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SEP-05-2003 FRI 09;27 AM ~'" AND GESSO LLC FAX NO,~ 274 8329 ~ Page 2 September 4, 2003 In the case of a gravel ptt two conditions would have to occur before the pit could impact local groundwater conditons. First the pit must obviously be dug to a depth below the groundwater surface, This common occxrrrence results in the formation of a pond in the bottom of the pik Once the pond has formed and stabilized, as described above, this condition has little or no impact on the groundwater surface. The second condition is that the water in the pond must be Powered below the elevation of the surcounding groundwater in order to form a cone of depression. This could occur through pumping or a drain system. Evaporation and increased infiltration into the underlying bedrock material will also occur if ponds are formed and would add to the drawdown caused by pumping. However, their impact on the gradient and elevation of the groundwater surtace would normally be quite small. 2. Hydrologic balance The hydrologic balance of the groundwater system Is an accounting, over time, of the water flowing into and out of a defined system .The change in the amount of water stored or released from the system also enters Into the balance. If we use the block of earth below the Haldorson site as the system then we can identify the components of the hydrologic balance. In the historic condition (without the gravel mine) the inflow consists of rainfall, applied ircigation water, groundwater flow in through the sides of the system coming from up-gradient regions and any surtace water drainage onto the site. Outflows consist of groundwater flow out through the sides of the system to downt~radient regions, evapotranspiratlon from crops and any surface water drainage leaving the /II site• There Is no appreciable change in storage of water on the site on an annual basis. In the case with the proposed gravel mine the Inflow consists of rainfall, groundwater flow in through the sides of the system coming from up-gradient regions, any surface water drainage on to the site and project water used for mine operation (note that the applicant has indicated that initially there will be no need for operation water. It is part of this discussion because tt may effect the balance in the future) . Outflows consist of groundwater flow out through the sides of the system to down-gradient regions, evaporation from ponds, seepage through the bottom of ponds and any surface water drainage leaving the she. Then; will be nb appreciable change In storage of water on the site. Note that this assumes that no water will ba pumped or drained out of the system unless it travels through one of the mentioned components. When compared, the historic and proposed conditions differ by only a few factors. On the inflow side the historic condition includes crop Irrigation water where the proposed has mine operation water. For the outflows, the historic case has crop evapotranspiration and the proposed has pond evaporaion and seepage. Any differences in the magnttude of these or the other factors, between the historic and proposed cases, must be attributable to a change 1n one or more of the remaining factors. Based on this model I see little difference between the historic and proposed cases that can be attributed directly to the gravel mine, The rainfall and.groundwater flow Into the system will remain the same. As per the proposed development plan (dry pit), the groundwater outflow will be virtually unchanged. The most significant impact will be the loss of applied Irrigation water as a system inflow. This same impact is being felt throughout the area as agricultural land Is convert to residential and commercial uses. Ultlmately the reclamation plan calls for reda(ming the area to cropland and hence a return of applied irrigation water. 3. pry versus Wet Pit The proposed mining plan states that the operation will be a dry pik Based on the hydrology of the area it Is very likely that a groundwater surface does exists above the shale bedrock, at least during the irfgation season. Six test holes were augured in anorth-south alignment across the proposed site. The four holes toward the north were to a depth of 60 feet and the two southern holes were augured to 32 feet. These depths equal or exceed the maximum potential depth of excavation in the various phases of the proposed project development. Water was not encountered in any of the test holes. Since they P, 03