Stevens Creek Shoreline Nature Study Area Geotechnical Study

The Midpeninsula Regional Open Space District (District) proposes to conduct a geotechnical study to support the Stevens Creek Shoreline Nature Study Area Restoration Project (Project). The Project site is located within the City of Mountain View in Santa Clara County and is located west of the National Aeronautics and Space Administration (NASA) Ames Research Center, east of Stevens Creek, and south of the Don Edwards San Francisco Bay National Wildlife Refuge. A segment of the San Francisco Bay Trail travels along levees to the north and west of the property. The 55-acre Stevens Creek Shoreline Nature Study Area Open Space Preserve (Preserve) is owned and managed by the District. The Preserve is not hydrologically connected to Stevens Creek or the San Francisco Bay, and acts as a stormwater retention basin for runoff from the NASA facility during wet months. The District’s consultants would perform a geotechnical technical study to help assess the feasibility of future restoration of the Preserve into either a tidal marsh or managed pond. The study would require approximately 3 borings, 10 core penetrometer tests (CPTs), and 5 vibracore (VC) / direct push core (DP) samples at depths ranging from 15 to 100 feet. Borings would be conducted using: (1) a mud-rotary drill mounted on a tracked rig positioned on the levees surrounding the basin; (2) a 2-inch steel rod pushed into the ground using a hydraulic system; and (3) a 2.5 or 4-inch aluminum pipe with plastic liner that is vibrated or directly pushed into the material using a hydraulic system from the back of a pontoon boat. Bore holes will be backfilled with approved sealing materials and using a tremie pipe when applicable, in accordance with Santa Clara Valley Water District standards. During the geotechnical investigation, several sediment samples will be taken from the pond bottom for screening and lab testing. All work will occur outside of the western snowy plover nesting season (March 1 to September 1). All staff and contractors will receive biological awareness training and worksite supervision from a qualified biologist prior to beginning work. Work will not occur if special status species are detected within the work area, consistent with the District’s Resource Management Policies and best management practices.