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Geotechnical Engineering Exploration Hall-Irwin Construction Company Project No. 21975089 • Groundwater -Groundwater was encountered in each test boring at approximate depths of five and one-half (5-112) to eight (8) feet below the surface at the time of the initial exploration. Water levels in this area are subject to change due to seasonal variations and fluctuations in the flow of the SL Vrain River located approximately 1/2 to 1 mile north of the subject site. Field and Laboratory Test Results Field test results indicate that the overburden clay and silt layers are soft to medium stiff in consistency, and the poorly graded sand and/or sand with silt strata are loose to medium dense in relative density. The poorly graded to well-graded coarse sand with gravel stratum varies from medium dense to dense in relative density. The bedrock stratum varies from weathered to well-cemented with depth. CONCLUSIONS AND DISCUSSION It is Terracon's understanding that the area under evaluation, approximately 250 net acres, is to be utilized as a gravel pit by Hall-Irwin Construction Company in Longmont, Colorado. Based on the test borings drilled at the site, it is Tenacon's opinion the sand with gravel I material encountered during the field exploration at various depths is suitable for use as ' construction aggregate material. The overburden thickness encountered in the test borings (inGuding the slightly cohesive Gay and silt strata) ranges from approximately three (3) to eight (8) feet The underlying granular sand with gravel strata thicknesses encountered during the drilling operation ranges from approximately eleven and one-half (11-1/2) to thirty-three (33) feet. Based on these thicknesses and approximate areas of potential mining operations, there are approximately 2.02 million cubic yards of overburden material that will have to be removed to obtain approximately S.6 million cubic yards of silty sand and gravel material. Hence, the ratio of sand and gravel volume to overburden volume is approximately 4.2. The gravel encountered appears to be of good quality and contains durable rock fragments composed of igneous and metamorphic rack fragments. Variations may be encountered in the field when gravel extractioNmining operations take place. Safe distances should be kept from property lines, roads, railroads, and waterways. Since the sand and gravel strata was encountered below the groundwater, temporary dewatering of the gravel pit or use of a dragline will be required to remove the sand and 5