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HomeMy WebLinkAboutCT 02-03; La Costa Oaks So PA 3.12/13; Storm water management plan; 2003-07-24PLANNING ENGINEERING SURVEYING IRVINE LOS ANGELES RIVERSIDE SAN DIEGO HUNSAKER ^ASSOCIATES SAN DIECO, INC. STORM WATER MANAGEMENT PLAN for LA COSTA OAKS SOUTH NEIGHBORHOODS 3.08 - 3.15 City of Carlsbad, California Prepared for: Real Estate Collateral Management Company c/o Morrow Development 1903 Wright Place, Suite 180 Carlsbad, CA 92008 W.O. 2352-39 July 24,2003 DAVE HAMMAR LEX WILLIMAN ALISA VIALPANDO Eric Mosolgo, R^.E. Water Resources Department Manager Hunsaker & Associates San Diego, Inc. L.»J 10179 Huennekens St. San Diego, CA 92121 (858) 558-4500 PH (858) 558-1414 FX www.HunsakerSD.com lnfo@HunsakerSD.com (yfo-i-^^ EMrsmm h:\sw quality\2352\39\swnip-oaks-south.doc W.O. 2352-39 7/28/03 10:38 AM wmul CL La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan TABLE OF CONTENTS CHAPTER 1 - Executive Summary 1.1 Introduction 1.2 Summary of Pre-Developed Conditions 1.3 Summary of Proposed Development 1.4 Results and Recommendations CHAPTER 2 - storm Water Criteria 2.1 Regional Water Quality Control Board Criteria 2.2 City of Carlsbad SUSMP Criteria CHAPTER 3 - Identification of Typical Pollutants 3.1 Anticipated Pollutants from Project Site 3.2 Sediment 3.3 Nutrients 3.4 Trash & Debris 3.5 Oxygen-Demanding Substances 3.6 Oil & Grease CHAPTER 4 - Conditions of Concern 4.1 Receiving Watershed Descriptions 4.2 Pollutants of Concern in Receiving Watersheds 4.3 Peak Flow Attenuation (Regional Detention Facility) CHAPTER 5 - Volume-Based Best Management Practices (BMPs) 5.1 Design Criteria 5.2 Extended Detention Basins 5.3 Pollutant Removal 5.4 Maintenance Requirements CHAPTER 6 - Flow-Based BMPs 6.1 Design Criteria 6.2 Vortechs Treatment Units 6.3 Pollutant Removal Efficiency Table 6.4 Maintenance Requirements EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 6:20 AM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water l\/lanagement Plan CHAPTER 7 - Source Control BMPs 7.1 Landscaping 7.2 Urban Housekeeping 7.3 Automobile Use CHAPTER 8 - Site BMP Design (Extended Detention Basin) 8.1 BMP Location 8.2 Detemnination of Treatment Volume 8.3 Water Quality Basin Design CHAPTER 9 - Site BMP Design (Vortechs Treatment Units) 9.1 BMP Locations 9.2 Determination of Treatment Flows 9.3 Vortechs Treatment Unit Selections CHAPTER 10 - References List of Tables and Figures Chapter 1 - Watershed Map Chapter 1 - BMP Location Map Chapter 3 - Pollutant Category Table Chapter 4 - San Diego Region Hydrologic Divisions Chapter 4 - Combined 1998 and Draft 2002 Section 303(d) Update Chapter 4 - Beneficial Uses of Inland Surface Waters Chapter 4 - Water Quality Objectives Chapter 5 - Pollutant Removal Efficiency Table (Volume-Based BMPs) Chapter 6 - Pollutant Removal Efficiency Table (Flow-Based BMPs) Chapter 8 - Extended Detention Basin Location Map Chapter 8 - Water Quality Basin Schematic (Profile) Chapter 8 - Stage-Storage Data Chapter 8 - Stage-Discharge Data for Water Quality Basin Dewatering Chapter 8 - 85'*^ Percentile Rainfall Isopluvial Map Chapter 9 - Neighborhood 3.9 West BMP Location Map Chapter 9 - Neighborhood 3.9 East BMP Location Map Chapter 9 - Neighborhood 3.12 BMP Location Map Chapter 9 - Neighborhood 3.15 BMP Location Map Chapter 9 - Design Runoff Determination Summary Table Chapter 9 - Vortechs Unit Treatment Capacity Table Chapter 9 - Vortechs System Data EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 11:47 AM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan Chapter 1 - EXECUTIVE SUMMARY 1.1 - Introduction The La Costa Oaks South development is located east of the existing alignment of Rancho Santa Fe Road, north of the existing extension of La Costa Avenue, and south of the Stanley Mahr Reservoir in the City of Carlsbad, California (see Watershed Map on the following page). Neighborhoods 3.08 through 3.15 comprise the Oaks South portion of the larger La Costa Oaks development. Per the City of Carlsbad SUSMP, the La Costa Oaks South project is classified as a Priority Project and subject to the City's Permanent Storm Water BMP Requirements. This Stomi Water Management Plan (SWMP) has been prepared pursuant to requirements set forth in the City of Carlsbad's "Standard Urban Storm Water Mitigation Plan (SUSMP)." All calculations are consistent with criteria set forth by the Regional Water Quality Control Board's Order No. 2001-01, and the City of Carlsbad SUSMP. This SWMP recommends the location and sizing of site Best Management Practices (BMPs) which include one water quality extended detention basin and four Vortechs treatment units (see BMP Location Map in this chapter). Furthermore, this report determines anticipated project pollutants, pollutants of concern in the receiving watershed, peak flow mitigation, recommended source control BMPs, and methodology used for the design of flow-based and volume-based BMPs. 1.2 - Summary of Pre-Developed Conditions As shown in the watershed map on the following page, the majority of the pre- developed La Costa Oaks South site drained to the Encinitas Creek watershed. The remainder of the site (portions of Neighborhoods 3.08 and 3.09) drained to the San Marcos Creek watershed via an existing inlet to the old Rancho Santa Fe storm drain system. The Regional Water Quality Control Board has identified both Encinitas Creek and San Marcos Creek as part of the Carlsbad Hydrologic Unit, San Marcos Hydrologic Area, and the Batiquitos Hydrologic Subarea (basin number 4.51). 1.3 - Summary of Proposed Development Development of the La Costa Oaks South site will include the construction of single- famliy homes as well as the associated streets, sidewalks, landscaping and utilities. As part of the development, a regional detention basin was constructed at the downstream end of the project in Neighborhood 3.12. EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 12:30 PM LEGEND WATERSHED BOUNDARY BASIN WATERSHED BOUNDARY NEIGHBORHOOD BOUNDARY AREA M-o«9 ^\ WATER QUALITY DEVICE BMP LOCATION MAP FOR LA COSTA OAKS SOUTH CITY OF CARLSBAD, CALIFORNIA SHEET 1 OF 1 Ri\02^9\lHyii\HTD-CnMPOSITE-l«P-i»i«.dWBC 2083]Jul-a3-a003cll>37 La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan The "Addendum to Preliminary Hydrology Study for Villages of La Costa - The Ridge & The Oaks", prepared by Hunsaker & Associates and dated October 23, 2001, details the design of the regional detention facility. As shown in the referenced report, the regional detention facility mitigates design peak flow increases below pre-development levels. In addition to peak flow attenuation, this basin also serves as a regional water quality basin. A riser extends from the basin bottom elevation of 285 feet to a top elevation of 293 feet. Storm water treatment occurs in this bottom 8 feet of the basin while peak flow attenuation is provided in the basin above elevation 293 feet. Four flow-based BMPs will be located at other site discharge locations. 85"^ percentile runoff will be treated in the proposed Vortechs systems at Paseo Conifera, Neighborhood 3.09, Avenida Junipero, and La Costa Avenue prior to discharging into the receiving drainage system. 1.4- Results and Recommendations The water quality / regional detention facility is located at the downstream (south) end of Neighborhood 3.12 (see BMP Location Map on the following page). Runoff from Neighborhoods 3.08, 3.10, 3.11, 3.12, 3.13, 3.14 and 3.15 drains to this location. Additionally, runoff from a large offsite area will also drain to the basin area. The combined watershed area draining the basin was determined to be 401 acres. Using the 85**^ percentile rainfall of 0.68 inches (see Ispoluvial Map at the end of this chapter) and assuming 20 percent imperviousness in the contributing watershed, HEC-HMS calculations predicted an 85'^ percentile runoff volume of roughly 3.0 acre- feet. The basin's stage-storage data shows that the water quality basin area has a peak storage volume of 3.0 acre-feet at the riser top elevation of 293 feet. The total basin storage volume for detention (above elevation 293 feet) is 7.6 acre-feet. Since the basin storage volume in the water quality portion of the basin equals the projected 85*'' percentile runoff volume, the BMP meets SUSMP criteria. Each of the proposed Vortechs units is an offline precast treatment unit. The 85"^ percentile design flow rate is forced into the treatment area by a diversion weir built in the upstream junction. Flows in excess of the design flow rate pass over the weir and proceed downstream. Vortechs Model 1000 units, with a treatment flow capacity of 1.6 cfs, are recommended for the treatment units at Neighborhood 3.09, La Costa Avenue and Avenida Junipero while a Model 2000 is recommended at Paseo Conifera. EM:EM h:\sw quallty\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 12:37 PM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan Chapter 2 - STORM WATER CRITERIA 2.1 - Regional Water Quality 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 prior to 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 runoff from municipal storm separate drainage systems draining the watersheds of San Diego County. Per the RWQCB Order, post-development runoff 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 storm water management techniques that are applied to manage construction and post- construction 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 storm 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. All structural BMPs shall be located to infiltrate, filter, or treat the required runoff volume or flow (based on the 85*'^ percentile rainfall) prior to its discharge to any receiving watercourse supporting beneficial uses. 2.2 - City of Carlsbad SUSMP Criteria Per the City of Carlsbad SUSMP, the La Costa Oaks South project is classified as a Priority Project and subject to the City's Permanent Storm Water BMP Requirements. These requirements required the preparation of this Storm Water Management Plan. The Storm Water Applicability Checklist, which must be included along with Grading Plan applications, is included on the following page. EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/24/03 10:44 AM storm Water Standards 4/03/03 VI. RESOURCES & REFERENCES APPENDIX A STORM WATER REQUIREMENTS APPLICABILITY CHECKLIST Complete Sections 1 and 2 of the following checklist to determine your project's permanent and construction storm water best management practices requirements. This form must be completed and submitted with your permit application. Section 1. Permanent Storm Water BMP Requirements: If any answers to Part A are answered "Yes," your project is subject to the "Priority Project Permanent Storm Water BMP Requirements," and "Standard Permanent Storm Water BMP Requirements" in Section III, "Permanent Storm Water BMP Selection Procedure" in the Storm Water Standards manual. If all answers to Part A are "No," and any answers to Part B are "Yes," your project is only subject to the "Standard Permanent Storm Water BMP Requirements". If every question in Part A and B is answered "No," your project is exempt from permanent storm water requirements. Part A: Determine Priority Project Permanent Storm Water BMP Requirements Does the project meet the definition of one or more of the priority project categories?* Yes No 1. Detached residential development of 10 or more units / 2. Attached residential development of 10 or more units / 3. Commercial development greater than 100,000 square feet • 4. Automotive repair shop 5. Restaurant 6. Steep hillside development greater than 5,000 square feet 7. Project discharging to receiving waters within Environmentally Sensitive Areas 8. Parking lots greater than or equal to 5,000 If or with at least 15 parking spaces, and potentially exposed to urban runoff / 9. Streets, roads, highways, and freeways which would create a new paved surface that is 5,000 square feet or greater / * Refer to the definitions section in the Storm Water Standards for expanded definitions of the priority project categories. Limited Exclusion: Trenching and resurfacing work associated with utility projects are not considered priority projects. Parking lots, buildings and other structures associated with utility projects are priority projects if one or more of the criteria in Part A is met. If all answers to Part A are "No", continue to Part B. 30 La Costa Oaks South (Neighborhoods 3.08 Storm Water Management Plan •3.15) Chapter 3 - IDENTIFICATION OF TYPICAL POLLUTANTS 3.1 - Anticipated Pollutants from Project Site The following table details typical anticipated and potential pollutants generated by various land use types. The La Costa Oaks South development will consist of detached single-family residences. Thus, the Detached Residential Development category has been highlighted to clearly illustrate which general pollutant categories are anticipated from the project area. General Pollutant Categories Priority Project Categories Sediments Nutrients Heavy IVIetals Organic Compounds Trash & : Debris Oxygen Demanding Substances Oil & Grease Bacteria & Viruses Pesticides Detached Residential Development X X X X X X X Attached Residential Development X X X p(i) p(2) P X Commercial Development >100,000ft^ p(1) p(1) p(2) X p(5) X p(3) p(5) Automotive Repair Shops X X(4)(5) X X Restaurants X X X X Hillside Development >5,000ft^ X X X X X X Parking Lots p(1) p(1) X X p(1) X p(1) Streets, Highways & Freeways X p(1) 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. EM:EM h:\sw quallty\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/24/03 11:09 AM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan 3.2 - Sediment Soils or other surface materials eroded and then transported or deposited by the action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills, reduce spawning habitat, smother bottom dwelling organisms, and suppress aquatic vegetative growth. 3.3 - Nutrients Inorganic substances, such as nitrogen and phosphorous, that 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. 3.4 - Trash & Debris Examples include paper, plastic, leaves, grass cuttings, and food waste, which 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. 3.5 - Oxvqen-Demandinq Substances 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 depletion of dissolved oxygen in a water body and possibly the development of septic conditions. 3.6 - Oil & Grease Characterized as high high-molecular weight organic compounds. Primary sources of oil and grease are petroleum hydrocarbon products, motor products from leaking vehicles, oils, waxes, and high-molecular weight fatty acids. Elevated oil and grease content can decrease the aesthetic value of the water body, as well as the water quality. EM:EM h:\sw quallty\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/24/03 11:04 AM IV La Costa Oaks South (Neighborhoods 3.08-3.15) Storm Water Management Plan Chapter 4 - CONDITIONS OF CONCERN 4.1 - Receivinq Watershed Descriptions As shown in the watershed map on the following page, the majority of the pre- developed La Costa Oaks South site drained to the Encinitas Creek watershed. In developed conditions, runoff from a 401-acre watershed drains through the regional detention facility near La Costa Avenue (in Neighborhood 3.12) and then discharges to a tributary of Encinitas Creek. Runoff from Neighborhood 3.09 discharges to a storm drain system constructed along with the new alignment of Rancho Santa Fe Road. This runoff, along with runoff from Rancho Santa Fe Road confluences with the aforementioned 401-acre watershed around the location of the La Costa Avenue - Camino De Los Coches intersection. At the southeast corner of the Oaks South site, a 5-acre watershed discharges to a side canyon near Avenida Junipero (in the headwater regions of Encinitas Creek). In developed conditions, the total drainage area from the site area (including offsite areas draining through the site) to the Encinitas Creek watershed is roughly 422 acres. Portions of Neighborhood 3.08 drain to the San Marcos Creek watershed via an existing inlet to the old Rancho Santa Fe storm drain system. In developed conditions, the developed condition drainage area from the site area to the San Marcos Creek watershed is roughly 24 acres. The Regional Water Quality Control Board has identified both Encinitas Creek and San Marcos Creek as part of the Carlsbad Hydrologic Unit, San Marcos Hydrologic Area, and the Batiquitos Hydrologic Subarea (basin number 4.51). 4.2 - Pollutants of Concern in Receivinq Watersheds Neither Encinitas Creek nor San Marcos Creek are listed on the EPA's 303(d) List of endangered watenways (included in this Chapter). Per the "Water Quality Plan for the San Diego Basin", the beneficial uses for both waterways include agricultural supply, contact water recreation, non-contact recreation, warm freshwater habitat, and wildlife habitat. Table 3-2 from the "Water Quality Plan for the San Diego Basin" (included at the end of this Chapter) lists water quality objectives for a variety of potential pollutants required to sustain the beneficial uses of the San Marcos hydrologic area. EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 8:20 AM ^^^^^^ ENCINITA^ %dx CREEK %/ S WATERSHEbasA._i/^^i^ CEflVD HUNSAKER & ASSOCIATES HYDROLOGY MAP FOR LA COSTA OAKS SOUTH CITY OF CARLSBAD, CAUFORNIA SHEET 1 OF 1 La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan 4.3 - Peak Flow Attenuation (Reqiona! Detention Facility^ The "Addendum to Preliminary Hydrology Study for Villages of La Costa - The Ridge & The Oaks", prepared by Hunsaker & Associates and dated October 23, 2001, details the design of the regional detention facility located near La Costa Avenue in Neighborhood 3.12. As shown in the referenced report, the regional detention facility mitigates design peak flow increases below pre-development levels. In addition to peak flow attenuation, this basin also serves as a regional water quality basin. A riser extends from the basin bottom elevation of 285 feet to a top elevation of 293 feet. Storm water treatment occurs in this bottom 8 feet of the basin while peak flow attenuation is provided in the basin above elevation 293 feet. EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/24/03 7:50 PM TABLE 1 SAN DIEGO REGION HYDROLOGIC DIVISIONS i i i k ii I I I k k k k BASIN BASIN HYDROLOGIC BASIN NUMBER HYDROLOGIC BASIN NUMBER HYDROLOGIC BASIN 1.00 SAN JUAN HYDROLOGIC UNIT 2.74 Burnt HSA 1.10 Laguna HA 2.80 Aguanga HA 1.11 San Joaquin Hills HSA 2.81 Vail HSA 1.12 Laguna Beach HSA 2.82 Devils Hole HSA 1.13 Aliso HSA 2.83 Redec HSA 1.14 Dana Point HSA 2.84 Tule Creek HSA 1.20 Mission VIeJo HA 2.90 Oakgrove HA • 1.21 Oso HSA 2.91 LAwerCulp HSA 1.22 Upper Trabuco HSA 2.92 Previtt Canyon HSA 1.23 Middle Trabuco HSA 2.93 Dodge HSA 1.24 Gobemadora HSA 2.94 Chihuahua HSA 1.25 Upper San Juan HSA 1.26 Middle San Juan HSA 3.00 SAN LUIS REY HYDROLOGIC UNIT 1.27 Lower San Juan HSA 3.10 Lower San Luis HA 1.28 Ortega HSA 3.11 Mission HSA 1.30 San Clemente HA 3.12 Bonsall HSA .'• 1.31 Prima Deshectia HSA 3.13 Mocsa HSA. 1.32 Segunda Deshecha HSA 3.14 Valley Center HSA 1.40 San Mateo Canyon HA 3.15 Woods HSA 1.50 San Onofre HA 3.16 Rincon HSA 1.S1 San Onofre Valley HSA 3.20 Monserate .HA-' 1.52 Las Puigas HSA 3.21 Pala HSA 1.53 Stuart HSA 3.22 - 3.23 Pauma La Jolla Amago .• HSA HSA 2.00 SANTA MARGARHTA HYDROLOGIC UNIT 3.30 Warner Valley HA 2.10 Ysidora HA 3.31 Warner HSA 2.11 Lower Ysidora HSA 3.32 Combs HSA 2.12 Chappo HSA 2.13 Upper Ysidora HSA 4.00 CARLSBAD HYDROLOGIC UNIT 2.20 DeiJiZ HA 4.10 Loma Alta HA 2.21 OeLuz Creek HSA 4.20 Buena Vista Creek HA 2.22 Gavilan HSA 4.21 El Salto HSA 2.23 Vallecitos HSA 4.22 Vista HSA 2.30 Murrleta HA 4.30 Agua Hedionda HA 2.31 Wlldomar HSA 4.31 LosMonos HSA 2.32 Murrleta HSA 4.32 Buena HSA 2.33 French HSA 4.40 Encinas HA 2.34 2.35 Lower Domenlgoni Domenigoni HSA HSA \ 4.!)U 1 4.51 San ivlarcos Batlouitos 2.36 Diamond HSA Richland HSA 2.40 Auld HA 4.53 Twin Oaks HSA 2.41 Bachelor Mountain HSA 4.60 Escondido Creek HA 2.42 Gertrudis HSA 4.61 San EIIJo HSA 2.43 Lower Tucalota HSA 4.62 Escondido HSA 2.44 Tucalota HSA 4.63 Lake Wohlford HSA 2.50 Pechanga HA 2.51 Pauba HSA 5.00 SAN DIEGUITO HYDROLOGIC UNIT 2.52 Wolf HSA 5.10 Solana Beach HA 2.S0 ' Wilson HA 5.11 Rancho Santa Fe HSA 2.61 Lancaster Valley HSA 5.12 La Jolla HSA 2.62 Lewis HSA 5.20 Hodges HA 2.63 Reed Valley HSA 5.21 Del Olos HSA 2.70 Cave Rocks HA 5.22 Green HSA 2.71 Lower Coahuila HSA 5.23 Fellcita HSA 2.72 Upper Coahuila HSA 5.24 Bear HSA 2.73 Anza HSA T-1-1 Table 4 - Combined 1998* and Draft 2002 Section 303(d) Update Hydrologic Descriptor Waterbody 21 Loma Alta HA (904.10) Pacific Ocean Shoreline 22 Loma Alta HA Loma Alta Slough (904.10) Segment / Area ^ at Loma Alta Creek Mouth 24 El Salto HSA (904.21) Carlsbad City Beach at Carlsbad Village Drive Carlsbad State Beach at Pine Avenue Pollutant / Stressor Bacterial Indicators^ Bacterial Indicators^ Eutrophic Bacterial Indicators^ Extent of Year 8 acres 0.65 miles Buena Vista Lagoon Bacterial Indicators^ Sedimentation / Siltation 350 acres 350 acres 25 Los Monos HSA (904.31) Agua Hedionda Lagoon 26 Los Monos HSA (904.31) 27 San Marcos HA (904.50) 28 Escondido Creek HA (904.60) 29 San Elijo HSA (904.61) Agua Hedionda Creek Pacific Ocean Shoreline Pacific Ocean Shoreline San Elijo Lagoon lower portion at Moonlight State Beach at San Elijo Lagoon Nutrients Bacterial Indicators^ Sedimentation / Siltation Diazinon 150 acres 5 acres Total Dissolved Solids Bacterial Indicators^ bacterial Indicators^ Bacterial Indicators^ 0.4 miles 0.8 miles 150 acres Eutrophic 330 acres Sedimentation / 1998 1998 1998 1998 lower 2 miles 2002 lower 8 miles 2002 1998 1998" 1998 1 acres •^0 San Dieguito HU 1 (905.00) Pacific Ocean Shoreline at San Dieguito Lagoon Mouth 0.8 miles 1998 •^0 San Dieguito HU 1 (905.00) Pacific Ocean Shoreline Torrey Pines State Beach at Del Mar (Anderson Canyon) — Dacieriai Indicators^ 0.8 miles 1998 31 Del Dios HSA 1 (905.21) Green Valley Creek Sulfate 1 mile 2002 1 32 Del Dios HSA (905.21) Hodges Reservoir Entire Reservoir Color Entire 2002 1 32 Del Dios HSA (905.21) Hodges Reservoir Entire Reservoir Nitrogen Phosphorus Total Dissolved Solids Reservoir 1 (905.23^ Felicita Creek Total Dissolved Solids lower 2 miles 2002 1 34 Felicita HSA (905.23) Kit Carson Creek Total Dissolved Solids 1 mile 2002 1 35 Highland HSA 1 (905.31) Cloverdale Creek Phosphorus Total Dissolved Solids 1 mile 2002 136 Sutherland HSA (905.53) Sutherland Reservoir Entire Reservoir Color Entire 2002 last updated 7/22/2003 S:\WQS\303dlist\SD Staff Report-2002\2002 draft 303d list\ http://www.swrcb.ca.gov/iwqcb9/pragramsra03dlistn-able 4 - Combined 1998 and 2002 UpdS^able 4 Table 2-2. BENEFICIAL USES OF INLAND SURFACE WATERS BENEFICIAL USE Inland Surface Waters '''^ Hydrologic M A 1 N P G F P R R B W C W R S Unit Basin U G 1 N R W R 0 E E 1 A O 1 A P Number N R D 0 R S W C C 0 R L L-R W C H 1 2 L M D D E N San Diego County Coastal Streams - continued Buena Vista Lagoon 4.21 See Coastal Waters-Table 2-3 Buena Vista Creek 4.22 + • • • • • Buena Vista Creek 4.21 + • • • • • • Agua Hedionda 4.31 See Coastal Waters-Table 2-3 Agua Hedionda Creek 4.32 • • • • • • • Buena Creek 4.32 • • • • • • • Agua Hedionda Creek 4.31 • • • • • • • Letterbox canyon 4.31 • • • • • • • Canyon de las Encinas 4.40 + 0 • • • San Marcos Creek Watershed Batiquitos Lagoon 4.51 See Coastal Waters- Table 2-3 San Marcos Creek 4.52 + • • • • • unnamed intermittent streams 4.53 + • • • • San Marcos Creek Watershed ^|San Marcos Creek 4.51 + • • • • • ^jEncinitas Creek 4.51 + • • • • • " •-. . • Existing Beneficial Use O Potential Beneficial Use + Excepted From MUN (See Text) Waterbodies are listed multiple times if they cross hydirologic area or sub area boundaries. Beneficial use designations apply to all tributaries to the indicated waterbody, if not listed separately. Table 2-2 BENEFICIAL USES 2-27 September 8,1994 Table 3-2. WATER QUALITY OBJECTIVES Concentrations not to be exceeded more than 10% of the time during any one one year period. Constitiuent (mg/L or as noted) Inland Surface Waters Hydrologic Unit Basin Number TDS Cl SO, %Na N&P Fe Mn MBAS B ODOR Turb NTU Color Units F SAN LUIS REY HYDROLOGIC UNIT 903.00 Lower San Luis HA 3.10 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Monserat HA 3.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Warner Valley HA 3.30 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 dCARLSBAD HYDROLOGIC UNlT^) 904.00 Loma Alta HA 4.10 ---------none 20 20 1.0 Buena Vista Creek HA 4.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Agua Hedionda HA 4.30 500 250 250 60 - a 0.3 0.05 0.5 0.75 none 20 20 1.0 Encinas HA 4.40 ---------none 20 20 1.0 (^n Marcos HA> 4.50 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Escondido Creek HA 4.60 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 SAN DIEGUITO HYDROLOGIC UNIT 905.00 Solana Beach HA 5.10 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Hodges HA 5.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 San Pasqual HA 5.30 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Santa Maria Valley HA 5.40 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Santa Ysabel HA 5.50 500 250 '250-60 . a 0.3 0.05 0.5 0.75 none 20 20 1.0 PENASQUITOS HYDROLOGIC UNIT 906.00 Miramar Reservoir HA 6.10 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 Poway HA 6.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0 HA - Hydrologic Area HSA - Hydrologic Sub Area (Lower case letters indicate endnotes following the table.) Table 3-2 WATER QUALITY OBJECTIVES Page 3-23 Septembers, 199^ V La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan Chapter 5 - VOLUME-BASED BMPs 5.1 - Design Criteria Volume-based BMPs shall be designed to mitigate the volume of runoff produced from a 24-hour 85**^ percentile storm event, as determined from the local historical rainfall record. The 85'^ percentile rainfall for the La Costa Oaks site is 0.68 inches (see figure in Chapter 7). Such facilities are usually designed to store the first flush runoff event below the principle spillway elevation (riser, weir, etc.) while providing a means for low flow dewatering. Outlet structures will be designed to convey runoff from the 100-year frequency storm to the basin. 5.2 - Extended Detention Basin The La Costa Oaks South site contains one volume-based BMP - the bottom portion of the regional detention facility that operates as an extended duration storm water quality basin. This basin will collect the first flush runoff volume and retain it in the basin for a period of 24-48 hours. 85"^ percentile runoff volume, contained below the overflow elevation of the basin riser, will be slowly discharged from the treatment control basin via low flow orifices in the basin riser. After passing through the riser, an outlet pipe will dewater the basin and discharge runoff to the natural drainage course downstream. Runoff in excess of the first flush runoff volume will bypass the basin via a large diameter riser opening (top elevation = 293 feet). 5.3 - Pollutant Removal As shown in the table (from the City of Carlsbad SUSMP) on the following page, extended detention basins provide the following treatment efficiencies: Sediment - High removal efficiency Nutrients - Medium removal efficiency Heavy Metals - Medium removal efficiency Trash & Debris - High removal efficiency Oxygen-Demanding Substances - Medium removal efficiency Oil & Grease - Medium removal efficiency EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/24/03 8:31 PM storm Water Standards 4/03/03 Table 4. Structural Treatment Control BMP Selection Matrix. Pollutant of Concern Treatment Control BMP Categories Sediment Nutrients Heavy Metals Biofilters M L M Detention Basins H U M Infiltration Basins(i) H M M Wet Ponds or Wetlands H M u Drainage Inserts L L 1 Filtration H M Hydrodynamic Separator SystemsP) M L Organic Compounds Trash & Debris Oxygen Demanding Substances Bacteria IVI U L L u IVI U H M 11 IVI U u M u n U U M 11 L L M L 1 H M H M L L M L Oil & Grease w M KJ M n U u U L L M H L L Pesticides IndiiHinn tronrhoc an U U U U L U L (2) Mso known as hydrodynamic devices and baffle boxes L: Low removal efficiency M: Medium removal efficiency H: High removal efficiency U: Unknown removal efficiency Sources: Gt/Wance Specifying Management Measures for Sources ofNonpoint Pollution in Coastal Wateis (1993) National Stoiwwater Best Management Practices Database (2001). and Guide for BMP Selection in Urban Developed Amas (ZOOM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan 5.4 - Maintenance Requirements Proper maintenance is required to insure optimum performance of the basins. General BMP inspections should check for structural integrity of the riser, debris and litter removal to prevent blockage of outlet orifices, etc. Fencing should be provided at the top of the basins to serve as protection to the public from the safety hazards inherent with standing water in the basin. Maintenance of the extended detention basin will be the responsibility of the Homeowners Association until the time at which the City of Carlsbad assumes maintenance responsibilities. For proper maintenance to be performed, the storm water treatment facility must be accessible to both maintenance personnel and their equipment and materials. Factors that affect the operational perfomiance of a volume-based extended detention ponds include mowing, control of pond vegetation, removal of accumulated bottom sediments, removal of debris from all inflow and outflow structures, unclogging of orifice perforations, etc. Periodic inspections should be performed following each significant storm. These basins should be inspected at least twice a year to evaluate facility operation. Periodic inspections of both Water Quality Basins should be performed at regular intervals throughout the year. Additional inspections will be required after major rainfall events (defined per this Maintenance Plan as 24-hour rainfall events in excess of 1 inch). During the periodic and post-major event rainfall inspections, the inspector must identify any repairs and maintenance activities deemed necessary, including the removal of trash, debris, and sediment from the upper chamber of the basin area. All riser orifices should be unclogged during the periodic and post-rainfall inspections. A Registered Civil Engineer will conduct an annual inspection of each basin. This inspection will include a thorough inspection of the basin area, outlet structure and internal gabion structure. The engineer will identify any required repairs as well as corrective maintenance activity required to maintain the hydraulic performance of the basins. Annual maintenance activities will include the removal of the heavy vegetation that will inevitably grow in the basin. Roughly !4 half of the vegetation should be removed from the basin at each annual maintenance session, including all woody or aquatic vegetation and other obstructions to flow. All sediment, trash, and debris should be removed from the upper and lower chambers of the basin at the annual maintenance session. Sediment removed during periodic, post-major rainfall event, and annual maintenance can be placed in a sanitary landfill or used for composting activities. If no basin maintenance takes places for a period of longer than 1 year, then trapped pollutants may be deemed hazardous and special requirements may apply to disposal activities. In such a case, removals would require testing prior to disposal in a sanitary landfill. EM:EIV1 h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/24/03 8:42 PM VI La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan Chapter 6 - FLOW-BASED BMPs 6.1 - Design Criteria Flow-based BMPs shall be designed to mitigate the maximum flowrate 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. Per the request of the City of Carlsbad, 85"^ percentile flow calculations were performed using the Rational Method. The basic Rational Method runoff 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 draining to the treatment unit was determined using the areas analyzed in the final engineering hydrology report. The runoff coefficient is based on the following characteristics of the 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 regulations and NPDES criteria have established that flow-based BMPs shall be designed to mitigate a rainfall intensity of 0.2 inch per hour. Watershed Area (A) - Corresponds to total area draining to treatment unit. 6.2 - Vortechs Treatment Units The Vortechs Storm Water Treatment System is designed to efficiently remove grit, contaminated sediments, metals, hydrocarbons and floating contaminants from surface runoff. Combining swirl-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. EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 6:55 AM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan 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 The tangential inlet to the system creates a swirling motion that directs settleable solids into a pile towards the center of the grit chamber. Sediment is caught in the swirling flow path and settles back onto the pile after the storm event is over. Floatable 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. 6.3 - Pollutant Removal Efficiency Table Pollutant of Concern BMP Categories Hydrodynamic Separation Devices*^' Vortechs™ Stormwater Treatment System Sediment M-H H Nutrients L-M L-M Heavy Metals L-M L-M Organic Compounds L-M L-M Trash & Debris M-H H Oxygen Demanding Substances L L Bacteria L L Oil & Grease L-H H Pesticides L L (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 Management Measures for Sources ofNonpoint Pollution in Coastal Waters (1993), National Stormwater Best Management Practices Database (2001), and Guide for BMP Selection in Urban Developed Areas (2001). EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 6:56 AM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan 6.4 - Maintenance Requirements Flow-based storm water treatment devices should be inspected periodically to assure their condition to treat anticipated runoff. Maintenance of the proposed Vortechnics units includes inspection and maintenance 1 to 4 times per year. Maintenance of the Vortechs units 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 perfomi the maintenance of the treatment unit. Properly maintained Vortechs Systems will only require evacuation of the grit chamber portion of the system. In some cases, it may be necessary to pump out all chambers. In the event of cleaning other chambers, it is imperative that the grit chamber be drained first. Proper inspection includes a visual observation to ascertain whether the unit is functioning properly and measuring the amount of deposition in the unit. Floatables should be removed and sumps cleaned when the sump storage exceeds 85 percent of capacity specifically, or when the sediment depth has accumulated within 6 inches of the dry-weather water level. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. EM:EM h:\sw quallty\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 6:57 AM VII La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan Chapter 7 - SOURCE CONTROL BMPs 7.1 - 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 vegetation in ornamental and required landscapes. Per the RWQCB Order, the following landscaping activities are deemed unlawful and are thus prohibited: Discharges of sediment Discharges of pet waste Discharges of vegetative clippings Discharges of other landscaping or construction-related wastes. 7.2 - Urban Housekeeping Fertilizer applied by homeowners, in addition 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 application 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 runoff contaminants. Per the RWQCB Order, the following housekeeping activities 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, patios, plazas, and outdoor eating and drinking areas (landscape irrigation 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 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.). EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 6:40 AM La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan 7.3 - Automobile Use Urban pollutants resulting from automobile use include oil, grease, antifreeze, hydraulic fluids, copper from brakes, and various fuels. Homeowners should be educated as to the proper use, storage, and disposal of these potential storm water contaminants. Per the RWQCB Order, the following automobile use activities are deemed unlawful and are thus prohibited: Discharges of wash water from the hosing or cleaning of gas stations, auto repair garages, or other types of automotive service facilities. Discharges resulting 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' education program. A monitoring program should also be implemented to insure compliance. EM:EM h:\sw quallty\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 6:42 AM VIII La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan Chapter 8 - SITE BMP DESIGN EXTENDED DETENTION BASIN 8.1 - BMP Location The water quality / regional detention facility is located at the downstream (south) end of Neighborhood 3.12 (see BMP Location Map on the following page). Runoff from Neighborhoods 3.08, 3.10, 3.11, 3.12, 3.13, 3.14 and 3.15 drains to this location. Additionally, runoff from a large offsite area will also drain to the basin area. The combined watershed area draining the basin was determined to be 401 acres. 8.2 - Determination of Treatment Volume Per the "Addendum to Preliminary Hydrology Study for Villages of La Costa - The Ridge and The Oaks (dated October 23, 2001)," HEC-HMS output shows the drainage area to the regional detention / water quality basin is 401 acres. The corresponding time of concentration (from a previous Rational Method analysis contained within the "Preliminary Hydrology Study for Villages of La Costa - The Ridge and The Oaks" is 22.3 minutes. Using the 85th percentile rainfall of 0.68 inches (see Ispoluvial Map at the end of this chapter) and assuming 20 percent imperviousness in the contributing watershed, HEC-HMS calculations predicted an 85**^ percentile runoff volume of roughly 3.0 acre- feet. 8.3 - Water Qualitv Basin Design The water quality / detention basin exhibit included in this chapter shows that the riser makes this basin double as a detention and water quality basin. The riser will extend from the basin bottom elevation of 285 feet to a top elevation of 293 feet. Detention basin stage-storage calculations (included in this chapter) show that no storage effects were considered below the riser top elevation of 293 feet. In other words, peak flow attenuation was attained in the basin storage area above the Water Quality Basin (above elevation 293 feet) The stage-storage data shows that the water quality basin area has a peak storage volume of 2.97 acre-feet at the riser top elevation of 293 feet. The total basin storage volume for detention (above elevation 293 feet) is 7.65 acre-feet. Stage-discharge data for the riser dewatering (included in this chapter) shows that the peak outflow from the water quality basin area is 9 cfs at elevation 293 feet. At lower elevations in the Water Quality Basin, the corresponding outflow is less (for instance, the discharge rate at elevation 288 feet is 2.4 cfs). EM: EM h:\sw quallty\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 8:06 AM BMP LOCATION MAP FOR WATER QUALITY BASIN CARLSBAD, CALIFORNIA HUNSAKER & ASSOCIATES SAN DIEGO, INC. PROJECT: L.C, OAKS PES.BY: rUlV CHECKED BY: DATE: <^/o/ VILLAGES OF LA COSTA STAGE- STORAGE DATA DETENTION BASIN AT NODE 106 without a water quality component with a water quality component lELEV. "AREA ' A STORAGE AS STORAGE Rft) ^ • <ac) Maclft)*;^^ 285.0 0.00 0.00 0.00 285.0 0.00 0.00 0.00 286.0 0.23 0.12 0.12 286.0 0.23 0.12 0.12 287.0 0.35 0.29 0.41 287.0 0.35 0.29 0.41 288.0 0.38 0.36 0.77 288.0 0.38 0.36 0.77 289.0 0.40 0.39 1.16 289.0 0.40 0.39 1.16 290.0 0.43 0.42 1.58 290.0 0.43 0.42 1.58 291.0 0.45 0.44 2.02 291.0 0.45 0.44 2.02 292.0 0.48 0.47 2.48 292.0 0.48 0.47 2.48 293.0 0.50 0.49 2.97 293.0 0.50 0.49 2.97 294.0 0.53 0.51 3.49 295.0 0.55 0.54 4.03 293.0 0.50 0.00 0.00 296.0 0.69 0.62 4.65 293.5 0.51 0.25 0.25 297.0 0.82 0.75 5.40 294.0 0.53 0.51 0.51 298.0 0.94 0.88 6.28 295.0 0.55 0.54 1.05 299.0 1.02 0.98 7.26 296.0 0.69 0.62 1.67 300.0 1.10 1.06 8.32 297.0 0.82 0.75 2.42 301.0 1.16 1.13 9.44 298.0 0.94 0.88 3.30 302.0 1.21 1.18 10.63 299.0 1.02 0.98 4.28 300.0 1.10 1.06 5.34 301.0 1.16 1.13 6.47 302.0 1.21 1.18 7.65 for stormwater quality for detention ll' VILLAGES OF LA COSTA - THE OAKS HYDRAULIC ANALYSIS OF RISER SLOTS AT NODE 106 Orifice Equation (for h > M) Q = Ca(2gh)'" (Equation 4-10, Kings Handbook) Q= Ca(64.32hr°; 0= 0.6 from Table 4-4. Kings Handbook Q = 4.612 a(h)° ^ where a = area of orifice opening, h = head (ft) above centerline of opening. Weir Formula (for h < M): Q= CLH 1.5 (Equation 5-10, Kings Handbool<) C= 3.2 from Fig. 5-3 H L For Riser where: d = 36 in., a = 7.07 sq. ft., L = 9.42 ft. @ elevation 293.0 ft. (top of riser), 285.0 ft. (floor of basin) and slots where: L= 0.5 In., M= 6.0 In., at 18.80 in. on center. Then area = 0.021 sq. ft., and # of slots per row = 6.0 i- Ilil M 1 ELEV. (feet) R0W1 ROW 2 ROW 3 ROW 4 ROWS ROW 6 ROW 7 TOTAL ELEV. (feet) H(ft) Q (cfs) H(ft) Q (cfs) H(ft) Q (cfs) H(ft) Q (cfs) H(ft) Q (cfs) H(ft) Q(cfs) H(ft) Q(cfs) Q (cfs) 285.0 0.0 0.0 0.0 0.6 286.00 1.00 0.60 0.00 0.0 — — — .1 0.6 286.50 1.50 0.67 0.50 0.57 — — — — , .1, . 1.2 287.00 2.00 0.80 1.00 0.60 0.00 0.0 — — , ____ 1.4 287.50 2.50 0.90 1.50 0.67 0.50 0.57 — — — — ' 2.1 288.00 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 — — -.11 —_ 2.4 288.50 3.50 1.09 2.50 0.90 1.50 0.67 0.50 0.57 3.2 289.00 4.00 1.17 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 — — 3.6 289.50 4.50 1.24 3.50 1.09 2.50 0.90 1.50 0.67 0.50 0.57 — — — 4.5 290.00 5.00 1.31 4.00 1.17 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 _ 4.9 290.50 5.50 1.38 4.50 1.24 3.50 1.09 2.50 0.90 1.60 0.67 0.50 0.57 5.9 291.00 6.00 1.45 5.00 1.31 4.00 1.17 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 6.3 291.50 6.50 1.51 5.50 1.38 4.50 1.24 3.50 1.09 2.50 0.90 1.50 0.67 0.50 0.57 7.4 292.00 7.00 1.57 6.00 1.45 5.00 1.31 4.00 1.17 3.00 1.00 2.00 0.80 1.00 0.60 7.9 292.50 7.50 1.62 6.50 1.51 5.50 1.38 4.50 1.24 3.50 1.09 2.50 0.90 1.50 0.67 8.4 293.00 8.00 1.68 7.00 1.57 6.00 1.45 5.00 1.31 4.00 1.17 3.00 1.00 2.00 0.80 9.0 slot 8/14/2001 ENCINITAS IX La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water IVIanagement Plan Chapter 9 - SITE BMP DESIGN VORTECHS TREATMENT UNITS 9.1 - BMP Locations The site design includes four Vortechs treatment units (shown on BMP Location Maps located on the following pages. Portions of Neighborhood 3.08 drain to the San Marcos Creek watershed via an existing inlet to the old Rancho Santa Fe storm drain system. Prior to discharge to the existing storm drain system, 85"^ percentile runoff will be treated in an offline Vortechs Model 2000 (near Paseo Conifera). In developed conditions, the developed condition drainage area from the site area to the San Marcos Creek watershed is roughly 24 acres. Runoff from Neighborhood 3.09 discharges to a stomn drain system constructed along with the new alignment of Rancho Santa Fe Road. Prior to discharge to the Rancho Santa Fe storm drain system, 85"^ percentile flow will be treated in an offline Vortechs Model 1000. In developed conditions, the contributing drainage area to this treatment unit is roughly 14 acres. At the southeast corner of the Oaks South site, a 5-acre watershed discharges to a side canyon near Avenida Junipero. Prior to discharge to the natural canyon, 85"^ percentile flow will be treated in an offline Vortechs Model 1000. Runoff from street areas not reaching the Water Quality Basin will be treated in an offline Vortechs Model in La Costa Avenue. The developed area from La Costa Oaks South to this treatment unit is 2 acres. 9.2 - Determination of Design Treatment Flows The 85"^ percentile design flow rates have been calculated using the Rational Method. Required data for the Rational Method treatment flow determination include the following: Runoff Coefficient I Rainfall Intensity (I) = 0.20 inches per hour Drainage area to treatment unit (A) Runoff coefficients were derived based upon a weighted average of each area tributary to the treatment unit and the associated runoff coefficient. EM:EM h:\sw quality\2352\39\swmp-oaks-south.cloc W.O. 2352-39 7/25/03 11:23 AM SCALE l'=200' BMP LOCATION MAP FOR NEIGHBORHOOD 3.09 VORTECHS UNIT CARLSBAD, CALIFORNIA BMP LOCATION MAP FOR NEIGHBORHOOD 3.15 VORTECHS UNIT CARLSBAD, CALIFORNIA ftkBHUllyAMII UHUUIL HIF A.J^ HUU-eWSr SCALE l'=200' BMP LOCATION MAP FOR LA COSTA AVENUE VORTECHS UNIT CARLSBAD. CALIFORNIA ft«i|ijJMUiii UHUiiii m J»J4 njj-BWBsr La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan The following table summarizes the parameters used for determination of design flows to each of the Vortechs treatment units. DESIGN RUNOFF DETERMINATION SUMMARY TABLE Treatment Unit Runoff Coefficient (C) Rainfall Intensity (in/hr) Drainage Area (acres) as'" Pet Design Flow (cfs) Neigh. 3.08 0.49 0.2 23.9 2.3 Neigh. 3.09 0.49 0.2 13.7 1.3 Avenida Junip 0.49 0.2 5.4 0.5 La Costa Ave 0.85 0.2 2.1* 0.4 9.3 - Vortechs Treatment Unit Selection Each of the proposed Vortechs units is an offline precast treatment unit. The 85*'' percentile design flow rate is forced into the treatment area by a diversion weir built in the upstream junction. Flows in excess of the design flow rate pass over the weir and proceed downstream. The following table shows the treatment capacities of each of the (4) proposed Vortechs units. VORTECHS UNIT TREATMENT CAPACITY TABLE Treatment Unit 85'" Pet. Design Flow (cfs) Recommended Vortechs Model Treatment Capacity (cfs) Neigh. 3.08 2.3 2000 2.8 Neigh. 3.09 1.3 1000 1.6 Avenida Junip 0.5 1000 1.6 La Costa Ave 0.4 1000 1.6 EM:EM h:\sw quality\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/25/03 11:37 AM Deration Plan View - Grit Chamber - - ifcisiThe swirling motion created by the p^'tangential inlet directs settleable " . -solids toward the center of this issehamber. Sediment is caught in '' -.the swirling flow path and setties back .onto, the^^pile "after the .stomr event is over. ' ^"^S'K Flow cohtroi,< Oil Chamber & Baffle Wall ^.Jhe center baffle traps floatables in ' B^the oil chamber, even during clean- •. '? *'?out. Highly resistant to flow surges. ' lEIevation View: DryA/Veather 1) Initial Wet Weather Phase During a twonnonth storm event the water level begins to rise above the top of the inlet pipe. This influent control feature reduces turbulence and avoids resuspension of pollutants. 3) Full Capacity Phase When the high-flow outlet approaches full discharge, sbonn drains are flowing at peak capacity. The \A:rtechs System is designed to match your design storm flow and provide treat ment throughout the range of storm events without bypass- ing. To accommodate very high flow rates, Vortechnics can assist designers with configuring a peak-flow bypass. Flow Control Chamber'-f**'° i The weir and qrifice flow controls: 1) Raise level and volume in the^j, « ^ fe^ system as flow rate increases'; and 2] gradually drain the system" as"" flow rate subsides. ' . t IA 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. Swiriing action increases at this stage, while sediment pile remains stable. 4) Storm Subsidence Phase/Cleaning Treated runoff is decanted at a controlled rate, restoring the water level to a low dryweather volume and revealing a conical pile of sediment. The low water level facilitates inspection and cleaning, and significantly reduces maintenance costs. The system's central baffle prevents transfer of floatables to the outlet during cleaning or during the next storm. Stormwater Treatment System Perforated Covers r 11 / 3'to5' INV.i 6'to 9' Typical 3'tD4' \4 1 r Plan View To begin the design of your Vortechs System, refer to the sizing chart below and com- plete a Specifier's Worksheet to provide details about your site and design flows. Then simply fax or mail the worksheet to Vortechnics with your site plan, and we'll produce detailed Vortechs System scale draw- ings free of charge. Elevation View Engineering Notes A) , For irvline VbptBohs SyBtams vwthout a: bypass, sizing ontaria Is based on providing one square foot of grit chamber surface area for eech 100 gpm of peak design storm flow rate (e.g. , lOVear storm]. For mora^ 'J details about Vortechnics siang ontana refer to Vbrtechnics Technical Bulletin 3. • B) Sediment storage volume assumes a 3 foot sump. C) Construction details, may vary depending on the specific application. Any alterations to the sizing chart specifi-cations will sppear on Vbrtechnics dimensional and shop drawings. Please call Vbrtechnics for the weioht bf soe-cific Vortechs systems if needed. ;; Special Note: Oil storage capaqity. when it is needed to meet a specific requirement for spill cohtairiment, cart be-' • sized to. meet the storage requirement with the selected, model. Vortechnics technical staff will optimize'systeriT i geometry to meet containment requirements within a correctly sized Vortechs System. Metric Speaficaaon Chan availaUe by calling Vortechnics at [307] 8780669. Vortechs System Inlet/Outlet Configurations Vortechs Systems can be configured to accommo- date various inlet and outlet 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 o f Side Inlet To tT Pretreatment To Outfall I I SECTION 02721 STORMWATER TREATMENT SYSTEM PART 1.00 GENFRAI 1.01 DESCRIPTION A, Work included: The Contractor, and/or a manufacturer selected by the Contractor and approved by the Engineer, shall furnish all labor, materials, equipment and incidentals required and install all precast concrete stormwater treatment systems and appurtenances in accordance with the Drawings and these specifications. B. Related work described elsewhere: 1. Unit Masonry 2. l\/liscellaneous IVIetals 3. Waterproofing 1.02 QUALITY CONTROL INSPECTION A. The quality of materials, the process of manufacture, and the finished sections shall be subject to inspection by the Engineer. Such inspection may be made at the place of manufacture, or on the work site after delivery, or at both places, and the sections shall be subject to rejection at any time if material conditions fail to meet any of the specification requirements, even though sample sections may have been accepted as satisfactory at the place of manufacture. Sections rejected after delivery to the site shall be marked for identification and shall be removed from the site at once. All sections which have been damaged beyond repair during delivery will be rejected and, if already installed, shall be repaired to the Engineer's acceptance level, if pemnitted, or removed and replaced, entirely at the Contractor's expense. B. All sections shall be inspected for general appearance, dimensions, soundness, etc. The surface shall be dense, close textured and free of blisters, cracks, roughness and exposure of reinforcement. C. Imperfections may be repaired, subject to the acceptance of the Engineer, after demonstration by the manufacturer that strong and permanent repairs result. Repairs shall be carefully inspected before final acceptance. Cement mortar used for repairs shall have a minimum compressive strength of 4,000 psi at the end of 7 days and 5,000 psi at the end of 28 days when tested in 3 inch diameter by 6 inch long cylinders stored in the standard manner. Epoxy mortar may be utilized for repairs. 1.03 SUBMITTALS A. Shop Drawings Tile Contractor shall be provided with dimensional drawings and, when specified, utilize these drawings as the basis for preparation of shop drawings showing details for construction, reinforcing, joints and any cast-in-place appurtenances. Shop drawings shall be annotated to indicate all materials to be used and ail applicable standards for materials, required tests of materials and design assumptions for structural analysis. Design calculations and shop drawings shall be certified by a Professional Engineer retained by the system manufacturer or contractor and licensed in the state where the system is to be installed. Shop drawings shall be prepared at a scale of not less than 1/4" per foot Six (6) hard copies of said shop drawings shall be submitted to the Engineer for review and approval. B. Affidavit on patent infringement The Contractor shall submit to the Engineer, prior to installation of the stormwater treatment system, an affidavit regarding patent infringement rights stating that any suit or claim against the Owner due to alleged infringement rights shall be defended by the Contractor who will bear all the costs, expenses and attomey's fees incun^ed thereof. PART 2.00 PRODUCTS 2.01 MATERIALS AND DESIGN A. Concrete for precast stormwater treatment systems shall conform to ASTM C 857 and C 858 and meet the following additional requirements: 1. The wall thickness shall not be less than 6 inches or as shown on the dimensional drawings. In all cases the wall thickness shall be no less than the minimum thickness necessary to sustain HS20-44 loading requirements as detennined by a Licensed Professional Engineer. 2. Sections shall have tongue and groove or ship-lap joints with a butyl mastic sealant confomning to ASTM C 990. 3. Cement shall be Type III Portland cement confonning to ASTM C 150. 4. Pipe openings shall be sized to accept pipes of the specified size(s) and material(s), and shall be sealed by the Contractor with a hydraulic cement confonning to ASTM C 595M 5. Internal metal components shall be aluminum alloy 5052-H32 in accordance with ASTM B 209. 6. Brick or masonry used to build the manhole frame to grade shall confonn to ASTM C 32 or ASTM C 139 and the Masonry Section of these Specifications. \\MDI\SYS\DATA\VORTECHN\EMAIL\STDETAIL\VORTSPEC.DOC SECTION 02721 Page 2 7. Casting for manhole frames and covers shall be in accordance with The Miscellaneous Metals Section of these Specifications. 8. Ail sections shall be cured by an approved method. Sections shall not be shipped until the concrete has attained a compressive strength of 4,000 psi or util 5 days after fabrication and/or repair, whichever is the longer. 9. A butimen sealant in conformance with ASTM C 990 shall be utilized in affixing the aluminum swiri chamber to the concrete vault 2.02 PERFORMANCE Each stomnwater treatment system shall adhere to the following perfomiance specifications at the specified design flows, as listed below: Table 2.02 Vortechs Model Swiri Chamber Diameter (ft) Design Treatment Capacity (cfs) Sediment Storage (yd^) 1000 3.67 2.3 1.00 2000 4 2.8 1.25 3000 5 4.5 1.75 4000 6 6.0 2.50 5000 7 8.5 3.25 7000 8 11.0 4.00 9000 9 14.0 4.75 11000 10 17.5 5.50 16000 12 25.0 7.00 Each stomiwater treatment system shall include a circular aluminum "swiri chamber" (or "grit chamber") with a tangential inlet to induce a swiriing flow pattern that will accumulate and store settleable solids in a manner and a location that will prevent re-suspension of previously captured particulates. Each swiri chamber diameter shall not be less than the diameter listed in Table 2.02 (neglecting chamber wall thickness). Each stomiwater treatment system shall be of a hydraulic design that includes flow controls designed and certified by a professional engineer using accepted principles of fluid mechanics that raise the water surface inside the tank to a pre-detemiined level in order to prevent the re-entrainment of trapped floating contaminants. Each stormwater treatment system shall be capable of removing 80% of the net annual Total Suspended Solids (TSS). Individual stomnwater treatment systems shall have the Design Treatment Capacity listed in Table 2.02, and shall not resuspend trapped sediments or re- entrain floating contaminants at flow rates up to and including the specified Design Treatment Capacity. Individual stomiwater treatment systems shall have usable sediment storage capacity of not less than the corresponding volume listed in Table 2.02. The systems shall be designed such \\MDI\SYS\DATA\V0RTECHN\EMAIL\STDETAIL\V0RTSPEC.DOC SECTION 02721 Pages that the pump-out volume is less than 'A of the total system volume. The systems shall be designed to not allow surcharge of the upstream piping network during dry weather conditions. A water-lock feature shall be incorporated into the design of the stormwater treatment system to prevent the introduction of trapped oil and floatable contaminants to the downstream S dunng routine maintenance and to ensure that no oil escapes the system during the ensuina ram event Direct access shall be provided to the sediment and floatable conSant storaae tS c^lrib?rfmaintenance. There shall be no appurtenances or restrictions within The stormwater treatment system manufacturer shall furnish documentation which supports all product performance claims and features, storage capacities and maintenance requirements. Stormwater treatment systems shall be completely housed within one rectangular structure. 2.03 MANUFACTURER Each stormwater treatment system shall be of a type that has been installed and used successful y for a minimum of 5 years. The manufacturer of said system shall have been regulariy engaged in the engineering design and production of systems for the physical treatment of stormwater runoff. Each stormwater treatment system shall be a Vortechs™ System as manufactured by vortechnics. Inc., 41 Evergreen Drive, Portland, Maine 04103, phone: 207-878-3662 tax: 207-878-8507; and as protected under U.S. Patent # 5,759,415. PART 3.00 EXECUTION 3.01 INSTALLATION A. Each Stormwater Treatment System shall be constructed according to the sizes shown on the Drawings and as specified herein. Install at elevations and locations shown on the Drawings or as othenwise directed by the Engineer. B. Place the precast base unit on a granular subbase of minimum thickness of six inches after compaction or of greater thickness and compaction if specified elsewhere. The granular subbase shall be checked for level prior to setting and the precast base section of the trap shall be checked for level at all four comers after it is set. If the slope from any comer to any other comer exceeds 0 5% the base section shall be removed and the granular subbase material re-leveled. ^' rS2n*S.^®f subsequent sections place butimen sealant in conformance with ASTM c.990-91 along the construction joint in the section that is already in place. D. After setting the base and wall or riser sections install the circular swiri chamber wall by bolting the swiri chamber to the side walls at the three (3) tangent points !?o .^^ ^"'"'^^ '"'s* using HILTI brand concrete anchors or equivalent "i'"'"!""^ length at heights of approximately three inches (3 ) off the floor and at the mid-height of the completed trap (at locations Of pre-dnlled holes in aluminum components). Seal the bottom edge of the swiri \\MDI\SYS\DATA\VORTECHN\EMAIL\STDETAIL\VORTSPEC.DOC SECTION 02721 Page 4 I E. G. H. chamber to the trap floor with the supplied aluminum angle flange. Adhere %" thick by 1" wide neoprene sponge material to the flange with half of it's width on the horizontal leg of the flange and half of it's width on the vertical leg. The aluminum angle flange shall be affixed to the floor with a minimum 3/8".diameter by 2-3/4" drop in wedge anchor at the location of the predrilled holes. Affix the swiri chamber to the flange with hex head %" x 1-1/2" zinc coated self- tapping screws at the location of the predrilled holes. Seal the vault sidewalls to the outside of the swiri chamber from the floor to the same height as the inlet pipe invert using butyl mastic or approved equal. Prior to setting the precast roof section, butimen sealant equal to ASTM C990 shall be placed along the top of the baffle wall, using more than one layer of mastic if necessary, to a thickness at least one inch (1") greater than the nominal gap between the top of the baffle and the roof section. The nominal gap shall be detennined either by field measurement or the shop drawings. After placement of the roof section has compressed the butyl mastic sealant in the gap, finish sealing the gap with an approved non-shrink grout on both sides of the gap using the butyl mastic as a backing material to which to apply the grout. Also apply non-shrink grout to the joints at the side edges of the baffle wall. After setting the precast roof section of the stormwater treatment system, set precast concrete manhole riser sections, to the height required to bring the cast iron manhole covers to grade, so that the sections are vertical and in true alignment with a 1/4 inch maximum tolerance allowed. Backfill in a careful manner, bringing the fill up in 6" lifts on all sides. If leaks appear, clean the inside joints and caulk with lead wool to the satisfaction of the Engineer. Precast sections shall be set in a manner that will result in a watertight joint. In all instances, installation of Stomiwater Treatment Systems shall conform to ASTM specification C891 "Standard Practice For Installation of Underground Precast Utility Structures". Plug holes in the concrete sections made for handling or other purposes with a nonshrink grout or by using grout in combination with concrete plugs. Where holes must be cut in the precast sections to accommodate pipes, do all cutting before setting the sections in place to prevent any subsequent jarring which may loosen the mortar joints. The Contractor shall make all pipe connections. \\MD1\SYS\DATA\V0RTECHN\EMAIL\STDETAIL\V0RTSPEC.D0C SECTION 02721 Page 5 VORTECHS^" STORMWATER TREATMENT SYSTEM DESIGN AND OPERATION Basic Operation The Vortechs System is sized on the basis of removing both sediment and floating pollutants from stormwater runoff. When the system is operating at its peak desan canaH^^^^^ max^um service rate will be approximately 100 gallons«ute pefs^re fS^o^ m chamber area (gpm/sf). The Vortechs System has been tested for flows up to and ?nclud?na this maximum rate and has been shown to produce positive removal efficienciL throu^^^^^^^^^^^ ^nii^S'^®''^^^^^?"'^ ^""u^' '•^"^°val efficiency in excess of 80% removal of Thi / f ^rt^ *yP''^^"y encountered in runoff from urban envSents The Vortechs System will also effectively capture and contain floatables in stormwarmnoff Jpntlr '"'^1^^®?^^ ^^^wiriing motion that directs settleable solids into a pile towards the cente of the gnt chamber. Sediment is caught in the swiriing flow path and settlerback onto c^Tnt^of to c%lt' ^"^^^P"^^"^ ^^hieved by si% the low flow pTp7-\t 2!mo^^^^ "^^^^ ^'^^ ~ to jusfsubm'erge the inle^ The Vortechs System is designed to create a backwater condition within the system in order to rnaximize removal efficiencies. The amount of backwater varies anS is deSn^dTv he condtnT ^° ''''''' '^^'9n of the system inco" all si Design Process During the Vortechs System design process consideration is given to both the ohvsical the~aS^^^^^^ and fh' M "'ff ^^^^^^ dLigned^diff^^^n^^ba'se'don threxpeSow^^^^ ^Pe^^'fi^^^'ly designed to accommodate low ^.P^°^'des Vortechs System rim and invert elevations, pipe sizes, design flow rate and design storm recun-ence interval. Another consideration is whether the sistem is s«ws less'^t: ii;" ''''''''^ -onnn. If regulatory authoritiesl^^w tre^^^^^^^ stomi flows less than the conveyance capacity of the piping system it mav be oossible to at^mLTTl^'^'^'^r configuration which Jll result i^ a cTsIsavings v^hout a significant reduction in pollutant removal efficiency. *«*vii.yb wiinout Sizing the SystPm Each system is custom designed based on the design conditions provided The weir orifice sump depth, and height of tank will vary depending on the site condifions and per^SrmS Standi. ^I^' ""^ '?';r' ^'^^^'r '^^^^^ height of the un t'me surnp depth, and the placement of the weir and orifice. Also affecfing the placement of the weir and VORTECHS™ STORMWATER TREATMENT SYSTEM orifice is the pipe size, the orientafion of the internal walls, and the potential for tailwater. The flow rates determine the size of the weir, orifice, and the baffle opening. Siz§: The size of the system depends on whether or not the system is on-line or off-line. An on-line system will be chosen such that the design flow rate is equal to or less then the Vortechs rated design flow. For an ofl'-line system, the 2-month flow rate is determined and the model number is chosen based on the grit chamber area such that 24 gpm/sf of flow is realized through the chamber. Sunm: Typically a three-foot sump depth is provided in Vortechs Systems. This depth is most common since it provides ample sediment storage and keeps the excavation depth to a minimum. However, because each Vortechs System is custom designed, the individual sump depths may vary to balance maintenance costs with capital costs. prifice: The function of the orifice is to raise the water level in the Vortechs System. This increases the area of the flow in the pipe, which decreases the velocity of the water flowing into the system. A reduction in turbulence is realized at the inlet; this aids in keeping the trapped sediment and floatables contained. In addition, the rise in water level causes the floatables to rise above the inlet and away from the baffle opening, thus preventing the floatables from becoming re-entrained and pulled under the baffle wall. The orifice is designed to pass a fiow approximately equal to that of a 2-month storm event. Weir: Any event greater than the 2-month event causes the water level in the Vortechs System to rise to the upper flow control, submerging the inlet. The upper flow control is normally a Cippoletti weir. A Cippoletti weir is a trapezoidal weir with 4 to 1 sloping sides. Like the orifice, the weir also causes the water level in the system to rise, which promotes sediment and floatable removal. As the water rises, the volume of water in the system increases, thus stabilizing the detention time and allowing sediment to settle out. The swiri is maintained by allowing continuous flow through the system via the weir and orifice. The weir is sized to pass the design flow rate minus the orifice flow at full head. Baffle: The baffle opening is designed to maintain a velocity such that re-entrainment of floatables and re-suspension of sediment is minimized. The baffle opening is at least 6 inches to ensure against clogging. The largest opening of 15 inches is chosen to maximize the distance between the floatable layer and the baffle opening. This keeps the floatables trapped and maintains the oil storage volume. In most applications, the flow under the baffle wall is approximately 1.0 foot per second. Bypass: For systems in an off-line configuration, a weir crest length and elevation is calculated for the diversion stnjcture that will be installed upstream of the specified Vortechs System. The goal is to achieve a water surface elevation during the 100-year storm that is at the same elevation as the top of the Vortechs Cippoletti weir. The area of flow over the bypass weir is calculated based on the 100-year flow. From this area, the height of flow is solved for a given weir length. Since the area of flow remains constant, the height of flow over the weir varies with the bypass weir length. See Tecfinical Bulletin 3A for more information. VORTECHS STORMWATER TREATMENT SYSTEM ^^^^'^^^^^'^^'^^^ Vortechs Model 5000 System tNs%^DoSL^yh?'" - J ' ^''^^ " d'^^ete^ chamber. In this application, the runoff rate for a rainfall event with a return frequency of 10 years is 6 13 re^'oMhe'^aT^^^^^^ l^V'''"" '''''' '''' (6.ir4rThe sur^aJe dMded by 3^^^^^^^^^^^ '''' '''' ^^'^ 2751 The low flow control is a trapezoidal orifice (Qonyice). Since the inlet is a 24-inch diameter pipe, the onfice must raise the water level 24 inches, or 2.0 feet, in a 2-month storm to flnw r![f • ^^^\ According to Vortechnics Technical Bulletin #3. the 2.month stomi Sasefon thffl'Z'^^^^^^^^^V?" ''"''^^^ 7- "^he orifice calculation cased on the full design flow is as follows: Qs-montt = Qioyea/--5-7 = 6.13 "5-7 = 0.88 Cfs Qortffce = C(/\)(2g/j)« = 0.56(0.14)(2.0x 32.2x2.0)°' = 0.89 cfs 4 Where C = Orifice contraction coefficient = 0.56 (based on Vortechnics laboratory testing) ^ - Onfice flow area, ft (calculated by Vortechnics technical staff) n = Design head, ft (equal to the inlet pipe diameter) ""f flow control (Q^,) which is conservatively designed for the system design fiow (Q.e,^„) of 6.13 cfs The weir calculations are as follows: ^ . mc weir Qweir =6.13 cfs Qweir = C(L)(H)i-5 = 3.37(0.50)(2.42)'' = 6.34 cfs 4 Where C = Cippoletti Weir coefficient = 3.37 (based on Vortechnics laboratory testing) Available head, ft (height of weir) L = Design weir crest length, ft (calculated by Vortechnics technical staff) I VORTECHS™ STORMWATER TREATMENT SYSTEM MAINTENANCE The Vortechs System requires minimal routine maintenance. However. It is important that the system be inspected at regular intervals and cleaned when necessary to ensuropttur^ morp n^l?.! K "^f °^ ^^^"^ '^"^'"9 w"' cause the grit chamber to fin more quickly but regular sweeping will slow accumulation. Inspection Inspection is the key to effective maintenance and it is easily performed. Vortechnics recommends ongoing quarteriy inspections of tiie accumulated sediment Note that is not L accumulation to be relatively light in the first year as initial sediment loads rpntnorfT T ^^^^^""^ ^° '^^^^ ^^s'" ^umps. Pollutant deposition and SSned outTthS" y^.^"; V^ar and quarterly inspections will help insure that systems are mnnrh. r appropnate time. Inspections should be performed more often in the winter montiis in climates where sanding operations may lead to rapid accumulations, or in equipment ^ofs pSer'" " "'"^ *° ' '""^'"^ °' """'^ '"'P"^"°"- A ^''"P'^ fomiKfng I^ar!!!o=r''^^^^*®"L.°"'^ *° '''^^"^^ inspection reveals that it is nearly full; spec fically when sediment depth has accumulated to within six inches of the dry-weathe water level. This detemiination can be made by taking 2 measurements with a stadia rod or fnn .r^^T"^ 'i^''!!^'- "measurement is the distance from the manhole opening to the l?.rf.L ifl ^''^^"^^ "manhole opening to the water !ho^!iH . measurements is less than six inches the system thrrl^S'^"!"^ *° underestimating the volume of sediment in the chamber, the measunng device must be lowered to the top of the sediment pile carefully. Finer sm parte es at the top of the pile typically offer less resistance to the end of the rod than I'arqer partcles toward the bottom of the pile. ^ In Vortechs installations where the risk of large petroleum spills is small, liquid contaminants HfLr? .""'"'t*® as quickly as sediment. However, an oil or gasoline spill should be ^!^n ""mediately. Oil or gas that accumulates on a more routine basis should be removed when an appreciable layer has been captured. Cleaning Cleanout of the Vortechs System with a vacuum truck is generally the most effective and convenient method. Cleanout should not occur within 6 houre of a rain event to allow the entire collection system to drain down. Property maintained Vortechs Systems will only require evacuation of the grit chamber portion of the system, in which case only the manhole cover nearest to the system inlet need be opened to remove water and contaminants. However, all v.!mch2.. K *° °^ system. In installations where a Clamshell is being utilized for solids removal, prior to removing the grit absorbent pads or pillows can be placed in the oil chamber to remove floating contaminants. Once this is done, sediment may then be easily removed with the clamshell. VORTECHS™ STORMWATER TREATMENT SYSTEM ISr' r tV^ °^ "'^""'"9 ^f^^^mbers it is imperative thaUhe grit chamber be thTc^frf • ^^T^^^ ^^^"'•^'y seated following clean! activities to en^re that surface runoff does not leak into the unit from above activities, to ensure X La Costa Oaks South (Neighborhoods 3.08 - 3.15) Storm Water Management Plan Chapter 10 - REFERENCES "Standard Urban Storm Water Mitigation Plan - Stonv Water Standards" City of Cartsbad, April 2003. "Standards for Design and Construction of Public Works Improvements in the City of Carlsbad", City of Carlsbad, California; Aprt11993. "Master Drainage and Storni Water Quality Management Plan", City of Carlsbad, California; March 1994. "Addendum to Preliminary Hydrology Study for Villages of La Costa - The Ridge and The Oaks", Hunsaker & Associates San Diego, Inc.; Revised October 23, 2001. "Hydrology Manual", County of San Diego Department of Public Works - Flood Control Division; Updated April 1993. "San Diego County Hydrology Manual - DRAFT", County of San Diego Department of Public Works - Flood Control Section; September 2001. "Order No. 2001-01, NPDES No. CAS0108758- Waste Discharge Requirements for Discharges of Urban Runoff from the Municipal Separate Stonv Sewer Systems (MS4s) Draining the Watersheds of the County of San Diego, the Incorporated Cities of San Diego County and San Diego Unified Port District", California Regional Water Quality Control Board - San Diego Region; February 21, 2001. "Water Quality Plan for the San Diego Basin", California Regional Water Quality Control Board - San Diego Region, September 8, 1994. "Vortechnics Storm Water Treatment System Manual", Vortechnics; Revised Mav 2000. EM:EM h:\sw quallty\2352\39\swmp-oaks-south.doc W.O. 2352-39 7/24/03 1:10 PM