Extended Site Assessment (ESA) and Long-Term Monitoring (LTM) Activities for Underground Storage Tank (UST) Sites, Naval Base Coronado Installations, CA.

The scope of work of this task order included the following activities: groundwater level measurements, biovent system operations and routine maintenance at Naval Air Station North Island (NASNI) Building 66 Area underground storage tank (UST) site, groundwater monitoring in support of the ESA for UST 2 at Naval Amphibious Base (NAB) Coronado, and soil, groundwater, and soil gas sampling in support of the Corrective Action Plan for UST 2 at Naval Outlying Landing Field Imperial Beach (NOLF IB).

The scope of work included the following activities: groundwater level measurements, biovent system operations, and routine maintenance at Naval Air Station North Island (NASNI) Building 66 Area underground storage tank (UST) site; groundwater monitoring in support of the ESA for UST 2 at Naval Amphibious Base (NAB) Coronado; and groundwater and soil gas sampling in support of the Corrective Action Plan for UST 2 at Naval Outlying Landing Field Imperial Beach (NOLF IB).

Building 66 Biovent Operations and Groundwater Monitoring

GCE operated the biovent system for Building 66 every two weeks in accordance with the Air Pollution Control District (APCD) permit for control of methane levels in the groundwater. To maintain aerobic conditions in the subsurface, the Building 66 UST site biovent system was operated for at least 40 hours every 2 weeks as part of the standard operation schedule. Typically, GCE ran the system for 2-3 days at a time. GCE also provided routine maintenance services to the biovent system as necessary to ensure optimal performance. GCE also prepared an annual monitoring report for the biovent operations at Building 66.

NAB Coronado UST 2 Sampling and Reporting

Previous investigation results indicated that contaminants had not been fully delineated and further site characterization was warranted in order to conduct a risk assessment and develop the appropriate alternatives for the site. GCE conducted the sampling required to support the extended site assessment for NAB Coronado UST 2, the old fuel farm. Three groundwater monitoring wells were installed and developed under a County of San Diego Department of Environmental Health (DEH) permit and groundwater samples collected and analyzed for BTEX (benzene, toluene, ethylbenzene and xylene) and polycyclic aromatic hydrocarbons (PAHs). At the conclusion of the sampling, a Monitoring Report was prepared and submitted to the regulatory agencies.

NOLF IB UST 2 Former NEX Gas Station Sampling

GCE collected groundwater sampling from 20 groundwater monitoring wells using dedicated bladder pumps. Groundwater samples were analyzed for: BTEX, methyl tert-butyl ether (MTBE), total petroleum hydrocarbons (TPH) diesel range organics, TPH gasoline range organics, TPH motor oil range organics, PAHs, total lead, methane, ferrous iron, total organic carbon, anions (chloride, nitrate, nitrite, and sulfate), and alkalinity.

GCE also collected soil vapor samples from multi-level (dual- and triple-nested) soil vapor probes. Site soil vapor probe samples were analyzed for: BTEX, MTBE, 1,1-Difluoroethane, TPHv gasoline, methane, carbon dioxide and oxygen, and the sample with the highest TPHv result was analyzed for volatile organic carbons (VOCs).

GCE also advance 20 soil borings in the former source area to determine if residual free product was still present in the vadose zone. Soil samples were analyzed for BTEX, VOCs, and TPH. At the conclusion of the sampling, an Annual Monitoring Report was prepared and submitted to the regulatory agencies.