2006_0327_Packet - Laserfiche WebLink

Home

March 2006 2 053-2442 Addition," also built as slab on grade, was erected sometime between 1974 and 1979. The Second Addition adj oins the First Addition immediately to the west. � The site is underlain by lake sediment deposits, consisting of fine- to medium-grained sand with minor amounts of silt and clay (Patterson, 1992). Based on review of well logs available for the area, bedrock, consisting of Ordovician-age St. Peter Sandstone, occurs at a depth of approximately 100 � feet beneath the site. Groundwater occurs at depths ranging frs�r�� approximately three to 11 feet below ground surface �,_„ (Braun, 2005). Based on the apparent extent of VOC-affected groundwater beneath the site and the suspected source area of VOCs, it appears groundwater flows to the east-northeast. � � � � I 1.3 Summary of Previous Investigations Six environmental investigations have been conducted at the site, the first of which was conducted during 1992 and the most recent was completed during the fall of 2005. Brief descriptions of these investigations and pertinent findings are described in the following sections. 1.3.1 UST Removal, Monitoring and Sampling (1992) One 500-gallon and one 2,000-gallon underground storage tanks (UST) were removed from the property during August of 1992. Both USTs were reportedly used to store No. 2 fuel oil. The 500- gallon UST was reportedly in poor condition at the time it was removed, and petroleum had been released at the site. Approximately five cubic yards of petroleum-impacted soil were excavated and the MPCA issued a closure letter for the leak attributed to the 500-gallon UST. A groundwater sample collected Gk��_� a depth of approximately seven feet below ground surface near the former 500- gallon UST reportedly contained elevated concentrations (2,900 milligrams per liter) of diesel-range organic compounds. � During November 1992, a groundwater sample was obtained from a three-inch diameter supply well that was located within five feet of the former 500-gallon UST. According to District information, the well was reportedly completed to a total depth of 88 feet below ground surface. The groundwater � sample was analyzed for a suite of VOCs (Minnesota Department of Health List 465.D). It contained detectable concentrations of VOCs, but at concentrations below Minnesota Department of Health Recommended Allowable Limits (MDH-RALs}. � According to Petroleum Tank Release Report filed for the two tanks, the 2,000-gallon UST was in good condition when it was removed from the subsurface. � 1.3.2 Water Well Sampling (1993) � An additional water sample was collected from the three-inch diameter supply well during July 1993. The well was purged of an unknown quantity of water over the period of one week prior to collecting the water sample. Analytical results for that water sample where similar to those measured in the � water sample collected the previous year, with VOCs measured at concentrations below MDH-TZALs. The supply well was subsequently sealed. � 1.3.3 Soil and Groundwater Sampling (1997) Four small diameter push probes were advanced near the former 500 gallon UST basin during January 1997 (probes P-1 through P-4, Figure 2). Four groundwater samples and five soil samples � �