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d MW11 on Figure 3). The screened intervals of these wells range from approximately 94 to 109.5 feet bgs. MW9 is located in the apparent downgradient direction with respect to the subject site. Apache Plastics well MW9 is located in close proximity to the former location of the Apache Plastics UST and according to Stratus ' quarterly groundwater monitoring report for the second quarter of 2005, is situated in a downgradient position with respect to the location of this former UST. It should be noted that groundwater samples collected from Apache Plastics well MW9 have historically contained high concentrations of petroleum hydrocarbons. Apache Plastics wells MW8 and MWII will serve to evaluate the intermediate groundwater plume to the southeast and southwest of the subject site, Pa V t respectively. Groundwater samples collected from Apache Plastics wells MW8 and MWll have rJ0 historically contained moderate and very low concentrations of petroleum hydrocarbons, respectively. In order to further evaluate the vertical extent of the impacted groundwater at the site, a deep monitoring well will be installed in the vicinity of MW6 . Groundwater samples collected from MW6 have historically contained the highest concentrations of petroleum hydrocarbons in groundwater - samples collected from wells screened in the intermediate zone. The proposed deep monitoring well ,A.. 4 will be installed to a depth of approximately 140 feet bgs. The proposed deep monitoring well will be a, r• .. constructed of 2-inch inside diameter schedule 40 PVC well screen and casing with approximately ten 9 feet of 0 .020 inch slot screened PVC. The deep well will be installed inside conductor casing Y extending to approximately 120 feet bgs to minimize contaminant migration from above. A sand pack {y ,. 1" will be placed in the annulus of the well extending from the bottom of the well screen to approximately five feet above the top of the screen. Approximately three feet of bentonite will be placed on top of the sand pack and hydrated with potable water. The remaining annulus will be grouted to surface with cement grout. To protect the integrity of the well, a locking, watertight well plug will be installed on the well and a watertight wellhead labeled "monitoring well' will be set in concrete over the well. The location of the proposed deep monitoring well is shown on Figure 3 . The three groundwater monitoring wells will be installed using a hollow stem auger equipped drilling rig. Drilling will be conducted by a State-licensed (C57) drilling company. A field geologist will be present to log drill cuttings. Descriptions of soil types encountered will be recorded on well logs. Soil samples will not be collected for laboratory analyses. Once the wells are installed, the tops of the well casings will be surveyed to sub-meter accuracy relative to a known benchmark. At least 48 hours after installation, the three new wells will be developed using surging and bailing techniques until the purged groundwater is relatively sediment free. The wells will be sampled at least 48 hours after they are developed. Prior to the collection of groundwater samples, the depth to groundwater will be measured in each well to evaluate the direction and magnitude of the groundwater gradient beneath the site and a minimum of three well volumes (casing and sand pack) of groundwater will be purged from each well. Temperature, pH, and electric conductivity will be measured and allowed to stabilize. Water samples will be collected using disposable bailers, one dedicated to each well. Sample Analyses Groundwater samples collected from the monitoring wells will be submitted under chain-of-custody procedures to a State-certified laboratory. The groundwater samples will be analyzed for total petroleum hydrocarbons quantified as gasoline (TPHg) utilizing EPA Method 8015M, and benzene, toluene, ethylbenzene, and xylenes (BTEX), methyl tertiary butyl ether (MTBE), ethyl tertiary butyl S:\Environmenta1\28349\wkp.doc 4 ATC Associates Inc.