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JUN-04-2003 02:46PM FROM-AGGREGATE INDUSTRIES +3036659295 T-562 P.OOZ F-640 <br />~: -.~-i~ fr{? <br />~. <br />JUPi i, ~ 2003 EXECLIITVE stIMM,A,Rx <br />;. <br />oivisionoi Minerals&Ge01~~t behalf of Aggregate Industries, Environmental Resources Management <br />(ERM) conducted an additional subsurface investigation of the Jeronimus <br />Property located approximately at the northwestern corner of l00~ Avenue <br />and Brighton Road in Adams County, Colorado. The objective of the <br />investigation was to address potential concerns identified during the <br />Limited Phase II Environmental Subsurface Investigation, dated January B, <br />2003. <br />To evaluate presence or absence of contamination in the alluvial <br />groundwater system, four monitoring wells were installed and <br />subsequently sampled. Two sets of clustered monitoring wells, one <br />screened <br />extending from the top of the bedrock underlying the subject property to <br />just below the groundwater table. <br />Laboratory analysis did not detect volatile organic compounds (VOCs) at <br />or above laboratory reporting limits in the groundwater samples collected <br />from the shallow wells JP-55 and JP-6S or the deep well JP-5D. Methyl <br />tertiary-butyl edger (MTBE) was detected at a concentration of 16 <br />micrograms per liter (}~g/L) in the groundwater sample collected from the <br />deep well JP-6D. The Colorado Department o£ Public Health and <br />Environment (CDPHE) has not developed remediation cleanup <br />requirements for this compound. The United States Environmental <br />Protection Agency (EPA) is proposing a drinking water standard for MTBE <br />in the range of 20 }~g/L to 40 y.g/L. <br />Based on the limited number of groundwater samples collected during this <br />and the previous investigation, the groundwater samples collected are not <br />impacted above established and/or proposed regulatory standards. The <br />analytical results from these investigations have shown VOCs are present <br />in the groundwater below action levels. The results of these investigations <br />only represent the water quality at the time of sampling, and the source of <br />the VOCs detected has not been determined. Water quality can change over <br />time due to seasonal variations, or as a result of pumping. <br />Saturated soils were not evaluated during either investigation. <br />Given the levels of VOCs measured in the groundwater, there is no <br />regulatory requirement for additional groundwater monitoring or <br />investigation. <br />Eh1Ri{ONMEVIALIlCEOVRG[S MANACEMEN7 1 r,\sago\zao:\Cm_swasJEnoNUavs\PFUSE III\DWORt~WtCA{.000 <br />