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HomeMy WebLinkAboutCT 01-03; CALAVERA HILLS VILLAGE E-1; WATER QUALITY TECHNICAL REPORT VILL E-1; 2003-04-11HUNSAKER ^ASSOCIATES SAN DIECO, INC. PLANNING ENGINEERING SURVEYING IRVINE RIVERSIDE SAN DIEGO WATER QUALITY TECHNICAL REPORT for CALAVERA HILLS VILLAGE E-1 City of Carlsbad, California City of Carlsbad Project # CT 01-03 City of Carlsbad Drawing # 405-6 Prepared for: Calavera Hills II, LLC 2727 Hoover Avenue National City, CA 91950 w.o. 1941-27 April 11, 2003 DAVE HAMMAR LEX WILLIMAN ALISA VIALPANDO DANA SEGUIN 10179 Huennekens St. San Diego, CA 92121 (858) 558-4500 PH (858)558-1414 FX www.HunsakerSD.com lnfo@HunsakerSD.com (aj^nd L. Martin, R.C.E. Project Manager Hunsaker & Associates San Diego, Inc. JC:jc h;\sw quallty\1941\27\wqtr-01 .doc w.o.1751-76 4/14/03 9:41 AM Calavera Hills E-1 Water Quality Technical Report TABLE OF CONTENTS SECTION Introduction I Introduction Vicinity Map Sumnnary of Results Pollutants and Conditions of Concern Pollutants and Conditions of Concern Regional Water Quality Control Board Criteria Identification of Pollutants of Concern Design Criteria and Examples of Treatment Control BMPs Maintenance of Treatment Control BMPs Source Control BMPs Storm Water Quality Treatment Best Management Practice III Structural Treatment BMPs Determination of Design Treatment Flow Santa Barbara Unit Hydrograph Methodology Treatment Unit Selection Attachments IV - Design Flow Determination Spreadsheets - Low Flow Diversion Spreadsheet - Vortechnics Cost, Treatment Flow and Treatment Area Spreadsheet - Vortechnics Specification, Features and Operation - San Diego County 85th Percentile, 24-Hour Rainfall Map Land Development Manual Developed Condition Site Map (Pocket) JC:jc h:\sw quallty\1941\27\wqtr-01 .doc w.o.1751-76 4/14/03 9:36 AM Calavera Hills E-1 Water Quality Technical Report Introduction JC:jc h:\sw quality\1941\27\wqtr-01.doc W.O.1751-76 4/14/03 9:11 AM Calavera Hills E-1 Water Quality Technical Report Introduction The following Water Quality Technical Report has been prepared to show the methodology and calculations used to detennine the sizing of the required storm water treatment unit. All calculations are consistent with criteria set forth by the Regional Water Quality Control Board's Order No. 2001-01, the "Model Standard Urban Storm Water Mitigation Plan for San Diego County, Port of San Diego, and Cities in San Diego County". The development of Calavera Hills consists of several ongoing individual subdivisions located within the City of Carlsbad, CA. Village E-1 is one of the subdivisions within the Calavera Hills development. Village E-1 is located at the southeast corner of the intersection of Carlsbad Village Drive and Glasgow Drive. This specific development is a multi-family condo project consisting of 39 buildings, each containing 3 residential units. PROJECT SITE VICINITYMAF N.T.S. The project will include improvements to four (4) proposed private roads (Esker Way, Jetty Point, Backshore Circle, and Artesian Way), improvements to the existing Glasgow road, grading the site to make it suitable for construction of multi-family units, and construction of underground utilities typically associated with residential developments. JC h:\sw quaUtyVig41\27\wqtr-01.doc W.O. 1941-27 4/16CT03 9:43 AM r Cabrera II Water Quality Technical Report Summary of Results Prior to discharge into an existing storni drain system located in Glasgow road, first flush runoff from the Calavera Hills Village E-1 project site will be treated in a Vortechs Model 4000 storm water treatment device. Following 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," flow-based Best Management Practices (BMPs) shall be designed to mitigate (treat) the maximum flow rate of runoff produced from a rainfall intensity of 0.2 inches of rainfall per hour. Section II ofthis report discusses the typical pollutants associated with storm water, conditions of concern, compliance with regulatory measures and typical techniques utilized to manage pollutant discharge during construction and post development conditions. Section ill of this report discusses the methodology and calculations used to determine the appropriate Vortechnics treatment unit size required to adequately treat the first flush storm runoff flow for the project site. JC:jc h:\sw quality\1941\27\wqtr-01.doc w.o.1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report Pollutants and Conditions of Concern JC:jc h:\sw quallty\1941\27\wqtr-01.doc w.o.1751-7676 4/14/03 9:11 AM Calavera Hills E-1 Water Quality Technical Report Pollutants and Conditions of Concern The purpose of this report is to address pollutants associated with residential developments, and to manage techniques used to reduce the concentration of pollutant discharge into waterways and bodies of water. The Calavera Hills Village E-1 project site is located in the Penasquitos watershed. After development, all runoff from the proposed project site will be collected in catch basins, and curb inlets and conveyed to the proposed Vortechnics treatment unit through a proposed storm drain system. After treatment, storm water is discharged into an existing storm drain system that ultimately discharges, after significant travel in the public storm drain system, into a tributary of Aqua Hedionda Creek. Aqua Hedionda Creek tributary that the public storm drain discharges into is not listed as an impaired water body on the 202 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 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 stonn 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 ofthe urban development ofthe property and the effects of automobile use. Runoff from paved surfaces can contain both sediment (in the fomn 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. Most harmful 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. Another source of storm water pollution is agricultural operations. JC:jc h:\sw quality\1941\27\wqtr-01 .doc W.O.1751-76 4/14/03 9:11 AM Cabrera II Water Quality Technical Report All structural BMPs shall be located to infiltrate, filter, or treat the required runoff volume or flow (based on first flush 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 of the first flush from the proposed development All grading operations for which a permit is required are subject to periodic inspection and monitoring. 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. Identification of Pollutants of Concern Urban runoff from a developed site has the potential to contribute pollutants, including oil and grease, suspended solids, metals, gasoline, pesticides, and pathogens to the storm water conveyance system and receiving waters. For the purposes of identifying pollutants of concern and associated stonn 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. Metals are raw material components in non-metal products such as fuels, adhesives, paints and other coatings. Metals of concern 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 JC:jc h:\sw qualityM 941\27\wqtr-01 .doc W.O.1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report 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 fonn 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. Oil and Grease are 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. Construction Materials are materials typically used at a construction site and have the potential to contribute to the discharge of pollutants other than sediment in storni water. The following table illustrates the typical construction processes, the typical materials associated with these processes and the potential pollutants resulting from the use of these materials: CATAGORY PRODUCT POLLUTANTS Adhesives Adhesives, Glues Resins, Epoxy Synthetics Calks, Sealers, Putty, Sealing Agents Coal Tars flvlaptha. Pitch) Phenolics, Formaldehydes Phenolics, Formaldehydes Asbestos, Phenolics, Formaldehydes Benzene, Phenols, Naphthalene Cleaners Polishes (Metal, Ceramic, Tile) Etching Agents Cleaners, Ammonia, Lye, Caustic Sodas Bleaching Agents Chromate Salts Metals Metals Acidity/Alkalinity Acidity/Alkalinity Chromium Plumbing Solder (Lead, Tin), Flux (Zinc, Chloride) Pipe Fitting (Cut Shavings) Galvanized Metals (Nails, Fences) Electric Wiring Lead, Copper, Zinc, Tin Copper Zinc Copper, Lead Painting Paint Thinner, Acetone, MEK, Stripper Paints, Lacquers, Vamish, Enamels Turpentine, Gum Spirit, Solvents Sanding, Stripping Paints (Pigments), Dyes VOC's Metals, Phenolics, Mineral Spirits VOC's Metals Metals Woods Savtrdust Particle Board Dusts (Formaldehyde) Treated Woods BOD Formaldehyde Copper, Creosote Masonry & Concrete Dusts (Brick, Cement) Colored Chalks (Pigments) Concrete Curing Compounds Glazing Compounds Cleaning Surfaces Acidity, Sediments Metals Asbestos Acidity Floors & Walls Flashing Drywall Tile Cutting (Ceramic Dusts) Adhesives* Copper, Aluminum Dusts Minerals JC:jc h:\sw quality\1941\27\wqtr-01.doc w.o.1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report Remodeling & Demolition* Insulation Venting Systems Dusts (Brick, Cement, Saw, Drywall) Asbestos Aluminum, Zinc Air Conditioning & Heating Insulating Coolant Reservoirs Adhesives* Asbestos Freon Yard 0 & M Vehicle and Machinery Maintenance Gasoline, Oils, Additives Marking Paints (Sprays) Grading, Earth Moving Portable Toilets Fire Hazard Control (Herbicides) Health and Safety Wash Waters* (Herbicides, Concrete, Oils, Greases) Oils and Grease, Coolants Benzene & Derivatives, Oils & Grease Vinyl Chloride, Metals Erosion (Sediments) BOD, Disinfectants (Spills) Sodium Arsenite, Dinitro Compounds Rodenticides, Insecticides Landscaping & Earthmoving Planting, Plant Maintenance Excavation, Tilling Masonry & Concrete* Solid Wastes (Trees, Shrubs) Exposing Natural Lime or Other Mineral Deposits Soils Additives Revegetation of Graded Areas Pesticides, Herbicides, Nutrients Erosion (Sediments BOD Acidity/Alkalinity, Metals Aluminum Sulfate, Sulfiir Fertilizers Materials Storage Waste Storage (Used Oils, Solvents, Etc.) Hazardous Waste Containment Raw Material Piles Spills, Leaks Spills, Leaks Dusts, Sediments Design Criteria and Examples of Treatment Control BMPs Storm water quality treatment (pollutant removal) will be attained either by flow-based methods or by volume-based water quality basins, depending on the tributary area of the storm drain system and space constraints. Treatment control (structural) BMPs are engineered system design and 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 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. Examples of flow-based BMPs include the devices designed by Vortechnics Engineered Storm Water Products. The Vortechs Stonn 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. 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 JC:jc h:\sw quality\1941\27\wqtr-01.doc w.o.1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report • Low pump-out volume and one-point access reduce maintenance costs • Design prevents oils and other floatables from escaping the system during cleanout The tangential inlet to the system creates a swirling motion that directs settleable solids into a pile towards the center ofthe grit chamber. Sediment is caught in the swirling flow path and settles back onto the pile after the storm even is over. Floatables entrapment is achieved by sizing the fow flow control to create a rise in the water level of the tank that is sufficient to just submerge the inlet pipe in the 2-month storm. Maintenance of Treatment Control BMPs Maintenance of the site BMPs will be the responsibility of the Homeowners Association. A maintenance plan should be developed to include the following information: • Specification 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 BMP inspections will be performed before and after stonn events and once each 24- hour period during extended storm events to identify BMP effectiveness. Depending on field conditions, design changes or repairs should be implemented as soon as feasible. 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 storm 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. JC:jc h:\swquality\1941\27\wqtr-01.doc w.o.1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report Inlet cleaning, ditch clearing, and street sweeping are examples of other commonly used maintenance practices. Maintenance 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 "vac-tor truck" which clears the grit chamber of the treatment unit by vacuuming all the grit and water from the sump. Typically a 3-man crew is required to perfonn the maintenance of the treatment unit. Flow-based storm water treatment devices should be inspected periodically to assure their condition to treat anticipated runoff. 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 properly 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 optimum 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. BMP inspections shall be perfonned before and after storm events and once each 24-hour period during extended stomri events to identify BMP effectiveness. Depending on field conditions, design changes or repairs should be implemented as soon as feasible. Inspection is the key to effective maintenance. Vortechnics recommends ongoing quarterly inspections ofthe accumulated sediment. According to Vortechnics literature, the systems needs only to be cleaned when the inspection reveals that the system is nearly full - specifically, when the sediment depth has accumulated within 6 inches of the dry-weather water level. Cleanout of the Vortechs System with a "vac-tor 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. JC:jc h:\sw qualityM 941\27\wqtr-01 .doc w.o. 1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report Source Control BMPs Source controls, which are implemented to prevent or reduce the presence of pollutants and minimize the contact between pollutants and urbar) 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 vegetation in ornamental and required landscapes. 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 construction-related wastes. 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 stomri 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 impen/ious 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. JC:jc h:\sw qualityM 941\27\wqtr-01 .doc W.O.1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report - Discharges of food-related wastes (grease, food processing, trash bin wash water, etc.). 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. JC.jc h:\sw qualityM 941\27\wqtr-01 .doc W.O.1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report Storm Water Quality Treatment Best Management Practice JC:jc h:\sw qualityM941\27\wqtr-01 .doc W.O.1751-7676 4/14/03 9:11 AM Calavera Hills E-1 Water Quality Technical Report Structural Treatment BMPs The improvement design incorporates the construction of a Vortechs Model 4000 storm water quality unit. One Vortechnics storm water treatment unit is being proposed to treat the first flush runoff for the Calavera Hills Village E-1 project. The storm water quality treatment unit has been sized to treat the runoff volume for the first flush condition. Determination of Design Treatment Flow The first flush runoff rate has been calculated using the Santa Barbara Urban Hydrograph Method (SBUH). The SBUH Method has many similarities to the SCS Unit Hydrograph Method. Both methods use the same SCS curve numbers, runoff equation, and rainfall distributions. Required input for the SBUH spreadsheet is as follows: Drainage Area = 28.5 acres 85"^ Percentile, 24-Hour Rainfall = 0.67 inches Time of Concentration = 10.3 minutes Percent Impervious = 65% Impervious CN = 98 Pervious CN = 68 (assuming dry antecedent moisture conditions) The 85'*^ percentile, 24-hour rainfall was derived from the isopluvial map provided by the County of San Diego (attached). The site's impervious percentage was derived based upon the total impervious area and the DU/Ac ratio, obtained by divided the total dwelling units by the total drainage area. Using the resultant dwelling units per acre ratio (DU/Ac) and the Table 3-1 from the San Diego County Hydrology Manual, the site's impervious percentage was estimated to be 65%. Based on the County of San Diego's 6-hour rainfall distribution, the SBUH predicts a peak first flush flow rate of 4.29 cfs (calculations attached). The corresponding peak hourly rainfall intensity was calculated to be 0.22 inches per hour (see Santa Barbara Method hydrograph output). This peak rainfall intensity was calculated by adding the incremental rainfall depths within the most intense hour of rainfall (between hour 2 and 3 ofthe 6-hour distribution). Santa Barbara Unit Hvdrograph Methodology The basic SBUH runoff procedure is as follows: 1) Compute the instantaneous hydrograph: The storm is divided into equal time increments (dt). At each increment, the SCS Runoff Equation is used to detemnine JC:jc h:\sw qualltyM941\27\wqtr-01 .doc W.O.1751-76 4/14/03 9:11 AM Cabrera II Water Quality Technical Report the precipitation excess. The difference between the successive values represents the instantaneous runoff at that point in time. 2) Compute the runoff hydrograph: The runoff hydrograph is obtained by routing the instantaneous hydrograph through an imaginary reservoir with a time delay equal to the time of concentration. The following equation is used to estimate the routed flow at each point in time: Q2 = Qi + w [ li + I2 - 2 Qi ] dt where w = 2 Tc -H dt Qi, Q2 = Runoff at beginning and end of interval dt (cfs) h, I2 = Instantaneous runoff at beginning and end of interval dt (cfs) dt = Calculation time increment (minutes) Tc = Time of concentration (minutes) w = Routing Coefficient The SBUH Method was developed for "urban" watersheds and its application to non- urban areas is not well established. For small urban areas, however, the SBUH Method produces adequate results and is usually more appropriate than the SCS Unit Hydrograph Method, since the SCS methods are empirically based on non- urban areas. Treatment Unit Selection Perthe "Vortechnics Engineered Stomnwater Products" manual, dated November, 2001 (exceprts attached), the Vortechs Model 4000 has a design flow rate of 6.0 cfs. This unit (details attached), as proposed on the improvement plans, is an offline precast treatment unit, meaning that the design flow rate is forced into the treatment area through a diversion structure, while flows in excess ofthe design flow rate pass over an inline weir and proceed downstream. Since the treatment unit is located offline there are no energy losses resulting from the treatment unit. However, the weir in the diversion structure will create a restriction, which will raise the HGL upstream ofthe weir. These losses will be analyzed in the Hydrology study to ensure that the potential for flooding occurrences during high return rainfall events is minimized to an acceptable level. JC:jc h:\sw qualityM 941\27\wqtr-01 .doc W.o. 1751-7676 4/14/03 9:11 AM Cabrera II Water Quality Technical Report Attachments JC:jc h:\sw qualityM 941\27\wqtr-01 .doc w.o.1751-7676 4/14/03 9:11 AM CALAVERA HILLS E-1 - Storm Water Quality Facility Sizing RUNOFF HYDROGRAPH (SBUH METHOD - 6-Hour Storm Event) Given: Area = 28.5 acres Pt 0.67 Inches (Total rainfall for an 85th percentile - 24 hour storm event) dt 10.0 min. Tc = 10.3 min. (Developed site conditions) % IMP = 65% PERVIOUS Parcel IMPERVIOUS Parcel Area = 10.0 acres Mea = 18.5 acres CN = 68 CN = 98 (assuming dry antecedent s 471 s 0.20 0.2S = 0.94 0.2S = 0.04 Developed Conditions Runoff hydrograph Column (3) = Rainfall Distribution for San Diego County Column (4) = Col. (3) x Pt = 85th percentile - 6 Hour Hyetograph at this location. Column (5) = Accumulated Sum of Col. (4) Column (6) = [If P <= 0.25] = 0; use PERVIOUS Area"S" value. [If P > 0.23] = (Col.{5) - 0.2S)^/(Col.(5) + 0.88); use PERVIOUS AreSS" value. Column (7) = Col.(6) of present time step - Col.(6) of previous time step Column (8) = Same method as for Col.(6), except use the IMPERVIOUS Area "S" value. Column (9) = Col.(8) ofthe present time step - Col.(8) ofthe previous time step. Column (10) = ((PERVIOUS area / Total area) x Col.(7)) + ((IMPERVIOUS area / Total area) x Col.(9)) Column (11) = (60.5 x Col.(10) x Total Area) / 10 (dt = 10 minutes); Routing Constant, w = dt / (2Tc + dt) =0.3279 Column (12) = Col.(12) of previous time step + (w x ICol.(11) of previous time step + Col.(11) of present time step - (2 x Col.(12) of previous lime step)]) Pervious Area I mpervlous Area (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) I Time Rainfall Incre-Accumu-Accumu-Incre-Accumu-Incre-Total Instant design ent distri-mental lated lated mental lated mental Runoff hydro-hydro-ent bution Rainfall Rainfall Runoff Runoff Runoff Runoff graph graph min. %OfPt in. In. In. In. in. in. In. cfs cfs 1 10 0.0166 O.om O.om 0.0000 0.0000 0.0000 0.0000 0.0000 0.00 0.00 2 20 0.0166 0.0111 0.0222 0.0000 0.0000 0.0000 0.0000 0.0000 0.00 0.00 3 30 0.0166 0.0111 0.0334 0.0000 0.0000 0.0000 0.0000 0.0000 0.00 0.00 4 40 0.0200 0.0134 0.0468 0.0000 0.0000 0.0002 0.0002 0.0001 0.02 0.01 5 50 0.0200 0.0134 0.0602 0.0000 0.0000 0.0017 0.0015 0.0010 0.17 0.06 6 60 0.0200 0.0134 0.0736 0.0000 0.0000 0.0045 0.0029 0.0019 0.32 0.18 7 70 0.0226 0.0151 0.0887 0.0000 0.0000 0.0091 0.0046 0.0030 0.51 0.34 8 80 0.0226 0.0151 0.1039 0.0000 0.0000 0.0149 0.0058 0.0038 0.65 0.50 9 90 0.0226 0.0151 0.1190 0.0000 0.0000 0.0217 0.0068 0.0044 0.76 0.63 10 100 0.0334 0.0224 0.1414 0.0000 0.0000 0.0332 0.0115 0.0075 1.29 0.89 11 110 0.0334 0.0224 0.1637 0.0000 0.0000 0.0462 0.0130 0.0085 1.46 1.21 12 120 0.0334 0.0224 0.1861 0.0000 0.0000 0.0604 0.0142 0.0092 1.59 1.42 13 130 0.0778 0.0521 0.2382 0.0000 0.0000 0.0971 0.0366 0.0238 4.11 2.36 14 140 0.0778 0.0521 0.2904 0.0000 0.0000 0.1373 0.0402 0.0261 4.50 3.63 15 150 0.0778 0.0521 0.3425 0.0000 0.0000 0.1799 0.0427 0.0277 4.78 4.29 16 160 0.0334 0.0224 0.3648 0.0000 0.0000 0.1988 0.0189 0.0123 2.12 3.74 17 170 0.0334 0.0224 0.3872 0.0000 0.0000 0.2180 0.0192 0.0125 2.15 2.69 «<peak SBUH-CDS-VORTECH.xIs 1 of 2 4/11/2003 CALAVERA HILLS E-1 - Storm Water Quality Facility Sizing (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) Time Time Rainfall Incre-Accumu-Accumu-Incre-Accumu-Incre-Total Instant design Increment distri-mental lated lated mental lated mental Runoff hydro-hydro- bution Rainfall Rainfall Runoff Runoff Runoff Runoff graph graph min. % of R In. in. in. in. in. In. in. cfs cfs 18 180 0.0334 0.0224 0.4096 0.0000 0.0000 0.2374 0.0194 0.0126 2.18 2.34 19 190 0.0316 0.0212 0.4308 0.0000 0.0000 0.2560 0.0186 0.0121 2.08 2.20 20 200 0.0316 0.0212 0.4519 0.0000 0.0000 0.2747 0.0188 0.0122 2.10 2.13 21 210 0.0316 0.0212 0.4731 0.0000 0.0000 0.2937 0.0189 0.0123 2.12 2.12 22 220 0.0234 0.0157 0.4888 0.0000 0.0000 0.3078 0.0141 0.0092 1.58 1.94 23 230 0.0234 0.0157 0.5045 0.0000 0.0000 0.3219 0.0142 0.0092 1.59 1.71 24 240 0.0233 0.0156 0.5201 0.0000 0.0000 0.3361 0.0142 0.0092 1.59 1.63 25 250 0.0213 0.0143 0.5344 0.0000 0.0000 0.3492 0.0130 0.0085 1.46 1.56 26 260 0.0213 0.0143 0.5486 0.0000 0.0000 0.3622 0.0131 0.0085 1.46 1.50 27 270 0.0213 0.0143 0.5629 0.0000 0.0000 0.3754 0.0131 0.0085 1.47 1.48 28 280 0.0175 0.0117 0.5746 0.0000 0.0000 0.3862 0.0108 0.0070 1.21 1.39 29 290 0.0175 0.0117 0.5863 0.0000 0.0000 0.3970 0.0108 0.0070 1.21 1.27 30 300 0.0175 0.0117 0.5981 0.0000 0.0000 0.4079 0.0109 0.0071 1.22 1.24 31 310 0.0183 0.0123 0.6103 0.0000 0.0000 0.4193 0.0114 0.0074 1.28 1.24 32 320 0.0183 0.0123 0.6226 0.0000 0.0000 0.4307 0.0114 0.0074 1.28 1.27 33 330 0.0183 0.0123 0.6349 0.0000 0.0000 0.4421 0.0114 0.0074 1.28 1.28 34 340 0.0175 0.0117 0.6466 0.0000 0.0000 0.4531 0.0110 0.0071 1.23 1.26 35 350 0.0175 0.0117 0.6583 0.0000 0.0000 0.4641 0.0110 0.0071 1.23 1.24 36 360 0.0175 0.0117 0.6700 0.0000 0.0000 0.4751 0.0110 0.0072 1.23 1.24 37 370 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.83 38 380 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.29 39 390 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.10 40 400 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.03 41 410 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.01 42 420 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.00 43 430 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.00 44 440 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.00 45 450 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.00 46 460 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.00 47 470 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.00 48 480 0.0000 0.0000 0.6700 0.0000 0.0000 0.4751 0.0000 0.0000 0.00 0.00 Tinne = 8.0 hours (Found by summing this column and multiplying by 600.600 Is the conversion required to convert SUM(O) In cfs to total volume in cubic feet as follows: V = SUM(Q)xdt (cu.tt.) = (cu.ft/s) x (10 min.) x (60 s/min.) Total Volume of Runoff = Peak Hour Rainfall Intensity = Total Flowrate of Runoff = 31938 cu.ft.* 0.73 ac-ft 0.223 in/hr 4.29 cfs SBUH-CDS-VORTECH.xls 2 of 2 4/11/2003 Calavera Hills E-1 HYDRAULIC ANALYSIS OF LOW FLOW DIVERSION & VORTECHS UNIT AT CLEANOUT LOW FLOW ORIFICE (Q = 4.29 cfs) Weir Formula for Orifices & Short Tubes (free & submerged) Q= Ca(2gh)° (Eqn. 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= 10 in. ,a= 0.83 sq.ft., invert elevation = 100.00 ft. H = 12 in. HIGH FLOW (Qso = 28.5 cfs) Weir Formula for Bypass Weir & Vortechs Weir Q = CLH^^; C = 3.3 for Bypass 6.2 for Vortechs (Eqn. 2) Bypass: L = 6.0 ft. ©elevation 101.83 ft. ( 1.83 ft.) Vortechs L = 2.0 ft. ©elevation 106.00 ft. LoFlow(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(cfe) H(ft) Q(cfe) H(ft) Q(cfs) Q(cfs) (feet) h(ft) Q(cfe) H(ft) Q(cfe) 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 5.40 0.00 0.00 0.75 12.9 18.3 100.17 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.67 2.17 5.51 0.00 0.00 0.84 15.2 20.7 100.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.75 2.25 5.61 0.00 0.00 0.92 17.5 23.1 100.33 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.83 2.33 5.72 0.00 0.00 1.00 19.9 25.6 100.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102.92 2.42 5^82 000 0.00 1.09 22.4 28.2 100.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.58 0.08 1.08 0.00 0.00 0.00 0.00 1.08 103.08 2.58 6.02 0.00 0.00 1.25 27.8 33.8 100.67 0.17 1.53 0.00 0.00 0.00 0.00 1.53 103.17 2.67 6.11 0.00 0.00 1.34 30.6 36.7 100.75 0.25 1.87 0.00 0.00 0.00 0.00 1.87 103.25 2.75 6.21 0.00 0.00 1.42 33.5 39.7 100.83 0.33 2.16 0.00 0.00 0.00 0.00 2.16 103.33 2.83 6.30 0.00 0.00 1.50 36.5 42.8 100.92 0.42 2.42 0.00 0.00 0.00 0.00 2.42 103.42 2.92 6.39 0.00 0.00 1.59 39.6 46.0 101.00 0.50 2.65 0.00 0.00 0.00 0.00 2.65 103.50 3.00 6.48 0.00 0.00 1.67 42.7 49.2 101.08 0.58 2.86 0.00 0.00 0.00 0.00 2.86 103.58 3.08 6.57 0.00 0.00 1.75 46.0 52.5 101.17 0.67 3.06 0.00 0.00 0.00 0.00 3.06 103.67 3.17 6.66 0.00 0.00 1.84 49.3 55.9 101.25 0.75 3.24 0.00 0.00 0.00 0.00 3.24 103.75 3.25 6.75 0.00 0.00 1.92 52.7 59.4 101.33 0.83 3.42 0.00 0.00 0.00 0.00 3.42 103.83 3.33 6.83 0.00 0.00 2.00 56.1 63.0 101.42 0.92 3.58 0.00 0.00 0.00 0.00 3.58 103.92 3.42 6.92 0.00 0.00 2.09 59.7 66.6 101.50 1.00 3.74 0.00 0.00 0.00 0.00 3.74 104.00 3.50 7.00 0.00 0.00 2.17 63.3 70.3 101.58 1.08 3.90 0.00 0.00 0.00 0.00 3.90 104.08 3.58 7.08 0.00 0.00 2.25 67.0 74.1 101.67 1.17 4.04 0.00 0.00 0.00 0.00 4.04 104.17 3.67 7.17 0.00 0.00 2.34 70.7 77.9 101.75 1.25 4.18 0.00 0.00 0.00 ^ QOO 4.18 104.25 3.75 7.25 0.00 0.00 2.42 74.5 81.8 ' IIVT 4 33 104.33 3.83 7.33 0.00 0.00 2.50 78.4 85.8 101.92' 1.42 4.45 0.00 0.00 0.09 0.51 4.96 104.42 3.92 7.41 0.00 0.00 2.59 82.4 89.8 102.00 1.50 4.58 0.00 0.00 0.17 1.39 5.97 104.50 4.00 7.49 0.00 0.00 2.67 86.4 93.9 102.08 1.58 4.71 0.00 0.00 0.25 2.52 7.23 104.58 4.08 7.56 0.00 0.00 2.75 90.5 98.0 102.17 1.67 4.83 0.00 0.00 0.34 3.87 8.70 104.67 4.17 7.64 0.00 0.00 2.84 94.6 102.2 102.25 1.75 4.95 0.00 0.00 0.42 5.39 10.34 104.75 4.25 7.72 0.00 0.00 2.92 98.8 106.5 102.33 1.83 5.07 0.00 0.00 0.50 7.07 12.14 104.83 4.33 7.79 0.00 0.00 3.00 103.1 110.8 102.42 1.92 5.18 0.00 0.00 0.59 8.90 14.08 104.92 4.42 7.87 0.00 0.00 3.09 107.4 115.2 102.50 2.00 5.29 0.00 0.00 0.67 10.86 16.15 105.00 4.50 7.94 0.00 0.00 3.17 111.8 119.7 vortechs 12tnch.xta APPROXIMATE VORTECHNICS COSTS MODEL . ^ . . ',C(Ve^tinj?nt ;. (Cf5S)-:. : ; MODEL . ^ . . ',C(Ve^tinj?nt ;. (Cf5S)-:. : ; CbMML. Model 1000 1.6 10 14 15 18 23 Model 2000 2.8 17 24 26 31 39 Model 3000 4.5 27 38 41 49 62 K/lbd'eT4000" • 37 Model 5000 8.5 52 72 78 94 117 Model 7000 11.0 73 102 110 132 165 Model 9000 14.0 93 129 140 168 210 Model 11,000 17.5 117 162 175 210 263 Model 16,000 25.0 167 231 250 300 375 * Equipment costs include delivery to jobsite (FOB) and assembly (not installation). THIS DOES NOT INCLUDE A WEIR DIVERSION BOX. ** Equipment and installation. Installation costs (25% - 30%) will vary depending on site conditions. Plan View Grit Chamber O'l Chamber/ Row Control Baffle Wall Chamber Elevation View: Dry-Weather Grit Chamber The swirling motion created by the tangential inlet directs settleable solids toward the center of this chamber. Sediment is caught in the swirling flow path and settles back onto the pile after the storm event is over. Oil Chamber & Baffle Wall The center baffle traps floatables in the oil chamber, even during clean- out. Highly resistant to flow surges. Flow Control Chamber The weir and orifice flow controls: 1] Raise level and volume in the *. system as flow rate increases; and 2) gradually drain the system as flow rate subsides. 1) Initial Wet Weather Phase During a two-month 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. p 3) Full Capacity Phase When the high-flow outlet approaches fuil discharge, storm drains are flowing at peai< capacity. The Vortechs 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. 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. the ^t)rtec1 Stormwater Treatment System • Plus 6' Typical Plan View a'In 5' INVi 3'tD4' Perforated Covers =1 / 6' to 9' Tvpical Elevation View 1 I 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 fox or mail the worksheet to Vortechnics with your site plan, and we'll produce detailed Vortechs System scale draw- ings free of charge. Vortechir,,'-' Model : •' GritChamber •iametsr/Area ft/fe ... ; r: ••. Paal<;: ••v^; •esign , ' , . Flaw*- ' - cfe;: • •Sediment '\ • Storage" • yds." Appra.x. Size • L X W • ft 3/7 1.6 .75 9x3 . . . 4/13 2.8 1.25 10x4 5/20 4.5 1.75 11x5 i;;:|:4(xiq; - , 6/28 6.0 2.5 12x6 7/38 8.5 3.25 8/50 11.0 4.0 ; •\14,-x8:M l^psigcoor 9/64 14.0 4.75 ncxn •pi0/79 17.5 5.5 16 •v.-16000 12/113 25.0 • •. 7.0' Engineering Nates A) For in-lina Vartecha Systenns without a bypass, sizing critarla is based on providing one square foot of grit chamber surface area for each 100 gpm of peak design storm flow rate (e.g., lO-yaar storm). For more details about Vortechnics sizing criteria refer to Vortechnics Tachnical Bulletin 3. B) Sediment storage volume assumes a 3 foot sump. C) Construction details may vary depending on the specific application. Any alterations to tha sizing chart specifh cations will appear on Vortechnics dimensional and shop drawings. Please call Vortachnica for the weight of spe- cific Vortechs systems if needed. Special Note: Oil storage capacity, when it is needed to meet a specific requirement for spill containment, can ba sized to meet the storage requirement with tha selected model. Vortechnics technicel staff will optimize system geometry to meet containment requirements within a correctly sized Vortechs System. /WeCnc Specification Chare avBiiable by calling \Ajrtechnics at (S07j 578-3662. Vortechs System Inlet/Outlet Configurations Vortechs Systems can be configured to accommo- date various inlet and outiet pipe orieni:ations. 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 Iniet jM Offline U f Side Inlet 0 To 11 Pretreatment Q^^,, .SBAD