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CT 02-21; VILLAGES OF LA COSTA GREENS 1.12; STORM WATER MGMT PLAN; 2003-08-17
HUNSAKER ^ASSOCIATES SAN DIECO, INC. PLANNING ENGINEERINC SURVEYING IRVINE LOS ANGELES RIVERSIDE SAN DIEGO BECBIVBD STORM WATER MANAGEMENT PLAN for LA COSTA GREENS Neighborhood 1.12 City of Carlsbad, California City of Carlsbad Project # CT 02-21 Prepared for: Real Estate Collateral Management Company c/o Morrow Development 1903 Wright Place, Suite 180 Carlsbad, CA 92008 DAVE HAMMAR LEX WILLIMAN ALISA VIALPANDO DAN SMITH RAY MARTIN 10179 Huennekens St, San Diego, CA 92121 (858) 558-4500 PH (858)558-1414 FX www,Hunsal<erSD,com lnfo®Hunsal<erSD,com W.O. 2352-71 August 17, 2003 Eric Mosolgo, R Water Resources Department Manager Hunsaker & Associates San Diego, Inc -J JC:kc h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 10:05 AM La Costa Greens - Neigtibortiood 1.12 Stormwater Management Plan TABLE OF CONTENTS SECTION Executive Summary I Introduction Vicinity Map Post Construction BMP Location Exhibit Summary of Results Storm Water Treatment Criteria and Methodology II Introduction Regional Water Quality Control Board Criteria Identification of Typical Pollutants Conditions of Concem Design Criteria and Examples of Treatment Control BMPs Maintenance of Treatment Control BMPs Source Control BMPs Site Design BMPs Storm Water Quality Treatment Best Management Practice lil Structural Treatment BMPs Determination of Design Treatment Flow Rational Method Treatment Flow Detennination Methodology Treatment Unit Selection Attachments IV - Design Flow Determination Spreadsheets (2) - Low Flow Diversion Spreadsheet - Flow Calculations provided by Vortechnics - Vortechnics Treatment Flow and Treatment Area Spreadsheet - Vortechnics Specification, Features and Operation - San Diego County 85th Percentile, 24-Hour Rainfall Map Land Development Manual - Quadrangle Map Watershed exhibit for La Costa Greens Developed Condition Site Map (Pocket) JC:TK h:\sw quailty\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan SECTION I EXECUTIVE SUMMARY JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan EXECUTIVE SUMMARY Introduction This Water Quality Technical Report has been prepared to show methodology and calculations used to determine the sizing of the required stomi water treatment unit. All calculations are consistent with criteria set forth by the Regional Water Quality Control Board's Order No. 2001-01, and the "Model Standard Urban Storm Water Mitigation Plan for San Diego County, Port of San Diego, and Cities in San Diego County." Phase 1 ofthe La Costa Greens project site is located north of Alga Road, south ofthe proposed extension of Poinsettia Lane, and east of the La Costa Golf Course. Neighborhood 1.12 is located roughly in the center of the development, east of Alicante Road, north of Neighborhood 1.13 and the SDG&E easement, and south of Neighborhood 1.09. Development of La Costa Greens Phase I consists of several individual subdivisions located within the City of Carlsbad, CA. Neighborhood 1.12 is one of the subdivisions within the La Costa Greens development. An exhibit showing the location of each treatment unit and the breakdown of the areas tributary to each treatment unit is included on the following page. OF MARCOS 11 THE GREENS 1.12 VICINITYMAF NTS JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Runoff from the northern portion of Neighborhood 1.12 will drain to a proposed storm drain outlet located at the southwest comer of Neighborhood 1.10 (at the Street "KK" cul-de-sac). This runoff discharges from the storm drain to the unnamed tributary of San Marcos Creek, which flows in a southerly direction along the west side of Neighborhood 1.10. Runoff from Neighborhood 1.09, Neighborhood 1.10, and the adjacent residential development east of La Costa Greens Phase 1 will also drain to this stomi drain outlet location. The offsite developed areas, which will drain to the stonn drain outlet located in Neighborhood 1.10 and 1.14 have been quantified in two hydrology studies; "Hydrology & Hydraulic Study - La Costa Greens Phase 1", prepared by O'Day Consultants May 25, 2002, and "Tentative Map Drainage Study for La Costa Greens - Phasel Neighborhoods 1.08 through 1.14," prepared by Hunsaker & Associates San Diego, Inc. April 17, 2003. The O'Day report identified a total of 98 acres of offsite developed area that contribute flow to the La Costa development in the vicinity ofthe 1.09 and 1.12 Neighborhood. The Hunsaker & Associates report identified two run on locations: one at the southeast corner of Neighborhood 1.09 consisting of 19 acres of area; and one at the northeast corner of Neighborhood 1.12 consisting of 79 acres of area. Runoff from the southern portion of Neighborhood 1.12 will drain to a proposed storm drain outlet located near the intersection of Goldstone Road and Street "GG" in Neighborhood 1.14. This runoff discharges an existing 42-inch RCP in the Alga Road stonn drain system. Runoff from Neighborhood 1.13, Neighborhood 1.14 and the adjacent development east of La Costa Greens Phase 1 will also drain to this storm drain outlet location. The O'Day report identified a total of 13 acres of offsite developed area that contribute flow to the La Costa development in the vicinity of Neighborhood 1.12 and 1.13. The Hunsaker & Associates report identified one run on location near the southeast corner of Neighborhood 1.12 and the northeast corner of Neighborhood I. 13 consisting of 13 acres of area. The Quadrangle Map Watershed Exhibit for La Costa Greens illustrates the extent of offsite areas draining to the La Costa Greens Phase I proposed development and has been included in the Attachment section of this report. The project will include construction of two (2) proposed roads, grading of the proposed site to make it suitable for constmction of single-family residential dwellings, construction of underground utilities typically associated with residential developments, and the construction of 36 residences. The proposed project site consists of 36 residential lots and 5 open space lots, for a total area of 23.50 acres (12.19 acres and II. 32 acres respectively). Approximately 48% will remain undeveloped. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM LEGEND WATERSHED TRIBUTARY TO TREATMENT UNIT • TREATMENT UNIT 0 OFFSITE RUN-ON LOCATION LA COSTA GREENS POST-CONSTRUCTION BMP LOCATION EXHIBIT FLOW-BASED BMP FOR NEIGHBORHOOD 1.08, OFFSnnE DEVELOPMEl AND AUCANTE ROAD FLOW-BASED BMP FOR NEIGHBORHOOD 1.09, 1.10, A PORTION OF 1.12, AND OFFSrrE DEVELOPMEI>n- FLOW-BASED BMP FOR NEIGHBORHOOD1.il FLOW-BASED BMP FOR NEIGHBORHOOD 1.13,1.14, PORTION OF 1.12, AUCANTE ROAD, AND OFFSITE DEVELOPMENT Ri\03a9\8.Hyd\Slte Location Map 8.5xU-U2.clwgC 1275Uun-ia-2003il4i53 La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Summary of Results For Neighborhood 1.12, stormwater will be treated in one of two treatment units; one located near the intersection of Goldstone Road and Street "GG" in Neighborhood 1.14 treats the runoff from the southem portion of 1.12, and one located at the southwest corner of Neighborhood 1.10 (at the Street "KK" cul-de-sac) treats runoff from the northem portion of 1.12. Prior to discharge into either the open channel or the stonn drain system in Alga Road, all stomn water will pass though a proposed diversion structure that will divert the entire 85*^ percentile flow into one ofthe two proposed storm water treatment units. Flows in excess of the treatment flow will bypass the treatment unit. The analysis perfonned in this report indicates that a Vortechs Model PCI 6x24 will be required to meet the water quality treatment requirements forthe northem portion of Neighborhood 1.12. The proposed Vortechs Model PC16x24 will be located offline from the main stonn drain system and is proposed to be located in the vicinity of the Street KK cul-de-sac. All stormwater runoff, including the 85*^ percentile flow, from the southern portion of Neighborhood 1.12 will be diverted to a proposed storm water treatment unit prior to discharge to the existing storm drain system. The proposed Vortechs Model 7,000 will be located offline from the main storni drain system near the intersection of Goldstone Road and Street GG. In addition to the primary treatment facilitated by the proposed Vortechs Model PCI 6x24 and Model 7000, stoma water treatment in excess ofthe Regional Water Quality Control Board requirements will be provided downstream ofthe storm drain outfalls. After discharge stonn water from the northern portion of Neighborhood 1.12 will drain through an existing vegetated constructed channel en route to the Alga Road culverts. This vegetated channel will provide additional treatment for 85th percentile flow (by reducing the flow velocities in the channel and in tum settling out pollutants). Storm water from the southern portion of Neighborhood 1.12 will be treated in the Model 7000 then discharge into the existing Alga Road stonn drain system. This system discharges into the unnamed tributary of San Marcos Creek south of Alga Road. The unnamed tributary south of Alga Road is also a vegetated channel that will provide additional treatment in the same manner as described previously in this paragraph. Since primary and additional treatment will be provided, a volume-based BMP will not be required. Maintenance of Vortechs units, which will be the responsibility ofthe Master Homeowners Association, is addressed in Section II ofthis report. The report replaces any post-construction BMP text included in the Preliminary SWPPP prepared along with the Master Tentative Map. SWPPP reports are typically required for storm water pollution prevention during interim construction activities. Desiltation basins previously designed for this project were intended only to collect sediment during the construction phase ofthe project and were not intended to be permanent facilities. This report specifies post-construction condition BMP treatment controls. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Anticipated pollutants of concern are included in Section II ofthis report. Tables included in Section II show that the proposed Vortechs system adequately treats the anticipated pollutants of concem to a degree previously determined acceptable by the Regional Water Quality Control Board. Treatment BMPs recommended for the project site are based on 85*^ percentile design flow calculations and are not based on quantitative pollutant loading analysis. Previous attempts to apply quantitative methods for estimating pollutant loading and removal efficiencies, such as in the 1993 Municipal Handbook, are no longer considered accurate for southem Califomia. Section II also presents a listing of recommended non-structural source control BMPs, which include landscaping, urban housekeeping, etc. 85th percentile calculations included in this report were generated using the Rational Method. This method calculates the resultant 85**^ percentile fiow rate based upon a peak rainfall intensity of 0.2 inches per hour. This is consistent with criteria set forth in the "Model Standard Urban Storm Water Management Plan for San Diego County, Port of San Diego, and Cities in San Diego County," JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan SECTION II STORM WATER TREATMENT CRITERIA & METHODOLOGY JC:TK h:\sw quaiity\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan STORM WATER TREATMENT CRITERIA & METHODOLOGY The purpose of this report is to address pollutants associated with residential developments, and to recommend techniques used to reduce the concentration of pollutant discharge into waterways and bodies of water. Treatment BMPs recommended for the proposed project site are based on 85*^ percentile design flow calculations and are not based on quantitative pollutant loading analysis. Previous attempts to apply quantitative methods for estimating pollutant loading and removal efficiencies, such as in the 1993 Municipal Handbook, are no longer considered accurate for southern Califomia. The La Costa Greens Village 1.12 project site is located in the Batiquitos watershed. After development, 85*^ percentile flow from the proposed project site will be collected in catch basins, curb inlets, and brow ditches and conveyed to one ofthe two proposed Vortechnics treatment units through proposed storm drain systems. After treatment, storm water from the northem portion of Neighborhood 1.12 will be discharged into a drainage swale, which will confluence with the unnamed tributary of San Marcos Creek, and ultimately into San Marcos Creek. After treatment, storm water from the southern portion of Neighborhood 1.12 will be discharged into an existing 42-inch RCP storm drain system located in Alga Road, which also discharges into an unnamed tributary of San Marcos Creek and ultimately into San Marcos Creek. San Marcos Creek is not listed as an impaired water body on the 2002 CWA Section 303(d) List of Water Quality Limited Segment. Regional Water Qualitv Control Board Criteria All runoff conveyed in the proposed storm drain systems will be treated in compliance with Regional Water Quality Control Board regulations and NPDES criteria priorto discharging to natural watercourses. California Regional Water Quality Control Board Order No. 2001-01, dated February 21, 2001, sets waste discharge requirements for discharges of urban mnoff from municipal storm separate drainage systems draining the watersheds of San Diego County. Perthe RWQCB Order, post-development mnoff from a site shall not contain pollutant loads which cause or contribute to an exceedance of receiving water quality objectives or which have not been reduced to the maximum extent practicable. Post-construction Best Management Practices (BMPs), which refer to specific stonn water management techniques that are applied to manage construction and post-constmction site runoff and minimize erosion, include source control - aimed at reducing the amount of sediment and other pollutants - and treatment controls that keep soil and other pollutants onsite once they have been loosened by stonn water erosion. Post construction pollutants are a result of the urban development of the property and the effects of automobile use. Runoff from paved surfaces can contain both sediment (in the form of silt and sand) as well as a variety of pollutants transported by the sediment. Landscape activities by homeowners are an additional source of sediment. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Most hannful pollutants accumulate within three feet of the curb. Many of these pollutants adhere to fine materials, thus avoiding removal by old-time street-sweepers. Harmful pollutants are also present in high concentrations in urban "hot spots" such as automotive, cleaning, or servicing shops. All structural BMPs shall be located to infiltrate, filter, or treat the required runoff volume or flow (based on 85*' percentile rainfall) prior to its discharge to any receiving watercourse supporting beneficial uses. The BMPs will be designed to reduce toxin, nutrient and/or sediment loading ofthe 85'^ percentile design flow from the proposed development. All grading operations forwhich a pennit is required are subject to periodic inspection and monitoring. Flow-based BMPs shall be designed to mitigate the maximum flow rate of runoff produced from a rainfall intensity of 0.2 inch per hour These BMPs utilize either mechanical devices (such as vaults that produce vortex effects) or non-mechanical devices (based on weir hydraulics and specially designed filters) to promote settling and removal of pollutants from the runoff. identification of Tvpical Pollutants 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 receivinq waters. Treatment BMPs recommended for the proposed project site are based on 85 percentile design flow calculations and are not based on quantitative pollutant loading analysis. Previous attempts to apply quantitative methods for estimating pollutant loading and removal efficiencies, such as in the 1993 Municipal Handbook, are no longer considered accurate for southem California. Perthe model SUSMP, this report identifies the removal efficiencies ofthe following pollutants using Vortechs Stonnwater Treatment unit in terms of low, medium and high removal. For the purposes of identifying pollutants of concern and associated storm water BMPs, pollutants are grouped in the following general categories: Sediments are soils or other surface 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, smother bottom dwelling organisms, and suppress aquatic vegetative growth. Nutrients are inorganic substances, such as nitrogen and phosphorous. They commonly exist in the form of mineral salts that are either dissolved or suspended in water. Primary sources of nutrients in urban mnoff 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. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Metals are raw material components in non-metal products such as fuels, adhesives, paints and other coatings. Metals of concem include cadmium, chromium, copper, lead, mercury, and zinc. At high concentrations, metals can be toxic to aquatic life. Organic Compounds are carbon-based and commonly found in pesticides, solvents, and hydrocarbons. Organic compounds can, at certain concentrations, constitute a health hazard. Dirt, grease, and grime retained in cleaning fluid or rinse water may also adsorb levels of organic compounds that are harmful or hazardous to aquatic life. Trash & Debris, such as paper, plastic, leaves, grass cuttings, and food waste, 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. In areas where stagnant water is present, 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 include biodegradable organic material as well as chemicals that react with dissolved oxygen in water to form other compounds. Compounds such as ammonia and hydrogen sulfide are examples of oxygen- demanding compounds. The oxygen demand of a substance can lead to depletton of dissolved oxygen in a water body and possibly the development of septic conditions. Oil and Grease are characterized as high high-molecular weight organic compounds. Primary sources of oil and grease are petroleum hydrocariDon products, motor products from leaking vehicles, oils, waxes, and high-molecular weight fatty acids. Elevated oil and grease content can decrease the aesthetic value ofthe water body, as well as the water quality. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Table 1 below, details the typical anticipated and potential pollutants generated by various land use types, based on the draft model SUSMP prepared bythe copermittees. The La Costa Greens Neighborhood 1.12 development will consist of detached single-family residences, and the Detached Residentiai Development category has been highlighted to cleariy illustrate which general pollutant categories are anticipated from the project area. TABLE 1 General Pollutant Catei gories Priority Project Categories Sediments Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Substances Oil& Grease Bacteria & Viruses Pesticides w Attached Residential Development X X X pd) p(2) P X Commercial Development >100,000 ft^ p(1) pd) p(2) X p(5) X p(3) p(5) Automotive Repair Shops X XW(5) X X Restaurants X X X X Hillside Development >5,000 ft^ X X X X X X Parking Lots pd) pd) X X pd) X pd) Streets, Highways & Freeways X pd) X X(4) X p(5) X Retail Gas Outlets X X(4) X X 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. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Conditions of Concern The Master Drainage Study for La Costa Greens addresses the City of Carisbad Standard Urban Storm Water Mitigation Plan requirements per Section III -1 C for identifying the conditions of concem. After treatment, storm water will be discharged into an unnamed tributary of San Marcos Creek and ultimately into San Marcos Creek. San Marcos Creek is not listed as an impaired water body on the 2002 CWA Section 303(d) List of Water Quality Limited Segment. In order to meet water quality objectives, the pollutants that will be treated and addressed in this report are sediment, nutrients, trash and debris, oxygen demanding substances, oil and grease, bacteria and vimses, and pesticides. Design Criteria and Examples of Treatment Control BMPs Storm water quality treatment (pollutant removal) will be attained by flow-based methods. Treatment control (stmctural) BMPs are engineered system designs constructed to remove pollutants from urban runoff by simple gravity settling of particulate pollutants, filtration, biological uptake, media absorption, or any other physical, biological, or chemical process. Flow-based BMPs shall be designed to mitigate the maximum flow rate of runoff produced from a rainfall intensity of 0.2 inch per hour. Such basins utilize either mechanical devices (such as vaults that produce vortex effects) or non-mechanical devices (based on weir hydraulics and specially designed filters) to promote settling and removal of pollutants from the runoff. Examples of flow-based BMPs include hydrodynamic separation devices, such as those designed by CDS Technologies, Vortechnics, HIL Technologies, etc.. For the La Costa Greens development, the storm drain system design incorporates the use of Vortechnics' Vortechs stormwater treatment units. The table on the following page compares the removal efficiencies of comparable hydrodynamic separation devices to the removal efficiencies of Vortechs stormwater treatment units. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Treatment Control BMP Removal Efficiencies (1) Pollutant of Concern Sediment Nutrients Heavy Metals Organic Compounds Trash & Debris Oxygen Demanding Substances Bacteria Oil & Grease Pesticides BMP Categories Hydrodynamic Separation Devices^^^ M-H L-M L-M L-M M-H L-H (1) The County will periodically assess the performance characteristics of these BMPs to update this table. (2) Proprietary Structural BMPs. Not all serve the same function. L (Low): Low removal efficiency (roughly 0-25%) M (Medium): Medium removal efficiency (roughly 25-75%) H (High): High removal efficiency (roughly 75-100%) U: Unknown removal efficiency, applicant must provide evidence supporting use Sources: Guidance Specifying Managennent Measures for Sources of Nonpoint Pollution in Coastal Waters (1993), National Stomiwater Best Management Practices Database (2001), and Guide for BMP Selection in Urban Developed Areas (2001). The Vortechs Storni Water Treatment System is designed to efficiently remove grit, contaminated sediments, metals, hydrocarbons and floating contaminants from surface runoff Combining swiri-concentrator and flow-control technologies to eliminate turbulence within the system, the Vortechs System ensures the effective capture of sediment and oils and prevents resuspension of trapped pollutants for flows up to 25 cfs with the use of their precast treatment units. Vortechnics also provides design and system components that are cast-in-place (CIP). These CIP treatment units have the ability to treat much greater flows. Other features of the Vortechs Systems include the following: • Large capacity system provides an 80 percent net annual Total Suspended Solids (TSS) removal rate • Unit is installed below grade • Low pump-out volume and one-point access reduce maintenance costs • Design prevents oils and other floatables from escaping the system during cleanout • Enhanced removal efficiencies of nutrients and heavy metals with offline configuration JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan The tangential inlet to the system creates a swiriing motion that directs settleable solids into a pile towards the center of the grit chamber. Sediment is caught in the swiriing flow path and settles back onto the pile after the storm event is over. Floatables entrapment is achieved by sizing the low flow control to create a rise in the water level of the vault that is sufficient to just submerge the inlet pipe with the 85**^ percentile flow. Maintenance of Treatment Control BMPs Maintenance of the site BMPs will be the responsibility of Uie Master Development Homeowners Association. A maintenance plan should be developed to include the following information: • Speciflcation of routine and non-routine maintenance activities to be performed • A schedule for maintenance activities • Name, qualifications, and contact information for the parties responsible for maintaining the BMPs For proper maintenance to be performed, the storm water treatment facility must be accessible to both maintenance personnel and their equipment and materials. Amenities such as depressed curbs, hand and safety rails, gates, access roads and manholes expedite both inspection and maintenance efforts and help to reduce costs and improve efficiency. The use of strong, durable and non-corroding materials can greatly expedite maintenance efforts. These include strong, lightweight metals (orifice and weir plates), reinforced concrete for outlet structures and headwalls, disease resistant vegetation for channel bottoms and side slopes, and durable rock for gabions and riprap lining. A variety of contaminants that may be classified as hazardous or toxic may enter stonn water management systems. These contaminants include heavy metals, petroleum hydrocarbons, pesticides, and a variety of organic chemicals. Federal and state laws may apply to the disposal of sediments that are captured in these storm water systems. Inlet cleaning, ditch clearing, and street sweeping are examples ofother commonly used maintenance practices. Mamtenance of Flow-Based Treatment Units Maintenance of Vortechnics units includes inspection and maintenance 1 to 4 times per year, and maintenance involves the use of a "vactor truck" which clears the grit chamber of the treatment unit by vacuuming all the grit, oil and grease, and water from the sump. Typically a 3-man crew is required to perform the maintenance of the treatment unit. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Flow-based storm water treatment devices should be inspected periodically to assure their condition to treat anticipated mnoff. Soon after installation, the condition ofthe unit should be checked after every runoff event for the first 30 days. Proper inspection includes a visual observation to ascertain whether the unit is functioning properiy and measuring the amount of deposition in the unit. During the wet season, units should be inspected at least once every 30 days. Floatables should be removed and sumps cleaned when the sump storage exceeds 85 percent of capacity. The Vortechs System should be inspected at regular intervals and cleaned when necessary to ensure opfimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. During the wet season, units should be inspected at least once every 30 days. During constmcfion, BMP inspecfions shall be performed before and after stonn events and once each 24-hour period during extended stomn events to identify BMP effecfiveness. Inspecfion is the key to effective maintenance. Vortechnics recommends ongoing quarteriy inspecfions ofthe accumulated sediment. According to Vortechnics literature, the systems needs only to be cleaned when the inspection reveals that the system is neariy full - specifically, when the sediment depth has accumulated within 6 inches of the dry-weather water level. Cleanout of the Vortechs System with a "vactor truck" is generally the most effective and convenient method. Properly maintained Vortechs Systems will only require evacuation ofthe grit chamber portion ofthe system. In some cases, it may be necessary to pump out all chambers. In the event of leaning other chambers, it is imperative that the grit chamber be drained first. The estimated annual maintenance cost associated with the Vortechs treatment unit proposed for Neighboriiood 1.09,1.10 and the northern portion of 1.12 is approximately $4,000. The estimated annual maintenance cost associated with the Vortechs treatment unit proposed for Neighborhood 1.13,1.14, a portion of Neighboriiood 1.12 is approximately $2,500. These costs will vary depending on site condifions and the frequency of runoff producing rainfall events. During the life span of the treatment unit, a record of maintenance should be kept current. This will aid in determining the frequency of maintenance activities, and therefore provide a more accurate appnDximafion of the annual maintenance costs required to keep the unit functioning properiy. JC:TK h:\sw quallty\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan SECTION III STORM WATER QUALITY TREATMENT BEST MANAGEMENT PRACTICE JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Source Control BMPs Source controls, which are implemented to prevent or reduce the presence of pollutants and minimize the contact between pollutants and urban runoff, include the following: • Landscaping - Manufactured slopes shall be landscaped with suitable ground cover or installed with an erosion control system. Homeowners should be educated as to the proper routine maintenance to landscaped areas including trimming, pruning, weeding, mowing, replacement or substitution of vegetafion in ornamental and required landscapes. In the event that landscaping work requires materials such as fill, gravel, dirt, loam, mulch, etc. to be piled for more than a single day, the pile(s) should be securely covered in order to prevent suspension of the loose material in runoff from any storm event. Per the RWQCB Order, the following landscaping activities are deemed unlawful and are thus prohibited: - Discharges of sediment, pet waste, vegetative clippings, or other landscaping or construcfion-related wastes. Urban Housekeeping - Fertilizer applied by homeowners, in addifion to organic matter such as leaves and lawn clippings, all result in nutrients in storm water runoff. Consumer use of excessive herbicide or pesticide contributes toxic chemicals to runoff. Homeowners should be educated as to the proper applicafion of fertilizers and herbicides to lawns and gardens. The average household contains a wide variety of toxins such as oil/grease, antifreeze, paint, household cleaners and solvents. Homeowners should be educated as to the proper use, storage, and disposal of these potential storm water mnoff contaminants. Per the RWQCB Order, the following housekeeping activifies are deemed unlawful and are thus prohibited: - Discharges of wash water from the cleaning or hosing of impervious surfaces including parking lots, streets, sidewalks, driveways, pafios, plazas, and outdoor eafing and drinking areas. Landscape irrigafion and lawn watering, as well as non-commercial washing of vehicles in residential zones, is exempt from this restriction. - Discharges of pool or fountain water containing chloride, biocides, or other chemicals. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan - Discharges or runoff from material storage areas containing chemicals, fuels, grease, oil, or other hazardous materials. - Discharges of food-related wastes (grease, food processing, trash bin wash water, etc.). • Automobile Use - Urban pollutants resulfing from automobile use include oil, grease, antifreeze, hydraulic fluids, copper from brakes, ahd various fuels. Homeowners should be educated as to the proper use, storage, and disposal of these potential stomn water contaminants. Per the RWQCB Order, the following automobile use activifies are deemed unlawful and are thus prohibited: - Discharges of wash water from the hosing or cleaning of gas stafions, auto repair garages, or other types of automofive service facilifies. - Discharges resulfing from the cleaning, repair, or maintenance of any type of equipment, machinery, or facility including motor vehicles, cement-related equipment, port-a-potty servicing, etc. - Discharges of wash water from mobile operations such as mobile automobile washing, steam cleaning, power washing, and carpet cleaning The Homeowners Association should make all homeowners aware of the aforementioned RWQCB regulations through a homeowners' educafion program. A monitoring program should also be implemented to insure compliance. Site Design BMPs The proposed project site consists of 36 residential lots and 5 open space lots, for a total area of 23.50 acres (12.19 acres and 11.32 acres respectively). Approximately 48% of the project site, 11.32 acres, will not be developed and will be preserved as open space. This will minimize the pollutant loads generated and potenfially discharged from the site. Furthermore, while the project does not depend on this open space to provide treatment of potential pollutants, there will be a natural benefit derived from its existence, both as a natural buffer between the site and water bodies and as a cleansing mechanism. JC:TK h:\sw quallty\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Structural Treatment BMPs The improvement design for the project site incorporates the constmction of two stonnwater treatment devices. Runoff from the northern portion of Neighborhood 1.12 will be treated by a Vortechs Model PC16x24 stonn water quality unit, and runoff from the southem portion of Neighborhood 1.12 will be treated by a Vortechs Model 7000. The storm water quality treatment unit, treafing mnoff from the northem portion of the project site, has been sized to treat 85'^ percentile design flow from Neighborhood 1.09,1.10, a portion of Neighborhood 1.12 and offsite areas to the east, all which drain through Neighborhood 1.10. The stomn water quality treatment unit, treafing runoff from the southem portion of the project site, has been sized to treat 85*^ percenfile design flow from Neighborhood 1.13,1.14, the southern portion of Neighborhood 1.12, and offsite areas to the east. Determination of Design Treatment Flow The 85*^ percenfile flow rate forthe northem portion of Neighborhood 1.12 has been calculated using the Rational Method. Required data forthe Rational Method Treatment flow determinafion is as follows: - Drainage Area (A) = 196.05 acres (Neighborhoods 1.09,1.10, northern portion of 1.12, and offsite areas) Rainfall Intensity (I) = 0.20 inches per hour Runoff Coefficient (C) = 0.53 The northem portion ofthe site's overall runoff coefficient was derived based upon a weighted average of each area tributary to the treatment unit and the associated mnoff coefficient Using this method, the site's runoff coefficient was esfimated to be 0.53. Bases on this data the treatment fiow for the storm water treatment unit was detennined to be 20.78 cfs. The 85*^ percenfile flow rate forthe southern portion of Neighborhood 1.12 has been calculated using the Rational Method. Required data forthe Rational Method Treatment fiow determination is as follows: - Drainage Area (A) = 75.92 acres (Neighborhoods 1.13, 1.14, the southern portion of 1.12, and offsite areas) Rainfall Intensity (I) = 0.20 inches per hour Runoff Coefficient (C) = 0.40 The site's overall runoff coefficient was derived based upon a weighted average of each area tributary to the treatment unit and the associated runoff coefficient. Using this method, the site's runoff coefficient was estimated to be 0.40. Bases on this data the treatment flow for the storm water treatment unit was determined to be 7.12 cfs. JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Rational Method Treatment Flow Determination Methodologv As stated in the Introducfion of Secfion II, Regional Water Quality Control Board regulations and NPDES criteria have established that fiow-based BMPs shall be designed to mitigate a rainfall intensity of 0.2 inch per hour. The basic Rational Method mnoff procedure is as follows: Design flow (Q) = (C) * (I) * (A) Runoff Coefficient (C) - In accordance with the County of San Diego standards, the weighted runoff coefficient for all the areas tributary to the treatment unit was detennined using the areas analyzed in the hydrology report. A runoff coefficient of 0.63 was used forthis analysis. The mnoff coefficient is based on the following characteristics ofthe watershed: • Land Use - Single Family Residential in Developed Areas • Soil Type - Hydrologic soil group D was assumed for all areas. Group D soils have very slow infiltration rates when thoroughly wetted. Consisting chiefly of clay soils with a high swelling potential, soils with a high permanent water table, soils with clay pan or clay layer at or near the surface, and shallow soils over nearly impervious materials. Group D soils have a very slow rate of water transmission. Rainfall Intensity (I) - Regional Water Quality Control Board regulafions and NPDES criteria have established that fiow-based BMPs shall be designed to mitigate a rainfall intensity of 0.2 inch per hour. Water Shed Area (A) - Project Area - Neighborhood 1.12 north totaling an area of 196.05 acres; Neighborhood 1.12 south totaling an area of 75.92 acres. JC:TK h:\sw quallty\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan Treatment Unit Selection Per the "Vortechnics Engineered Stonnwater Products" manual, dated November, 2001 (excerpts attached), the Vortechs Model 9000 has a design fiow rate of 14.0 cfs, and per the special design prepared by Scott Gorneau of Vortechnics included in a fax, dated May 20, 2003 (excerpts attached), the Vortechs Model PCI 6x24 has a design flow rate of 40.0 cfs. These units (details attached), as proposed on the improvement plans, are both conflgured as offline precast treatment units, meaning that the design flow rate is forced into the treatment area through a diversion structure, while flows in excess of the design flow rate pass over an inline weir and proceed downstream. The weir in the diversion structure will create a restriction, which will raise the HGL upstream of the weir. These losses will be analyzed in the Hydrology study to ensure that the potential for flooding occun-ences during high retum rainfall events is minimized to an acceptable level. As discussed in the Stmctural Treatment BMP section the design flow using the Rational Method was calculated to be 30.9 cfs. The Vortechs Model PCI 6x24, with a peak treatment flow design capacity of 40.0 cfs, was selected because ofthe results of the Flow Calculation spreadsheet, provided by Vortechnics and included in the Attachments section ofthis report, show that during the 100-yr storm the diversion weir would divert 39.5 cfs through the treatment unit. Therefore the unit has been sized to handle the flow of 39.5 cfs. For the southern portion, the Vortechs Model 9000, with a peak treatment flow design capacity of 14.0 cfs, was selected because ofthe results ofthe Low Flow Diversion spreadsheet, included in the Attachments section ofthis report, show that during the 100-yr storm the diversion weir would divert 11.7 cfs through the treatment unit. Therefore the unit has been sized to handle the fiow of 11.7 cfs. JC:TK h:\sw quaiity\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM La Costa Greens - Neighborhood 1.12 Stormwater Management Plan SECTION IV ATTACHMENTS JC:TK h:\sw quality\2352\71\wqtr-05.doc w.o. 2352-71 4/16/04 9:32 AM VILLAGES OF LA COSTA NEIGHBORHOOD 1.09, 1.10 AND PORTION OF 1.12 (NORTH) TDtiAXH/icMT Cl rrtA/ r-tc-rcDiv/riM A-ri/-\M. Q=C*I*A TREATMENT AREA 196.05 ACRES RAINFALL INTENSITY 0.20 IN/HR WEIGHTED CURVE NUMBER 0.53 Q = 20.78 CFS 10:45 AM8/18/2003 Sheetl RM-TREATMENT FLOW.xIs VILLAGES OF LA COSTA NEIGHBORHODD 1.13, 1.14, AND PORTIONS OF 1.12 (SOUTH) Q=C*I*A TREATMENT AREA 75.92 ACRES RAINFALL INTENSITY 0.20 IN/HR WEIGHTED CURVE NUMBER 0.40 Q = 6.07 CFS 12:43 PM8/18/2003 Sheetl RM-TREATMENT FLOW-12-13-14.xls Vortechs Wefr Cd = 0.56 Cd = 0 A(ft^ = 6.31 Weir Crest Lenglh (fl) = 0 Crest Elevation fll) = ICB.OO Crest Elevation fll) = m.m FLOW CALCULATIONS La Costa Greens >flllage Neighborhood Carisbad, CA PC16X26 Bypass Wetr Ccl = 3.3 Weir Crest Lsngth 01) = 16 Crest Elevation (ft) =101.5 Head Elevation Oriflce Flow Weir Flow Bypass Fiow Totel Flow m m m m (cfe) (cfe) o.cn m.QQ 0.00 0.CH3 0.03 0.03 0.25 100.25 1.34 0.00 0.OQ 1.34 0.50 100.50 3.78 0.00 0.00 3.78 0.75 1CB.75 6.94 0.00 0.00 6.94 1.00 101.00 io.ra 0.00 0.00 10.68 1.25 101.25 14.93 0.00 0.00 14.93 1.50 101 .a) 19.63 0.00 0.00 19.63 1.75 101.75 24.73 0.00 s.m 31.33 2.00 m.m 30.08 0.00 18.67 48.75 2.25 102.25 33.26 0,00 34.:;^ 67.55 2.50 its.aj 36.15 0.03 S2.m 88.95 2,75 102.75 38.84 0.00 73.79 112.63 3.00 103.(B 41.34 0.00 97.CO 138.34 3.25 1(0.25 4371 0.00 122.23 165.94 3.50 103.33 45,% 0.00 149.34 195,29 4.34 104,34 52.82 0.0Q 253.18 336.00 Calculated b Y: WSG 6WW3 ichecked bv: 1 UJ 105X) 1045 104.0 1035 103.0 1025 102U 101.5 101 i) 1005 100.0 395 Vortechs^ System Stage Discharge Curve f / 0.0 9).0 100.0 150.0 203.0 2S0i) 300.0 SSOJ) Discharge (cfs) La Costa Greens Neighborhoods 1.12,1.13, and 1.14 HYDRAULIC ANALYSIS OF LOW FLOW DIVERSION & VORTECHS UNIT AT CLEANOUT LOW FLOW ORIFICE (Q= 6.07 cfs) Weir Formula for Orifices & Short Tubes (free & submerged) Q= Ca(23h)'" fEar.. 1^ Q= Ca(64.32h)°*; C=0.56 Q = 4.491 a(h)° ^ where a = area of orifice opening, h = head (ft) above centeriine of orifice Orifice Size, L= 16 in. ,a= 1.33 sq.ft., invert elevation = 100.00 ft. H = 12 in. HIGH FLOW (Qioo = 130.7 cfs) Weir Formula for Bypass Weir & Vortechs Weir Q = CLH^ ^ C = 3.3 for Bypass 6.2 for Vortechs (Eqn. 2) Bypass: L = 10.0 ft. ©elevation 101.50 ft. ( 1.50 ft.) Vortechs L = 1.0 ft. ©elevation 105.00 ft. 1.50 ft.) ELEV. Lo Flow (Eq. 1) Weir Flow (Eq. 2) LoFlow(Eq. 1) Weir Flow (Eq. 2) ELEV. Orifice Vortechs Bypass TOTAL ELEV. Orifice Vortechs Bypass TOTAL (feet) h(ft) Q(cfs) H(ft) Q(cfs) H(ft) Q(cfs) Q(cfs) (feet) h(ft) Q(cfs) H(ft) Q(cfs) H(ft) Q(cfs) Q (cfs_]_ 100.00 0.0 0.0 0.0 0.0 0.0 0.00 0.0 102.58 2.08 8.64 0.00 0.00 1.08 37.2 45.9 100.17 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.67 2.17 8.81 0.00 0.00 1.17 41.6 50.4 100.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.75 2.25 8.98 0.00 0.00 1.25 46.1 55.1 100.33 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.83 2.33 9.15 0.00 0.00 1.33 50.8 60.0 100.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.92 2.42 9.31 0.00 0.00 1.42 55.6 65.0 100.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 103.00 2.50 9.47 0.00 0.00 1.50 60.6 70.1 100.58 0.08 1.73 0.00 0.00 0.00 0.00 1.73 103.08 2.58 9.62 0.00 0.00 1.58 65.7 75.4 100.67 0.17 2.44 0.00 0.00 0.00 0.00 2.44 103.17 2.67 9.78 0.00 0.00 1.67 71.0 80.8 100.75 0.25 2.99 0.00 0.00 0.00 0.00 2.99 103.25 2.75 9.93 0.00 0.00 1.75 76.4 86.3 100.83 0.33 3.46 0.00 0.00 0.00 0.00 3.46 103.33 2.83 10.08 0.00 0.00 1.83 81.9 92.0 100.92 0.42 3.87 0.00 0.00 0.00 0.00 3.87 103.42 2.92 10.23 0.00 0.00 1.92 87.6 97.8 101.00 0.50 4.23 0.00 0.00 0.00 0.00 4.23 103.50 3.00 10.37 0.00 0.00 2.00 93.3 103.7 101.08 0.58 4.57 0.00 0.00 0.00 0.00 4.57 103.58 3.08 10.52 0.00 0.00 2.08 99.2 109.7 101.17 0.67 4.89 0.00 0.00 0.00 0.00 4.89 103.67 3.17 10.66 0.00 0.00 2.17 105.2 115.9 101.25 0.75 5.19 0.00 0.00 0.00 0.00 5.19 103.75 3.25 10.80 0.00 0.00 2.25 111.4 122.2 101.33 0.83 5.47 0.00 0.00 0 00 0 00 5 47 103 83 3 33 10 93 CCT 0 00 2 2.. 1176 128 6 101.42 0.92 5.73 0.00 0.00 0 00 OJDO 5 73 103 92 3 42 '11 07 cc • 0 00 ' 2,42 124 0 135 0 . 101.50 ICO 5.99* '0 00' 0.00 0 00 0.00, 5.99 104.00 3.50 11.20 0.00 0.00 2.50 130.4 141.6 101.58 1.08 6.23 0.00 0.00 0.08 0.79 7.03 104.08 3.58 11.34 0.00 0.00 2.58 137.0 148.4 101.67 1.17 6.47 0.00 0.00 0.17 2.25 8.71 104.17 3.67 11.47 0.00 0.00 2.67 143.7 155.2 101.75 1.25 6.70 0.00 0.00 0.25 4.13 10.82 104.25 3.75 11.60 0.00 0.00 2.75 150.5 162.1 101.83 1.33 6.91 0.00 0.00 0.33 6.35 13.27 104.33 3.83 11.72 0.00 0.00 2.83 157.4 169.1 101.92 1.42 7.13 0.00 0.00 0.42 8.88 16.00 104.42 3.92 11.85 0.00 0.00 2.92 164.4 176.2 102.00 1.50 7.33 0.00 0.00 0.50 11.67 19.00 104.50 4.00 11.98 0.00 0.00 3.00 171.5 183.4 102.08 1.58 7.54 0.00 0.00 0.58 14.70 22.24 104.58 4.08 12.10 0.00 0.00 3.08 178.7 190.8 102.17 1.67 7.73 0.00 0.00 0.67 17.96 25.69 104.67 4.17 12.22 0.00 0.00 3.17 186.0 198.2 102.25 1.75 7.92 0.00 0.00 0.75 21.43 29.36 104.75 4.25 12.35 0.00 0.00 3.25 193.3 205.7 102.33 1.83 8.11 0.00 0.00 0.83 25.10 33.21 104.83 4.33 12.47 0.00 0.00 3.33 200.8 213.3 102.42 1.92 8.29 0.00 0.00 0.92 28.96 37.25 104.92 4.42 12.58 0.00 0.00 3.42 208.4 221.0 102.50 2.00 8.47 0.00 0.00 1.00 33.00 41.47 105.00 4.50 12.70 0.00 0.00 3.50 216.1 228.8 SO USE MODEL 7000 vortechsl 2lnch-mi-02.xls APPROXIMATE VORTECHNICS TREATMENT AREAS Model 1000 1.6 10 14 15 18 23 Modei 2000 2.8 17 24 26 31 39 Model 3000 4.5 27 38 41 49 62 Modei 4000 6.0 37 51 55 66 83 Modei 5000 8.5 52 72 78 94 117 Modei 7000 11.0 73 102 110 132 165 Modei 9000 14.0 93 129 140 168 210 Model 11.000 17.5 117 162 175 210 263 Modei 16,000 25.0 167 231 250 300 375 Plan View GritChamber ^^S^S^f^C- FlowConttxjl "-"i Wall. . • Chamber -VBevation Mew: Dry-VVeather . 1) Initicd Wet Weather Phase During a two-month slnrm event tiie water level begins to rise above the top ofthe inlet pipe. This influent control feature reduces turbulence and avoids resuspension of pollutants. 3) Full Capacity Phase When the high-flow outlet approaches full dischsrge, stcrm drains ars flowing at peak capacity. "ITie Vortechs SystHn is designed to match your design storm flow and provida Ixeat- ment throughout the range of storm events without bypass- Grit Chamber The swiriing motion created by the tangential inlet directs settleable solids toward the center of this chamber. Sediment is caught in ^ the swirling flow path arid settles : back onto the pile after the storm • 1 •event is over. -.•••'. .i i Oil Chamiber & Baffle Wall' ''' ' The center baffie traps floatables in ' 1 •the oil chamber, even during clean- ••^j ..'.out. Highly resistant to flow .surges, Flow Control Chamber -i ^''] ...The weir and oriffca flow conirois^^''-' i Raise level and volurhe in.the. -:.;::.;! systerfi as flow rate increases; and*;^1 2J gradually drain the'system^as -^-^' -"-^ . flow rata subsides.' .' "" ;. i . •••.j:y'•'• "i 2) Transition Phase As the inflow rate increases above the controlled outflow rate, the tank fills and the floating contaminant layer accu- mulated from past storms rises. Swirling action increases at this stage, while sediment pile remains stable. 4) Storm Subsidence Phase/Cleaning Treated runoff is decanted at a contralled rate, restoring the water level to a iow dryweather volume and revealing a conical pile of sediment The low water levei facilitates inspection and cleaning, and significantly reduces maintenance costs. The '^MS^^.r-^-f.-fi' ^- 'Mi Stormwater Treatment System rerrGracea LBvers INV S'M 3" IVpical ^ / .Seal t 3to4f I 3 Plan View To begin the design of your Vortechs Systein, refer to the siaing chart below and com- plete a Specifier's Worksheet to provide details about yotxr site and design flows. Then simply- fax or mcril the worksheet to Vortechnics with your site plan, and we'll produce detailed Vortechs System scale draw- ings free of charge. Bevation View .if ' •.';..•.•':.-'.. •'•-i Engineering Notes' S'';.•',::^: . - •; 'A] fee WKe Vortachs Syseams without abypM,-siw chamher-surfaca area for' aach TOO gpm atpa^ design storm flow rata (e.g., K^yaar storm). For mors i . - datans about VbrtBchnic3 sizing criteria refer • • .Bl'Sadmant storage yolurT]? assume* a-3 loot aurnp..- • : - • . ,'--.v .. c .. °'. g- ConaGTuctian dataiti' may-vary dspsndirig on'-Oie kjjedfiQ sppBcatibri. Any alteraUans Co tha sizing chart specifi- .-. cataona wB appear gn yiM-tachnics_dim.enaiaisl and sliop tfrawinga. Plaasa- call Vbrtechnica fbp tha weigfit of spe-- .•"dHo-VAirtBCha systamaifnaadad.,-. ..-..j ' • ; .• • Special Nota: Ql storage capacitj.wheo it ia naedad to,iiiBat a specific rsquirBmBnt fop spii containment, can ba . °'sizad to meat cha storage raquirisment'withthe selecCad modeL \Airtachnic3 technical staff wiH optimiza s^tem.' ' . geomatry to .meet containtTient paquiramehta within a corractiy sized VAirtachs System-. " '{.MetrkSpadllcatxinamit^ ' , • Vortechs System Inlet/Outlet Configurations Vortechs Systems con be configTired to accommo- date various inlet and cutlet pipe orientations. The inlet pipe can enter the end or side of the tank at right angles - outlet pipes can exit the end or the side of system at most angles. End Inlet 0 1 Side Inlet To Palish H Offline U Pretreatment To Cucfall IQ -, , 2 LACastA PREPARED FOR: HUNSAKER & ASSOCIATES 5AN Df[CC\ INC PIANNINC 1009 HuBinkois Sum ENCINEEIUNC San l>ego, Ca 92121 SURVEYING PH(858)5SM500- fX(BS«3SS«-m4 QUADRANGLE MAP WATERSHED EXHIBIT FOR LA COSTA GREENS CARLSBAD, CALIFORNIA , — — 1