Vadose Zone Recharge Through Shallow Hydraulic Fracturing

Project Development

Effective utilization of water is an ever-increasing concern throughout the world. Finding new ways to store and effectively utilize water received from rainfall events is crucial to mitigate flooding and to recharge the Earth's subsurface aquifiers. In a growing and changing world, the need for adaptive and cost-effective solutions to water storage and utilization is critical.

Solutions Centered Engineering (SCE) set out to find an economical an denvironmentally friendly solution to the collection and storage of water. WE were specifically searching for ways to reduce runoff and recharge water in the vadose zone. The vadose zone is below the ground surface but above the water table.

Alternatives

Our team considered four options to face the vadose zone recharge issue:

Alternative Analysis

The criteria considered for analyzing the alternatives were cost, storage capacity, client input, runoff reduction, water quality, and operation and management (O&M).

Since this project is research based, client input was the greatest factor in choosing an alternative followed by water quality and cost. SCE ranked the alternatives on a scale of 1 to 4 with 4 being the highest and 1 being the lowest, then multiplied the rank by the weight to produce a score. Based on the criteria, SCE chose the shallow hydraulic fracturing option as the recommended alternative.

Water Quality Analysis

Rainwater runoff will be used to store and recharge the vadose zone. Injections of rainwater into the wells need to be examined for possible pollutants. This study analyzed the quality of rainwater runoff from composite samples of two different types of roofs.

It was important to evaluate the leaching potential of nutrients and trace elements from the receiving soil. There are primary standards and maximum contaminant levels in place for potable water. The parameters measured were:

Soil Leaching

• Water in contact with soil after injection can immobilize contaminants
• Concentration increase in aluminum, iron, total N

Roof Comparison

Most of the parameters analyzed were higher for the asphalt shingle roof with exception of a few metals. DOC values for asphalt shingle roof is more than five times higher than metal roof.

Final Design

After significant searching, SCE found a location in Cache Valley that would be suitable to test the methods of hydrofracking. A USU research farm in Wellsville, UT will be used as the testing site. The site consists of fine sands, silty fines, and a deep water table. Low permeable soils are needed to produce effective fractures.

Six wells will be pushed to a depth of 10 ft. A slurry will then be injected into the well at a pressure of 40 psi. The slurry will consist of water, sand or bio-degradable beads, and guar gum. The pressurized slurry will make and keep fractures open in the soil. The fractures can then be filled with water.

Acknowledgements

This project took a lot of work, and it could not have been done without the support and help of various individuals. We would like to give a special thanks to all those who helped make this project a success:

• Mark Ankeny (Client)
• Dr. Ryan DuPont (Faculty Advisor)
• Dr. John Rice (External PE)
• Professor Austin Ball (Instructor)