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1 GROUNDWATER MONITORING AND MITIGATION PLAN FOR HEIT AGGREGATE RESOURCE OPERATION-WELD COUNTY AQUATIC AND WETLAND NURSERY AND COYLE PROPERTIES 1.0 INTRODUCTION/PURPOSE This report was prepazed on behalf of the applicant of the proposed Heit Aggregate resource operation in Weld County to provide a recommended groundwater monitoring and mitigation plan for the Aquatic and Wetland Nursery (AWC) and Coyle properties adjacent to the operation. The scope of this plan includes: 1) a proposed groundwater monitoring program, 2) a recommended level of change in groundwater that would "trigger" implementation of mitigation measures, and 3) a discussion of potential mitigation measures. Wright Water Engineers, Inc. (WWE) completed a preliminary evaluation of potential effects on groundwater from the proposed pit in a report entitled Groundwater Evaluation for Proposed Heit Aggregate Operation, Weld County, Colorado (Mazch 2003). This monitoring and mitigation plan was prepared based on the findings of this previous report, a meeting with Jay and Brad Windell (AWC) and Laura Coyle on July 1, 2003, and subsequent evaluations. Additional work may be necessary to implement any of the recommendations in this plan, and the recommendations could be modified pending more fieldwork. 2.0 BACKGROUND The Heit Pit is a proposed aggregate operation on approximately 110 acres in the E % of Section 13, T2N, R67W in Weld County. Figure 1 is a vicinity map. It is proposed to construct a slurry wall around the mine azea prior to aggregate removal. This scurry wall will reduce effects on groundwater levels adjacent to the pit during mining and enable the site to be used for water storage after mining. Concern was raised by property owners with possible impacts from the mine on local groundwater levels. AWC operates a nursery on land immediately north of the proposed pit 021-110.030 Wright Water Engineers, Inc. Page 1 July 2003