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December 13,2016 TTC Page 6 of 8 analyzed for polynuclear aromatic hydrocarbons(PAHs), polychlorinated biphenols (PCBs); semi- and volatile organic compounds (SVOCs and VOCs); TPH as oil and grease; TPHd; and TPHg. Groundwater Monitoring Well Installation ATC will contract with a C-57 licensed drilling company to advance a total of seven borings using hollow stem auger (HSA) drilling equipment. The borings will be completed as groundwater monitoring wells and include one on-site and three off-site shallow monitoring wells; and three on- site deep monitoring wells. Proposed well locations are shown on Figure 2. The boreholes for the shallow wells will be advanced using 8-inch diameter HSA drilling equipment to a total depth of approximately 65 feet bgs. To complete the shallow monitoring wells, two-inch diameter schedule 40 PVC casing, with a well screen consisting of 0.020-inch slot screen extending from 50 feet to 65 feet bgs,will be placed in the borehole. A filter pack consisting of #3 sand or equivalent will be emplaced in the annular space surrounding the well casing, extending up to a depth of approximately 48 feet bgs, over which, a 3-foot thick layer of hydrated bentonite chips will be placed. The remainder of the annular space will be backfilled with cement grout to a depth of approximately one foot bgs. The well casings will be set within flush-mounted traffic-rated well vaults. The boreholes for the deep wells will be advanced using 8-inch diameter HSA drilling equipment to a total depth of approximately 80 feet bgs. To complete the deep monitoring wells, two-inch diameter schedule 40 PVC casing, with a well screen consisting of 0.020-inch slot screen extending from 75 feet to 80 feet bgs, will be placed in the borehole. A filter pack consisting of #3 sand or equivalent will be emplaced in the annular space surrounding the well casing, extending up to a depth of approximately 73 feet bgs, over which, a 3-foot thick layer of hydrated bentonite chips will be placed. The remainder of the annular space will be backfilled with cement grout to a depth of approximately one foot bgs. The well casings will be set within flush-mounted traffic-rated well vaults. Soil samples will be collected at 5-foot intervals for logging purposes. At least two soil samples from each boring will be submitted for laboratory analysis. Any submitted soil samples will be sent under chain-of-custody procedures to a California State-certified laboratory and analyzed for TPHd by EPA Method 8015 and TPHg, BTEX, and fuel oxygenates by EPA Method 8260. Well Surveying Following installation, the newly-installed groundwater wells will be surveyed by a licensed surveyor to a local benchmark relative to mean sea level. Well Development The monitoring wells will be developed by rigorously surging each well over the length of the screen interval and by purging until the extracted groundwater is deemed clear(up to a maximum of 10 casing volumes of water from each well). Well Sampling Groundwater samples will be collected and analyzed for the presence of TPHd by EPA Method 8015 and TPHg, BTEX, and fuel oxygenates by EPA Method 8260B. Upon completion of the initial groundwater sampling activities, the groundwater monitoring wells will continue to be sampled quarterly during the first year.