Drainage Area 46 Grayson Creek Bypass-Phase 1B

Drainage Area 46 Grayson Creek Bypass-Phase 1B

The Contra Costa County Flood Control District proposes to install 145 linear meters (475 linear feet) of twin 102 inch spiral ribbed metal pipe from the existing terminus of a prior year pipe installation, upstream to a point approximately 180 feet north of Boyd Road. The purpose of Drainage Area 46 Grayson Creek Bypass Phase 1b is to extend the storm water bypass pipe to a point off Sequoia Middle School property. The bypass pipe will eventually become an integral component to the Drainage Area 46 Plan. The trench will be excavated to a dimension of 7 meters (23 feet) wide and 4.6 meters (15 feet) in depth. The pipes will be bulkheaded at the upstream terminus to allow for future extension. The pipe will be placed in the trench, and the trench back-filled. The spoils not used to backfill the trench will disposed of by the contractor at an offsite location. Due to the depth of the excavation the contractor will be required to shore the excavation, and California State Architect approved permanent shoring will be placed along a school building. Four small storm drain lines, originating form the adjacent school site, will be connected to the western most pipe. A chain link fence will be temporarily removed and replaced at the conclusion of the project. The installation of the pipe will result in the removal of 469 square meters (5,046 square feet) of riparian habitat. This incudes approximately nineteen mature trees that have a diameter at breast height greater than 6", seventy-two saplings which have a dbh of 1"-6", and one hundred seventy-two seedlings with a dbh of 1" or less. The riparian vegetation is predominately characterized by the presence of valley oaks, although some coast live oak and non-native ornamental trees are also found.

Pleasant Hill

Contra Costa

California Department of Conservation (DOC), California Department of Fish and Wildlife, Bay Delta Region 3 (CDFW), California Department of Parks and Recreation, California Native American Heritage Commission (NAHC), California Regional Water Quality Control Board, San Francisco Bay Region 2 (RWQCB), California State Lands Commission (SLC), Department of Water Resources, Office of Historic Preservation, Resources Agency, California Department of Transportation, District 4 (DOT)

California Department of Transportation, District 4 (DOT)

Other (Flood Control)

Aesthetics, Air Quality, Cultural Resources, Drainage/Absorption, Flood Plain/Flooding, Geology/Soils, Growth Inducement, Hazards & Hazardous Materials, Hydrology/Water Quality, Land Use/Planning, Mineral Resources, Noise, Population/Housing, Public Services, Recreation, Transportation, Vegetation, Wetland/Riparian, Wildlife