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HomeMy WebLinkAboutSTERLING SPECIAL REVIEW - COUNTY REFERRAL - 40-88 - CORRESPONDENCE - SUPPLEMENTAL INFORMATIONWater Engineering & Technology, Inc • S.A. Schumm, Ph.D. M.D. Harvey, Ph.D. C.C. Watson, PE., Ph.D. 419 Canyon, Suite 225 Fort Collins, Colorado 80521 U.S.A. 1-303-482-8201 March 21, 1988 March and Myatt 110 East Oak, Suite 200 Fort Collins, Colorado 'Attention: Ms. Lucia A. Liley Subject: Impact of Sterling Sand and Gravel Co. operations on local groundwater levels Dear Ms. Liley: At the request of landowners on North Taft Hill Road, Water Engineering and Technology, Inc. has reviewed existing geologic information and compiled climatic data pertinent to the above subject. Mr. Daniel Gregory visited the offices of the Larimer County Planning Department on March 16 and 18, 1988 to review technical data within files relevant to Sterling Sand and Gravel Co. operations. Specific files reviewed include files * Z-47-87, Z-46-87, and Z-46-85. Mr. Jay Schug compiled climatic data that included both precipitation data at Fort Collins and streamflow data for the Cache la Poudre River at the mouth of Poudre Canyon. Annual precipitation data for the CSU main campus station were provided by the landowners. Streamflow data were obtained from the U.S. Geological Survey WATSTORE database, a publically -accessible computer data base of all water data collected by ' the Water Resources Division of the U.S. Geological Survey. The gage at the mouth of Poudre Canyon is located downstream of several diversions. Although the presence of diversions is likely to have an impact on flow at the gage these data are the best available means of estimating streamflow conditions in the Cache la Poudre watershed. Discussions between Dr. Mike Harvey, Dr. Chester Watson and Mr. Dan Gregory led to the following tentative conclusions regarding the above subject: 1. Based upon existing data contained within the Sterling Sand and Gravel 1987 Amendment it is reasonable to conclude that.' dewatering operations within the Seaworth pit could have reduced water levels within adjacent water wells and ponds. This 0 0 Ms. Lucia A. Liley March and Myatt March 21, 1988 Page 2 assumes that information gathered within the mine permit area is representative of conditions beneath landowners' property. 2. Based upon available data it is reasonable to conclude that the proposed pit expansion to the north of the Seaworth pit will reduce water levels in adjacent ponds and water wells. The proposed expansion will be closer to the landowners' property than the Seaworth pit, and therefore, it is possible that the impacts of the pit expansion will be greater than the alledged impacts of the Seaworth pit. This assumes that existing data for areas within the permit area are representative of geologic conditions beneath the landowners' property. 3. Climatic and hydrologic data from stations in the Fort Collins area do not substantiate the contention by Sterling that the present decline in landowners' well and pond water -surface elevations are caused by climatic fluctuations. Precipitation and average streamflow records for the Poudre River indicate that several years of low streamflow and precipitation have occurred during the last twelve years. The 1987 data does not indicate an extremely dry year. If climate was the major cause of the present decline in water levels then it is reasonable to' assume that similar declines should have been observed in at least three to four of the last twelve years. 4. Several procedures and tests can be conducted which will prove beyond reasonable doubt whether or not dewatering of Sterling pits is responsible for local declines in water level. A pump test under controlled conditions can provide suitable information on the influence of pit dewatering. Observation wells must be placed within the boundaries of the landowners property where water level declines have been observed in the past. Existing wells can serve as observations wells, if these are accessible. However, it is likely that some additional observation wells will be necessary. Testing must be conducted during the dry season when conditions are most likely to impact pond and well water levels. This will ensure that confounding effects from saturated soils ((Jue to snowmelt) and irrigation flows do not bias the water levels in observation wells. Several individuals at Water Engineering and Technology, Inc. have been involved in the analysis and discussion of information pertinent to the decline of water levels in wells and ponds adjacent to Sterling Sand and Gravel operations. A resume for each of the four persons is attached. Dr. Michael D. Harvey is Vice -President and Principal i Ms. Lucia A. Liley March and Myatt March 21, 1988 Page 3 Geomorphologist for Water Engineering and Technology, Inc. Dr. Harvey has a broad range of experience in field mapping and analysis of recent stream and river deposits. His expertise in identifying and mapping variations in alluvial deposits is central to determining the variability of geologic materials in the Cache la Poudre River valley. Mr. Daniel Gregory is a geomorphologist and he has been with Water Engineering and Technology, Inc. for over five years. His experience with the U.S. Geological Survey in groundwater exploration in addition to field experience with Water Engineering and Technology, Inc. enhances the companies ability to analyze groundwater problems. Dr. Chester Watson, President of Water Engineering and Technology, Inc., is a hydraulic engineer with considerable experience in river engineering problems. Mr. Jay Schug is completing graduate work at CSU in Watershed Science and has been with Water Engineering and Technology, Inc. for approximately two years. These four professionals bring a total of 50 years of experience in the engineering and geological sciences to bear on the problem of groundwater decline in the vicinity of Sterling s gravel mining operation. DIG:sp Very truly yours, Water Engineering and Technology, Inc. By: Daniel I. Gregory Geomorphologist/Project Manager