R2011-182 AUTHORIZING EXECUTION OF TASK ORDER NO. 16

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DEPARTMENT OF WATER MANAGEMENT Memorandum No. 2011-20 November 14, 2011 TO: Mayor Michael T. McElroy and City Council FROM: Ryan P. McCrady, City Manager Keith D. Alexander, Director of Water Management SUBJECT: Shallow Groundwater Supply- Potential Well Site Exploration SUMMARY RECOMMENDATION: Council adopt the attached Resolution authorizing Task Order No. 16 for Potential Well Site Exploration for the Continuing Agreement for Engineering Services with Black & Veatch Corporation for a fee not to exceed $367,400. BACKGROUND: Our community needs 10,000 acre feet of supplemental water supply to ensure that we have enough water during a severe drought lasting approximately 8 months. This supplemental water may also be invaluable in case of other extreme emergency situations involving our water system. The Archer Daniels Midland Company has developed a plan to obtain 5,200 acre feet and the City continues to investigate the most cost effective options to obtain the remaining 4,800 acre feet of water. As authorized by Council, Black & Veatch completed an evaluation of shallow groundwater resources near the South Water Treatment Plant, and presented their findings to Council on November 7,2011. The evaluation preliminarily concluded that: There appears to be a 40 feet thick water bearing sand and gravel aquifer adjacent to the Lake Decatur shoreline in the vicinity of the South Water Treatment Plant. The aquifer is between 40 and 80 feet below ground surface. • A shallow groundwater collector well constructed in this vicinity could potentially yield 2,350 to 4,030 acre feet of water, and two collector wells could potentially yield approximately twice that amount. • The preliminary cost estimate for one collector well is $2.4M and $4.8M for two wells. Since the preliminary findings are that a two collector well system can provide at least 4,700 acre feet of water at a reasonable cost, it is recommended that Council approve Task Order No. 16 to determine with a very high degree of certainty: 1) exactly where a collector well system or systems should be located, 2) what the water yield will be, and 3) what the collector well site specific design criteria should be.