Under this contract, Ahtna performs operation and maintenance (O&M) of three groundwater treatment plants (GWTP) and one soil vapor extraction (SVE) system, and a network of 364 groundwater extraction and monitoring wells, and 45 soil vapor extraction and monitoring wells at the Sharpe Army Depot in Lathrop, California. Monthly GWTP monitoring and reporting, monthly SVE monitoring and quarterly reporting, quarterly groundwater monitoring and reporting, quarterly monitoring and reporting of two groundwater in situ treatment sites, annual groundwater model updates, and significant groundwater treatment system upgrades to improve operational control and efficiency are also performed. The groundwater remediation tasks also include installation of additional extraction and monitoring wells, and decommissioning of 22 wells. Additionally, Ahtna has been tasked with site investigations/waste characterizations at six sites involving soil, soil gas, and groundwater sampling for COCs including volatile organic compounds (VOCs), lead and chromium; a Remedial Investigation/Feasibility Study of a former burn pit with radiological contamination; and a risk assessment of exposure to soil and soil vapor contaminants including VOCs, metals, pesticides, and petroleum hydrocarbons, which allowed for limited duration residential-type use of the area for a California Army National Guard academy for troubled youth. Ahtna also provides land use control and biological monitoring, health and safety, quality assurance, and community relations support to the Army.