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Home My WebLink About850840.tiff RICHARD D. LAMM INQ "X.r: O, JERIS A. DANIELSON Governor State Engineer OFFICE OF THE STATE ENGINEER DIVISION OF WATER RESOURCES 1313 Sherman Street-Room 818 Denver, Colorado 80203 WELD COUNTY 1:9"'"""r"rp (303) 866-3581 --Ir-,�,nr7r".r 1_.riiI. ' SEP 31985 August 23, 1985 GRELLEY. COLO. Weld County Board of County Commissioners 915 10th Street Greeley, Colorado 80631 Dear Board Members: I am writing to inform you of changes in the requirements for subdivision water supply plan submittals which are dependent upon on-lot wells using Denver basin bedrock aquifers. These changes are a result of new ground water legislation passed this year by the General Assembly of Colorado. This legis- lation, commonly referred to as Senate Bill 5, became effective July 1 , 1985. Subdivision water supply plan reviews by our office subsequent to this date will reflect this new legislation. Among other things, Senate Bill 5 defined non-tributary ground water in part as follows: "Non-tributary ground water" means that ground water, located outside the boundaries of any designated ground water basins in existence on January 1 , 1985, the withdrawal of which will not, within one hundred years, deplete the flow of a natural stream, including a natural stream as defined in sections 37-82-101 (2) and 37-92-102 ( 1 ) (b), at an annual rate greater than one-tenth of one percent of the annual rate of withdrawal . Senate Bill 5 requires that a plan for augmentation be approved by the Water Court to replace the total depletion caused by new tributary wells in the Dawson aquifer. Senate Bill 5 also requires a plan for augmentation to replace the total depletion caused by new wells within one mile of the con- tact of the Denver, Arapahoe or Laramie-Fox Hills aquifers with any stream alluvium. For wells beyond one mile whose depletion will be greater than one-tenth of one percent, the augmentation plan must replace 4 percent of the annual volume pumped to the affected stream or streams. 850840 t2-1,,, 4.9 Aeltdo Weld County Board of County Commissioners August 23, 1985 Page 2 Senate Bill 5 requires this office to promulgate rules and regulations by December 31 , 1985 for the Dawson, Denver, Arapahoe and Laramie-Fox Hills aquifers to the extent necessary to assure that the withdrawal from these aquifers will not materially affect vested water rights on any natural stream. These rules and regulations will be available by that date and will contain maps for each aquifer indicating where the non-tributary areas are located. The analysis required to determine the impact that pumping ground water will have on surface streams is difficult in many cases. It has been deter- mined that a Glover analysis is only acceptable for the Dawson aquifer and then only in certain situations. Stream basin modeling is required to accu- rately determine the impacts in the other Denver basin aquifers. Our office is developing a Denver basin model to determine where aquifers are non-tributary at each location in the Denver basin. This model should be complete by September 30, 1985. This model will provide information for the development of rules and regulations. Until rules and regulations are pro- mulgated, we will review subdivision water supply plans on a case-by-case basis in accordance with the criteria and procedures of Senate Bill 5 and this letter. The cumulative impact on streams of several on-lot wells is similar to the impact of one large capacity well . We have historically required sub- division water supply plans to take into account the cumulative impact of on-lot wells on streams. Our review of water supply plans has always been based on the cumulative impact of the on-lot wells. We have made recom- mendations to the counties to disapprove subdivisions where the cumulative impact may be injurious. We will require that the water supply plans include an analysis as des- cribed earlier of the cumulative impact of all proposed wells on surrounding surface streams. We will only recommend preliminary plan approval of those subdivisions dependent upon individual wells when the wells are shown to be non-tributary in the water supply plan or are a part of a court approved augmentation plan. In certain areas, we may have to wait until rules and regulations are promulgated before commenting. In these instances, we will recommend that the subdivision not be considered until after December 31 , 1985. The requirements of Senate Bill 5 do not presently affect subdivision proposals in designated ground water basins. At this time, our review of water supply plans in these areas will be consistent with past review. However, the Colorado Ground Water Commission may resolve in the future to implement all or part of Senate Bill 5. Weld County Board of County Commissioners August 23, 1985 Page 3 Finally, we would like to assure the counties that previous commitments to them concerning well availability will be honored. We will issue well permits in compliance with existing subdivision review letters. Sincerely, J• is A. Danielson Sta e Engineer JAD/JRH:ma/5325H cc: Bob Longenbaugh Reiner Haubold Steve Lautenschalger Keith Kepler George Van Slyke Alan Berryman Bob Jesse Hello