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27 February 2015 AGE-NC Project No. 96-0235 Page 2 of 10 Mountains in the south to the Klamath Mountains in the north. The California Coast _ Range and the Sierra Nevada form the western and eastern boundaries of this province. Rocks composing the basement complex of the province have not been completely defined but are believed to be of metamorphic and igneous origin. The - northern and southern portions of the Great Valley Province have been designated the Sacramento and San Joaquin Valleys, respectively. The Modesto, Riverbank, and Turlock Lake Formations and overlying recent alluvium are the principal source of domestic ground water in the 13,500-square-mile San Joaquin Valley Ground Water Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River. 2.2. PREVIOUS REMEDIATION FEASIBILITY EVALUATION AND RECOMMENDATIONS The SJCEHD had previously directed the preparation of a groundwater remediation feasibility evaluation for the southern UST area. Shallow soil remediation was previously performed in two separate phases at each UST area; primarily during the UST removals and subsequently during deeper excavations of impacted soils extending to the upper portion of the water table. Assessment of deep, dissolved MTBE, east of the former northern UST area has been mostly completed. However, assessment of all dissolved petroleum east of the former UST No. 3, southern area has not been completed and dissolved hydrocarbons are - likely migrating east to northeast of the southern UST area. Well MW-8B, located between the UST areas, has not been impacted by significant petroleum hydrocarbon concentrations, and during routine monitoring events was non-detect for all petroleum hydrocarbons. The EHD has directed the limits of the dissolved plumes in the HU2 zone be defined to determine if the remaining dissolved impact meets the criteria established in the Low- 31S/�S Threat UST Case Closure Policy (LTCP), as a requirement for site closure. Based on depth to groundwater measurements colle��d in 2013 at the site, first-encountered (:5-W r`'bs- groundwater in the area is approximately � feet bsg, while deeper groundwater is significantly impacted between 40 and 60 feet bsg. The site groundwater monitoring well network lacks wells to define the later extent of deeper dissolved petroleum hydrocarbons and thus is an impediment to site closure. 3.0. SCOPE OF WORK AGE proposes to advance three (3) and potentially up to four (4) soil probe borings and three monitoring wells for the collection of repeatable groundwater samples to define Advanced GeoEnvironmental Inc.