One Phase 1A Multipurpose Basin (Streambed Alteration Agreement EPIMS Notification No. PLA-39468-R2)

One Phase 1A Multipurpose Basin (Streambed Alteration Agreement EPIMS Notification No. PLA-39468-R2)

The project is limited to the grading and construction of a multipurpose storm water basin with a storm water outfall in a 5.3-acre area within the PRSP area that discharges to University Creek, an ephemeral drainage. The multipurpose basin is further delineated as ‘Basin F1’ and ‘Basin F2.’ Basin F1 will include a 36-inch outfall with trash rack and riprap. Basin F1 will be constructed with six-inch perforated subdrains roughly 15-feet apart under the basin floor and have a 10-foot-wide emergency spillway. Storm water intercepted by Basin F1 via the 36-inch storm drain will move north into Basin F2 via a connection to a 60-inch storm drain also connected to the development area south of Sunset Boulevard. Basin F2 will include three riprap dissipation pads and 36-inch outfalls with trash racks. From Basin F2, treated storm water will be discharged to the ephemeral drainage via a 42-inch outfall and vegetated swale having a two-foot-wide bottom, 3:1 slopes, and a 0.25% grade. The outfall will include an emergency spillway and riprap dissipation pad. Basin F2 will be divided into three sub-basins connected by 18-inch equalization culverts, and the sub-basin closest to the ephemeral drainage will be constructed with six-inch perforated subdrains roughly 15-feet apart under the basin floor.

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Northern California

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