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Operation and Maintenance of the Groundwater Transfer and Injection Pilot Project at Shellmound, MS
Proceedings of the 2022 Mississippi Water Resources Conference

Year: 2022 Authors: Cummins B., O'Reilly A.M., Wren D.G.

The Groundwater Transfer and Injection Pilot (GTIP) project is an innovative effort to not only mitigate further depletion of the Mississippi River Valley Alluvial Aquifer (MRVAA), but also to potentially raise water levels in an area of excessive drawdown by artificially recharging the aquifer. This project is a collaborative effort between the U.S. Army Corps of Engineers (USACE) Vicksburg District and the U.S Department of Agriculture - Agricultural Research Service (USDA-ARS). The Pilot Study project site is located in Shellmound, MS, which is approximately 8 miles northwest of Greenwood, MS, and is situated to the west of the Tallahatchie River.

The system extracts water from within the MRVAA at a natural recharge zone, due to bank filtration of the adjacent Tallahatchie River, and then conveys the water approximately two miles, via subsurface pipeline, to two injection wells where it is re-introduced into the MRVAA. The USACE managed design and construction of the facility and collaborates with USDA-ARS to maintain its operation and conduct maintenance activities. To evaluate the aquifer's response to the artificial recharge, USDA-ARS has been monitoring, sampling, and analyzing data from multiple observation wells near and within the project vicinity.

Each injection well was receiving water at a rate of 750 gpm and the system was running 24 hours a day, seven days a week for nearly 3 months. The system was functioning as designed; however, after approximately 3 months of continuous injection, both injection wells experienced hydrostatic pressures that exceeded the threshold of the top-stratum blanket of fine-grained sediments, causing cracks due to soil heaving and the presence of boils at the ground surface. Additionally, upon visual inspection of the wells using a downhole camera, the presence of iron-related bacteria and/or iron oxides were observed coating the inside of the well screens. Rehabilitation efforts were performed by USACE Vicksburg District using chemical treatment with a dilute oxalic acid solution at each injection well, and then site repairs were completed using low-strength flowable fill to re-establish the top-stratum blanket. Future planning for optimal operation and maintenance of the GTIP project facility is an ongoing mission to ensure (1) that the data needed to determine feasibility is achieved and (2) that best practices and procedures are identified for use if it is determined that larger scale aquifer recharge is feasible for this region.

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