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4.12 Water Resources Draft EIR

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4.12 Water Resources Draft EIR Canoga Transportation Corridor Project 4.12 Water Resources Draft EIR 4.12 WATER RESOURCES This section addresses the water resources, hydrology and water quality that would change due to the proposed project. 4.12.1 EXISTING SETTING The project site is located in the Los Angeles River Watershed. The Los Angeles River is 51 miles long from the western end of the San Fernando Valley to the Queensway Bay and Pacific Ocean at Long Beach. It has a total drainage area of approximately 834 square miles. The project is in the upper portion of this watershed just below the eastern portions of the Santa Monica Mountains, Simi Hills, and Santa Susana Mountains. Where the Los Angeles River crosses the Metro ROW it flows in an easterly direction and the upstream tributary area, including Chatsworth Reservoir, Chatsworth Creek, Bell Creek and Arroyo Calabasas is approximately 44.5 square miles and is 28% impervious. This project area is about 5% of the total drainage area for the Los Angeles River Watershed. The project site is primarily within the Metro Right-of-Way (ROW) along the east side of Canoga Avenue from the existing MOL Canoga Station to the Chatsworth Metrolink Station and portions of Canoga Avenue’s ROW. The Metro ROW varies from 40-ft. to 275-ft. with the majority being 100-ft. wide. Portions of the project are adjacent to the Metro ROW in public ROW for Canoga Avenue. DRAINAGE FACILITIES The Santa Susana Creek also crosses the Metro ROW and alignments, flowing in a southeasterly direction. The area tributary to the Santa Susana Creek upstream of the project is approximately 2.5 square miles and is 49% impervious. South of Parthenia, the Santa Susana Creek flows into Browns Canyon Wash and then another 2.5 miles to the Los Angeles River confluence. The Santa Susana Creek is a county facility. At the location where it crosses the proposed BRT alignment it is a reinforced concrete rectangular channel 10-ft. deep with bottom width of 28-ft. At the northerly end of the alignments, just east of the Metrolink Chatsworth Station, Browns Canyon Wash flows in a southerly direction. Browns Canyon Wash is a reinforced concrete rectangular channel with a depth of 10-ft. and width of 60-ft. Browns Canyon Wash is a Los Angeles County facility. Near the southerly end of the project, Kelvin Channel (just east of De Soto Avenue) crosses the existing De Soto Metro Orange Line Station flowing in a northerly direction just upstream of the confluence with the Los Angeles River. The tributary area upstream is about 4.0 square miles and 42% impervious. The Los Angeles River, Santa Susana Creek, and Browns Canyon Wash are all identified as “Zone A (areas of 100-year flood) contained in channel.”1 The Study area is all Zone C (areas of minimal flooding) except the crossings of the Los Angeles River and Santa Susana Creek. 1 FEMA. Flood Insurance Rate Maps 060137 0018 C, 060137 0027 C and 060137 0036 C, effective December 2, 1980. 4.12-1 Canoga Transportation Corridor Project 4.12 Water Resources Draft EIR The Los Angeles River is a Los Angeles County facility. At the location where it crosses the BRT it is a reinforced concrete trapezoidal channel 17.5-ft. deep with bottom width of 45-ft. and side slopes of 2.25 Horizontal to 1 Vertical. The channel invert has a 1% cross slope towards the center. There are 12-ft. wide paved roadways on each bank. The construction of the channel was completed in 1958 by the U.S. Army Corps of Engineers with operation and maintenance transferred to Los Angeles County Flood Control District. The design discharge was 24,000 cfs with 2.1-ft. of freeboard to the top of the channel lining. Velocity in this reach of the channel is 23.5 ft. per second (fps). DRAINAGE PATTERNS The proposed alignments run along the east side of Canoga Avenue. Between the Los Angeles River and the Santa Susana Creek crossings, the runoff is generally in a southeasterly direction. Offsite flow is intercepted by the curb and gutter of Canoga Avenue before reaching the Metro ROW. In Canoga Avenue, offsite flow is conveyed southerly, from a point near the Santa Susana Creek crossing on the surface. A 4.0-ft. wide by 0.9-ft. high City of Los Angeles culvert (P-28181) conveys flow in Canoga Avenue across Parthenia Street and discharges back to the curb and gutter of Canoga Avenue. City of Los Angeles culverts also convey flow in Canoga Avenue across Roscoe Boulevard and discharge back to the curb and gutter of Canoga Avenue. Just before reaching Saticoy Street, the surface flow in Canoga Avenue is collected in a City of Los Angeles storm drain (D-23389). Record drawings indicate this portion of the storm drain was constructed in 1975 and had a 10-year design discharge of 265 to 352 cfs. This 75-inch diameter reinforced concrete pipe storm drain continues to convey flow in a southerly direction in Canoga Avenue past Valerio Street where it joins the County of Los Angeles storm drain (No. 478). This 81-inch to 96-inch diameter reinforced concrete pipe storm drain continues to convey flow in a southerly direction in Canoga Avenue to the Los Angeles River. At the south end of the project, runoff is generally in a northeasterly direction. Offsite flow is intercepted by the curb and gutter of Victory Boulevard and Canoga Avenue before reaching the Metro ROW. In Victory Boulevard, offsite flow is conveyed easterly and collected in a City of Los Angeles storm drain (D-18020) under the street that conveys storm water to Kelvin Channel. This 54- inch to 66-inch diameter storm drain was constructed in 1963. Kelvin Channel is a Los Angeles County facility (Project No. 112) that flows northerly along the easterly side of De Soto Avenue. In Canoga Avenue, offsite flow is conveyed northerly and collected in a City of Los Angeles storm drain (D-22847) under the street that conveys storm water to the Los Angeles River. This storm drain is an 8.5-ft. wide by 10.0-ft. high reinforced concrete box. North of Santa Susana Creek, the Metro ROW continues along the east side of Canoga Avenue. In this area runoff is generally in a southeasterly direction. Offsite flow is intercepted by the curb and gutter of Canoga Avenue before reaching the Metro ROW. In Canoga Avenue, offsite flow is conveyed southerly, from the end of the project on the surface until it reaches Nordhoff Street. At this intersection it is conveyed under Nordhoff Street in City of Los Angeles culverts that discharge back to the curb and gutter of Canoga Avenue. Flow continues southerly in Canoga Avenue until collected in City of Los Angeles storm drain (D-21230). This 42-inch diameter reinforced concrete pipe storm drain, constructed in 1967, discharges into the Santa Susana Creek. 4.12-2 Canoga Transportation Corridor Project 4.12 Water Resources Draft EIR 4.12.2 REGULATORY FRAMEWORK The Water Quality Act of 1987 added Section 402(p) to the 1972 federal Clean Water Act (CWA) (33 U.S.C § 1251-1387). This section requires the United Stated Environmental Protection Agency (USEPA) to establish regulations setting forth National Pollutant Discharge Elimination System (NPDES) requirements for storm water discharges in two phases. On November 16, 1990, Phase I storm water regulations were directed at municipal separate storm sewer systems (MS4s) serving a population of 100,000 or more, including construction activities. On December 8, 1999, Phase II storm water regulations were directed at storm water discharges not covered in Phase I, including small MS4s (serving a population of less than 100,000), small construction projects (one to five acres), municipal facilities with delayed coverage under the Intermodal Surface Transportation Efficiency Act of 1991. The Porter-Cologne Water Quality Act of 1969 established the principal California program for water quality control. This Act authorizes the State Water Resources Control Board (SWRCB) to preserve and enhance all beneficial uses of the state’s immensely complex waterscape and divides the State of California into nine Regional Water Quality Control Board (RWQCB) areas. Sections of the Porter- Cologne Act were used as a basis for the 1972 CWA and responsibility for implementing the federal provisions was assumed by the state. The project is located in the Los Angeles Regional Water Quality Control Board (LARWQCB) Region 4. The General Construction Activity Storm Water Permit (92-08-DWQ) adopted September 8, 1992 covered construction activities disturbing 5 acres or more. On August 19, 1999 the SWRCB reissued the General Construction Storm Water Permit (99-08-DWQ) which decreased the covered project size from 5 to 1 acre. Construction activity subject to this permit includes clearing, grading and disturbances to the ground such as stockpiling, or excavation. The Construction General Permit requires the development and implementation of a Storm Water Pollution Prevention Plan (SWPPP). The SWPPP should contain a site map(s) which shows the construction site perimeter, existing and proposed buildings, lots, roadways, storm water collection and discharge points, general topography both before and after construction, and drainage patterns across the project. The SWPPP must list Best Management Practices (BMPs) the discharger will use to protect storm water runoff and the placement of those BMPs. Additionally, the SWPPP must contain a visual monitoring program; a chemical monitoring program for "non-visible" pollutants to be implemented if there is a failure of BMPs; and a sediment monitoring plan if the site discharges directly to a water body listed on the 303(d) list for sediment.
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