1940) Design Point FIGURE Computation of Effective Slope for Natural Watersheds Orange County 32*45' Riverside County = p'-^T- j--/ \ -1 )- v-ipb- -a / / ^ j/v- ••2;5- 3 . . ' ^ ^» .-•S- .•• .(5 • " - I County of San Diego Hydrology Manual Rainfall Isopluvials 100 Year Rainfall Event - 6 Hours isoptuviai (inches) DPW .-^^^^^ ^GIS 5ahGIS C MWCHWWTMIUTVUD FTTMESS *0R *PW-|CULU)KI>m3S 3 0 3 Miles s 33*30' — Orange County k" /^f/ ./ i^ Riverside County; 33*3<r *5 4.4 ...v.. !j.:-..r...':.... • ... «, { /"y itp - in. \. 1....-T-.0- Wf'"^^' ~-X.:r.!".v.-;-.';>... • / ..--^z^ii .... 'y\. / ; ill W /'TT^ 33W /.«:9,"":^j^?S.^....^ ( .... V'^'X"**^-"* e-. ^--tfl -i.'-- \ u ^N-'' • • Mexico County of San Diego Hydrology Manual Rainfall Isopluvials 100 Year Rainfall Event - 24 Hours Isopluvial (Inches) ^GJS SaHGIS 3 0 3 Miles HMP EXEMPTION EXHIBIT APPENDIX C (5. HYDROLOGY MAP) HYDROLOGY PLAN FOR: STATE & OAK EXISTING CONDITION JN i:i-038 "WITH MEDIA TTDME — FLTER FL43.85 I- lU LU Q: I-co LU I- CO Q, =1.1CFS 100 END CURB. GUTTER & SIDEWALK TC 44 66-FL 44 20 =0.68CFS~-100 EXIST 35" RCP STORM DRAIN PIPE PER OWGif 365-2 SHEET 16 LU EX ^2" INTERCEPTOR SEWER PES 3WG|f 355-2 SHEET ' OAK AVENUE EXIST SD MH 46.00RIM 36 53IE EXIST CURS INLET EXIST SD t. 45.01 RIM 40.91IE a: LU LU LU a: DRAINAGE LEGEND COEFFICIENT FACTOR AREA (ACRES) 1 OD- YR RUNOFFS BASIN BOUNDARY 3RAPHIC SCALE: 1" = 10' K&S ENGINEERING, INC. Planning . Engineering . Surveying HYDROLOGY PLAN FOR: STATE & OAK PROPOSED CONDITION JN 3-():i8 ATTACHMENTS PERMANENT TREATMENT BMP INFORMATION Bioretention Facilities Bioretention TC-32 Design Considerations • Soil for Infiltration • Tributary Area • Slope • Aesthetics • Environmental Side-effects Description Tlie bioretention best management practice (BMP) functions as a soil and plant-based filtration device tiiat removes pollutants tlu-ough a variety of physical, biological, and chemical treatment processes. These facilities nonnally consist of a grass buffer strip, sand bed, ponding area, organic layer or mulch layer, planting soil, and plants. The runoff's velocity is reduced by passing over or through buffer strip and subsequently distributed evenly along a ponding area. Exfiltration of the stored water in the bioretention area planting soil into the underlying soils occurs over a period of days. California Experience None documented. Bioretention has been used as a stormwater BMP since 1992. In addition to Prince George's Coimty, MD and Alexandria, VA, bioretention has been used successfully at urban and suburban areas in Montgomery County, MD; Baltimore County, MD; Chesterfield County, VA; Prince William County, VA; Smith Mountain Lake State Park, VA; and Gary, NC. Advantages • Bioretention provides stormwater treatment that enhances the quality of downstream water bodies by temporarily storing runoff in the BMP and releasing it over a period of four days to tlie receiving water (EPA, 1999). • The vegetation provides shade and wind breaks, absorbs noise, and improves an area's landscape. Limitations • The bioretention BMP is not recommended for areas with slopes greater than 20% or where mature tree removal would Targeted Constituents Si Sediment EI Nutrients 0 Trash B Metals 0 Bacteria 0 Oil and Grease 0 Organics Legend (Removal EffecVveness) • Low • High • Medium January 2003 California Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com 1 of 8 TC-32 Bioretention be required since clogging may result, particularly if the BMP receives runoff with high sediment loads (EPA, 1999). • Bioretention is not a suitable BMP at locations where tlie water table is within 6 feet of the ground surface and v(diere tlie surrounding soil stratum is unstable. • By design, bioretention BMPs have the potential to create veiy attractive habitats for mosquitoes and other vectors because of liighly organic, often heavily vegetated areas mixed with shallow water. • In cold climates the soil may freeze, preventing runoff firom infiltrating into the planting soil. Design and Sizing Guidelines • The bioretention area should be sized to capture the design storm runoff. • In areas wiiere 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, altliough the preferred width is 25 feet. Excavated depth should be 4 feet. • Area should drain completely witliin 72 hours. • ^^proximately 1 tree or shrub per 50 ft* 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 stonnwater pollutants through ph3rsical and biological processes, including adsorption, filtration, plant uptake, microbial activity, decomposition, sedimentation and volatilization (EPA, 1999). Adsorption is tlie process whereby particulate pollutants attach to soil (e.g., clay) or vegetation surfaces. Adequate contact time between fhe surface and pollutant must be provided for in the design of the system for this removal process to occur. Thus, fhe infiltration rate of the soils must not exceed diose 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 fi'om stormwater include particulate organic matter, phosphorus, and suspended sohds. 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 fi'om the soils, with woody plants locking up these nutrients throu^ the seasons. Microbial activity within the soO also contributes to the removal of nitrogen and organic matter. Nitrogen is removed by nitrifying and denitrifying bacteria, while aerobic bacteria are responsible for tlie decomposition of the organic matter. Microbial processes require ojg^gen and can result in depleted oxj^en levels if the bioretention area is not adequately 2 of 8 California Stormwater BMP Handbook January 2003 New Development and Redevelopment www.cabmphandbooks.com Bioretention TC-32 aerated. Sedimentation occurs in the swale or ponding area as flie velocity slows and soUds fall out of suspension. Tlie 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, syntlietic 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 ai. (1998); PGDER (1993) Pollutant Removal Rate Total Phosphonis 70-83% Metals (Cu, Zn, Fb) 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 ofthe pollutants analyzed. Doubling or halving the influent pollutant levels had Uttle 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 tlian tiiose detennined for infiltration BMPs. Siting Criteria Bioretention BMPs are generally used to treat stonnwater 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 Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com 3 of 8 TC-32 Bioretention Additional Design Guidelines Hie layout of the bioretention area is determined after site constraints such as location of utihties, underlying soils, existing vegetation, and drainage are considered (EPA, 1999). Sites witli loamy sand soils are especially appropriate for bioretention because the excavated soil can be backfiUed and used as the planting soil, thus eliminating the cost of importing planting soU. Tlie use of bioretention may not be feasible given an unstable surrounding soil stratum, soils witli 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 flie existing drainage system (EPA, 1999). Tlie 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, tlie maximum drainage area for a bioretention area is determined by the expected rainfall intensity and runoff rate. StabiHzed areas may erode when velocities are greater than 5 feet per second (1.5 meter per second). The designer should detemiine the potential for erosive conditions at the site. The size of the bioretention area, which is a function of tlie drainage area and the runoff generated from the area is sized to capture die water quality volume. Hie recommended minimum dimensions of fhe 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 repUcating a natural forest and creating a microcUmate, thereby enabUng the bioretention ai-ea 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. EssentiaUy, 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 tiie ponding deptii 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 witli 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 soU should range between 5.5 and 6.5, wiiere pollutants such as organic nitrogen and phosphorus can be adsorbed by the soil and microbial activity can flourish. Additional requirements for the planting soil include a 1.5 to 3 percent organic content and a maximum 500 ppm concentration of soluble salts. 4 of 8 Califomia Stormwater BMP Handbook January 2003 New Development and Redevelopment www.cabmphandbooks.com Bioretention TC-32 Soil tests should be perfonned 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 bail and 4 feet (1.2 meters) altogether. This depth will provide adequate soil for tlie 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 deptii. Planting soil depths of greater tlian 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 hfts and lightly compacted until the desired depth is reached. Since high canopy trees may be destroyed during maintenance fhe 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 sliould be planted when conditions are favorable. Vegetation should be watered at tlie 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. Tlie designer should assess aesthetics, site layout, and maintenance requirements when selecting plant species. Adjacent non-native invasive species should be identified and the designer should take measures, such as providing a soil breach to eUminate the threat of these species invading the bioretention area. Regional landscaping manuals should be consulted to ensure that tlie planting of the bioretention area meets the landscaping requirements established by the local authorities. Tlie designers should evaluate the best placement of vegetation within the bioretention area. Plants should be placed at irregular intervals to rephcate a natural forest. Trees should be placed on the perimeter ofthe area to provide shade and shelter from the wind. Trees and shrubs can be sheltered from damaging flows if fliey are placed away from tlie path of tlie incoming runoff. In cold climates, species that are more tolerant to cold winds, such as evergreens, should be placed in windier areas of fhe 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 ofthe growing season. Mulch should be placed immediately after trees and shrubs are planted. Two to 3 inches (5 to 7.6 cm) of commercially-available fine sliredded hardwood mulch or shredded hardwood cliips 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, chmatic, and watering conditions should be selected for use in the bioretention cell, .^propriately selected plants will aide in reducing fertilizer, pesticide, water, and overall maintenance requirements. Bioretention system components shouid blend over time througli plant and root growth, organic decomposition, and the development of a natural January 2003 California Stormwater BMP Handbook 5 of 8 New Development and Redevelopment www.cabmphandbooks.com TC-32 Bioretention soil horizon. These biologic and physical processes over time will lengthen the faciUty's life span and reduce the need for extensive maintenance. Routine maintenance should include a biannual health evaluation of tlie trees and sluTibs and subsequent removal of any dead or diseased vegetation (EPA, 1999). Diseased vegetation should he 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 vectore because of highly organic, often heavily vegetated areas mixed witli shallow water. Routine inspections for areas of standing water within the BMP and corrective measures to restore proper infiltration 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 oi-der 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, tlie 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 he the primary maintenance function. Other potential tasks include replacement of dead vegetation, soil pH regulation, erosion repair at iiilow points, mulch replenishment, unclogging fhe underdrain, and repairing overflow structures. There is also the possibihty that the cation exdiange capacity of the soils in the cell will be significantly reduced over time. Depending on pollutant loads, soils may need to be replaced witliin 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 (Coffinan, 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 demoUtion of existing concrete, asphalt, and existing structures and the replacement of fill material with planting soil. The costs of retrofittuig a commercial site in Maryland, Kettering Development, vnth 15 bioretention areas were estimated at $111,600. In any bioretention area design, the cost of plants varies substantiaUy and can account for a significant portion of the expenditures. While these cost estimates are sUghtly greater tlian 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 lie required regardless of die bioretention installation should be subtracted when determining the net cost. 6 of 8 Califomia Stormwater BMP Handbook January 2003 New Development and Redevelopment www.cabmphandbooks.com Bioretention TC-32 Perhaps of most importance, however, die 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 stormwater conveyance systems at a site. A medical office building in Maryland was able to reduce the amount of storm drain pipe tliat 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 becoine a part of each property owner's landscape, reducing the public burden to maintain large cenb'aUzed facilities. Matnteiiance Cost Tlie operation and maintenance costs for a bioretention facility will be comparable to those of typical landscaping required for a site. Costs bq^ond the normal landscaping fees will include the cost for testing tlie soils and may include costs for a sand bed and planting soil. References and Sources of Additional Information Coffinan, 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," WEFTEC2000 Conference Proceedings on CDROM Research Symposium, Nitrogen Removal, Session 19, Anaheun CA, October 2000. Hsieh, C.-h. and Davis, A.P. "Engineering Bioretention for Treatment of Urban Stormwater Runoff," Watersheds 2002, Proceedings on CDROM 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 Office 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 fi:om Urban Roadways," 5th International Conference Diffiise/Nonpoint Pollution and Watershed Management Proceedings, CS. Melching and Emre Alp, Eds. 2001 Intemational Water Association January 2003 California Stormwater BMP Handbook 7 of 8 New Development and Redevelopment www.cabmphandbooks.com TC-32 Bioretention CURB STOPS- PARKINGIDTSHEETFLOW' iilii OVERFLOW ORAVEL CURTAIN DRAIM OVERFLOW UNDERDRAIN COLLECTION SYSTBM PLAN VIEW t'jajmouisoiL $•'PERFORATED PIPE IN r ORAVEL -FILTER FABRIC TYPICAL SECTION -f»ROFttE Schematic of a Bioretention Facility (MDE, 2000) 8 of 8 Califomia Stormwater BMP Handbook New Development and Redevelopment www.cabmphandbooks.com January 2003 ATTACHMENT C BMP NUMERIC SIZING K&S K&S ENGINEERING, INC. Planning Engineering Surveying By Date -DcCiHiJi. Sheet # L of A Subject E''MP Job No. 7801 Mission Center Court, Suite 100 • San Diego, CA 92108 (619) 296-5565 Fox (619) 296-5564 ! 1 ! j \ j ' \ 1 1 i 1 "hat i-o I I 1 .m .1.1 " ? ..... \ DA ? • = .m .1.1 " ? ..... r j •« ' oS '/ /« = .m .1.1 " ? — -efl + Oft f " SI 4 V .m .1.1 + ........ )A b s 1 5 ;si I *^ 7, + ........ •i ........ .......... I ( ft,' la,,.. ck .3:. .......... .......... Eos 4 ' \Z' > ( .......... 1 _ w Eos 4 ' \Z' > ( \^ .F — -z NC /* '/^ ,t. t — 5 z 27 T V. ^< £i ,t. t ) 11 o5 —f... i •/. — — ^< £i F ....... F — — ....... <^ ' F 1 1 — ! 1 — — •j — — j — j -j '} I ' — j — — 1 j i — — — — — — — — — ........ — i ........ — \ 1 1 ATTACHMENT D CITY SUSMP FORMS STORM WATER Develooment Services Land Development Engineering STANDARDS Develooment Services Land Development Engineering \>. * r, ^ CITY OF QUESTIONNAIRE E-34 1635 Faraday Avenue 760-602-2750 CARLSBAD QUESTIONNAIRE E-34 w/ww.carlsbadca.gov INSTRUCTIONS: To address post-development pollutants that may be generated from development projects, the City requires that new development and significant redevelopment priority projects incorporate Permanent Storm Water Best Management Practices (BMP's) into the project design per the City's Standard Urban Stormwater Management Plan (SUSMP). To view the SUSMP, refer to the Engineering Standards (Volume 4, Chapter 2) at vww.carisbadca.qoWstandards. Initially this questionnaire must be completed by the applicant in advance of submitting for a development application (subdivision, discretionary penmits and/or construction permits). The results of the questionnaire detemiine the level of storm water standards that must be applied to a proposed development or redevelopment project. Depending on the outcome, your project will either be subject to 'Standard Stormwater Requirements' or be subject to additional criteria called 'Priority Development Project Requirements'. Many aspects of project site design are dependent upon the storm water standards applied to a project. Your responses to the questionnaire represent an initial assessment of the proposed project conditions and impacts. City staff has responsibility for making the final assessment after submission of the development application. If staff determines that the questionnaire was incorrectly filled out and is subject to more stringent stonn water standards than initially assessed by you, this will result in the return ofthe development application as incomplete. In this case, please make the changes to the questionnaire and resubmit to the City, If you are unsure about the meaning of a question or need help in detemining how to respond to one or more of the questions, please seek assistance from Land Development Engineering staff. A separate completed and signed questionnaire must be submitted for each new development application submission. Only one compleled and signed questionnaire is required when multiple development applications for the same project are submitted concurrently. In addition to this questionnaire, you must also complete, sign and submit a Project Threat Assessment Form with constmction permits for the project. Please start by completing Step 1 and follow the instructions. When completed, sign the form at the end and submit this with your application to the city. To determine if your project is a priority development project, please answer the following questions: YES NO 1. Is your project LIMITED TO constructing new or retrofitting paved sidewalks, bicycle lanes or trails that meet the following criteria: (1) Designed and constructed to direct storm water runoff to adjacent vegetated areas, or other non-erodible permeable areas; OR (2) designed and constructed to be hydraulically disconnected from paved streets or roads; OR (3) designed and constructed with permeable pavements or surfaces in accordance with USEPA Green Streets guidance? / 2. Is your project LIMITED TO retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in acconjance with the USEPA Green Streets guidance? / If you answered "yes" to one or more of the above questions, then your project is NOT a priority development project and therefore is NOT subject to the storm water criteria required for priority development projects. Go to step 4, mark the last box stating "my project does not meet PDP requirements" and complete applicant infonnation. If you answered "no" to both questions, then go to Step 2. E-34 Page 1 of 3 Effective 6/27/13 ^ CITY OF CARLSBAD STORM WATER STANDARDS QUESTIONNAIRE E-34 Development Services Land Development Engineering 1635 Faraday Avenue 760-602-2750 www.carlsbadca.gov TO BE COIII«TED AU;^ OR Ra)EWa.OPIIEMT m To determine if your project is a priority development project, please answer the following questions: YES NO 1. Is your project a new development that creates 10,000 square feet or more of impervious surfaces collectively over the entire project site? This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land. / 2. Is your project creating or replacing 5,000 square feet or more of impervious surface collectively over the entire project site on an existing site of 10,000 square feet or more of impervious surface? This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land. / 3. Is your project a new or redevelopment project that creates 5,000 square feet or more of impervious surface collectively over the entire project site and supports a restaurant? A restaurant is a facility that sells prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption. / 4. Is your project a new or redevelopment project that creates 5,000 square feet or more of impervious surface collectively over the entire project site and supports a hillside development project? A hillside development project includes development on any natural slope that is twenty-five pement or greater / 5. Is your project a new or redevelopment project that creates 5,000 square feet or more of impervious surface collectively over the entire project site and supports a parking lot A parking lot is a land area or facility for the temporary parking or storage of motor vehicles used personally for business or for commerce. / 6. Is your project a new or redevelopment project that creates 5,000 square feet or more of impen/ious surface collectively over the entire project site and supports a street, road, highway freeway or driveway? A street, road, highway, freeway or driveway is any paved impervious surface used for the transportation of automobiles, trucks, motorcycles, and other vehicles. / 7. Is your project a new or redevelopment project that creates or replaces 2,500 square feet or more of Impervious surface collectively over the entire site, and discharges directly to an Environmentally Sensitive Area (ESA)? "Discharging Directly to' includes flow that is conveyed overiand a distance of 200 feet or less from the project to the ESA, or conveyed in a pipe or open channel any distance as an isolated flow from the proiect to the ESA (i.e. not commingles with flows from adjacent lands).' / 8. Is your project a new development that supports an automotive repair shop? An automotive repair shop is a facility that is categorized in any one of the following Standard Industrial Classification (SIC) codes: 5013, 5014, 5541, 7532-7534, or 7536-7539. / 9. Is your project a new development that supports a retail gasoline outlet (RGO)? This category includes RGO's that meet the following criteria: (a) 5,000 square feet or more or (b) a project Average Daily Traffic (ADT) of 100 or more vehicles per day. / 10. Is your project a new or redevelopment project that results in the disturbance of one or more acres of land and are expected to generate pollutants post construction? / 11. Is your project located within 200 feet of the Pacific Ocean and (1) creates 2,500 square feet or more of impervious surface or (2) increases impervious surface on the property by more than 10%? / If you answered "yes" to one or more of the above questions, you ARE a priority development project and are therefore subject to implementing structural Best Management Practices (BMP's) in addition to implementing Standard Stonn Water Requirements such as source control and low impact development BMP's. A Storm Water Management Plan (SWMP) must be submitted with your application(s) for development. Go to step 3 for redevelopment projects. For new projects, go to step 4 at the end of this questionnaire, check the "my project meets PDP requirements" box and complete applicant information. If you answered "no" to all of the above questions, you ARE NOT a priority development project and are therefore subject to implementing only Standard Stonn Water Requirements such as source control and low impact development BMP's required for all development projects. A Storm Water Management Plan (SWMP) is not required with your application{s) for development. Go to step 4 at the end of this questionnaire, check the "my project does not meet PDP requirements" box and complete applicant information. E-34 Page 2 of 3 Effective 6/27/13 STORM WATER Develooment Services Land Development Engineering STANDARDS Develooment Services Land Development Engineering CITY OF QUESTIONNAIRE E-34 1635 Faraday Avenue 760-602-2750 CARLSBAD QUESTIONNAIRE E-34 www.carlsbadca.gov RENT PROJECTS THAT ARE PRIORITr DEVELOPEMENT PROJECTS ONLY Complete the questions below reaarding your redevelopment project: YES NO Does the redevelopment project result in the creafion or replacement of impervious surface in an amount of less than 50% ofthe surface area ofthe previously existing development? If you answered "yes," the structural BMP's required for Priority Development Projects apply only to fhe creation or replacement of impervious surface and not the entire development Go to step 4, check the "my project meets PDP requirements" box and complete applicant information. If you answered "no," the structural BMP's required for Priority Development Projects apply to the entire development Go to step 4, check the "my project meets PDP requirements" box and complete applicant information. STEP4•. 'HUeckTHE jffWWPRlATE BOX AMD COMPLETE APPLICANT WffORMATIOM QT My project meets PRIORITY DEVELOPMENT PROJECT (PDP) requirements and must comply with additional stormwater criteria per the SUSMP and I understand I must prepare a Storm Water Management Plan for submittal at time of application. I understand flow control (hydromodification) requirements may apply to my project, Refer to SUSMP for details. • My project does not meet PDP requirements and must only comply with STANDARD STORMWATER REQUIREMENTS per the SUSMP. As part of these requirements, I will incorporate low impact development strategies throughout my project Applicant Information and Signature Box Address: 3069 STATE STREET Applicant Name; Applicant Signature: Accessor's Parcel Number(s): 203-297-06, 08 & 09 Applicant Title: Date: This Box for City Use Only City Concurrence: YES I NO By: Date; Project ID: * Environmentally Sensitive Areas include but are not limited to all Clean Water Act Secfion 303(d) impaired wafer 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 presen/es or their quivalent under the Multi Species Conservation Program within the Cities and County of San Diego; and any other equivalent environmentally sensitive areas which have been identified by the Copermittees. E-34 Page 3 of 3 Effective 6/27/13