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09.e Hume Report for Water Apppropration Appeal k.cammilleri From:Dave Hume <dave.hume@lrewater.com> Sent:Tuesday, January 18, 2022 2:25 PM To:k.cammilleri Subject:LRE Water Opinion on the MM increased water appropriation Hello, Ken. The purpose of this correspondence is to provide the City of Scandia with LRE Water’s (LRE) opinion on Martin Marietta’s (MM) proposed amendment to their water appropriation permit application for the sand and gravel mining operation (formerly owned Barton and Tiller) on Manning Avenue (Site). MM is proposing to increase their annual use from 20 to 30 million gallons per year (MGY). Background Groundwater at the Site is pumped from a 16-inch diameter production well screened from 69 to 98 feet below grade in the uppermost Quaternary-age sand and gravel water table aquifer (aquifer). Water from the well is pumped into storage ponds for washing sand and gravel for aggregate and asphalt production. The ponds help to reduce the amount of groundwater pumped by recycling the stored water in addition to providing some recharge to the aquifer through infiltration. In 2020, Tiller (acquired by MM in 2021) reported the annual water use to be just over 11 MGY and correspondence with Christina Morrison of MM indicated the typical annual use is 13 to 14 MGY from May through October. The current Annual Operating Permit (AOP) allows operations from 7:00 AM to 7:00 PM Monday through Friday; therefore, the maximum period of time that the well could pump continuously is 12 hours per day. Christina Morrison indicated the maximum pumping rate from the production well will not exceed 500 gpm as proposed in the amended water appropriation permit application. Aquifer Properties and General Characteristics The aquifer is unconfined at the Site and therefore quickly recharged from infiltration of precipitation and any leakage from the storage ponds. The aquifer has a saturated thickness of approximately 80 feet or more at the production well when it was installed and is likely greater than that now with the observed increase in groundwater levels across the Site. 1 The transmissivity (T) is a physical property that describes the ability of the aquifer transmit water through its entire thickness. This parameter and can be used with other information to estimate the drawdown (i.e., the decline in groundwater level) at specific distances from a pumping well. 2 The T of the aquifer was estimated to be approximately 2,250 feet squared per day (ft/day) by Dr. Han-Olaf Pfannkuck in his “Revised Groundwater Study Plan for Barton Sand & Gravel Co. Manning Operations” report submitted March 6, 1988. The T value and an aquifer storage coefficient of 0.1 was used by Dr. Pfannkuck to estimate the drawdown caused by the production well assuming it was pumping at a rate of 600 gallons per minute (gpm) for 12 hours. Under these assumptions, only 5 feet of drawdown was estimated 100 feet from the production well and 0 feet of drawdown at a distance of 300 feet. LRE confirmed this estimate from our calculations. LRE also estimated the T from a specific capacity (Q/s) test on the production well after it was constructed in 1980. The Q/s was calculated to be 36 gallons per minute per foot of drawdown 2 (gpm/ft). Based on this value, the T was estimated to be approximately 7,300 ft/day. Under these assumptions, only 2.25 feet of drawdown was estimated 100 feet from the production well after 12 hours pumping at 500 gpm, the maximum rate proposed by MM The T, aquifer thickness, and Q/s values indicate this is very productive aquifer. Because of the high T value, saturated thickness, recharge potential, rest periods between pumping (a minimum of 12 hours), and minimal water use from November through April, water levels in the aquifer will likely recover to their pre-pumping levels before the next pumping period starts resulting no short-term or long-term negative impacts to the aquifer, users of the aquifer, or groundwater dependent resources. Conclusion In LRE’s professional opinion, there is little to no risk to the aquifer as a result of increasing the water use appropriation from 20 to 30 MGY. Recommendation To confirm the aquifer recovers to pre-pumping water levels following period of pumping and there is no long-term decline in water levels as a result of pumping during periods of high use, it recommended that a short-term monitoring plan be developed for measuring water levels in the production well and observation well PZ-3. Thank you, and please contact me with any questions. Dave Hume, PG Sr. Project Manager & VP Midwest Operations Cell: 612-805-0919 Dave.Hume@LREwater.com 2 To help protect your privacy, Microsoft Office prevented automatic download of this picture from the Internet. https://docs.google.com/uc? export=download&id=1ZgZJa5PBM88dpJKl8FXEhbjjOVMmhf20&revid=0B9ET645uFt4MUVh lRzY3bjkvUmRrVURHaUQ2dnVnQXUzemtFPQ LREWATER.COM **CONFIDENTIALITY NOTICE: This email message is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. Thank you. 3