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SEA-05-2003 FRI 0927 AM BAN~AND GE5S0 LLC FAX N0, 3174 8329 P, 04 • Page 3 September 4, 2003 were drilled in early spring oP 2003, prior to initiation of Initiation, this data represents a point in time measurement of the natural conditions in this area. The groundwater level certainly changes throughout the year as well as from year to year, depending on the prevailing climatic and irrigatlon conditions. Because of this, a pit that is dry in December may became wet In July. The proposed plan indicates that ff water is encountered excavation will stop and a two-foot layer of fill material will be placed over the area. This development plan virtually assures a dry pit. If at some point the applicant decides that it is feasible to mine below the groundwater level, a monitoring system should be developed to gain an understanding of the water levels and gradients in the area. At that time I would recommend that a set of groundwater observation piezometers be installed and data routinely collected to monitor the location and fluctuation of the water surface. As discussed above, even ff the pit is operated as a wet pit, with the appropriate augmentation plan, it will have very litlle effect on down-gradient springs, ponds or drainages. The extent to which a pond could alter the groundwater hydraulics respons(ble for transport of water through She aquifer would be proportional to the amount of drawdown created by continuously pumping the ponds to a Level lower than the prevailing surrounding level. It is hard to imagine pumping down a gravel pit pond by more than a couple of feet resulting In a very small wee of depression in the worst-case scenario. In this case, the wntlnued supply of groundwater flow to the nearby springs is more directly related to the inflow and storage components of the hydrologic balance. 4. Storm water runoff The State Engineers policy requires that Impounded storm water runoff be released to the stream system within 72 hours of impoundment. Because of the historic agricultural nature of this site there are no natural drainages. Storm water from the fields is collected by a system of wastewater ditches and moves offsfte In this manner. For the proposed project, stone water directed toward the excavation area and impounded will need to be pumped or gravity piped to a stream or wastewater ditch in order to meet this requirement. 5. Water quality Two possible water quality issues should be addressed. The first is sediment contamination from storm water runoff released to a downstream ditch or steam channel. The nature of the proposed gravel mine mandates that all surface flow toward the pit is confined within the pit. The impoundment of storm water runoff in a detention pond is designed to allow rime for settling of sediments prior to release. Tha second issue is confaminaton of surface and/or groundwater from chemicals such as petroleum products used (n the operation. All pertinent State of Colorado health and environmental regulations regarding the transport, use and storage of chemical and petroleum products should be strictly adhered to. 6. Hydrologic Impacts The previous discussion identifies issues and' hydrologic impacts of the proposed project. Those that have received the most attention by project opponents and those that I feel are significant are summarized here. • The act of digging a pit and operating a dry mine will not impact downstream water rights or flows to other springs, ponds or drainages. • If at some point in the future the applicant modifies the applicatlon to allow ponds, I do not foresee any significant impact on the fiowrate or volume to downstream water rights, etc., if done according to plans and state regulations including; o no pumping of pit water outside of the project area o no rerouting of flow from one end of project to the other o appropriate augmentation to account for evaporation and seepage losses • The elimination of applied irrigation water may have a significant effect It should 6e noted however, that this could occur with or without the proposed project.