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qJ 1 Qsik Stop Market No. 132 October 30, 1990 Job No. 349132-32 Page 2 groundwater samples collected from monitoring wells MW-3 and MW-4 detected no petroleum hydrocarbon related contaminates. Analysis of groundwater samples from MW-2 detected 1 ppb benzene and detectable levels of ethyl benzene and total xylenes. Groundwater monitoring well MW-1 was destroyed on October 3, 1990, due to concerns of its passibility connecting two water bearing units which may represent separate shallow aquifers. This groundwater monitoring well is to be replaced with two groundwater monitoring wells, one to monitor the upper water bearing unit and one to monitor the lower water bearing unit. These installations are included in this work E plan. During the above activities, a leak was discovered in the subsurface piping and F excavations to remove the contaminated soils indicated that the contamination had affected the tank backfill and possibly the soil beneath the tank backfill. Upon issuance of the proper permits, the three underground storage tanks (USTs) will be removed to - I -" provide sampling access to the soil beneath the USTs. PROPOSED SCOPE OF WORK I -� Exceltech proposes to.drill and sample four exploratory soil borings MWAR, MW-5, MW-6, and MW-7 at the locations shown in Figure 2. These borings will be converted to groundwater monitoring wells upon their completion. The purpose of monitoring well MW-IP, will be to monitor the groundwater in a lower sandy unit located beneath g a silty clay which may represent a. confining layer. MW75 will monitor the groundwater in an upper unit which is located above this silty clay as will proposed groundwater monitoring wells MW-6 and MW-7. We will therefore, at the completion of this phase, have groundwater monitoring wells MW-IR, MW-2, MW-3, and MW-4 =nionitoring the groundwater in the lower sandy unit and groundwater monitoring wells MW 5, MW-6, and MW-7 monitoringthe groundwater in the gr upper unit. If the results s ,�. of the groundwater analysis of these wells show that hydrocarbons are present, Exceltech will install wells where appropriate to fill any data gap in an attempt to define the extent of contamination. The location of additional wells, if necessary, will be determined to 1) define lateral contamination with cross-gradient monitoring walls and 2)define the source of contamination with monitoring wells downgradient. Exploratory Drilling and Soil Sampling A Before field work begins, Exceltech will determine utility locations through contacting Underground Services Alert. Exceltech will drill four exploratory borings at the approximate.locations shown on Figure 2.--The locations were selected in an attempt to a assess the vertical-and horizontal limit of soil and groundwater contamination. The { ? borings f,-;r:the monitoring wells will be.drilled with an Exceltech truck-mounted drill { rig using hollow-stem auger as directed by the on-site Exceltech geologist. Boring PAW-IR`will be drilled to approximately 30 feet and MW-5, MW-6, and MW-7 to