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Home My WebLink AboutSDP 12-04; Hoehn Buick Cadillac; Site Development Plan (SDP) (3)PRELIMINARY STORM WATER MANAGEMENT PLAN For Grading & Improvements RECPJVED SDP 12-04 / CDP 12-26 CITY OF CAR' QR (CD 14-01) PUNM^NGDIvS At Hoehn Buick Cadillac 5334 Paseo Del Norte Carlsbad, CA 92008 Lot 5, Carlsbad Tract No. 72-3, Map No. 7492 APN: 211-060-02 PREPARED FOR: Bill Hoehn 5334 Paseo Del Norte Carlsbad, CA 92008 PREPARED BY: Jones Cahl and Associates 18090 Beach Blvd., Suite 12 Huntington Beach, CA 92648 March 10, 2014 TABLE OF CONTENTS Storm Water Management Plan 1.0 Project Setting 2.0 Identification of Pollutants of Concern 3.0 Selection of Treatment Control BMP's 4.0 Drainage Study Report summary 5.0 Source Control Measures 6.0 BMP Facility Maintenance Requirements A. City of Carlsbad Development Services Storm Water forms (E-34 and E-35) B. Vicinity Map C. Post Construction BMP and Drainage Site Plan D. Biotreatment BMP fact sheet E. Harvest and Use BMP fact sheet F. Educational Materials from CASQA BMP Handbook G. Permanent Stormwater Quality BMP Maintenance Agreement 2 I P a g e SWMP Certification "The section, sizing, and preliminaiy design of stormwater treatment and other control measures in this plan meet the requirements of Regional Water Quality Control Board Order R9-2007-0001 and subsequent amendments." DaryfelRubio, PE Registered Civil Engineer, California No. 60934, Exp. 12/31/2014 l||e>|l4 Date 3 I Page 1.0 Project Setting A. Project Name, Location, Description, Vicinity Map Project Name: Hoehn Buick Cadillac Project Address: 5334 Paseo Del Norte, Carlsbad, CA 92008 Project Size: 2.99 Acres of contiguous property Run-on Size: 2.99 Acres Area disturbed: 0.53 Acres Latitude/Longitude: 33° 08" 02"N, 117° 19' 34"W Expected Duration of the project: 200 Days Construction Site Priority: Subject to Priority Project Requirements based on Storm Water Standards Questionnaire E-34 (See Tab A). Hoehn Buick Cadillac owns 3 acres of land near the corner of Paseo Del Norte and Cannon Road in the City of Carlsbad, California. The dealership is doing an addition to its existing Sales Building and replacing some of the existing pavement. The proposed improvements disturb a total of 0.53 acres ofthe existing site. Since the proposed improvements disturb less than 50% ofthe total site treatment will be limited to the disturbed areas. Undisturbed areas with existing impervious surfaces will not be treated with the proposed stormwater facilities but will be directed over landscaped areas where possible. The project location is shown on the Vicinity Map included under Tab B. B. Existing Site Features and Conditions The project site is approximately 2.99 acres of contiguous property and is surrounded by developed properties to the north, south, east and west. Topographically the site is located against a 40% slope to the east and level with the sites to the north and south. The elevation ranges from 68 feet above mean sea level (msl) to 82 feet above msl. Offsite storm water does not enter the site, the adjacent sites drain to the street and a concrete gutter along the east property line directs runoff from the slope to the north where it discharges into another site. The east facing slope extends beyond the property line to an elevation of approximately 99 feet above msl. To the north and south, the adjacent properties are car dealerships with an easement for public utilities. Site soils are primarily Tertiary Silty or Clayey Sand. Ground water was not encountered at the depth of the borings, 30 feet. The subject site is not situated in an area of historic occurrence of liquefaction to indicate a potential for permanent ground displacement. 4 I P a g e C. Proposed Land Use and Anticipated Activities that would affect Stormwater The existing and proposed land use is a commercial car sales business with maintenance and storage for vehicles. Anticipated activities include vehicle maintenance and possible fluid leakage, car washing, and landscape maintenance. D. Opportunities and Constraints for Stormwater Control and Treatment The principal constraints on site design are: existing paved areas and curb where we will be matching existing grades. Proposed drainage will need to tie into existing drainage course. E. Nearby Water Bodies, Existing Storm Drain Systems Existing drainage sheet flows over the site into curb drains which direct some runoff into the landscaped strips along the frontage of the property and the rest drain through the curb face and into the curb and gutter along Paseo Del Norte. From there the runoff is directed into a storm drain located at the southwest property corner along the east curb face on Paseo Del Norte. The existing drainage ofthe disturbed 0.53 acres is 33% (0.175 Ac) is pervious and 67% (0.355 Ac) is impervious. The runoff coefficient, C, forthe existing conditions of this site is selected from the San Diego Hydrology Manual, corresponding Soils Hydrologic Groups Map and site soils report. The site falls under General Commercial development with soils group B. Soil Group B has a Cp=0.25 which will be used for pervious areas and a Ci=0.90 will be used for impervious areas. Pre-developed weighted runoff coefficient C is determined as follows: (per San Diego Hydrology Manual Section 3.1.2) C= (0.90 * % Impervious Area) + (0.25 * % Pervious Area) C= (0.90 * 67%) + (0.25 * 33%) = 0.686 F. Rough Grading Drainage Conditions The existing site will be rough graded for the improvements to the sales building and the new maintenance building. Underground utilities will also be part of this early stage of construction. In the stage of rough grading, the percentage of pervious areas increases to 5 I P a g e be 85%. The percentage of impervious areas will be 15%. The runoff coefficient, C, for this site is calculated using accepted values for pervious and impervious land from the San Diego Hydrology Manual. A C=0.25 will be used for pervious areas and a C=0.90 will be used for impervious areas. Rough graded-developed weighted runoff coefficient C is determined as follows: C= (0.90 * % Impervious Area) + (0.25 * % Pervious Area) C= (0.90 * 15%) + (0.25 * 85%) = 0.348 Since the storm drain, concrete ditch, curb outlets and other drainage improvements were sized for the developed condition this C value was not actually used in any drainage calculations. G. Proposed Drainage Conditions The proposed project includes the construction of an addition to the existing Sales and Display building. Site improvements will include underground utilities, concrete gutters, landscaping and limited pavement to tie into existing areas. Stormwater from the proposed building, new impervious surfaces and the proposed structure will be directed into vee-gutters and collected with catch basins at the low points. These catch basins will direct the runoff into designed Bioretention Facilities to store and treat and ultimately discharge runoff into the city storm drain system. All other site runoff, provided from existing unimproved areas, will be directed through sheet flow over landscaped areas and into Paseo Del Norte and into the city storm drain system. Landscaped areas located at the north west and southwest property corners will be designed with Bioretention areas and will receive stormwater from all improved Impervious areas (Please also see Post Construction BMP Site Plan under Tab C for exact location). The proposed site improvements result in 65.8% (0.35 acres/0.53 acres) impervious and 34.2% (0.18 acres/0.53 acres) pervious area (based on the area ofthe entire drainage basin). A Cp=0.25 will be used for pervious areas and a C|=0.90 will be used for impervious areas for the post construction site. The post-construction weighted runoff coefficient C is determined as follows: C= (0.90 * % Impervious Area) + (0.25 * % Pervious Area) C= (0.90 * 65.8%) + (0.25 * 34.2%) = 0.68 6 I P a g e See Section 4.0 for a summary ofthe Drainage Report. H. Project Special Conditions None. 7 I P a g e 2.0 Identification of Pollutants of Concern Urban runoff from a developed site has the potential to contribute pollutants, including oil and grease, suspended solids, metals, gasoline, pesticides, and pathogens to the storm water conveyance system and receiving waters. For the purposes of identifying pollutants of concern and associated storm water BMPs, pollutants are grouped in nine general categories as follows: Sediments - Sediments are soils or other superficial materials eroded and then transported or deposited bythe 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. Nutrients - Nutrients are inorganic substances, such as nitrogen and phosphorus. They commonly exist in the form of mineral salts that are either dissolved or suspended in water. Primary sources of nutrients in urban runoff 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. Metals - Metals are raw material components in non-metal products such as fuels, adhesives, paints, and other coatings. Primary sources of metal pollution in storm water are typically commercially available metals and metal products. Metals of concern 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. 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. Trash- Trash (such as paper, plastic, polystyrene packing foam, and aluminum materials) and biodegradable organic matter (such as leaves, grass cuttings, and 8 I Page 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. Oxygen-Demanding Substances- Oxygen-Demanding Substances 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. Oil and Grease- 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. 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 human and aquatic life. Also, the decomposition of excess organic waste causes Increased growth of undesirable organisms in the water. Pesticides - Pesticides (including herbicides) are chemical compounds commonly used to control nuisance growth orjDrevalence of organisms. Excessive application of a pesticide may result in runoff containing toxic levels of its active component. A. Identify Pollutants Associated with Type of Land Use Table 2-1 (City of Carisbad SUSMP-March 24, 2010) associates pollutants by Land Use Type. Hoehn Buick Cadillac Improvement project best fits under the Priority Project Categories of Commercial Development >1 acre. Automotive Repair Shop, and Parking Lots. 9 I P a g e Table 2-1 Anticipated and Potential Pollutants Generated by Land Use Type General Pollutant Categories Priority Project Categories Sediments Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Substances 0il& Grease Bacteria & Viruse Pesticides Detached Residential Development X X X X X X X Attached Residential Development X X X P(1) P(2) P X Commercial Development >one acre P(1) P(1) X P(2) X P(5) X P(3) P(5) Heavy Industry X X X X X X Automotive Repair Shops X X(4)(5) X X Restaurants X X X X P(1) Steep Hillside Developments >5,000 ft2 X X X X X X Parking Lots P(1) P(1) X X P(1) X P(1) Retail Gasoline Outlets X X X X X Streets, Highways & Freeways X P(1) X X(4) X P(5) X X P(1) 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 The Anticipated and Potential Pollutants generated by Land Use Type for the Hoehn Buick Cadillac project site are sediments, nutrients, heavy metals, organic compounds, trash & debris, oxygen demanding substances, oil & grease, bacteria & viruses, and pesticides. B. Identification of Watershed, Hydrologic Unit Basin Number and Receiving Water that Project Contributes to The Hydrologic Unit basin number is 904.31, as provided by the San Diego Regional Water Quality Control Board. The site drains via sheet flow to the city storm drain system that leads to Agua Hedionda Lagoon which drains into the Pacific Ocean in the City of Carisbad. IND - Industrial Service Supply (IND) - Includes uses of water for industrial activities that do not depend primarily on water quality including, but not limited to, mining, cooling water supply, hydraulic conveyance, gravel washing, fire protection, or oil well repressurization. 10 I P a g e NAV - Navigation (NAV) - Includes uses of water for shipping, travel, or other transportation by private, military, or commercial vessels. REC1 - Contact Water Recreation (REC-1) - Includes uses of water for recreational activities involving body contact with water, where ingestion of water is reasonably possible. These uses include, but are not limited to, swimming, wading, water-skiing, skin and SCUBA diving, surfing, white water activities, fishing, or use of natural hot springs. REC2 - Non-contact Water Recreation (REC-2) - Includes the uses of water for recreational activities involving proximity to water, but not normally involving body contact with water, where ingestion of water is reasonably possible. These uses include, but are not limited to, picnicking, sunbathing, hiking, beachcombing, camping, boating, tide pool and marine life study, hunting, sightseeing, or aesthetic enjoyment in conjunction with the above activities. COMM - Commercial and Sport Fishing (COMM) - Includes the uses of water for commercial or recreational collection offish, shellfish, or other organisms including, but not limited to, uses involving organisms intended for human consumption or bait purposes. BIOL - Preservation of Biological Habitats of Special Significance (BIOL) - Includes uses of water that support designated areas or habitats, such as established refuges, parks, sanctuaries, ecological reserves, or Areas of Special Biological Significance (ASBS), where the preservation or enhancement of natural resources requires special protection. EST - Estuarine Habitat (EST) - Includes uses of water that support estuarine ecosystems including, but not limited to, preservation or enhancement of estuarine habitats, vegetation, fish, shellfish, or wildlife (e.g., estuarine mammals, waterfowl, shorebirds). WILD - Wildlife Habitat (WILD) - Includes uses of water that support terrestrial ecosystems including, but not limited to, preservation and enhancement of terrestrial habitats, vegetation, wildlife (e.g., mammals, birds, reptiles, amphibians, invertebrates), or wildlife water and food sources. RARE - Rare, Threatened, or Endangered Species (FiARE) - Includes uses of water that support habitats necessary, at least in part, for the survival and successful maintenance of plant or animal species established under state or federal law as rare, threatened or endangered. MAR - Marine Habitat (MAR) - Includes uses of water that support marine ecosystems including, but not limited to, preservation or enhancement of marine habitats, vegetation such as kelp, fish, shellfish, or wildlife (e.g., marine mammals, shorebirds). MIGR - Migration of Aquatic Organisms (MIGR) - Includes uses of water that support habitats necessary for migration, acclimatization between fresh and salt water, or other temporary activities by aquatic organisms, such as anadromous fish. SPWN - Spawning, Reproduction, and/or Early Development (SPWN) - Includes uses of water that support high quality aquatic habitats suitable for reproduction and early development of fish. This use is applicable only for the protection of anadromous fish. WARM - Warm Freshwater Habitat (WARM) - Includes uses of water that support warm 11 I P a g e water ecosystems including, but not limited to, preservation or enhancement of aquatic habitats, vegetation, fish or wildlife, including invertebrates. SHELL - Shellfish Harvesting (SHELL) - Includes uses of water that support habitats suitable for the collection of filter-feeding shellfish (e.g., clams, oysters and mussels) for human consumption, commercial, or sport purposes. C. List of Impaired Water Bodies per 303d Listing that Project Contributes to Per RWQCB 9's 303d list, the Agua Hedionda Lagoon is on the list of impaired water bodies. D. Summary of Primary Pollutants of Concern Agua Hedionda Lagoon has indicator bacteria and Sedimentation/Siltation as pollutants of concern. E. Watersheds with Special Pollutants of Concern Local receiving water conditions may require specialized attention. The four local conditions to consider Include: - Ocean water designated as an "Area of Special Biological Significance" (ASBS). o At the date of this SUSMP (June 3, 2013), there are no locations that affect projects in Carisbad. - Pacific Ocean as described In Mello I the Local Coastal Program. 0 At the date of this SUSMP (June 3, 2013), there are no locations that affect projects In Carisbad. - 303(d) listed water. o As stated in 2.B. under Identification of Pollutants of Concern, Agua Hedionda Lagoon is impaired indicator bacteria and Sedimentation/Siltation as the pollutants of concern. However, the listing does not demand that a particular BMP Is selected on the basis ofthe impairment, rather the project design be cognizant of the impairment and the future implications a TMDL may have on the land. - Waters with established TMDLs. 0 At the date of this SUSMP (June 3, 2013), no TDML's have been established within Carisbad. 12 I P a g e 3.0 Selection of Standard and Treatment Control BMP's for Project Standard Stormwater Requirements (BMPs) At a minimum Standard Stormwater Requirements must be met by all projects. Since the proposed Hoehn Buick Cadillac project is a Priority Development Project additional requirements will follow later in Section 3.C. The Standard Stormwater Requirements are set up to Incorporate methods to minimize the introduction of pollutants generated by urban runoff. BMP 1 Minimize Impervious Surfaces • Limit the use of impervious surface. Increase building density (number of stories above or below ground). The building density has been increased by removing the check-In building at the maintenance entrance and attaching the proposed building space to the existing Showroom/Sales building. • Install pervious pavement or pavers on walkways to reduce the Imperviousness of the project. Walkways located against the building addition and the against the existing sales building, will be done with pervious pavers to allow for Infiltration and Increase the amount of permeable surface on site. The proposed pervious pavers will have a square footage of 6,030 square feet. What isn't collected by the pervious pavers will then sheet flow Into gutters and directed into bioretention facilities. BMP2 Disconnect Discharges. • Direct runoff from Impervious surfaces to discharge over landscaped/planter areas or pervious surfaces to the maximum extent practicable. Parking lots are existing. Runoff will be directed into bioretention planter areas at the front of the property. • Where landscaping is proposed, drain rooftops into adjacent landscaping prior to discharging to the storm water conveyance system. Roof drains will be directed into landscaped areas located adjacent to the buildings, and designed as bioretention facilities to store and treat runoff. • Direct roof drains to drain over turf or landscape areas prior to being collected by storm drain inlets. 13 I P a g e Roof drains will be directed into landscaping located adjacent to the buildings and collected into bioretention facilities. • If inlets are necessary to collect runoff from Impervious surfaces, then the drain system shall be discharged over pervious/landscape areas priorto discharge from the site. Does not apply to this project. • If sump-pumps are necessary to serve areas that cannot drain by gravity means, the discharge ofthe sump-pump shall discharge so that it drains over landscape/turf area prior to discharge from the site. Not necessary for this project. BMP 3 Conserve Natural Areas • Conserve natural areas, soils and vegetation and provide buffer area between natural water bodies /water courses and the project footprint. No natural areas remain, the site Is already a developed car dealership. • Cluster the development on the least environmentally sensitive portions of a site while leaving the remaining land In a natural, undisturbed condition. The site is already a developed car dealership, no environmentally sensitive areas remain in a natural, undisturbed condition. • Use the buffer area between natural water bodies/water courses and the project footprint to discharge runoff to filter pollutants prior to discharge from the site. Does not apply to this project. • Leave natural vegetated drainage courses versus replacing them with lined or Impervious channels or underground storm drain systems unless deemed necessary to repair or enhance unstable channels. Does not apply to this project. BMP 4 Stenciling Inlets and Signage • Provide stamping or equivalent, of all applicable Inlets collecfing runoff from impervious areas. The stenciling shall Include prohibitive language such as "No Dumping - I Live Downstream." 14 I P a g e Concrete stamping, or equivalent, of all storm water conveyance system inlets and catch basins within the project area will be provided with prohibitive language within the project area. • Install signs and/or graphic icons which prohibit dumping at public access points along channels and creeks within the project area, trailheads, parks, and building entrances/exists. Signs and prohibitive language and/or graphical Icons which prohibit dumping will be posted within the project area. BMP 5 Landscape Design • Design landscape area layout and select native, drought-tolerant species that do not require excessive irrigation in accordance with the City of Carisbad Landscape Manual, latest version. Additional native or adapted ornamental plants will be a part of the on-site landscaping. • Maximize canopy interception and employ water conservation by preserving native trees and shrubs. Existing trees and shrubs within the site will be preserved. • On those areas that are disturbed, plant additional native or drought tolerant trees and large shrubs In place of non-drought tolerant exotics. Additional native or adapted ornamental plants will be a part ofthe on-site landscaping. BMP 6 Water Efficient Irrigation • Design new Irrigation systems to reduce over-irrigation, employ rain shutoff devices prevenfing irrigation after rainfall events and minimize unnecessary runoff per Chapter 18.50 ofthe Municipal Code and the City of Carisbad Landscape Manual. Rain shutoff devices to prevent irrigation during and after precipitafion will be employed. BMP 7 Protect Slopes and Channels • Minimize disturbances to natural drainages or downstream properties by conveying runoff safely from the tops of slopes and ensure slopes are properiy vegetated or protected to avoid slope erosion. 15 I P a g e Runoff from top of slopes will be routed through concrete ditches and Into the proposed storm drainage system. Slopes will be vegetated with native or drought tolerant vegetation to avoid slope erosion. • Install energy dissipaters at the ouflets of storm drains, culverts, conduits or channels. Outlets shall be designed to slow velocifies down to non-erosive veloclfies. Concrete vee-gutter on-site Is existing and Its outlet is off site. Nothing Is designed for the locafion where it outlets. BMP 8 Trash Receptacles • Construct trash storage areas per City Standard drawing G-16, unless otherwise approved by the City. Onsite trash storage areas will be built per City Standard G-16. BMP 9 Material Storage Areas • Identify areas for storing urban materials that have the potential to contaminate storm runoff. These materials shall be placed in an enclosure such as, but not limited to, a cabinet, shed or similar structure that prevents contact with rain and runoff. Hazardous materials with the potential to contaminate urban runoff will be placed In an enclosure such as a cabinet, shed or similar structure to prevent contact with rain, runoff or spillage to the storm water conveyance system. • Some projects may want to incorporate a secondary containment system such as dikes, berms or curbs. The storage areas will be paved and sufficiently impervious to contain leaks and spills, and will have a storm filter unit to minimize direct precipitation within the maintenance area which will be self contained. Treatment Control BMP's A. Treatment Control BMP's to Target Pollutants of Concern Table 2-3 (City of Carisbad SUSMP- March 24, 2010) shows how various types of treatment facilifies perform for each group of pollutants. (Note: This table excludes LID treatment facilities and includes Filter Inserts.) 16 I P a g e Table 2-3 Groups of Pollul ants and relative effectiveness of treatment 1 facilities. Pollutants of Concem Bio retention Facility Settling Basins (Dry Ponds) Wet Ponds and Constnjc ted Wetlands Media Filters HIgherrate media filters HIgherrate biofilters Trash Racks & Hydrody namic Devices Vegetated Swales Filter Inserts Coarse Sediment and Trash High High High High High High High High High Pollutants that tend to associate with fine particles during treatment High High High High Medium Medium Low Medium Low Pollutants that tend to be dissolved following treatment Medium Low Medium Low Low Low Low Low Low The available Treatment BMPs and selection rationale: B. Selection Criteria for each available treatment BMP Infiltrafion Facilities are some ofthe better and more efficient treatment facilities; Infiltrafion Facilifies and landscape designs capture, retain, and infiltrate a minimum of 80% of runoff into the ground. Infiltrafion facilifies are generally only feasible in permeable (Hydrologic Soil Group A or B) soils. Volume and area of infiltrafion facilifies depends on soil permeability and safety factor used. Since the project site has soil from the Hydrologic Soil Group of B, infiltration is an appropriate solufion for the Hoehn Buick Cadillac project. Bioretention areas - Treatment occurs by percolating runoff through 18 inches or more of engineered soil. This removes most pollutants before the runoff is collected in a perforated subdrain. Because there is concern about the infiltrafion rate onsite, a perforated subdrain is used. Setfiing Basins (Dry Ponds) - This would require stormwater to pond onsite and infiltrate. Since the infiltration rate is unknown at this point ponding is not a recommended solution so this was not selected as a Treatment BMP. Wet Ponds and Constructed Wetlands - This would require stormwater to pond onsite and infiltrate. Since the infiltration rate is unknown at this point ponding is not a recommended solution so this was not selected as a Treatment BMP. 17 I P a g e Media Filters -Since the infiltrafion rate ofthe site is unknown at this point and we are able to store and treat the runoff of the improved areas with a Vault and Bioretention Area, media filters were not selected as a Treatment BMP. Higher Rate Media Filters - Since the infiltrafion rate ofthe site is unknown at this point and we are able to store and treat the runoff of the Improved areas with a Vault and Bioretention Area, media filters were not selected as a Treatment BMP. Higher Rate Biofilters - Since the infiltration rate of the site Is unknown at this point and we are able to store and treat the runoff of the Improved areas with a Vault and Bioretention Area, Biofilters were not selected as a Treatment BMP. Trash Racks and Hydrodynamic Devices - These are less effective treatment devices selected in a treatment train. The site was able to work with the selection of other treatment devices. Vegetated Swales - Treatment occurs as runoff flows through grass or other vegetation before exiting as the downstream end. Some landscaped areas are use to run existing water runoff over but it was not used in the calculations for this project. C. Numeric Sizing Criteria and BMP Sizing calculations The Treatment Control BMPs selected for the Hoehn Buick Cadillac project are two Bioretenfion Facilifies, labeled B and C, and one Flow-Through planter, labeled A, on the enclosed BMP Site Plan. Criteria Bioretention facility. See the BMP Site Plan for bioretenfion facilifies. The area of the bioretention facility must be sized to treat the maximum discharge flow, assuming a percolation rate of 5" per hour through the engineered soil. Flow-Through Planter. See the BMP Site Plan for flow-through planters. The area ofthe bioretention facility must be sized to treat the maximum discharge flow, assuming a percolation rate of 5" per hour through the engineered soil. Hydromodiflcation: Using the Hydromodification Applicability Determination from the City of Carlsbad SUSMP we determined that this project is exempt for Hydromodificafion. Node 3: This project does not Increase the anriount of 18 I P a g e impervious area. Page 5, Section E of this report states the pre-project Impervious area is 67% (0.355 Ac or 15,464 sf). The post-project impervious area has decreased to 65.8% (0.35 Ac or 15,246 sf). Node 4: This project does not Increase unmifigated peak flows to any outlet location. Page 23 of this report shows the peak flow Is unchanged. Therefore, the project is exempt from hydromodification. Details Preventing mosquito harborage. Bioretenfions should be designed to drain completely, leaving no standing water. Drains should be located flush with the bottom. Alternatively—or in addition—all entry and exit points, should be provided with traps or sealed or screened to prevent mosquito entry. Note mosquitoes can enter through openings 1/16" or larger and will fly for many feet through pipes as small as 1/4". DMA Tributary Area (sf) Runoff Volume (cf) Area Provided for Bioretenfion (sf) Depth of Gravel Req. Bioretention Storage Volume Provided (cf) A (Flow-Through Planter) 5,054 253 453 6" 475 B (Bioretention Planter) 4,310 178 282 6" 249 C (Bioretention 1 Planter) 13,652 543 469 12" 574 AREA"A" NAME AREA SURFACE FACTOR AxF A1 4,228 SF ROOF 1.0 4,228 A2 826 LS 0.1 83 MIN PROV. TOTAL 4,311 SF 0.04 173SF 453 SF IMP AREA FOR FLOW BASED FACILITIES (PER COUNTY OF SAN DIEGO SUSMP - CHAPTER 2) Q=CIA C = WEIGHTED RUNOFF COEFFICIENT ROOF/BUILDING = 1.0 (83.7% OF AREA) LANDSCAPE = 0.1 (16.3% OF AREA) C = (1.0x0.837)+ (0.1 X 0.163) = 0.853 19 I P a g e I = INTENSITY = 0.2 IN/HR (PER COUNTY SUSMP THE 0.2 INCHES PER HOUR CRITERION IS THE BASIS FOR A CONSISTENT COUNTYWIDE SIZING FACTOR FOR BIORETENTION FACILITIES WHEN USED FOR STORMWATER TREATMENT ONLY) A = 5,054 SF = 0.116 Ac Q = CIA = (0.853) X (0.2 IN/HR) x (0.116 Ac) = 0.02 CFS FOR VOLUME BASED FACILITIES (PER COUNTY OF SAN DIEGO SUSMP - CHAPTER 2) AREA MUST BE DESIGNED TO INFILTRATE, FILTER, OR TREAT THE VOLUME OF RUNOFF TH PRODUCED FROM A 24-HOUR 85 PERCENTILE STORM EVENT AS DETERMINED FROM THE TH COUNTY OF SAN DIEGO'S 85 PERCENTILE PRECIPITATION ISOPLUVIAL MAP TH UNIT VOLUME = 0.6 IN = 0.05 FT (PER 85 PERCENTILE PRECIPITATION ISOPLUVIAL MAP) VOLUME = TRIBUTARY AREA x RUNOFF FACTOR x UNIT VOLUME = (5,054 SF) X (0.853) x (0.05 FT) = 216 CF DRAWDOWN TIME: SOIL MIX MINIMUM PERCOLATION RATE = 5 IN/HR DEPTH OF WATER = VOLUME / PROVIDED AREA = (216 CF) / (453 SF) = 0.477 FT = 5.7 IN DRAWDOWN TIME = DEPTH / PERCOLATION RATE = (5.7 IN)/(5 IN/HR) = 1.14 HR AREA"B" NAME AREA SURFACE FACTOR AxF Bl 999 SF PAVERS 0.2 200 B2 4,147 SF AC 1.0 4,147 B2 483 SF LS 0.1 48 MIN PROV. TOTAL 4,395 SF 0.04 176 SF 282 SF IMP AREA FOR FLOW BASED FACILITIES (PER COUNTY OF SAN DIEGO SUSMP - CHAPTER 2) Q=CIA C = WEIGHTED RUNOFF COEFFICIENT AC PAVEMENT = 1.0 (73.7% OF AREA) LANDSCAPE = 0.1 (8.6% OF AREA) PAVERS = 0.2 (17.7% OF AREA) C = (1.0 x 0.737) + (0.1 X 0.086) + (0.2 x . 177) = 0.781 I = INTENSITY = 0.2 IN/HR (PER COUNTY SUSMP THE 0.2 INCHES PER HOUR CRITERION IS THE BASIS FOR A CONSISTENT COUNTYWIDE SIZING FACTOR FOR BIORETENTION FACILITIES WHEN USED FOR STORMWATER TREATMENT ONLY) 20 I P a g e A = 5,629 SF = 0.129 Ac Q = CIA = (0.781) X (0.2 IN/HR) x (0.129 Ac) = 0.02 CFS FOR VOLUME BASED FACILITIES (PER COUNTY OF SAN DIEGO SUSMP - CHAPTER 2) AREA MUST BE DESIGNED TO INFILTRATE, FILTER, OR TREAT THE VOLUME OF RUNOFF TH PRODUCED FROM A 24-HOUR 85 PERCENTILE STORM EVENT AS DETERMINED FROM THE TH COUNTY OF SAN DIEGO'S 85 PERCENTILE PRECIPITATION ISOPLUVIAL MAP TH UNIT VOLUME = 0.6 IN = 0.05 FT (PER 85 PERCENTILE PRECIPITATION ISOPLUVIAL MAP) VOLUME = TRIBUTARY AREA x RUNOFF FACTOR x UNIT VOLUME = (5,629 SF) X (0.781) x (0.05 FT) = 220 CF DRAWDOWN TIME: SOIL MIX MINIMUM PERCOLATION RATE = 5 IN/HR DEPTH OF WATER = VOLUME / PROVIDED AREA = (220 CF) / (282 SF) = 0.78 FT = 9.4 IN DRAWDOWN TIME = DEPTH / PERCOLATION RATE = (9.4 IN) / (5 IN/HR) = 1.9 HR AREA"C" NAME AREA SURFACE FACTOR AxF C1 5,096 SF PAVERS 0.2 1,019 C2 273 SF TRASH 1.0 .27 C3 9,564 SF AC 1.0 9,564 MIN PROV. TOTAL 10,856 SF 0.04 434 SF 469 SF IMP AREA FOR FLOW BASED FACILITIES (PER COUNTY OF SAN DIEGO SUSMP - CHAPTER 2) Q=CIA C = WEIGHTED RUNOFF COEFFICIENT AC PAVEMENT = 1.0 (64.1% OF AREA) TRASH ENCLOSURE = 1.0 (1.8% OF AREA) PAVERS = 0.2 (34.1% OF AREA) C = (1.0 x 0.641) + (1.0 X 0.018) + (0.2 x 34.1) = 0.727 I = INTENSITY = 0.2 IN/HR (PER COUNTY SUSMP THE 0.2 INCHES PER HOUR CRITERION IS THE BASIS FOR A CONSISTENT COUNTYWIDE SIZING FACTOR FOR BIORETENTION FACILITIES WHEN USED FOR STORMWATER TREATMENT ONLY) A = 14,933 SF = 0.343 Ac Q = CIA = (0.727) X (0.2 IN/HR) x (0.343 Ac) = 0.05 CFS 21 I Page FOR VOLUME BASED FACILITIES (PER COUNTY OF SAN DIEGO SUSMP - CHAPTER 2) AREA MUST BE DESIGNED TO INFILTRATE, FILTER, OR TREAT THE VOLUME OF RUNOFF TH PRODUCED FROM A 24-HOUR 85 PERCENTILE STORM EVENT AS DETERMINED FROM THE TH COUNTY OF SAN DIEGO'S 85 PERCENTILE PRECIPITATION ISOPLUVIAL MAP TH UNIT VOLUME = 0.6 IN = 0.05 FT (PER 85 PERCENTILE PRECIPITATION ISOPLUVIAL MAP) VOLUME = TRIBUTARY AREA x RUNOFF FACTOR x UNIT VOLUME = (14,933 SF) X (0.727) x (0.05 FT) = 543 CF DRAWDOWN TIME: SOIL MIX MINIMUM PERCOLATION RATE = 5 IN/HR DEPTH OF WATER = VOLUME / PROVIDED AREA = (543 CF) / (469 SF) = 1.16 FT = 13.9 IN DRAWDOWN TIME = DEPTH / PERCOLATION RATE = (13.9 IN) / (5 IN/HR) = 2.78 HR 22 I P a g e San Diego County 85th Percentile Isopluvials Draft 8/7/2003 Legend ijkm NOTE The 85«h percentile s a 24-hour rainfill total It represents a value such that 85% oflhe obterved 24-hour rental totals VMII be less trian that value San Diego County 85th Percentile Isopluvials Draft 8/7/2003 Legend Munnp*! BemMhM NOTE: Ttie SSOi percentile is a 24-hour rairtfall total 11 represents a value such that S5% of the observed 24-hour ranfal totals will be less ttian Oiat value CHAPTER 2: CONCEPTS AND CRITERIA • Design and construct pervious areas, if any, to effectively receive and infiltrate runoff from impervious areas, taking into account soil conditions, slope, and other pertinent factors. • Construct a portion of paved areas with low traffic and appropriate soil conditions with permeable surfaces. To demonstrate compliance with these minimum standards the LID design procedure in Cliapter 4 incorporates these requirements into an integrated design which also meets sizing requirements for stormwater treatment facilities and flow-control (hydromodification management) requirements. • SIZING REQUIREMENTS FOR STORMWATER TREATMENT FACILITIES The guidance in Chapter 4 was crafted to ensure LID facilities comply with the NPDES permit's hydraulic sizing requirements for stormwater treatment facilities and flow-control facilities. The municipal permit requires all Priority Development Projects to implement treatment control facilities. The technical background follows. Most runoff is produced by frequent storms of smaU or moderate intensity and duration. Treatment facilities are designed to treat smaller storms and the first flush of larger storms— approximately 80% of average annual runoff The NPDES permit identifies two types of treatment facilities—^volume-based and flow-based. Volume-based faciiities must be designed to infiltrate, filter, or treat the volume of runoff produced from a 24-hour 85* percentile storm event as determined from the County of San Diego's 85* Percentile Precipitation Isopluvial Map. As shown on the map, rainfall depths vary from about 0.55" to 1.55". For flow-based facilities, the NPDES permit specifies the rational method be used to determine flow. The rational method uses the equation Q = CiA, where Q = flow C = weighted runoff factor between 0 and 1 i = rainfall intensity A = area The permit identifies two altematives for calctilating rainfall intensity: 1. the 85th percentile rainfall intensity times two, or 2. 0,2 inches per hour. 48 County SUSMP— August 2012 CHAPTER 2: CONCEPTS AND CRITERIA It is typically found that both methods yield similar results. The 0,2 inches per hour rainfall intensity should be used for sizing flow-based treatment facilities within the County's jtirisdiction. The 0.2 inches per horn criterion is the basis for a consistent countywide sizing factor for bioretention facilities when used for stormwater treatment only (i.e., not for flow control). The factor is based on maintaining a minimum percolation rate of 5 inches per hour through the engineered soil mix. The sizing factor is the ratio of the design intensity of rainfall on tributary impervious surfaces (0.2 inches/hour) to the design percolation rate in the facility (5 inches/hour), or 0.04 (dimensionless). • FLOW-CONTROL (HYDROMODIFICATION MANAGEMENT) The NPDES permit specifies for applicable projects: ... post-project runoff flow rates and durations shall not exceed pre-project runofif flow rates and dtirations where the increased discharge flow rates and durations vdll result in increased potential for erosion or other significant adverse impacts to beneficial uses, attributable to changes in flow rates and durations. Refer to Appendix G to review the final Hydromodification Management Plan (HMP) developed by the San Diego Copermittees and approved by the RWQCB in July 2010, A simimary of the HMP doctiment is provided in Chapter 1 of this document. The NPDES permit restricts the design and location of "infiltration devices" that, as designed, may bypass filtration through surface soils before reaching groundwater. These devices include: • Infiltration basins. • Infiltration trenches (includes French drains), • Unlined retention basins (i.e., basins with no outiets). • Unlined or open-bottomed vaults or boxes installed below grade (dry wells). Infiltration devices may not be used in: • Areas of industrial or Ught industrial activity; areas subject to high vehicular traffic (25,000 or greater average daUy traffic on main roadway or 15,000 or more average daily traffic on any intersecting roadway); 1 ^ 49 County SUSMP—August 2012 t JONES, CAHL & ASSOCIATES cmsmnm CLIENT PROJECT oei^ ^Um^ CALOUIATIONS FOR ^B^TIO^OI^ JOB NO. is> mm SHEET OF _ D«nE_ MADE BY. CHECKED BY w l/: 4. i£mtw^j$*^f^ pGpTif4 * 0 JONES, CAHL & ASSOCIATiS C0NSUU1NS CLIENT . j4bet4^ BMICJC^ PRaigcT 9^B4 PA^^ CALCULATIONS FOFt C^£^710^K>&. JOB NO. _ SHEET OF _ MACE BY DKTE. OHEOCED BY DATE. JONES, CAHL & ASSOCIATES camumm ENGINEERS CUENT nut>tTf^ tj^w^f'^ JOB NO. l3' 'ZOSl PRn-iFCT f^^^} pec AJ&mm SHEET OF _ HAI ran ATIONS FOR S^^fi^J^'h MADE BY DATE. ^ . CHECKED BY DATE . /I 4.0 Drainage Study Report Summary The average annual rainfall for the City of Carisbad area Is about 10.70 Inches. In both the existing condition and the proposed condition there are multiple stormwater outlet points from the site. The table below sums the discharges from the mulfiple outlet locafions into one value for each storm period. This site was analyzed for the 2-Year, 10-Year and 50-Year and 100-Year Storm event per San Dlego County Hydrology Manual (Section 3.1- Rafional Method). Q = CxlxA C = 0.90 (%imp) + Cp (1 - %imp) Cp = 0.80 (General Commercial) I = 7.44 X Pe X D-°^^^ (In/hr) A = Area (Ac) (Section 3.1.2) (Table 3-1) (Section 3.1.3) Exisfing Proposed Conditions Condifions 2-Year Storm 1.11 cfs 1.11 cfs 10-Year Storm 1.62 cfs 1.62 cfs 50-Year Storm 2.03 cfs 2.03 cfs 100-Year Storm 2.43 cfs 2.43 cfs The following table breaks down the site by the region ofthe oufiet locafion to compare existing conditions and proposed condifions by acreage and 100-year storm fiows. Direction of drainage flow Existing Condifions Area (acres) Existing Conditions Qioo (cfs) Proposed Condifions Area (acres) Proposed Conditions Qioo (cfs) North 0.073 0.154 0.073 0.154 South 0.339 0.707 0.339 0.707 The outlet locafions have equal flow from the existing condition to the proposed condition. The unchanged flow corresponds to the minimal change In runoff coefficient because of a slight Increase of pervious area. 23 I P a g e 5.0 Source Control Measures The Stormwater Pollutant Sources and Source Control Checklist (Appendix 1 of City of Carisbad SUSMP-March 24, 2010) was used to develop the following Table 3-1 including only applicable Source Controls. Table 3-1 Source Control BMPs Permanent and Operational. Potential source of runoff pollutants Permanent source control BMPs Operational source control BMPs On-site storm drain inlets BMP-4 see section 3.0 Maintain and periodically repaint or replace inlet marking. Provide stormwater pollution prevention information to new site owners, lessees, or operators. See Fact Sheet SC-44, "Drainage System Maintenance" in the CASQA Handbook. Include the following in lease agreements: "Tenant shall not allow anyone to discharge anything to storm drains or to store or deposit materials so as to create a potential discharge to storm drains." Interior floor drains and sump pumps Interior floor drains and sump pumps will be plumbed to sanitary sewer. Inspect and maintain drains to prevent blockages and overflow. Need for future indoor & structural pest control Note building design features that discourage entry of pests. Provide Integrated Pest Management information to owners, lessees, and operators. Landscape/Outdoor Pesticide Use Final Landscape plans will preserve existing native trees, shrubs, and ground cover to the maximum extent possible. Final Landscape plans are designed to minimize irrigation and runoff, to promote surface infiltration where appropriate, and to minimize the use of fertilizers and pesticides that can contribute to stormwater pollution. Maintain landscaping using minimum or no pesticides. See Fact Sheet SC- 41,"Building and Grounds Maintenance," in the CASQA Handbook. Provide IPM information to new owners, lessees, and operators. 24 I Page Potential source of runoff pollutants Permanent source control BMPs Operational source control BMPs Final Landscape plan specifies plants that are tolerant of saturated soil conditions where landscaped areas are being used to retain or detain stormwater. Landscape/Outdoor Pesticide Use (cont) Final Landscape plans select plants appropriate to site soils, slopes, climate, sun, wind, rain, land use, air movement, ecological consistency, and plant interaction to insure successful establishment of plants. Refuse areas State how site refuse will be handles and provide supporting detail to what is shown on plans. Provide adequate number of receptacles. Keep receptacles covered. Prohibit/prevent dumping of liquid or hazardous wastes. Signs will be posted on or near dumpsters with the words "Do no dump hazardous materials here" Inspect receptacles regularly; repair or replace leaky receptacles. Inspect and pick up litter daily and clean up spills immediately. Keep spill control materials available on-site. See Fact Sheet SC-34, "Waste Handling and Disposal" in CASQA Handbook Fire Sprinkler Test Water Provide a means to drain fire sprinkler test water to the sanitary sewer. See Factsheet SC-41, "Building and Grounds Maintenance," in CASQA Handbook. Miscellaneous drain or wash water: Roofing, gutters, and trim. Avoid roofing, gutters, and trim made of copper or other unprotected metals that may leach into runoff. Plazas, sidewalks, and parking lots. Plazas, sidewalks, and parking lots shall be swept regulady to prevent the accumulation of litter and debris. Debris from pressure washing shall be collected to prevent entry into the storm drain system. Washwater containing any cleaning agent or degreaser shall be collected and discharged to the sanitary sewer and not discharged to the storm drain. 25 I P a g e 6.0 BMP Facility Maintenance Requirements A. Maintenance of Best Management Practices in perpetuity • The owner of the Hohen Buick Cadillac project and the future management company of the property shall be responsible for the operation and maintenance of all LID, Source Control and Treatment Control BMPs In this Stormwater Management Plan. • Trash receptacles shall be empfied a minimum biweekly, unless site condifions require more frequent maintenance. Exact frequency will be determined by site maintenance personnel via trial and error. • Landscaped areas shall be maintained by mowing, pruning and hedging as needed to prevent vector infestafion and to prevent fire hazards. Prior to mowing, all trash and debris shall be removed and disposed of appropriately. • The owner shall contract with the landscape maintenance crew to ensure the plants and sprinklers are checked when they maintain the site. Any dead plants shall be replaced by the next scheduled maintenance date. Any broken sprinkler heads or lines shall be repaired within 24 hours of discovering the broken part. The owner shall also convey to the landscape maintenance crew that pesficides and fertilizers shall only be applied when absolutely necessary, and caufion shall be taken to prevent the chemicals from entering the storm drain system. • All catch basins located within the project site shall be cleaned prior to October Istof each year to remove any debris that may have entered it during the non- rainy season. The catch basin shall be cleaned at minimum once a month during the rainy season. Refer to Tab E for Proprietary Manufacturer's Maintenance Procedures. The parking lot areas shall be swept by a street sweeping service at minimum weekly to prevent trash and other debris from entering the storm drain system. • Bioretenfion Facilities: The primary maintenance requirement for bioretenfion 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 landscape areas. Plants that are appropriate for the site, climafic, and watering conditions shall be selected for use in the bioretention cell. Appropriately selected plants will aide in reducing fertilizer, pesficide, water, and overall maintenance requirements. (Refer to Tab F for references on CASQA TC- 32 for bioretention area maintenance.) 26 I P a g e Typical costs of a bioretention area may vary from $3 to $4 per square foot depending upon soil conditions and types of plants used. Annual costs for maintaining bioretention areas are comparable to those of typical landscaping required for a site. Costs beyond the normal landscaping fees will Include the cost for tesfing the soils and may Include costs for a sand bed and planfing soil. The property owner shall provide employee training for maintenance work. Emphasis shall be placed on subjects related to Source Control Best Management Practices, Good Housekeeping Measures, and Spill Prevenfion and Clean Up procedures. Employees shall be trained on the appropriate disposal of liquid and solid wastes, including appropriate recycling of these materials whenever applicable. Information has been included for food service, and other similar fields. The property owner may supplement the informafion with additional informafion as it applies to the activifies proposed for the site. 27 I P a g e CITY CARLSBAD O F STORM WATER STANDARDS QUESTIONNAIRE E-34 Development Services Land Development Engineering 1635 Faraday Avenue 760-602-2750 www.carlsbadca.gov ,<V;^Ai.:, 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 www.carlsbadca.qov/standards. Initially this questionnaire must be completed by the applicant in advance of submitting for a development application (subdivision, discretionary permits and/or construction permits). The results of the questionnaire determine 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 Stonnwater 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 storm 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 determining 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 completed 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 construction permits for the project. Ptease start by completing Step 1 and follow tiie instructions. Wtien compteted, sign ttie fonv at the end and submit this with your application to the city. i—i 1-^ ' ^ •••• •:. - A: To determine if your project is a priority development project, please answer the following questions: YES NO 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? X Is your project LIMITED TO retrofitting or redeveloping existing paved alleys, streets, or roads that are designed and constructed in accordance with the USEPA Green Streets guidance? X If you answered "yes" to one or more ofthe 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 information. If you answered "no" to both questions, then go to Step 2. E-34 Page 1 of 3 Effective 6/27/13 CITY OF STORM WATER Development Services Land Development Engineering CITY OF STANDARDS Development Services Land Development Engineering CITY OF QUESTIONNAIRE E-34 1635 FaradayAvenue 760-602-2750 CARLSBAD QUESTIONNAIRE E-34 www.carlsbadca.gov 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. X 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 pmjects on public or private land. X 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. X 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 percent or greater X 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. X 6. 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 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. X 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 overland 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 fmm the pmject to the ESA (i.e. not commingles with flows fmm adjacent lands).* X 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. X 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 pmject Average Daily Traffic (ADT) of 100 or mom vehicles per day. X 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? X 11.1s 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%? X 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 Storm 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 thie end of tliis 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 Storm 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 Development Services Land Development Engineering STANDARDS Development Services Land Development Engineering ^ CITY OF CARLSBAD QUESTIONNAIRE 1635 FaradayAvenue ^ CITY OF CARLSBAD E-34 760-602-2750 www.carlsbadca.gov STEP 3 TO BE COIVIPLETEO FOR REDEVELOPMENT PROJECTS THAT ARE PRIORITY DEVELOPEMENT PROJECTS ONLY Complete the questions below regarding your redevelopment project: YES NO Does the redevelopment project result in the creation or replacement of impervious surface in an amount of less than 50% of the surface area of the previously existing development? If you answered "yes," the structural BMP's required for Priority Development Projects apply only to the 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. STEP 4 CHECK THE APPROPRIATE BOX AND COMPLETE APPUCANT INFORMATION Q My projecl 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: 5334 Paseo Del Norte Accessor's Parcel Number(s): 211-060-02 Applicant Name: Applicant Signature: Applicant Title: Date: This Box for City Use Only City Concurrence: YES NO City Concurrence: By: Date: Project ID: * Environmentally Sensitive Areas include but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special Biological Significance by the State Water Resources Control Board (Water Quality Control Plan for the San Diego Basin (1994) and amendments); water bodies designated with the F?ARE 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 STORM WATER Development Services MANAGEMENT PLAN (SWMP) Land Development Engineering ^ CITY OF REQUIREMENTS CHECKLIST 1635 FaradayAvenue PARI ^RAD ^-35 760 602 2750 *JU#\L^ www.carlsbadca.gov Storm Water Management Plan • 1. Project Setting • A. Project Name, Location, Description, Vicinity Map • B. Existing site features and conditions • C. Proposed land use and anticipated activities that would affect stormwater • D. Opportunities and constraints for stormwater control and treatment • E. Nearby water bodies, existing storm drain systems • II. Applicable Stormwater Standards • A. Completed Storm Water Standards Questionnaire (SWSQ) • B. HMP Applicability Determination using expanded narrative from SUSMP • 1) HMP exemption, if any, with backup justification • 111. Identify Pollutants-of-Concern • A. Identify pollutants associated with type of project/use • B. Identify watershed and hydrologic unit basin number and receiving waters project contributes to • C. List Impaired water bodies per 303d listing (latest) that project contributes to • D. Beneflcial uses of receiving water • E. Summarize primary pollutants-of-concern • IV. Source Control Measures • A. Description of site activities and potential sources of pollutants • B. Complete table showing sources, permanent source controls, and operational source controls • v. Low Impact Development (LID) Design Strategies, see section 4 of SUSMP • A. Optimization of site layout 1) Limitation of development envelope 2) Preservation of natural drainage features 3) Setbacks of creeks, wetlands, and riparian habitats 4) Minimization of imperviousness 5) Using drainage as design element • B. Layout and use of permeable pavements or other pervious surfaces • 0. Dispersal of runoff from Impervious areas to pervious areas • VI. Integrated Management Practices (IMP's), if applicable (not required if choosing TCBMP and/or hydromodification sizing approach below) • A. Selection process for IMP'S targeting pollutants-of-concern for project. • B. Sizing factors for IMP's • 1) Lower flow threshold determination a) SCCWRP analysis. If chosen • 2) HMP Decision Matrix • 0. Geotechnical recommendation on soil Infiltration rates (if IMP facilities to drain through native soil) • D. Infiltration calculations (drawdown time) for any self-retaining areas serving as an IMP • Vll. Treatment Control BMP's (TCBMP's), if applicable (not required If choosing IMP sizing approach) • A. Selection process for TCBMP's to target the pollutants-of-concern for your project. Use TCBMP's that are the most efficient at removing the target pollutants. Consider treatment trains. Include narrative on selection criteria for each available TCBMP for this project and why the other TCBMP's were not chosen • B. Sizing factors for TCBMP's using LID procedure, or describe numeric sizing criteria approach (flow-based or volume based) • C. Geotechnical recommendation on soil Infiltration rates (If TCBMP facilities to drain through native soil) E-35 Page lof 3 1/14/11 /^^f^ STORM WATER Development Services MANAGEMENT PLAN (SWMP) Land Development Engineering ^ CITY OF REQUIREMENTS CHECKLIST 1635 FaradayAvenue CARI ^RAD ^-35 760 602 2750 »l—*JiJ/\t-^ www.carlsbadca.gov • Vlll. Hydromodification, if applicable (not required if choosing IMP sizing approach) • A. Lower flow threshold determination • 1) SCCWRP analysis, if chosen • 2) HMP Decision Matrix • B. Continuous simulation model, subject to city approval (see final HMP for analysis guidelines), or • C. Print-outs of pond sizing criteria and results using BMP sizing calculator • D. Tabulation of Flow-control facility sizes and design criteria • IX. Documentation of Stormwater Water Design (for IMP or TCBMP approach) • A. Hydrology maps showing tributary areas to each TCBMP or DMA's to IMP's • B. Print-outs from BMP sizing calculator, if used • C. Tabulation (depending on applicable stormwater standards) • 1) Drainage Management Areas (DMA's) • 2) Tabulation of DMA areas (SF) • 3) DMA descriptions (e.g.: pavement, roof, self-treating, etc) • 4) Listing all IMP, TCBMP's, or flow control facilities serving each DMA • 5) Sizing Calculations • X. BMP Facility Maintenance Requirements • A. Describe ownership and responsibility of maintenance of BMP's in perpetuity 1) Describe commitments to execute any necessary agreements 2) Statement accepting responslblllty for operation and maintenance of facilities until that responsibility Is formally transferred • B. Summary of maintenance requirements for each stormwater facility • XI. SWMP Certification Statements • A. Preparer's statement • B. Owner's statement Attachments: Copy of completed Storm Water Standards Questionnaire (SWSQ) Single sheet post-construction BMP exhibit DMA/IMP sizing exhibit (for integrated LID-IMP approach) DMA/TCBMP sizing exhibit (for altemative to LID approach) Proprietary BMP product Infonnation and independent 3^" party studies on pollutant removal efficiency E-35 Page 2 of 3 1/14/11 ^^hf^ STORM WATER Development Services MANAGEMENT PLAN (SWMP) Land Oev^lonment EnpineerinP ^ CITY OF REQUIREMENTS CHECKLIST CARLSBAD '^^'^^^'^'^^'^^ ^'-^1^^^'^^^ Land Development Engineering 1635 Faraday Avenue 760-602-2750 www.carlsbadca.gov Single sheet Post-Construction BMP Exhibit Requirements • Use City standard single sheet post-construction BMP template (see city website) • Show entire property included on one map (use key map if multi-sheets) • Show drainage areas/direction of flows • Show property lines and streets/driveways • Show and callout private and public stonn drain systems • Show nearby water bodies or natural channels • Show location of all inlets and outlets of storm drain system • Show and callout location of proposed post construction stormwater controls and BMP's, Including detention basins • Show locations of Impervious and pervious areas (use distinguishable symbols) • Show location where materials would be exposed to stormwater • Show areas of potential erosion • Show location of building and activity areas (e.g. fueling Islands, garages, waste container area, wash racks, hazardous material storage areas, etc.) • Show and callout all site design and Source Control BMP's, (e.g. disconnecting runoff, stenciling of Inlets, trash storage areas, material storage areas, efficient irrigation/landscape design, etc.) • Show all TCBMP's, IMP, or flow-control facilities detailed and called out on the plan sheet • Delineated areas draining to each TCBMP, IMP, or flow-control facility • Signature Block for City Engineer • Inspection Signature Blocks for Building, Landscape and Engineering Inspectors E-35 Page 3 of 3 1/14/11 VICINITY MAP NOT TO SCALE SWMP NO SDP 12-04 CDP 12-26 V 13-02 MAllfTENANCE AGREEMENT DOCUMENT VES_ RECOreXMIOH NO PARTY RESPONSIBLE FOR MAINTENANCE: NAME HOEHN BUICK CADILLAC CONTACT BUI HOEHN ADDRESS 5334 PASCO DEL NORTE PHONE ND PLAN PREPARED BY: NAME DANIEL RUBIO COMPANY JONES CAHL ic ASSOOATES ADOWESS '8090 BEACH BLVD. SUITE 12 HUNTINGTON BEACH. CA 92648 PHONE NO (714) 848-0566 CERTIFICATWN BMP NOTES: 1 THESE BMPS ARE MANDATORY TO BE INSTALIED PER MANUFACTURER'S RECOMMENDATIONS OR THESE PLANS 2 NO CHANGES TO THE PROPOSEO BMPS ON THIS SHEET WITHOl/T PRIOR APPROVAL FROM THE QTY ENGINEER 3 NO SUBSTITUTIONS TO THE MATERIAL OR TYPES OR PLANTING TYPES WTTHOUT PRIOR APPROVAL FROM THE CITY ENGINEER 4 NO OCCUPANCY Wia BE GRANTED UNTIL THE CITY INSPECTION STAFF HAS INSPECTED THIS PROJECT FOR APPROPRIATE BMP CONSTRUCTION ANO INSTALLATION OWNER- LEQEND EXISTING CONTOURS EXISTING ELEVATIONS PROPERTY LINE EASMENT LINE CHAIN LINK FENCE SEWER LINE WATER LINE GAS LINE BUILOING LANDSCAPING PERVIOUS PAVERS ASPHALTIC CONCRETE ABOVE GROUND BUILDING BOTTOM OE STEP BACK OE SIDEWALK CENTERLINE CHAIN UNK FENCE BUILDING COLUMN SURVEY CONTRa POINT FINISHED EL OOR EIRE HYDRANT ELOW LINE FINISHED SURFACE GAS METER LANDSCAPE AREA LIGHT NATURAL GRADE STRUCTURE OVERHANG SEWER MANHOLE SIDEWALK TOP OE CURB TCP OF STEP TOP OF WALL WA TER METER WATER VALVE HOEHN BUICK CADILLAC 5475 CAR COUNTRY DRIVE CARLSBAD. CA 92018 CONTACT: MR. BILL HOEHN CITY OF CARLSBAD ENGINEERING DEPARTMENT BkIP SrrE PLAN SDP 12-04 CDP 12-26 V 13-02 HOEHN BUICK CADILLAC 5334 PASEO DEL NORTE APPROVED GLEN K. VAN PESKI SEMWR OW. ENGINEER PC 41204 EXPRES 3/31/" DATE DWN BY: . CHKD BY: RVWD BY: PROJECT NO. CHAPTER 4: LID DESIGN GUiDE • CRITERIA Impenrioiis roadways, driveways, and parking lots account for much of tlie hj^drologic impact of land development. Li contrast, pervious pavements allow rainfall to collect in a gravel or sand base course and infiltrate iato native soil. Pervious pavements are designed to transmit rainfall through the surface to storage in a base course. For example, a 4-inch-deep base course provides approximately 1.6 inches of storage. Runoff stored in tlie base course infiltrates to native soils over time. Except in tlie case of solid pavers, the surface course provides additional storage. Areas with the foEowing pervious pavements may be regarded as "self-treating" and require no additional treatment or flow control if they drain off-site (not to an IMP). • Per~vious concrete • Porous asphalt • Cmshed aggregate gravel) • Open pavers witli grass or plantings • Open pavers witli gravel • Artificial turf Areas with these pervious pavements can also be seM-retaining areas and may receive runoff from impervious areas if they are bermed or depressed to retain the first one inch of rainfall, including runoff from the tributary impervious area. Solid unit pavers—such as bricks, stone blocks, or precast concrete shapes—^are considered to reduce iiuioff compared to impervious pavement, when the unit pavers are set in sand or gravel with d" gaps between the pavers. Joints must be filled with an open-graded a^regate free of fines. Best Uses • Areas with permeable native soils • Low-traffic areas • Where aestlietic quality can justify liigher cost Advantages • Variety of surface treatments can complement landscape design Limitations • Initial cost • Placement requires specially trained crews • Geotechnical concems, especially in clay soils • Concerns about pavement strengtii and surface integrity • Some municipalities do not allow in public right of way CHAPTER 4: LID DESIGN GUIDE When draining pervious pavements to an IMP, use the runoff factors in Table 4-2. • DETAILS Permeable pavements can be used in clay soils; however, special design considerations, including an increased depth of base course, typically apply and will increase the cost of this option. Geotechnical fabric between the base course and underlying clay soil is recommended. Pavement strength and durability typically determines the required depth of base course. If underdrains are used, the outlet elevation must be a minimum of 3 inches above the bottom elevation of the base course. Pervious concrete and porous asphalt must be installed by crews with special training and tools. Industry associations maintain lists of qualified contractors. Parking lots with crushed aggregate or unit pavers may require signs or bollards to organize parking. • DESIGN CHECKLIST POR PERVIOUS PAVEMENTS n No credible areas drain on to pavement. n Subgrade is uniform. Compaction is minimal. n Reservoir base course is of open-graded crushed stone. Base depth is adequate to retain rainfall and support design loads. O If a subdrain is provided, outlet elevation is a minimum of 3 inches above bottom of base comse. • Subgrade is uniform and slopes are not so steep that subgrade is prone to erosion. • Rigid edge is provided to retain granular pavements and unit pavers. • Solid unit pavers are installed with open gaps filled with open-graded a^regate free of fines. n Permeable pavements arc installed by industry-certified professionals according to vendor's recommendations. n Selection and location of pavements incorporates Americans with Disabilities Act requirements, site aesthetics, and uses. Resources • Soudiem Califomia Concrete Producers www.concreteresourcesjiet • California Asphalt Pavement Association lasssMm^ falifomi«p»vyiTimtii og/jt9iiBVirt«,htiiil • latedoddog Concrete Pavement Institute • Start at the Source Des^ Manualftr Water Quality Protection, j^. 47-53. www.basindj^a • Porous Pavements, by Bmce K. Ferguson. 2005. ISBN 0-8493-2670-2. 110 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE Bioretention Faciiities 18* mm. cwKl/con^xist ink Ckmt 2 pani, 12* duplli \yp. and pnimotod pfto Use suing kKka K> dBtiamna mninnini aaa Biof etetition SKibty configured for tteatment-onhr lequiiements. Bmetcntion £acilities can lectstngulai, Itneai, or neadv any shs^pc. Bioretention detains nmoff in a smface reseivoii, filters it tiirough plant roots and a biologically active soil mix, and tlien infiltrates it into tlie ground. Wliere native soils are less permeable, an imderdrain conveys treated rimoff to storm drain or surface drainage. Bioretention facilities can be configiued in nearly any shape. \Xlieii coiifignred as linear swales, tliey can convey liigli flows wliile percolating and treating lower flows. Bioretention facilities can be configured as in-gromid or above- ground planter boxes, witli die bottom open to allow infiltration to native soils imderneath. If infiltration cannot be allowed, use die sizing factors and criteria for die Flow-Tluougli Planter. • CRITERIA For development projects subject only to nmoff treatment requirements, die following criteria apply: Best Uses • Commercial areas • Residential subdi\'isioiis • Industrial developments • Roadways • Parking lots • Fit in setbacks, medians, and odier landscaped areas Advantages • Can be any shape • Low maintenance • Can be landscaped Limitations • Require 4% of tributary impeivious square footage • Typically requires 3-4 feet of head • Irrigadoii typically required Parameter Soil mix depth Soil mix minimum percolation rate Soil mix surface area Criterion 18 inches minimum 5 inches per hour minimum sustained (10 inches per hour initial rate recommended) 0.04 times tributary impervious area (or equivalent) 111 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE Parameter Surface reservoir deptii Underdrain Criterion 6 inches minimum; may be sloped to 4 inches where adjoiaing walk^s^ays. Required in Group "C" and "D" soils. Perforated pipe embedded in gravel ("Class 2 permeable" recommended), connected to storm drain or odier accepted discharge point. • DETAILS Plan. On tiie siuface, a bioretention facility should be one level, shallow basin—or a series of basins. As runoff enters each basin, it should flood and fiU tiiroughout before ninoff overflows to die ouflet or to the next downstream basin. This will help prevent movement of surface mulch and soil mix. Use chedt dau» Inear bkH£t«itkm fildlifies (sodes) oaa slope. In a linear swale, check dams should be placed so that the lip of each dam is at least as high as the toe of fhe next upstream dam. A similar principle applies to bioretention facilities built as terraced roadway shoulders. Inlets. Paved areas draining to the facility should be graded, and inlets should be placed, so that nmoff remains as sheet flow or as dispersed as possible. Curb cuts should be wide (12" is recommended) to avoid clogging with leaves or debris. Allow for a minimum reveal of 4"-6" between the inlet and soil mix elevations to ensure turf or niulcli buildup does not block the inlet In addition, place an apron of stone or concrete, a foot square or larger, inside each inlet to prevent vegetation from growing up and blocking tlie inlet 112 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUiDE Wliere ranoff is collected in pipes or gutters and conveyed to the facility, protect tlie landscaping from high-velocity flows ^litli energy-dissipating rocks, hi larger installations, provide cobble- lined channels to better distribute flows tiiroughout flie fadlity. Uptumed pipe ouflets can be used to dissipate energy when ninoff is piped from roofs and upgradient paved areas. Soil mix. The required soil mix is similar to a loamy sand. It must maintain a minimum percolation rate of 5" per hour throughout flie life of flie facility, and it must be suitable for maintaining plant life. Typically, on-site soils will not be suitable due to clay content. storage and drainage layer. "Class 2 permeable," Caltrans specification 68-1.025, is recommended. Open-graded criished rock, washed, may be used, but requires 4"-6" washed pea gravel be substituted at flie top of the cmshed rock gravel layers. Do not use filter ^bric to separate flie soil mix from the gravel drainage layer or flie gravel drainage layer from die native soil. Underdrains. No imderdrain is required where native soils beneath tiie facility are Hydrologic Soil Group A or B. For treatment-only facilities where native soils are Group C or D, a 113 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE perforated pipe must be bedded in flie gravel layer and must tenninate at a storm drain or other approved discharge point Outlets. In treatment-only facilities, ouflets must be set liigh enougli to ensure the surface reservoir fills and flie entire siuface area of soil mix is flooded before the oudet eWation is reached. In swales, tiiis can be achieved wifli appropriately placed check dams. The ouflet should be designed to exclude floating mulch and debris. Vaults, utility boxes and light standards. It is best to locate utilities outside tiie bioretention facility—^in adjacent walkways or in a separate area set aside for fliis purpose. If utility stractures are to be placed within die facility, the locations should be anticipated and adjustments made to ensme the mimmum bioretention siuface area and volumes are acliieved. Leaving the final locations to each individual utility can produce a haphazard, unaestiietic appearance and make the bioretention fadlity more difficult to maintain. Emergency overflow. Tlie site grading plan should antidpate extreme events and potential clogging of flie overflow and route emergency overflows safely. Trees. Bioretention areas can accommodate small or large trees. Tiiere is no need to subtract the area taken up by roots fi:om the effective area of the fadlity. Extensive tree roots maintain soil permeability and help retain riinoff. Normal maintenance of a bioretention facility should not affect tree lifespan. Tlie bioretention facility can be integrated with a tree pit of flie required depth and filled witii stmctural soil. If a root barrier is used, it can be located to allow tree roots to spread throughout flie bioretention facility while protecting adjacent pavement. Locations and planting elevations should be selected to avoid blocking flie facility's inlets and outiets. ROOT BARRIER ts— STRUCTURAL SOIL KcdX!tenlkin 6ic3itf condoled as st tixe well The loot bamer is optional 114 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE • APPLICATIONS Multi-purpose landscaped areas. Bioretention facilities are easily adapted to seiv^e multiple purposes. The loamy sand soil mix will suppoit tiuf or a plant palette suitable to the location and a well-drained soil. Example landscape treatments: • Lawn wifli sloped transition to adjacent landscaping. • Swale in setback area • Swale in parking median • Lawn with hardscaped edge treatment • Decorative garden with formal or informal plantings • Traffic island with low-maintenance landscaping • Raised planter wifli seating • Bioretention on a terraced slope • 1 ^- ..V ....... Koietniticm &c3ity cco^iiffid as a iiK£s«x{ deixxaticE BkxetefdK» &did^ cx>n%ui)ed and planted as a kym/ 115 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE Residential subdivisions. Some subdivisions are designed to drain roofs and driveways to the streets (in fhe conventional manner) and then drain the streets to bioretention areas, with one bioretention area for each 1 to 6 lots, depending on subdivision layout and topography. If allowed by the local jurisdiction, bioretention areas can be placed on a separate, dedicated parcel with joint ownership. Bkxelnilicm &dldy lecenii^ doini^ finm iiidnidaal lots aod the stieet in a lesidenbal subdiviskxi- Sloped sites. Bioretention facilities must be constracted as a basin, or series of basins, with the circumference of each basin set level. It may be necessary to add curbs or low retaining walls. •JNOfF TO PlAHmi <•»- nMONC- (MQIfUW ouncT- BkaetmtxiD &c3i^ coafiguiBd as a poddog inedtaa Note use of boOaids in pface of cud», dnnmatn^ the oeed fi» cud} cuts. 116 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE Residential subdivisions. Some subdrdsions are designed to drain roofs and driveways to flie streets (in the conventional manner) and flien drain the streets to bioretention areas, with one bioretention area for each 1 to 6 lots, depending on subdivision layout and topography. If allowed by the local jurisdiction, bioretention areas can be placed on a separate, dedicated parcel wifli joint ownersliip. Bk^Ktenfkia&dlit^ieceivingdiain^ &t»n iodividud and the stieet in atesirtcnhal subdivisitML Sloped sites. Bioretention facilities must be constracted as a basin, or series of basins, with the circmnference of eadi basin set level. It may be necessary to add curbs or low retaining walls. O^BmjM OUtlET- Bionstention &cili^ Goofigu^ as a paddiig mediaa NotE use of bdlaids in place of a)d», ^minating the need foi cud> cuts. 116 County SUSMP— August »)12 CHAPTER 4: LID DESIGN GUIDE Design Checklist for Bioretention O Volume or depth of surface reservoir meets or exceeds minimxjm. O 18" deptii "loamy sand" soil mix with minimuni long-term percolation rate of 5"/hour. O Area of soil mix meets or exceeds minimum. O Perforated pipe underdrain bedded in "Class 2 perm" with connection and sufi&cient head to storm drain or discharge point (except in "A" or "B" soils). O No filter febric. • Underdrain has a clean-out port consisting of a vertical, rigid, non-perforated PVC pipe, with a minimum diameter of 6 inches and a watertight cap. n Location and footprint of facility are shown on site plan and landscaping plan. O Bioretention area is designed as a basin (level edges) or a series of basins, and grading plan is consistent ^t^ith these elevations. If facility is designed as a swale, check dams are set so the lip of each dam is at least as high as the toe of the next upstream dam. O Inlets are 12" wide, have 4"-6" reveal and an apron or otiier provision to prevent blockage when vegetation grows in, and energy dissipation as needed. O Overflow connected to a downstream storm drain or approved discharge point. • Emergency spillage will be safely conveyed overland. O Plantings are suitable to the dimate and a weU-drained soil. O Irrigation system with comiection to water supply. D Vaults, utility boxes, and light standards are located outside the niinimtim soil mix surface area. O ^Taen excavating, avoid smearing of the soils on bottom and side slopes. Minimize compaction of native soils and "rip" soils if clayey and/or compacted. Protect the area from construction site runoff. 117 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE mmnx. EMEKGOtCy SMLLWAV TOt> CO' 8ASM PLAN VIEW NOT 10 SCALE TOP OF wsm FOREWV/OiWWUT CLASS z pam. PERFORATED HPC (UfKKRORA»l} e Vi STORAGE (MOTE 2) SECTION -18' aPEoreD NOTE SURFACE AREA LIMIT DCTHMNEB Bf tXTOtt SPEaFK!) PtANTINe MIX, WHICH IS ooveoNO ei* TOE OWLET sm. aevsAttoN. fm (mmm SUWACE AREA REFER TO TW FACTORS AND EQUATIONS IN THE STO»a««iATER CS CUDEBOOK. \^ STORAGE ACCtMPUSHEO WITH INFILTRATION ARCHES. PERFORATED PIPES, CtASS 2 PERM OR 0T»«(( AT TNE OESKMERS OiSCRmOi, Bioretention Facility 118 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE FLANGE * OMflCE pure OWNECTION (SEE NOTE 1) CLOSED MESH GRATE (OEN. NOTES 4 WRU 7) PLAN N.T.S, CATCH BASIN SPEOflED S0«. MIX 1 2, -CLOSED UtSH onm (OEN. NOTES 4 THRU fj N,T.S. ORIFICe PUOE: MIN SOUARE OlliKNSIONS 1.0 FT KSATIR THAN PIPE t»A. l«r-DtP GALV««ZED PLATE AFTER HouES HAVE mm mazo NOTE i*MAi( 1. ORIFICE PLATE * FLANGE CONNGCnON TO CONCRCTE SHALL BE Frrreo wrrH 30 Duiic»iierii« HBumm RINC. f4<IN 8" (TTP) cm INFLOW PIPE eu SKEB "^fDIA inCE OAMETER (DBO SIZCO PER DESICN CRfTEMA HOLE (TYP) FLOW C€»rrROL ORIFICE PtATE Bioretention Fadlity Outlet Detail - A 119 County SUSMP— August »)12 CHAPTER 4: LID DESIGN GUIDE This page intentionally left blank. 120 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE How-through Planter i Portlaixl 2004 Stormwate Manual Best Uses • Management of roof ninoff • Next to buildings • Dense luban areas • Wliere infiltration is not desired Advantages • Can be nsed next to stnictures • Versatile • Can be any shape • Low maintenance Limitations • Can be nsed for flow-control only on sites witli "C" and "D" soils • Requires nnderdrain • Requires 3-4 feet of head Flow-tlirongli planters treat and detain nmoff \^-itliout allowing seepage into tlie underlying soil. Tliey can be used next to buildings and on slopes where stability might be affected by adding soil moisture. Flow-tiuough planters topically receive nmoff via downspouts leading from the roofs of adjacent buildings. However, tliey can also be set in- ground and receive sheet flow from adjacent paved areas. Pollutants are removed as nmoff passes tiirough tlie soil layer and is collected in an midedying layer of gravel or drain rock. A perforated-pipe underdrain is typically comiected to a storm drain or other discharge point. An overflow inlet conveys flows wliich exceed the capacity of die planter. • CRITERIA Treatment only. For development projects subject only to nmoff treatment requirements, die following criteria apply: Parameter Soil mix deptii Soil mix minimum percolation rate Criterion 18 inches minimum 5 inches per hour minimum sustained (10 inches per hour initial rate recommended) CHAPTER 4: LID DESIGN GUIDE Parameter Criterion Soil mix surfece area 0.04 times triburary impervious area (or equivalent) Surface reservoir depth 6" minimum; maj' be sloped to 4" where adjoining walkwaj^, Underdrain Typically used. Perforated pipe embedded in gravel ("Class 2 permeable" recommended), comiected to storm drain or otiier accepted discharge point. • DETAILS Configuration. Tlie planter must be level. To avoid standing water in the subsurface layer, set the perforated pipe underdrain and orifice as nearly flush wifli flie planter bottom as possible. Inlets. Protect plantings from high-velocity flows by adding rocks or other energy-dissipating structures at downspouts and oflier inlets. Soil mix. The required soil mix is similar to a loamy sand. It must maintain a minimum percolation rate of 5" per hour tiiroughout die life of the facility, and it must be suitable for maintaining plant life. Typically, on-site soils wiU not be suitable due to clay content. Gravel storage and drainage layer. "Class 2 permeable," Caltrans specification 68-1.025, is recommended. Open-graded crashed rock, washed, may be used, but requires 4"-6" of washed pea gravel be substituted at flie top of flie crashed rock layer. Do not use filter fabric to separate the soil mix from flie gravel drainage layer. Emergency overflow. The planter design and installation should antidpate extreme events and potential clogging of flie over-flow and route emergency overflo\x?s safely. • APPLICATIONS Adjacent to buildings. Flow-through planters may be located adjacent to buildings, where flie planter vegetation can soften the visual effect of tiie building walL A setback with a raised planter box may be appropriate even in some neo-traditional pedestrian-oriented urban streetscapes. At plaza level. Flow-through planters have been successfully incorporated into podium-style developments, with the planters placed on the plaza level and receiving rimoff from the tower roofs above. Runoff from tiie plaza level is typically managed separately by additional flow- flirougli planters or bioretention facilities located at street level. Steep slopes. Flow-dirougli planters provide a means to detain and treat ranoff on slopes that camiot accept infiltration from a bioretention facility. Tlie planter can be built into the slope similar to a retaining wall. Tlie design should consider the need to access flie planter for periodic ^22 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE maintenance. Flows from the planter imderdrain and overflow must be directed in accordance with local requirements. It is sometimes possible to disperse fliese flows to the downgradient liillside. FIov-tiuoA^ plantec cn the plaza kf^ of a podium-st0e devek^KTKnt I^low-tfaoi:^ f^asdiH bult into a billsx5e. I^TtPs fix^ ovei&ra'must be dkected in acccxdaiKe with kx»l cequkei^^ 123 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE Design Checklist for Flow-through Planter n Reservoir depth is 4-6" minimum. • 18" depth "loamy sand" soil mix widi minimum long-term infiltration rate of 5"/hour. O Area of soil mix meets or exceeds minimum. • "Class 2 perm" drainage layer. • No filter fabric. O Perforated pipe underdrain with outlet located flush or nearly flush with planter bottom. Connection with sufficient head to storm drain or discharge point. O Underdrain has a clean-out port consisting of a vertical, rigid, non-perforated PVC pipe, with a minimum diameter of 6 inches and a watertight cap. d Overflow connected to a dowiistream storm drain or approved dischar^ point. O Location and footprint of facility are shown on site plan and landscaping plan. n Planter is set level. d Emergency spillage will be safely conveyed overland. O Plantings are suitable to the climate and a well-drained soil. O Irrigation system with connection to water supply. 124 County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE EMERGENCY CVERFLOW ORATE (SEE FLOW-THROUGH PLAKtER OUTLET CSTTAIL) CONOKTE OR OTI«R STRUCTURAL PLANTER WALL WITH »«TERPRO«TNS pum» otmxr (SEE aO*-THrS)U0H PLANTER OUnjET DETAIL) "te-jv TO AN APPROVED OiSCHARIK TO AN APPROVED LOCATION ONE-WAY eCWNECt»NS NOTES: PERFORATED PfPE- (UNDGRORAIN) MIN aj3PE=0.5!t SECTION ORlFKe DRIU£D MTO >MULT WWi. FORM A t.5' 6R00VE IN COMCRETE AMD PROVIDE A CONTINUOUS WAIERtlGHT CONNECTION. USMG AN APPftWEO SEAUNT aOW-TMROl«H PLANTER »tAU. M SEED TO MEET CCe«P eWTERIA FOR TKEA1MENT AND/OR flCm COWtlWL. MMIMUM SUITACC AI%A OF PLANTER IS 4!V OF TWMirARy IMpmnOUS AMA FOR Tf«EATMENr ONLY t^SICN. FOR aOW COKmOl. AND TREAIMENT, REFER TO tXOm> SIZINO TOOL CRTTERIA. SHAPE Of PLANIER CAN VARY TO MOT PROJECT DESSN RCQUREMEKtS AND LOCATION. OJSS 2 PERMEAH£ MATERUU. DOWNSPOinS/IKIJEr PIPES REQUIRE ENEROY DSSIPATION. USE COUNTY APPROVED ADOItWE MIXTURE FOR WATERPROOFtNO CONCRBTE. PUWtlNeS: SEE CCCWP ISOOMMENDED PWNT UST ANO «OaiN£S. PLAtnCR OESISN MAY I^OURE STRUCTURAL ENCIN^NG IXSIGN. AfEA = W « L (ABOVE). EStCLWeS AREA VAULT Flow-Throu^ Planter Detail 12S County SUSMP— August 2012 CHAPTER 4: LID DESIGN GUIDE SIEEL VAULT FRAWE (NCflt CIRCUIAR ORfflCE OWU£0 INTO GALVANt2!£D STEa mtvc aOSEO MESH eWTE (GEN. NOTES 8 TWW S) VAULT-PLANTtR BOX CONNOTWI PLAN 1. HOr-DIP CALWWKE ENTIRE FRAME ASSEMBLY AFTER FABRICATION AND AFTER HOES HAVE KEN DRILLED, FOR mTERTlGHT CONNECIKW. WSTAU. i" TO 1" THICK X 2' WEie CONTWUOUS 30 OUROIOTS NBOPRO^E CASKET, Aa AROUND VAM.T FRAME. LOCKED. REM0VA8LE CLOSE-MESH GRAT^ SLOPED INSTALUTION OeCHARCE ==f ^ TOAN \ APPROVED LOCATION ORIFICE DRUED INTO VAULT WALL SECTION N.T.S. GENERAL OUTLET DETAIL NOTES: 1. OUTFALL t>m SHAU. BE SSED TO CONVEY DESBN STORM PER CCCWP DESSN OWERIA. 2. SRATE SHALL BE MOUNTED USINC STAINL&SS STEEL HARDWARE AM) PROVIDED WTH HINGED ANO UXSUAE <m eOLTASX ACCESS PAtKLS. 3. GRATE SHALL BE STAINLESS STEEL. ALUMINUM OR STEEL STEa GRATES SHALL % HOT DIP GALIMNIZEO AND MAY BE HOT POWDER PAINItO AFTER GALVANIZING. *. GRATE SHALL BE KSIGNEO SUW THAT TKE DIAGONAL DIMENSION OF EACH OPENING IS SMALLER THAN THE DIAMETER OF TKE OUTLET PIPE, S. STRUCTURAL DESICN Of C»iATE SHALL BE etSlD ON FULL KrDROSTATIC HEAD WITH ZERO l«AO DOWNSTREAM Of GRATE, Flow-Thiottgh Planter Outlet Detail 126 County SUSMP—August 2012 Scheduling EC-1 Description and Purpose Sdiedtiling is the development of a written plan that indudes sequencing of construction activities and the implementation of BMPs such as erosion control and sediment control vN^ile taking locai climate (rainfall, wind, etc.) into consideration. Hie purpose is to reduce the amount and duration of soil exp<>sed to erosion by wind, rain, runoff, and vehicle tracking, and to perform the construction activities and control practices in accordance with the planned schedule. Suitable Applications Proper sequencing of construction activities to reduce erosion potential should be Incorporated into the schedule of every construction project especially during rainy season. Use of other, more costly yet less effective, erosion and sediment control BMPs may often be reduced tiirough proper constniction sequencing. Limitations • Environmental constraints such as nesting season prohibitions reduce the full capabilities of this BMP. Implementation • Avoid rainy periods. Schedule major grading operations during dry months when practical, ^iow enough time before rainfall begins to stabilize the soil with vegetation or physical means or to Install sediment trapping devices. • Plan the project and develop a schedule shomng each phase Categories EC SE TC WE NS WM Erosion Conlrol Sedvnent Conttol Tracddng Control Wind Erosion Corttrol Non-Stormwatsr Management Controi waste Managenrierrt and Materials PoUlion Control Bl Ltgtn&i 0 Primary Obiective Q Secondary Directive Targeted ConsUtuents Sedinwnt NtAieitfs Trash Metals Bacteria OK and Grease Organics Potential Alternatives None CAUKMIMtA «YO*M««Am November 2009 Califomia Stormwater BMP Handbook Cofistruction www.casqa.org 1 of 3 Schadylirig EC-1 of ajristnictlon. Clearly show how the rainy season relates to soil disturbing and re- stabilization activities. lncor|»rate the instruction schedule into the SWPPP. • Include on the ^hediile, details on the rainy season implementation and deployment of: Erosion contnol BMPs - Srftment control BMPs Tracking control BMPs Wind erosion wjntrol BMPs Non-storm wa.ter BMPs Waste management and materials polhition <»ntroI BMft* • Include dates for activities that may require non-stormwater discharges such as dewatering, sawaitting, grinding, drilling, boring, crushing, blasting, painting, hydro-demolition, mortar mixing, pavement cleaning, etc. • Work out the sequencing and timetable for tiie start and completion of eadi item such as site clearing and grabbing, grading, excavation, pawing, foundation pwiring utiliti« installation, etc., to minimize the active constniction area during the rainy season. - Sequence trenching activities so that most open :portions are closed before new trenching begins. I ncor|K(rate staged seed ing and re-vegetation of graded slop^ as work pn^e&s^. - Sch^ule establishment of permanent vegetation during appropriate planting time for specified vegetation. • Non-active areas should be stabiltad m soon as praaical after the ce^tton of soil disturbing acllvilies or one day prior lo the onset of precipilation, • Monitor the weather forecast for rainfall • When rainfall is predicted, adjust the constniction schedule to allow the implementation of soil stabili^tion and sediment treatment controls on all disturb^ areas prior to the onset of rain. • Be prepared year round to deploy erosion control and sediment contro! BMPs. Erosion may be aiused during dry seasons by un-seasonal rainfall, wind, and vehicle tracking. Keep the site stabili^ year round, and retain and maintain rainy season sediment trapping devices in operational condition. • Apply permanent erosion control to areas d^med substantially complete during the project's defined s«ding window. Costs instruction scheduling to rt^lu^ erosion may increase other construction fmU due to reduced economies: of scale In performing site grading. The cost effectiveness of scheduling twjhniques should be compared with the other less effective erosion and sdlimeirtation controls to achieve a mst effective balance. Novembar 2009 Califomia Stomiwator BMP Handbook 2 of 3 CofisfryctSon Schedylliig EC-i Inspection and Naintenance • Verify that work Is progressing in accordance with die schedule. If progress deviates, take <»rr«tive actions. • Amend the schrfule when change; are warranted. • Amend the schedule prior to the rainy season to show uf^ated Informttion on the deployment and Implementation of CMinstniction site BMPs. Rcrferences Stormwater Quality Handbooks Constniction Site fet Management Practice. (BMPs) Manual, State of California Ctepartraent of Transportation (Caltrans), Movemlxr 2<K>O. Stormwater Manapment for Construction Activities Developing Pollution Prevention Plans and Best Management Practice (EPA 832-R-92-005), U.S, Environmental Protection Agency, OMm of Water, i^ptember 1992. Novembar 2009 California Stomiwatw BMP Handboak 3 of 3 street Sweeping and Vacuuming SE-7 Description and Purpose Street sweeping and vacuuming includes use of self-propelled and walk-behind equipment to remove sediment from streets and roadways, and to dean paved surfaces in preparation for final paving. Sweeping and vacuuming prevents sediment from the project site from entering storm drains or receiving waters. Suitable Applications Sweeping and vacuuming are suitable anywhere sediment is tracked from the project site onto public or private paved sti%ets and roads, typically at points of egress. Sweeping and vacuuming are also applicable during preparation of paved surfaces for final paving. Limitations Sweeping and vacuuming may not be effective when sediment is wet or when tracked soil Is caked (caked soil may need to be scraped loose). Implementation • Controlling the number of points where vehicles can leave the site will allow sweeping and vacuuming effbrts to be focus^, and perhaps save money. • Inspect potential sediment tracking locations daily. • Visible sediment tracking should be swept or vacuumed on a daily basis. • Do not use kick brooms or sweeper attachments. These tend to spread the dirt rather than remove it. Categories EC Erosion Control SE Sediment Control Q TC TracMig Control Bl WE Wirtd Erasian Control IM Non^Stonrmator nS Managemmt Control wu Wasto Management and Materials PoiJfon Conlrol L«g«nd: ES MiMry OlijMtiv* B SwBondary ObJ«ctlv« Targeted Constitumts Sedinent Nutrients Trash Metels Bactsfia ai and Grease Orgarucs m BI Potential Alternatives None CAUNMIKU noKMWAna. January 2011 California Stormwater BMP Handbook Construction www.casqa.0r9 lof2 street Sweeping and Vacyuming SE-7 • If not mixed with debris or trash, consider incorporating the removed sediment teck into the project Cosl^ Rental rates for self-prope11«l sweepers vary depending on hopper si?« and duration of rental- Expect rental rates from IsS/hour (3 yd^ hopper) to $88/hour {9 ydi hopper), plus operator ®§ts. Hourly production rates vary with the amount of area to be swept and amount of sediment. Match the hopper she to the area and expect sediment load to minimize time spent dumping. Inspection dnd Maintenance • Inspect BMPs in aca)rdance with General Permit rf«|uir«ments for the associated project type and risk level. It is recommendesdl that at a minimum, BMPs be inspected weeW}^ prior to forecasted rain events, daily during extended rain events, and after the eonehision of rain events. • When actively in use, points of ingr^ and egi«ss must be insp«ted daily. a When tracked or spilled s^liment is observcxi outside the ounslniction limits, it must be removed at least daily. More frequent removal, even continuous removal, may be required in some Jurisdictions. • Be careftil not to sweep up any unknown sutetana or any object that may be potentiaUy ha^rdoiis. • Adjust brooms fr«iuently; maximiK efficient of svroping operations. m After swiping is finish^, properly dispose of swwsper wastes at an approved dumpsite. Heferences stormwater Quality Handbooks - Oonstniction Site Best Management Practi«s (BMPs) Manual, State of Califomia Depart ment of Trttisportition (Caltnns), November 2000. Labor Surcharge and Equipment Rental Rates, State of Qilifornia Department of Transportation (Caltrans), April 1,2002 - March 31,2003. January 2011 California Stormwater BMP Handbook 2 of 2 Sandbag Barrier SE-8 Description and Purpose A sandbag barrier is a series of sand-fiUed bags placed on a level contour to intercept or to divert sheet flows. Sandbag barriers placed on a level contour pond sheet flow ninoff, allowing sediment to settle out. Suitable Applications Sandbag barriers may be suitable: B As a linear sediment control measure: Below the toe of slopes and erodible slopes. As sediment traps at culvert/pipe outlets. Below other small cleared areas. - Along the perimeter of a site. - Down slope of exposed soil areas. Around temporary stockpiles and spoil areas. - Parallel to a roadway to keep sediment off paved areas. - Along streams and channels. • As linear erosion control measure: - Along the face and at grade breaks of exposed and erodible slopes to shorten slope length and spread nmoff as sheet flow. Categories EC SE TC WE NS Erosion Control Sediment Conini Tradung Control Wind Erosion Control Non-Stormwater Managenwnt Control 0 yyj^ Waste Management and Matenals Polluljon Control Legend: Primary Category HI Secondary Category Targeted Constituents Sediment Nutrients Trash Metals Bacteria Oil and Grease Organics 0 Potential Alternatives SE-1 Silt Fenoe SE-5 Fiber Rolls SE-6 Gravel Bag Bemt SE-14 Biofilter Bags < ^IIIIHIMA MltllMM VM* November 2009 Califomia Stormwater BMP Handbook Construction www.casqa.org 1 ore Ima 81 m ^awP wKiF awi^ TWS K li W ^IBP m- wit^ - At the top of slopes to divert runoff away from disturbed slopes. « As check dams across mildly sloped, constniction roads. Limitations • It is neossary to limit the drainage area upstream of the barrier to s acres. • Sandbag, are not intended to be; used as filtration devi«.s. • Easily damaged by instraction ^uipment • Degraded sandbap may rupture when removed, spilling sand. • Sand is e^ily transported by nmoff If bag is damaged or raptured. • Installation can be labor intensive, • Durability of sandbap is somewhat limited and bags may need to be replaad when instaltetion is required for longer than 6 months. When used to detain concentrated flows, maintenance requirements mcrease. • Buriap should not be used for sandbags. Implementation Gemml A sandbag barrier consists of a row of sand-illed Mgs plac«l on a level ointour. When appropriately pla«dl, a sandbag terrier interrepls and slows sheet flow mnoflf, causing temporaiy ponding. Hie temporary ponding aIlo« sdliment to settie, Sand-flHed bags have limited porosity, which is lurther Itmitioi as the fine sand tends to quidkly plug wth s«iiment, limiting or completely blwking the rate of flow through the barrier. If a porous barrier Is d«irdl, consider SE-i, Silt Pence, SE-s, Fiber Rolls, SE-6, Gravel Bag Berms or SE-14, Biofilter Bags. Sandbag barriers also Intemipt the slope length and thereby reduce erosion by reducing the tendency of sh«t flows to concentrate into rivulets which erode rills, and ultimately gullies, into disturbed, sloped soils. Sandbag barriers are similar to gravel bag berms, but less porous. Generally, sandbag barrieira should be used in wnjunrtion with temporaiy soil staWlizatbn controls up slope to provide effective erosion and sediment control. Design and iMyout m Locate sandbag barriers on a level contour. • When used for slope interniption, the following slope/sh^ flow length c^mbtnations apply: - Slope inclination of 4: i (H:V) or flatter: Sandbafi should be placed at a maximum Interval of 20 ft, with the firat row near the sloj^ toe. - Slope inclination between 4:1 and 2:1 (H:V): Sandbags should be placed at a maximum interval of 15 ft. (a closer spacing is more effective), with the fii^t row near the slope toe. Slo^ inclination 2:1 (H: V) or greater: Sandbags should be placed at a ma«imum interval of 10 ft. (a cloi^r spacing is more effective), with the fii^t row near the slope toe. Movember 2009 California Stormwater BMP Handbook 2 of 6 OwstniOlon www.cisqa.org Sandbag Barrier SE*8 • Tunt the ends of the sandbag barrier up slope to prevent ranoff from, going around the barrier, • Allow sufficient space up slope from the baitier to allow ponding, and to provide room for sediment storage. • For installation near the toe of the slope, sand bag barriers should be set tock from the slope toe to facilitate cleaning. Wiem specific site (Mjuditions do not allow for a set-back, the sand bag barrier may be constructed on the toe of the slope. To prevent flows behind the barrier, bapi can be placed perpendicular to a berm to serve as cross barriers. • Drainage area should not exited $ acres. • Stack sandbags at least three bags high. • Butt, ends of bags tightly. • Overlap butt Joints of row beneath with each suci^sive row. • Dm a pyramid approach when stackl ng bags. • In non-traffic areas - Height = 18 in. maximum - Top vridth = 24 in. minimum for thwt or more layer construction - Side slope = 2:1 (H: V) or flatter • In instruction traffic areas - Height ^ 12 in. maximum - Top width = 24 in. minimum for thrre or more layer construction. - Side sloj^ = 2:1 (H:V) or flatter. • Sm typical sandbag barrier installation details at the end of this fact sheet. Matmimhs m SimdSmg Maimimh Sandb^ should be woven polypropylene, polyethylene or i^lyamlde fabric, minimum unit weight of 4 ounc«s/yd*, Mullen burst strength ©coding 300 lb/in« in conformance with the requiremenfe in mm designation D3786, and ultrawolet stability exceeding 70% in cx>nforman«! with the requirements In ASTM designation D-^sg. Use of burlap is not an a<^ptable substitute, as sand can more easily mobilize out of burlap. • Sandbag Bim-: Each sand.-lllcd. bag should have a length of 18 in,, width of 12 in,, thickness of 3 In., and mass of approximately 33 Ibs. Bag dimensions are nominal, and may vary based on locally available materials. Plovemb€r 2009 CalSfomia StormwiCer BMP Handbook 3 of 6 Consmiction www.casqa.org Sandbao Barrier SE-8 • MM Material: Alt sandbag fill materi.al should be non-cohesive. Class 3 (Caltrans Standat^ Specification, Section 25) permeable material free from clay and deleterious material, such as peeled concrete or asphalt.. Costs Empty sandbags ^t $0.25 - $0.75- Average c«t of fill material is $8 per yd*. Additional la^r is required to ill the bap. Pre-filled sandtap are m.ore expnsive at $1.50 - $a.oo per bag. ni.ese coste are based upon vendor research. Inspection and Maintenance • BMPs must h€ inspected in accordance with (general Permit requirements for the a^oclated project ^pe and risk level. It is rewmmended that at a minimum, BM^ be inspect«l weekly, prior to forecasted rain events, daily during extend.ed. rain events, and after the conclusion of rain events. • Sandbags exposed to sunlij^t will need to be replaced every two to three months due to d.egradation ofthe bags. • RiKhape or replace sandbags m needed. • Repair washouts or other damage as n^ed. • Sediment that accumulates behind the BMP should be periodiadly removed in order to maintain BMP effectiveness. Sediment should be removed when the :Sedlment aaumulation reachK one-tfiird of the barrier height • Remove sandbap when no longer needed and recycle sand fill >^enewer possible and properly dispose of bag material. Remove sediment accumulation, and clean, re-grade, and stabilize the area. References Staiidard Specifications for Constniction of Uical Streets and Roads, Califomia Departinent of 'ftansportation (Caltrans), July 2002. Stormwater Qualif' Handbooks - Constmction Site Be^ Management Practices (BMPs) Manual, State of California Department of T^nsportation (Caltrans), Mareh 2003. Erosion and Sediment Control Manual, Oregon Department of Environmental Quality, Febroary 2005. MmmmMr Z&IB Caltfomla Stormwato' BMP Handbook 4 of 6 Construdion www.ctsqa.org O o Hi Q P 8 I » Wt «B IP \ yo* r««ch SDO* ( Set f>«is i) I. Ciis-m btxrm - / f S»f mim *) dl a mm CD o 1. t'mMitmi Ihe l*nflh of eocfi rtssH SQ feat Ihi chunks to bsse «?ltif«|i»n Oieiref the cecch ^se-s anst esscweo 1/2 tt'e htifd af t'^« f.'n«!Sf bofflef. In fi» e«-se SRsSs iht ftoch i«rtf«xce«8 500'. Dlfii^fs*!©^ very w fit fi«§^ ceflS'ftisft.: "SondbSQ: bort;** snoi a mmmiam of 3 609s high. The ef^<l i3( |R« 8o*ft«!' 9hs>s turfjed up stcsst, C^OISS Ijsssiers shoH &« s! rnin 1/2 onij 0 f^fsx «f J/J ihf heiijhj ti« nn-ior Harris?. HI Itl 9 K O Q D 1 S* - tft is 8 9 <B fit b 2 09 I m 3 OP 8 j.EGENp §ift£cri<»( Of rtow 1 A 3 w ""I •I o 9 CROSS amsm mrm. T SECTiOH C-C iTI storm Drain Inlet Protection SE-10 Description and Purpose Storm drain inlet protection consists of a sediment filter or an impoimding area in, around or upstream of a storm drain, drop inlet, or curb inlet. Storm drain inlet protection measures temporarily pond runoff before it enters the storm drain, allowing sediment to settle. Some filter configurations also remove sediment by filtering, but usually the ponding action results in the greatest sediment reduction. Temporary geotextile storm drain inserts attach underneath storm drain grates to capture and filter storm water. Suitable Applications Every storm drain inlet receiving nmoff from unstabilized or otherwise active work areas should be protected. Inlet protection should be used in conjunction with other erosion and sediment controls to prevent sediment-laden stormwater and non-stormwater discharges from entering the storm drain system. Limitations • Drainage area should not exceed i acre. B In general straw bales should not be used as inlet protection. • Requires an adequate area for water to pond without encroaching into portions of the roadway subject to traffic. Categories 0 EC Erosion Control SE Sediment Control TC Tradang Cont[o\ WE Wind Erosion Control Non-Stormwater NS Management Control ^ Waste Management and Matenals Pollubon Control Legend: Primary Category H) Secondary Category Targeted Constituents Sediment Nutrients Trash Metals Bactena Oil and Grease Organk» 0 Potential Alternatives SE-1 Silt Fence SE-5 Fiber Rolls SE-6 Gravel Bag Benn SE-8 Sandbag Bamer SE-14 Biofilter Bags November 2009 Califomia Stormwater BMP Handbook Construction www.casqa.org 1 of 10 storni Drain Inlet Protection SE-lO • Sediment removal may be inadequate to prevent sediment discharge in hi^ flow conditions or if runoff is heavily sediment laden. If high flow conditions are expected, use other onsite sediment trapping tahniques in conj unction with Inlet protection. • Frequent maintenance is required. • Limit drainage area to i acre maximum. For drainage areas larger than i acre, runoff should be routed to a iediment-trapping devii^ designed, for larger flows. See BMPs SE-2, Sediment Basin, and SE-3, Sediment Traps, • Excavated drop inlet sediment trap® a.re appropriate where relatively hea'^ flows are expected, and overflow capabilify is needed. Implementation Geneiml Inlet control measurs presented in this handbook should not be used for inlets draining more than one acre. Runoff from larger disturbed areas should be first routed through SE-2, Sediment Basin or SE-3, Sediment Trap and/or used in coryunction with oAer drainage rontrol, eri^ion control, and Ciment control BMPs to protect the site. Different ty]^ of inlet protection are appropriate for different applications depending on site conditions and the ty|^ of inlet. Alternative methods are available in addition to the methods descriiby /shown herein such as prefabricated inlet insert devices, or gutter protection deviees. Design andiM^oui Identify existing and planned storm drain inlets that have the iwtential to receive sediment- laden surface runoff. Dilermine if slorm drain inlet proieelion is needed and which melhcKl to use, • The key to successful and safe use rtf storm drain inlet prota^tlon devii^ is to know^ where ntnoff that is directed toward the iftlet to be protected vrill pond or be: diverted as a r^ult of Installing the prot«tion device, - Determine the acceptable location and extent of ponding In the vicinity ofthe drain Inlet. I'he aoMptable location and extent of ponding will influence the type and d«ign ofthe storm drain Inlet protection device. - Determine the extent of potential runoff divereion cau;^ by the storm drain inlet protection device. Runoff ponded by inlet prot««*tiott device may flow around the device and towards the next downstr^m inlet. In mme cases, this is aoreptablc; in other ases, serious erosion or downstream property damage can be camai by th«e divereions. The IKJSsibility of ninoff diversions vrill influena whether or not storm drain inlet pirt(^ion is suitable; and, if suitable, the type and design of the devi«. • Hie location and extent of ponding, and the extent of diversion, can usually be controlled through appropriate plawment of the Inlet protection device. In some cas«, moving the inlet protection device a short distant upst ream of the actual inlet am provide more efficient Ciment mntrol, limit landing to desired areas, and prevent or i»ntrol diversions. Mcwember 2009 California Stormwater BMP Hamdbo&k 2 of lO Coo^ractSofi storni Drain Inlet Protection SE^IO • Sk types of Inlet protection are pr«ented beiow. However, it is rerognized that other effective methods and proprietery devias exist and may be selected, - Silt Wmmt Appropriate for drainage basins with less than a 5% slope, sheet flows, and flows under o,g cfs. - Excavate Drop Inlet S^iiment Trap: Aa excavated aiea around the Inlet to trap sediment (SE-3), - Gravel bag barrier: Used to create a small sediment trap upstreara of inlets on sloped, paved streets. Appropriate for sheet flow or when concentrated flow may ex^ed o.g cfs, and where overtopping is rex|ulred to prevent flooding. - Block and Gravel Filter. Appropriate for flows greater than 0.5 cfe. - Temporaiy Geotextile Storm drain Inarte: Different products provide different featiir^. Rrfer to .manufacturer details for targeted pollutants and additional futures. - Biofilter Bag Barrier: Used to create a small retention area upstream of inlets and can be located on pavement or soil. Biofilter bags slowly filter ninoff allowing sediment to settle out. Appropriate for flows under 0.5 cfs. • Selecl the appropriale lype of inlet proieclion and design as referred lo or as d^cribed in this fad: sheet. • Provide area around the inlet for water to j^nd without flooding structures and property. • Grat^ and spaass around all inlefe should be sealed to prevent seepage of sediment-laden water. • Exmvaie sediment sumps (where needed) 1 lo 2 ff with 2:1 side slopes around the inlet. InstalMtion m DIPmtection Type t - BiltFmtcm - Sim.ilar to constnicing a silt fence; see BMP SE-i, Siit Fence. Do not place fabric underneath the inlet grate since the collected sediment may fall Into the drain inlet when the fabric Is removed or replaced and water flov^r through the grate will be blocked resulting in flcK^ing. See ^'pical Type 1 installation details at the end of this fart sheet. 1. Excavate a trench approximately 6 in. wide and 6 in. d«p along the line of the silt imm inlet protwtion devi.oe. 2. Place 2 in. by 2 in, wooden stakes around the perimeter of the inlet a maximum of s ft apart and drive them at least iS in, into the ground or 12 in. below the bottom of the trench. *fh<e stakes should be at least 48 in. 3, Lay fabric along bottom of trench, up side of trendi, and then up stakes. S« SE-i, Silt Pence, for details. The maximum silt fence heighl around the inlet is 24 in. 4, Staple the Alter fabric (for mterials and specifications,« SE-i, Silt Fen«) to wooden stakes. Use hea.vy-duty wire staples at least i in. in length. tovembtr 20® Callfemj* Stormwater BMP Handbook 3 of lO Conduction www.casqa.org storni Drain Inlet Protection SE-iO 5. Backfill the trench with gravel or compacted earth all the way around. DI Protection Type st - Escmuateil Drop Inlet Sediment Unap - Install filter fabric fence in acoordancg: wth DI Protect.ion Type 1, Bim excavatdl. trap to provide a minimum storage capactty^ calculated at the rate 67 yd^f acre of drainage ar^. See typiral Type 2 installation details at the end of this fact sheet. DI Protection Tlrpe 3 - Graml bag - .Flow from a severe storm should not overtop the cu.rb. In are^ of high clay and silte, use filler fabric and gravel m ad.ditional filter media, Ctonstract gravel ba^ in aorordanoe with SE-6, Gravel Bag Berm. Gravel bags should be us^ due to their high perm^bllity. See ^ical Type 3 Installation details at the end of fliis fact sheet. 1, Construct on gently sloping street. 2, Leave room upstream of barri er for water to pond and srflment to settle. 3. Place several layers of gravel bags - overlapping the bags and packing them tightly together. 4. Leave gap of one bag on the top row to serve m a spillwiy. How from a severe storm (e.g,, 10 year storm) should not overtop the curb, DIPmtection Tgpe 4 - Biack €md Grmml FiMer - Block and gravel filtere are suitable for curb inlets commonly used in residential, commercial, and Industrial consiruction. See typical T>pe 4 installation details at the end of this fact sheet. 1. Place hardware cloth or comparable wire mesh vwth 0.5 in. openings over the drop Inlet so that the wire extends a minimum of i ft beyond each side ofthe inlet stmcture. If more than one strip is necessary, overlap the strips. Place woven geotextile over the wire mesh, 2. Place concrete blocks lengthwise on their sides in a single row around the perimeter of the inlet, so that the open ends face outward, not upward. The ends of adjacent blocks should abut. The height of the barrier can be varii^ depending on design needs, by stacking ojmbinations of blocte that are 4 in.» 8 in,, ard 12 in. wide. The row of blocks should be at least 12 in. but no grMter than 24 in, high. 3. Place vwre mesh over the outside vertical face (open end) of the concrMe blocks to prevent sione from being washed throu]^ the blocks. Use hardware cloth or comparable wire mesh with 0.5 in. opening. 4. Pile washed stone against the wire mesh to the top of the blcdcs. Use 0.75 to 3 in, DI Protection !%jpe 5 - Tempomry Geotextile Insert (proprietary) - Many types of temporaiy iiiserts are availtble, M(Kt i nserts fit underneath the grate of a drop inlet or inside of a curb inlet and are festendi to the outeide of the grate or curb. Th^ inserts are removable and many can be cleaned and reused. Installation crfth^e inserts differe between mtnwfactureR. Please refer to manufacturer instruction for installation of propri.etaiy deuces. November 2009 Califoniia Stomiwatw BMP Handbook 4 of 10 ConslaticMon storni Drain Inlet Protection SE-10 • DI Froteci^on Type 6 - Bi^fter hags - Biofllter bags may be used, as a substitute for gravel bags in low-flow situations, Biofilter should conform to specifiattions defeiiled in SE-14, Biofilter bap, 1. Construct in a gently sloping wtm. 2. Biofilter bags should be placed a round inlets to i ntercept runoff flows. 3. All bag joints should overlap by 6 in. 4. leave room upst.rea.m for water to pond and for sediment to settle out. 5. Stake bags lo the ground .as described in the following detail Stakes may be omitted if b^ are placed on a pavrf suiface, Cosl^ • Average annual cost for installation and maintenance of DI Type 1-4 and 6 (one year useful life) is $200 per inlet • Temporal geotextile inserts are proprietaiy and ajst vme& by r^on. These inserts can often be reused and may have greater than 1 year of use if maintalnMl and kept imdamaged. Average «^t per insert ranges from $50-75 plus installation, but costs ca.n exceed $100, This oost do^ not include maintenance. Inspection and Maintenance • BM Ps must be inspected in aaonJance with General Permit requirements for the a^ociated project ^e and risk level It is reojmmended that at a minimum, BMF^ be inspect^ weekly, prior to forecasted rain events, dally during extendc^l rain events, and after the tXJnclttsion of rain events. • Silt Fences. If the fabric be«>mes clogged, tom, or degrades, It should be replaced. Make sure the stakes are securely driven in the ground and are in good shape (I.e., not bent, cracked, or splintered, and are reasonably pcipendicular to the ground). Replace damaged stakes. At a minimum, remove the sedim.enl behind the febric fence when accumulation reach^ one-third the height of the fence or barrier height. « Gravel Filters. If the gravel bea>m« clogged with sediment, it should be ca.reftilly removed from the inlet and either cleaned or replaced Sinoe cleaning gravel at a construction site may be difficult, consider using the s^lment-laden stone as fill material and put fresh stone around the inlet. Inspect bags for htAm, gash^, and snag^ and replay bags as needed.. Ch«k gravel bi^s for proper arrangement and displacement. • Sediment that accumulates In the BMP should be periodically removed in order to mamtain BMP effi^ivene«. Sediment should be removed when the s^iment accumulation reach^ one-third ofthe barrier height, • Inspect and maintain temporary geotextile insert devices aocording to manufad;urer*s sp«*iieations, • Remove storm drain Inlet protection once the drainage area is stabillasd, Nav«mb«r mm Caltfornia Stormwater BMP Handbook 5 of 10 Con!»niction corifi Lfrciiii jLiiicsi. t^roi.isci.iQii SIIZ-JLIJ - 0ean and regrade area around the inlet a.n.d clean the Inside of the storm drain inlet, as it should be free of sediment and debris at flie time of final inspection. References Stormwater Quality Handbooks - Construction Site Best Management Practices (BMPs) Manual, State of California Departmentof Trans^rtation (Caltrans), March 2003, Stormwater Management Manual for The Puget Sound Basin, Washington State Deprtment of B»li^, Public Review Draft., 1991. Erosion and &diment Control Manual, Oregon l^partment of Environmental Quality, February 2005. Movember 2009 Caltfornia Stomiwater BMP Handbook 6 of lO CoflstnidSofi www.casqfl.ofg storni Drain Inlet Protection iSE"" JL 0 Geotextile Bionket ^ Drain inlet / /—•Sill Fence per Sk,-01 X / SECTiON A-A Gcre Tl-. I 4.;;Jf i » ' i PLAN / -6" Min overlap ot enc of silt fence- A •Geotextile BianKst •—Silt Fence per SE-01 Di F jr. 'V ; For use in mms where groding hos been completed ond finof soil stobiiization cod seeding ore penelifig. 2. Not oppiicobie in poved areos. 3. Nst oppricoDle Willi concent?uted flowa. Movamtor 1009 Caltfornia Stormwater BMP Handb»k Constnidion 7 Of 10 storm Drain Inlet Protection SE-10 /—Stabiiizc onea and / grade ynifofmly / oround perimeter --Sill fence Per St-01 t2 yin 24" Mox Note: ""vmiW ifsre reochin one-third full Section A-A Concentrated • OW Sheet flow 0 _^,^Rock. f!!ter(use if flow is concenlroted) •I -X IQi •Edge of sediment trap -Droin inlet -tjeotexlile Blanket |-*—Siit fence Per SE-0 D Notes 1. For use in clfored and grubbed and ir^ graced oreos. 2. Shope bosin so Ibot lontjest Inflow area faces longest length of trop. 3.. For co^ceniralod flows, snope boslo in 2:1 rotfo with lerigth oriented towords dlreciiof! of flo*. November 2009 Caltfornia Stormwattr BMP Handbook Construction 8ef 10 storni Drain Inlet Protection r '""^ r-Edge of I Pove^neol iiiiilBt 2" bogs nigh ryPlCAL PROTECTION FOR IMLET QN SUMP 1 , 2~bcgs high Spisiway, 1-bog hiah ~J \_Sendbcgs v^'iCA. P^rAC CN FOR iM ' Of^i GRADE NOTES: 1. inlended i» shoft-lerm use. 2. Use to inht&rt oor:-storm woler fiow, 3. Aiiow tor proper meintenance or*s ci«onwp, 4. 8ogs most be removed efler edjoceni ofierotion is cQmp'mt%<i 5. Not Qpplkoble in ofeos with i'i'oF sills ond cloys w'thoyl ftlt«r fobr'c. Di PROTECTION TYPt 3 "'WOTTOSCIEt November 2009 Caltfornia Stonnwatftr BMP Handbook ConstorycMoft 9 of 10 storni Drain Inlet Protection Concrete bioclt ioid lengthwise on sides jerimeter of opening — Hprdwofe clotti or wire mesh Runoff with sediment Hordware cloth wire mesh 1 iltered water 01 PROTECT:ION NOT TO SCALE ~YPF 4 Curb inlet November 2009 California Stormwater BMP Handbook CoftstrucWon 10 of 10 Wind Erosion Control WE-1 Categories EC Erosion Cootrol SE Sedtnent Control TC Tracking Control WE Wind Erosion Control Non^^inwater NS M^iagement Control Waste Managem»Tt and fcfatenabPofciHon Control LcQend: SI Primary Category IS Secondary Category Description and Purpose Wind erosion or dust control consists of applying water or other chemical dust suppressants as necessary to prevent or alleviate dust nuisance generated by constniction activities. Covering small stockpiles or areas Is an alternative to applying water or other dust palliatives, California's Mediterranean climate, with a short "wet" season and a typically long, hot "dry" season, allows the soils to thoroughly dry out. During the dry season, constmction activities are at their peak, and dLsturbed and expastnl areas are Increasingly subject to wind erosion, sediment tracking and dust generated by construction equipment. Site conditions and climate can make dust control more of an erosion problem than water based erosion. Additionally, many local agencies, including Air Quality Management Districts, require dust control and/or dust control permits in order to comply with local nuisance laws, opacity laws (visibility Impairment) and the requirements of the Clean Air Act. Wind erosion control is required to be implemented at all construction sites greater than 1 acre by the General Permit. Suitable Applications Most BMPs that provide protection against water-based erosion will also protect against wind-based erosion and dust control requirements required by other agencies will generally meet wind erosion control requirements for water quality protection. Wind erosion control BMPs are suitable during the following constroctlon activities: Targeted 0>nstituents Sediment Nutriente Trash Metals Bacteiia Oil and Crease Oganics Potential Altematives EC-5 Soil Binders November 2009 Califomia Stormwater BMP Handbook ConstrucUon www.casqa.org 1 of 5 Wind Erosion Control WE-1 • Constr«ctl.on vehicle traflHc on unpavrf roads • Drill Ing and blasting activi.ties • Soils and debris stora^ pies • Batch drop from front-end loader It Areas with unstabilized soil • Finai grading/site stabiUzation Umitations • Watering prevents dust only for a short period (generally less than a few hours) and should be applied daily (or more often) to be effective, • Over watering may mum erosion and tf ack--out. • Oil or oil-treated subgrade should not be uwd for dust control because the oil may migrate into drainageways and/or seep into the .soil • Cheroleal dust suppre^lon agents may have potential environmental impacts. Selected chemical dust a>ntrol agents should be environmentally benign. • Effcctivene^ of controls depends on soil, temperature, humidity, wind veiodty and traffic, • Chemical dust suppression agents should not be within too feet of wetlands or water bodies. • Qtemlcally treated subgrades may make the soil water repliant, interfering with long-term infiltralion and the vcgctatlon/rc-v^tatbn ofthe site, ^mc chcmioil dust suppressants may be subj^ to freering and may contain solvents and should be handle properly. • In <»mpacted areas, watering and other liquid dust control m.e^ures may wash ediment or other constituents into the drainage system. • If the soil surface has minimal natural moisture, the affected area may n«!d to be pre-wetted so that chemical dust control agents can uniformly penetrate the soil urface. Implemen^tion Dust Control Practi&es Dust ^ntrol BMPs generally stabilize exposed surfac and miiilin.ia adtM.ties that suspend or track dust partides. The following table presents dust Mrntrol practice that can be applied to varying site conditions that rould potentially cause dust. For heavily traveled and disturibed areas, wet suppr^ion (watering), chemical dust aippr^ion, gravel asphalt surfadng, temporaty gravel <»nsinietion entmnaes, ^uiproent wash«o«t areas, and haul truck mmm can be emplo>«d as dust control applications. Permanent or temporaiy vegetation and mulching can be employ^ for areas of occasional or no construction traffic. Preventive measures include minimizing surface areas to be disturbed!, limiting onsite vehicle traffic to 15 mph or less, and controlling the number and activity of vehicles on a site at any ^ven time. November 2009 California Storniwatesr BMP Handbook 2 of 5 Construction Wind Erosion Control WE-1 Chemical dust suppressants include: mulch and fiber based dust lalliatives (e,g, pai»r mulch with gypiuro binder), salts and brines (e.g, calcium chloride, magnesium chloride), non- petroleum based o^nics (e.g. v^etable oil, lignosulfonate), petroleum based oi^nics (e.g, asphalt emulsion, dust oils, petroleum resins), synthetic polymea (e,g. |»Iyvinyl acetate, vinyls, acrylic), clay additives (e.g. bentonite, montimorillonlte) and electrochemical produdbs (e.g. ensjymes, lonfc products). DUM Control PrKtket iUtir MulrliluK (WalnrinjU CHWt .S,l|»|imH.bin IMT .\«l>lu>li ri-ai|»iw]r ttrmrt t *«>nAlrw lion WMII fimn S>n)iirllr ''''jM^Mytfi' Traffir X X X X X X Tmffic X X X %M 111 X I t X X X % X X X X Tkmh TmflbiMi % 3£ X X TrvcUoc X 3£ Additional preventive measures include: • SdhaJule ^nstruttion activities to m inimise exposed area (me EC-i, ^hedul ing). • Quickly teat expceed soils using water, mulching, chemical dust suppressants, or stone/gravel layering. • Identily and stabiliEC key ac«ss points prior to ajmraencement of construction, • Miiirai^ the impct of dust by antidpting titae dir^ion of prevailing winds. « Restrict conviction tmffic to stabiiized roadways within the project site, as practicAle. • Water should applied by means of pr«sure-type distributor or pipelines equipped with a spray isystem or hoses and norfes that will ensure even distribution, • All distribution equipment should be equipped with a positive means of shutoff, • Unless water is applied by means of piplines, at least one mobile unit should be available at all ttai^ to apply water or dust palliative to the project. a If rrelaimed waste water is us«l, the sources and discharge must meet California Department of Health Service water reclamation criteria and due Regional Water Quality November 2009 Caltfornia Stormwater BMP Handbook Conrtpuctjon 3 of 5 Wind Erosion Control WE-1 <^ntrol Board (RWQCB) requirements. Non-potable water should not be oonv^ed in tanks or drain pipes that will be u«d to conv^' potable water and there should be no connection betkf ^n potable and non-potable supplies. Non-potable tanks, plp«, and other «»nv^anc.« should be marked., "NON-POTABLE WATER - DO MOT DRIN.K.* • Pave or chemically stabilla access points where unpaved traffic surface adjoin paved roa.d8, • Provide covers for haul trucks transporting materials that contribute to dust, • Provide for rapid clean up of sediments deposited on paved roads. Furnish stabilized construction road entrances and wh««l wash areas, • Stabllu!^ inactive are^ of construction sites using temptraiy vegetation or chemical stabilisation methods. For chemical stabilization, there are many products available for chemically staMliring gravel roadwap and stc«kpiles. If chemical stabilixatlon is UKd, the chemicals should not create any adverse effects on stormwater, plant life, or groundwater and should meet all applicable regulatory re€iuirem.eftts. Installation costs for water and chemical dMt suppression vary based on tibe method us«J and the length of cff«tivene^. Annual c»sts may be high sinoe some of these measures are eff<^tive for only a few hours to a few days. Inspection and Maintenance • Inspect and verify that activity-bas«dl BMPs are in place prior to the commen«ment of asscciated activities. • BMPs must be ins|>«ted in accordance with General Pemiit requirerrieuts for the associated project type and risk level. It is reoommendiwi that at a minimum, BMPs be inspected w©iMy, prior to forecasted rain even^, dally during exteiddl. rain events, and after the conclusion of rain events. • Check areas protected to ensure coverage. m Most water-bi^dl dust control measuress require frequent application, often daily or even multiple times per day. Obtain vendor or independent infbrmation on longevity of chemical dust suppre^nts. References Ifest Management Practias and Erosion Control Manual for Constraction Sites, Flood Ctontrol District of Maricopa Coun^, Arizona. September 1992. California Air Pollution Control Uws, CaHfomia Air Resources Board, updatrf annually. CJonstniction Manual, Chapter 4, Sation 10, *Diist (^ntroF; Sertion 17, "Watering**; and Section 18, 'Dust Palliative", CMliforn.la D^rtment of Transportation (Caltrans), July 2001. November 2009 Caltfornia Stomiwat«r BMP Handbook 4 of 5 www.cassp.org Wind Erosion Control WE-1 Prcwspects for Attaining the State Ambient Air Quality Standards for Suspended: Particulate .M.a.tter (PMio);, Visibility Reducing Particte, Sulfates, Lead, and .Hydrogen Sulfide, California Air Resources Board, April 1991. Stormwater Quality Handbooks Construction Site Best Managen^t Practices (BMPs) Manual, State of CaHfomia i^partmentof Transpjrtotion (Caltrans), Ma.reh 2003. November 2009 Caltfornia Stormwatar BMP Handbook S of 5 Conia;njctlon stabilized Construction Entrance/Exit TC-1 Description and Purpose A stabilized constniction access is defmed by a point of entrance/exit to a constmction site that is stabilized to reduce the tracking of mud and dirt onto public roads by construction vehides. Suitable Applications Use at constniction sites: • Where dirt or mud can be tracked onto public roads. • Adjacent to water bodies. • Where poor soils are encountered. • Where dust is a problem during dry weather conditions. Limitations • Entrances and exits require periodic top dressing with additional stones. • This BMP should be used in conjunction with street sweeping on adjacent public right of way. • Entrances and exits should be constructed on level ground only. • Stabilized constniction entrances are rather expensive to construct and when a wash rack is included, a sediment trap of some kind must also be provided to collect wash water nmoff. Categories EC SE TC WE NS Erosion Control M SecNment Conlrol IS Tracking Control 0 Wind Frosion Contml Non-Stormwater Management Control Waste Managemwit and htateriatsPolufion Control Legend: El Primary Ol^ectlve @ Secondary Objective Targeted Constituents Sediment Nutrients Trash Metals Bacteria Oil and Grease Organics Potential Alternatives Mone January 2011 California Stormwater BMP Handbook Construction www,casqa.org 1 of 6 stabilized Construction Entrance/Exit TC-1 Implementation Oeneml A steibiliied construction entranci is a pad of aggrapte underiain with filter dotti loated at any point where traffic will be entering or leaving a constmciion site lo or from a public right of way, stieet, alley, sidewalk, or parking area. The purpose of a stabiliirf eonstrurtion entrance is to reduce or eliminate the tracking of sediment onto public rights of way or struts. Reducing tracking of sediments and other plhitants onto paved roads help prmmt deposition of sedimente into local storm drains and pi^uction of airbome dust. Where traffic wil! be entering or leaving the constniction site, a stabilized ojiistruction entrance should be used. NPDI^ permits require that appropriate measures be implementdl to prevent tracking of sediments onto paved roadways, where a significant source of adimenis is derived from mud and dirt carridl out ftom unpaved roads and construdion sit^. Stabilized onstniction entrances are moderately effective in removing «dimcnt from equipment leaving a i»nstroction site. The entrance should be built on level ground. Advantages of the Stabiliad Oonstract.ion Entrance/Exit is lhat It does remove some sediment from isquipment and serves to channel construdion traffic in and out of the site at sp^fied locations. Efficiency is greatly increased when a washing rack is induded as part of a stabihzed construction entrance/exit. Design and iMyout m (instmct: on level ground where possible. • Select 3 to 6 In. diameter stones. • Use minimum depth of stones of 12 in. or as recommended by soils engineer. • Constract length of 50 ft or maximum site will allow, and 10 ft minimum width or to aaajmmodale Iralfic. • Rumble racks constnictal of stal pnels witih ridges and installed ii the stablliad. entrant/exit will help remove additional sediment and to kmp adjacent streets clean. • Provide ample tuming radii as part of the entrance. • Limit the points of entrance/exit to the construrtion site. • Limit spaed of vehicles to wntrol dust. • Properly grade each constritrtlon entrance/exit to prevent runoff from leaving the a)nstruction site. • Route nmoff from stabilized entrances/exits through a s^iment trapping device before dlschai^e. • Design stabilized. enlrance/eKit to support heavi^t vehicles and equipment that will use it. January 2011 California Stormwater BMP Handbook 2 of 6 Cor»s6fiittlo« stabilized Construction Entrance/Exit TC-1 • Select constmction acx«s stabilization (aggregate, asphaltic concrete, concrete) based on longevity, required performance, and site conditions. Do not use asphalt concrete (AC) grinding for stabillEed construction aa«s/roadway. • If aggr^ate is selected, place crushdl aggregate over geotextile fabric to at least 12 In. depth, or place aggregate to a depth re«»mmended by a geotechnical engineer. A cmshed aggregate greater than 3 in. but smaller than 6 in. should be used. • Designate combination or single purpose entrances and exits to the constmction site. • Require that all employee, subcontractor, and suppliers utilize the stabilized ronstraction ac^s. • Implement SE-7, Street Sweeping and Vacuuming, as needed. • All exit locations intended to be used for more than a two-week period should have stabilized construction entrance/exit BMPs. Inspection and Maintenance • Inspect and verify that activi^-based BMPs are in place prior to the rommencement of associated activities. While activities associated vrith the BMPs are under way, inspecl BMPs in aarordance with General Permit requirements for the associated project ifype and risk level It is recommended that at a minimum, BMPs be inspected weekly, prior to forecasted rain events, daily during extended rain events, and after the ironduslon of rain events. • Inspect local rtrads adjacent to the site dally. Sweep or vacuum to remove visible accumulated sediment. • Remove aggregate, separate and dispose of sediment if constructbn entrance/exit is clogged with sediment. • Keep all temporary roadway ditches dear. • Check for damage and repair as needed, • Replace gravel material when surface voids are visible, • Remove all sediment deposited on paved roadwa)^ within 24 hours, a Remove gravel and filter fabric at completion of oonstractlon Average annual cost for Installation and maintenance may vary from $1,200 to $4,800 each, averaging $2,400 per entrance. Costs will Incr^e with addition of washing rack, and sediment trap. With wash rack, costs range from $1,200 - $6,000 each, averaging $3,600 per entrance. References Manual of Standards of Ersion and Sediment Control Measures, Association of Bay Area Governments, May 1995, January 2011 California Storntwater BMP Handbook 3 of 6 Constryctk« www.casqa.org stabilized Construction Entrance/Exit TC-1 National Mani^eraent Measures to Control Nonpoint Source Pollution from Urban Areas, USEPA Agency, 2002, Proposed Guidance Specifying Management .Measures for Sources of Nonpoint Pollution in ODastal Waters, Work Group Working Paper, USEPA, April 199a. Stormwater Quaiii^ H.andbooks Construction Site Best Management Practice (BMPs) Manual, State of CaJiforoia Department of Traraportation (Caltrans), November 2000. Stormwater Management of the Puget Sound Basin, Technical Manual, Publication #91-75, Washington State Departmentof Ecology, Febmary 1992. Virginia Erosion and Srflmentation (Control Handbook, Virginia Department of Conservation and Recreation, .Division of &>il and Water Conservation, 1991. Guidance Specifying Management Mmsures for Nonpoint Pollution in Osaastai Waters, EPA 840-B-9-002, USEPA, Office of Water, Washington, DC, 1993.. Water Qualify Management Plan for the Lake Tahc« Region, Volume II, Handbook of Management Practices, Tahoe Regional .Planning Agency, November 1988. January 2011 Caiifornta Stormwatsr Handbook 4 of 6 CofismjOton www.casqa.org stabilized Construction Entrance/Exit TC-1 _Crush«d ag§r«f ete greater thon .3* "fcwt ssamoller thon 6 Ortgiliiol lit •12 Mii, mimi oiii.mwlm spmMmi by o lois engfeeer NOTE- Ciansrtrtiet .SMsdira^il barrier ** ' ond chonneltee runoff to sediment tr^i^kig device Ex.istirtg Grode 50* or md^dmum «i*la«i^ by 8?t# or foyr tlmt* ttie ©1rc«mfer(iRc« of the forg4^t cimtlntctlort v#ilcle tb-e, »?hich«wr tt ytater 10' mM or OS required to (i^eomodQte tmtle|>ot#d tfafflc, itilcfiww^ h ir*atef January 2011 California Storrnwate" BMP Handl}«>k Censtrwaiow www.ca sqs.org 5 of 6 stabilized Construction Entrance/Exit TC-1 Cfu^ed Offtefote rareota^ thm 3" but OTtoWif thon 6 . r Flter fobric t-l2* Min. unl«s9 ottierwise i^ecifW by o sols wigffteer SECTION B-B Origin!^ f ungin Cry#i«d oggregote p-eot^r Ihon 3" but smolltr ttian 6", Ccrrugoted sted pcmds Ortgiriol groda 12" Min. unless olh«^is« FBter fabric mw-. Construct ^ttneHtt Ijarrier ond cbonnetize nmtilt to sedknent trt^ping device Sedimwit trop^fif de^^ce Cofru9ot#d steel panels A r*B "10' unin or m r«M:|uired to oecomodotd anticipated traffic, «#iJd»ew«r ..i,,„,,te ^§QtM. , 24L ltf yMlllTTmillTllllltlllll M Mill lr max ailowi^ by site 50* or moximum ollowed by stte Match Existing (Srode or four times the clrcurnfer«rtce of the {(roest consiruction vehh^e tire, mkMvm Is greater January 2011 Caiifornia Stormwater BMP Handbook Construction W4m.casq3.org 6 of 6