ARCHIVED REPORTS XR0002718 - Laserfiche WebLink

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- Ff ��.+l�l?�'1` x11� �� y',€•' _—. -_. - _. . .. ...I. 1 that the hydrocarbon source had not been. identified. The TRC recommended that one additional monitoring well be installed on-site to confirm that impacted soil was removed from the old tank excavation, and that two monitoring wells be installed off-site, on the north side of Harding Way, to further evaluate the possible existence of an off-site source ' of petroleum hydrocarbons. On March 24 and 25, 1994, three additional monitoring wells were installed on or near the ' site. Monitoring wells MW-6 and MW-7 were installed in the sidewalk along the north side of Harding Way. Monitoring well MW-8 was installed within the former UST cavity, near the southern portion of the property. ' Noetroleum hydrocarbons were detected in any of the analyzed soil samples from MW-6, P , MW-7 or MW-S. Analytical results of soil samples are included in Table 4. 1991 through April,1994 3.6 Groundwater Sampling, September g p . . , A monthly groundwater monitoring program was established at the site and groundwater depths were measured six times between November 10, 1993 and April 13, 1994. A Solinst water meter was used to measure water depth in each well. ,Table. 6 .summarizes the, groundwater depth data. Monthly monitoring was terminated following the April monitoring. Groundwater samples have been collected from the site on seven occasions between 4 September 1991 and April 1994. TPH as gasoline and toluene were detected in only one sample at concentrations of 140 ppm and 1.5 ppb respectively (MW-4/9-13-93). No TPH as gasoline or volatile aromatics have been detected in any other well at the site.. site. Diesel was detected in TPH as diesel was detected m three monitoring wells at the si .e _ MW-1 in January 1994; in MW-4 during the September 1993 and April 1994 monitoring ' events; and in MW-5 during the September 1993 monitoring. No TPH as diesel was detected in any other well. The analytical results from all water samples are summarized on-Table 5. 3.7 Groundwater Sampling, July 1994 ' In a letter dated May 25, 1994 the PHS/EHD stated that "sampling and monitoring of the on-site and off-site wells shall be conducted on a quarterly basis beginning this second quarter (May, June, and July)." In accordance with the requirement of the PHS/EHD, GeoAudit performed quarterly monitoring procedures at the site on July 19, 1994. ' In accordance with quarterly monitoring procedures, the groundwater depth in each well was measured. The groundwater depths were measured using a Solinst water level meter. The relative piezometric level in each well and hydraulic gradient were determined by subtracting ' the depth to groundwater from the relative casing elevation (Table 6). C6A.S�i Am&Se�1... 7 pj.S nUDW Sus.6a.a-si