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Mr. Stephen P. Swanson <br /> August 28, 1997 <br /> Page 2 <br /> The iron content at the pump discharge of the DeWitt County wells is approximately 4 <br /> ppm. The stilling basin is intended to reduce the iron concentration to below 2 ppm in the <br /> lagoon and 1 ppm in the stream as per the terms of the discharge permit. <br /> During the last period of operation of the well field in November of 1996, the owners of <br /> several private wells claimed to have experienced drawdowns that affected the function of <br /> their pumping equipment. The City wishes to deternune the safe reliable capacity of the <br /> wellfield, the most efficient operating schedule for the wells, and the potential impact to <br /> surrounding wells. <br /> The Cisco wellfield has was installed over 40 years ago. One of the wells is currently <br /> inoperable. Both weUs have submersible pumps with electrical service. The wellfield <br /> discharges into a small surface channel that drains into the Sangamon River. The USGS <br /> determined that approximately 65% of the wellfield discharge is lost to seepage. The City <br /> wishes to determine if the additional surface water furnished by these wells offsets the <br /> costs of rehabilitating and operating the wellfield. <br /> SCOPE OF SERVICES <br /> The objectives of the study are as follows; <br /> 1)Determine the reliable capacity of the DeWitt County and Cisco wellfields for time <br /> frames of 60, 90, and 200 days of continuous pumping, <br /> 2)Determine the most efficient operating schedule for the wells to crLnimi�e interference <br /> between the wells, <br /> 3)Predict the likely impact of operating the wellfields on surrounding wells, <br /> 4)Determine the existing condition of the wells and identify any actions needed to make <br /> the wells more reliable or efficient, and <br /> 5)Produce a working model of the aquifer to simulate the effects of pumping on the <br /> aquifer and that can be updated and modified by City personnel. <br /> We intend to conduct our operations in such a way as to minimize the obligations of City <br /> staff beyond providing information as needed and providing approval for field operations. <br /> Prior to starting the pumping tests, we will coordinate with the necessary agencies to <br /> inform them of our intentions and make any necessary arrangements. The agencies <br /> include: The City's department of Public Works, The Illinois Environmental Protection <br /> Agency(IEPA), the United Stated Environmental Protection Agency(USEPA), the <br />