ARCHIVED REPORTS XR0012829 - Laserfiche WebLink

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All monitoring wells were.sampled for analysis and the original three monitoring wells (MW#1-, i� MW#2, MW#3) were used to establish groundwater gradient. All samples were transported under chain of custody to a state certified laboratory for analysis by EPA methods 602 and 503018015. All water sample analysis and groundwater elevations are summarized in the attached tabular recap sheet. Original data sheets from laboratories are attached. FINDINGS The ground water table has raised about two feet over the site. The groundwater hydraulic gradient was calculated at S=0.008 with the down slope in the Northeast direction. The slope of the gradient is over double of past quarterly sampling event and should not be considered a normal condition. CONCLUSIONS There is no logical reason for the hydraulic gradient to change from a normal S=0.003 to S=0.008 of this period. Additional vent time on the monitoring wells should be used on future sampling events to insure an accurate groundwater elevation. REPORT OF CPT WORK CPT#3 INSTALLATION . The original work plan was to install CPT#3 in the sidewalk on the north side of Lafayette Street. This sidewalk area was too small for the CPT truck and this location had to be abandoned. The area in the parking lot under the State Route 4 Viaduct was chosen and will accommodate the CPT truck. CPT PROCEDURE The subcontractor, Gregg Drilling, used a 20 ton CPT push truck with a Piea_o Cone Penetrometer. Data collected was recorded by Cone Investigation Ltd. software with hard copy printout. Data was collected continuously for cone bearing (Qc), sleeve friction (Fs), and pore pressure (Ut). The procedure required one push run with the Penetrometer for data collection and one adjacent push with sample collection equipment for soil and groundwater samples. Three soil samples were extracted by the soil push tube method. Three groundwater samples were collected using the hydro- punch method. FINDINGS All soil samples extracted were analyzed as non-detect for all compounds per EPA method 8020, 5030,and 8260.The groundwater samples CPT#3@35',and CPT#3@55' indicated a small amount of MTBE is present at this location. Groundwater sample CPT#3@55' contains 50,000 ppm of TPHg, while both CPT#3@35' and CPT#3@100' were non-detect for TPHg. CONCLUSIONS The sand strata at depths between fifty and fifty-five feet continues to be the main contributor to the water born movement of the gasoline contamination(see SBT graph in Gregg Drilling Report).The presence of MTBE in some samples and not in others, continues to bring up the question of the origin of this compound. 3