Information that was used in the SSR - Michigan



As part of the site-specific review, Nestle Waters North America (NWNA) provided DEQ with the evaluations and groundwater modeling done by S.S. Papadopulos & Associate, Inc. (SSPA) Environmental and Water-Resource Consultants, Golder & Associates, Advanced Ecological Management, LLC, Arcadis, and the data sheets and graphs associated with the NWNA aquifer testing.SSPA reviewed the extensive aquifer data that are available in the vicinity of PW-101 from hydrogeologic investigations conducted by NWNA. (SSPA are well known experts in the field of water resource analyses and groundwater modeling. Their staff and associated staff consists of the industry experts in these fields and they routinely conduct training for hydrogeology professionals nationally.) The results of the review were submitted to NWNA in December 2015. SSPA used data from the thirty nine groundwater monitoring wells and fifty four drive points NWNA installed along with information from a stream-gaging system NWNA established. NWNA conducted a nine day aquifer test in PW-101 in June 2001 using a pumping rate of 400gpm.SSPA describes wells in the PW-101 area as identifying 195 feet of fine to coarse grained sand and gravel with minor silt overlying a thick clay unit. They noted that the saturated fine to coarse sands of the water table aquifer averaged approximately 35 feet below ground surface giving a saturated aquifer thickness of 160 feet. (DEQ’s review agrees with these findings.) SSPA found that over the 15 year period 2001 through October 2015, monitoring wells in the vicinity of PW-101 fluctuated over a range of approximately three feet. Attachment 5 Figure A-12 from the SSPA Groundwater Modeling Report indicates that up to an additional two feet of drawdown is predicted with the additional 150 gpm added.The aquifer test data estimates a transmissivity of 8,100 ft2/day and a storage value of 0.14 which is in the range of an unconfined aquifer and is consistent with the well information from the area. Drawdown graphs plotted by SSPA in the vicinity of PW-101 show the uniformity of the aquifer properties in that area. This is consistent with cross-sections constructed using the wells in the area that identify the thick glacial sand and gravel unit. SSPA used the aquifer test data to develop a Modflow groundwater model for the region (in attachment 5). The groundwater recharge rate for the groundwater model area was estimated through model calibration which also considered the type of soil cover present in various areas. The Modflow model parameters included recharge rate, rivers, streams, ponds wetlands, and groundwater use by the City of Evart. The calibrated Modflow model closely matched the water levels and aquifer test data. The SSPA calibrated Modflow model estimates an additional drawdown of 2 feet at the production well, approximately 1 foot of additional drawdown at 1,000 to 1,500 feet from the production well, and an additional 0.5 foot approximately 900 to over 3500 feet from the production well.NWNA also contracted with SSPA to provide an evaluation of index flows in the area that was presented in a February 2015 report that was also provided to DEQ. Golder Associates subsequently provided DEQ with additional information to consider during the site-specific review for the withdrawal increase in PW-101.The stream flow data provided by NWNA and information from their consultants was reviewed when DEQ conducted the index flow for the PW-101 SSR but did not change DEQ’s determination at this time. The aquifer properties from the test were used in the SSR review in conjunction with removing the safety factor after the index flow review, the requested additional withdrawal of 150 gpm for a total of 400 gpm was authorized.NWNA also provided DEQ with spreadsheet data from the PW-101 aquifer testing along with graphs and calculations that were used to determine the aquifer properties. DEQ is in agreement with the findings of the NWNA and SSPA’s analyses of the test data.Since this aquifer is unconfined, it will be recharged by precipitation infiltrating into the aquifer. The amount of precipitation available will be dependent upon the yearly climatic conditions that will likely fluctuate over time. The area of understanding the impacts of climate change on groundwater is starting to be researched as are means of determining means assessing recharge versus aquifer production to better prevent cases of overproduction. In the meantime, the Water Withdrawal Assessment Tool has been developed to be proactive in preventing large quantity water withdrawals that may cause adverse impacts to our surface waters and streams.The information on the sand distribution as used in the Modflow model is shown on the Attachment Figure 5 Modflow Model Sediment Zones. The thickness of the glacial drift in the area of the well ranges from 560 to approximately 700 feet. The 15 years from 2001 to 2015 appears to show that the recharge is sufficient to keep the groundwater level fluctuations within three feet in the area of the production well MW-101.(The ARC GIS map showing the DEQ Natural features inventory wetlands-fens is also attached to supplement the National Inventory Map for location reference sent in Leah’s email.) ................
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