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.
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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.
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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
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(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
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