Installation of Additional Wells at Assault Craft Unit Five (ACU-5), Marine Corps Base (MCB) Camp Pendleton, CA.

This task order includes the preparation of planning documents and implementation of field work associated with the installation of 5 new monitoring wells to aid in site characterization. This task also includes the preparation of a Revised Site Assessment Report. The project took place in endangered Coastal Diegan Scrub which was restored at the conclusion of the project.

A fuel leak was reported in a Site Assessment Report (SAR) for ACU-5 in May 2007. The leak was discovered during a routine inspection when fuel was noted in a sensor monitoring probe at one of the fuel pump stands. After further inspection, it was suspected that fuel had leaked from the low point just below the valve that is located at ground level inside a pit, evident by the presence of hydrocarbons on the ground surface.

The scope for this project included the installation of additional groundwater monitoring wells to delineate the extent of floating product and further assess soil and groundwater for total petroleum hydrocarbons quantified as gasoline, jet fuel (JP-5), diesel fuel, and motor oil, and volatile organic compounds. The installation of additional groundwater monitoring wells at ACU-5 included three vertical wells and two angled wells near French Canyon, adjacent to the bulk fuel storage facility at ACU-5. The objective of the angled wells was to monitor groundwater directly below French Canyon while the vertical wells were monitoring groundwater on the north and south sides of French Canyon. Each of the newly installed wells were sampled for groundwater quality after installation and again 6 months later. In addition, the presence of floating product was assessed in each new well.

Planning documents were prepared prior to well installation. The planning documents included a well installation Work Plan, Sampling and Analysis Plan, and an Accident Prevent Plan/Site Safety and Health Plan. Well installation permits were obtained from San Diego County Department of Environmental Health as required by San Diego County Code, Title 6, Division 4. Additionally, the 60-day well installation reports were submitted to the County as required. During drilling of each well, soil samples were collected ‑ 12 samples from the vertical borings and 15 samples from the angled borings ‑ for submission to the laboratory for analysis for the constituents of concern. All investigative derived wastes were characterized, profiled for disposal and, upon acceptance by the disposal landfill, transported under manifest to the disposal facility. Groundwater investigative derived waste was sent to the wastewater treatment facility on base via a pumper truck.

Biological surveys were conducted initially, and continuous biological monitoring was conducted during well installation due to the site being located within a biologically sensitive area and a documented nesting area of the California Gnatcatcher (CAGC), which is a threatened species. The well installation required the removal of potential CAGC habitat and occurred during the rainy season, resulting in the ground being damaged. Therefore, site restoration was conducted as specified in the National Environmental Policy Act Categorical Exclusion Decision Memorandum, resulting in replanting similar, local species of plants in approximately 1,500 square feet of disturbed endangered Coastal Diegan Scrub habitat in the French Canyon area adjacent to ACU 5. Additionally, in order to access the site, the chain-link perimeter fence was partially removed on both sides of French Canyon for rig assess, and the fence was replaced after site activities were completed.