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Home My WebLink AboutCDP 08-18; Saba Residence; Storm Water Management Plan; 2010-01-1810-01 RECORD COPY Initial Date STORM WATER MANAGEMENT PLAN FOR THE SABA RESIDENCE PATIO APN203-140-08 Prepared by: Robert Sukup The Sea Bright Company 4322 Sea Bright Place Carlsbad, CA 92008 760 - 720 - 0098 Prepared For Don Saba 2623 Ocean Street Carlsbad, CA 92008 January 18, 2010 TABLE OF CONTENTS INTRODUCTION ------------------------------------------------------------------------------- 1 1.0 Project Description -------------------------------------------------------------------- 1 1.1. Hydrological Unit Contribution ----------------------------------------------- 1 1 .2. Beneficial Use of Coastal Waters ------------------------------------------- 2 1.2.1. Inland Surface Waters --------------------------------------------- 2 1.2.2. Groundwater --------------------------------------------------------- 2 2.0 CHARACTERIZATION OF PROJECT RUNOFF ------------------------------ 2 2.1. Expected Discharges ----------------------------------------------------------- 3 ^.^ . Ovjii v^/Hcir ciciGnsuCo —————————————————— —————————— ————•-—••«•—————————————••— ^j 3.0 MITIGATION MEASURES TO PROTECT WATER QUALITY ------------- 3 3.1. Construction BMP's -------------------------------------------------------------- 3 3.2. Post construction BMP's ------------------------------------------------------- 3 3.2.1 .1 Appropriate Applications and Siting Constraints ---------- 4 4.0 OPERATIONS AND MAINTENANCE PROGRAM --------------------------- 4 5 0 FI^PAI RF9OURCF^ ___________________________ _____________ 5B^ i i ^ v^^Ai— IAL. wv/ w r\^^ ^ w —————————————— — ^j ATTACHMENTS A. Vicinity Map B. Project Map with BMPs shown C. Numeric calculation for BMP sizing D. Erosion Control Plan INTRODUCTION The Stormwater Management Plan [SWMP] requirement is required for projects that are categorized as a Priority Development Project [POP] pursuant to the City of Carlsbad Standard Urban Stormwater Management Plan [SUSMP] and Carlsbad's Local Coastal Program requirements. After completing the Storm Water Standards Questionnaire [SWSQ] this project is a POP. The purpose of this SWMP is to address the water quality impacts from the proposed improvements on the Saba Residence Patio project. Best Management Practices [BMP's] will be utilized to provide a long term solution to water quality. This SWMP is also intended to ensure the effectiveness of the BMP's through proper maintenance that is based on long term fiscal planning. The SWMP is subject to revisions as needed by the engineer. 1.0 Project Description The existing Saba Residence is on a small, narrow lot that fronts on the Pacific Ocean. The lot measures 25' x 140' or about .08 acres. There is an existing house, rear deck, and sidewalks on each side of the residence. They equal about 2,265 square feet. Westerly of the existing deck is a small ice plant area, followed by their private sand area that is protected by rock rip rap. The proposed project is to install a concrete patio where the ice plant is located. The proposed patio is to be banded by a dual decorative wall system with a planter between the two walls. The combined height of the 2 walls is 6 feet. The area of the patio is 285 square feet. The proposed patio results in an increase of impervious area by more than 10% as compared to pre-development conditions. 1.1 Hydrologic Unit Contribution The Saba Patio Project is located in the Carlsbad Hydrologic Unit and more specifically in the El Salto Hydrolic area [unit 4.21 as designated in the San Diego Basin Plan]. The project area is characterized by an existing fully developed residential neighborhood of both single family and multiple family homes. The proposed patio will sheet flow into a 1.25' wide planter. Any water filtered through the planter box will seep out of the weep holes at the bottom of the 3' wall and discharge into the existing all sand private beach area. The proposed project will not alter drainage patterns on the site or off site. The Stormwater discharge points will not divert runoff from existing conditions. Through implementation of Low Impact Design practices, such as routing runoff Page 1 through engineered planters, will help alternate flows and allow evapotransporation, thereby mitigating the additional flows from the project. 1.2 Beneficial Uses of Coastal Waters The beneficial uses for the hydrologic unit are listed below. They have been extracted from the water quality control plan for the San Diego Basin. The only one they I have elaborated on that I feel is appropriate is the REC 1. RECI - Contact Recreation: Includes uses of water for recreation activities involving body contact with water, where ingestion of water is reasonbly possible. The uses include, but are not limited to, swimming, wading, water skiing, skin and SCUBA diving, surfing, white water activities, or fishing. Other possible benefits indicated in Table 2-3 of the basin plan are Non Contact Water Recreation, Wildlife Habitat, Preservation of Biological Habitats of Special Significance, and Rare-Threatened or Endangered Species of Marine Habitat. 1.2.1 Inland Surface Waters Not Applicable 1.2.2 Groundwater Not Applicable 2.0 CHARACTERIZATION OF PROJECT RUNOFF Per the Carlsbad Local Coastal Program, the Pacific Ocean shall be considered an Environmentally Sensitive Area [ESA] and that any project proposed within 200 feet of the Pacific Ocean which adds more than 2,500 S.F. or increases the impervious area by more than 10% shall qualify as a Priority Development Project and be subject to SUSMP treatment BMP standards. According to the California 2006 303d list published by the San Diego Regional Water Quality Control Board, the impaired water body associated with this project is the Pacific Ocean. It's only listed Pollutant Stressor is "Indicator Bacteria" which the patio will not contribute to. Page 2 2.1 Expected discharges There is no sampling data available for the existing site condition. In addition, the proposed project is not expected to generate any amounts of non-visible pollutants. The following constituents are sometimes found on single family homes that could affect water quality but I do not see any of them to be applicable except number 1. 1. Sediment discharge due to construction activities and post construction areas left bare. 2. Nutrients from fertilizers. 3. Trash and debris deposited in drain inlets. 4. Hydrocarbons from paved areas. 5. Pesticides from landscaping and home use. 2.2 Soil Characteristics The project area is within soil group A, which is a very good draining soil. 3.0 MITIGATION MEASURES TO PROTECT WATER QUALITY To address water quality for the project, BMP's will be implemented during construction and post construction. 3.1 Construction BMP's The construction BMP's that will be utilized during construction are as follows: 1. Silt Fence 2. Street Sweeping if needed. 3. Stockpile management 4. Solid waste management 5. Gravel bag berms 6. Concrete waste management 3.2 Post Construction BMP's The project, in its effort to comply with L.I.D. requirements, is designed to have all drainage waters from the new patio [285 square feet] be filtered by the new Page 3 vegetated planter. Area calculations and specifications of the planter soil mix are in the Attachments. No potential pollutants other than dust should be generated by the small patio and it will be absorbed/filtered through the vegetated planter area. The filter material in the planter box is designed to treat/filter runoff generated by an 85th percentile storm event. For storm events exceeding the 85th percentile storm event, runoff will flow over the planter wall into the 100% sand area, where it will be absorbed, filtered and/or continue to drain to the west as it did historically. 3.2.1 Appropriate Applications and Siting Constraints This project is minor in size [285 square feet] but none the less, the design accommodates for the sheet flow run off from rain to go into a vegetated planter. Any filtered waters will seep through the weep holes of the wall, and continue to drain to the west as they historically have. The project has no material storage areas, no trash storage areas, no storm ** drain systems, and no Integrated Pest Management Program. The minor **••••" irrigation system for the existing ice plant will be eliminated. 4.0 OPERATION AND MAINTENANCE PROGRAM The maintenance of the planter will be by the homeowner as follows: 1. Verification that vegetation has grown and established itself in the planter. 2. Removal of excessive weeds from the planter. 3. Removal of sediment or trash debris that might get into the planter. The planter should be visited a minimum of once a month or after each large storm [.25" or more] during the first winter of existence. Any maintenance as described above needs to be done immediately. After the first full year of growth, maintenance of the planter should be on an as needed basis. The owner is required to execute a city standard Permanent BMP Maintenance Agreement that records against the property. This agreement outlines the Page 4 current, prospective and future property owner's obligations to inspect and maintain treatment BMP's on this property to ensure their effectiveness at removing pollutants from this project. 5.0 FISCAL RESOURCES Funds for maintenance will be paid by the owners. This Stormwater Management Plan has been prepared under the direction by the following Registered Civil Engineer: Robert O. Sukup ' uate lialio 1 Date Page 5 1106 1 VIA DIEGO2 VIA JUDY 3 VIA ROBERTO 4 VIA BOCAS 5 VIA SABIHAS 6 VIA VERA 7 VIA CAROEL 8 VIA DENISE 9 VIA MERUE VIA TOHALA 11 CL HACIENDA 12 VIA CAJITA I miles 1 in. - 1900 ft.MAP OT Line EXISTING RESIDENCE EXISTING PATIO DECK i EXISTING SAND AREA *B" t£lo P^TfO PATIO eeA * i*>x/e .- zas^ .c-o&5 Ac FLOW BASED CALCUlATlOKi RATE OF A « l-O x .006S v(i 04) 20-30% 20-30% 5 c y ^ C.I-O--IMF envious FATlO I*- OK 'c EXISTING RESIDENCE EXISTING PATIO DECK EXISTING SAND AREA COOTHQU ATTACH wem