GROUNDWATER DEVELOPMENT

PROPERTY TRANSFER
REMEDIAL INVESTIGATION & CLEANUP
EXPERT WITNESS
WELLHEAD PROTECTION
SOLID WASTE COMPLIANCE
WATER RIGHTS SUPPORT
DATA MANAGEMENT
GROUNDWATER MODELING
WATERSHED ASSESSMENT
AQUIFER STORAGE & RECOVERY
• Thurston County
• Clallam County
WASTEWATER & STORMWATER RECHARGE
 

Client: Thurston County Municipalities
Project: Feasibility Assessment for Recharge of Reclaimed Water
Location: Thurston County, Washington

Background
Thurston County and the Cities of Lacey, Olympia, and Tumwater wanted to expand their sewage treatment facility substantially. They explored various discharge alternatives, including recharging large volumes of treated wastewater to local groundwater systems using infiltration basins and injection wells. This required a feasibility assessment to identify suitable recharge sites and approaches.

Challenges
In addition to identifying sites with high recharge capacities, we needed to consider many water-quality issues in our assessment. At the injection wellhead, water quality issues were a concern because chemical reactions could cause incrustation buildup on the screens, decreasing the well's capacity. Water quality impacts could also potentially affect the local aquifer system and existing users.

Approach
To identify possible sites for injecting or infiltrating groundwater, we characterized various parameters throughout the county: soil types, land uses, water-level depths, subsurface geology, locations of water supply wells, and wellhead protection areas. A series of maps showed the results of these analyses and provided a basis for selecting possible recharge sites. We also reviewed literature on operational facilities to identify treatment approaches that would meet regulatory standards for water quality. Finally, we evaluated potential loading rates and soil treatment processes for recharge basins and calculated land requirements for a facility that could process 20 million gallons of treated water per day.

Outcome
The results of our feasibility assessment provided the basis for developing a new reclamation facility in the Hawkes Prairie area. We not only identified favorable sites for recharging reclaimed water, but we also noted key issues that would affect the ultimate design of a new facility.

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