Investigations & Permitting for the Upper Agua Fria Recharge Project

The Town of Prescott Valley operates a wastewater treatment facility that discharges to the Agua Fria River, a source of recharge for the regional aquifer system. Discharge to the river has been as large as 1,800 acre-feet per year; this rate will increase as the Town’s population grows.

OVERVIEW

M&A provided a range of hydrogeologic services to support feasibility investigations and design and permitting of recharge facilities to meet a growing need for storing effluent. We developed a phased approach that initially entailed acquiring a short-term Managed USF permit in 2003. This allowed the client to accrue storage credits while we collected the data needed to design full-scale facilities and obtain a long-term Constructed USF permit, which was issued in mid-2006. In 2007, we started investigations to evaluate additional recharge site(s).

We identified a site near the existing in-channel facility where surface infiltration basins were constructed. This location allows the client to integrate management activities for the two facilities, maximizing effluent storage within the notable hydrogeologic and land ownership constraints. In 2011, we prepared and submitted permit applications for a new USF permit and amended APP and assisted with the amended AZPDES permit. In 2017, M&A conducted a planning study to assess additional recharge alternatives to meet the Town’s growing supply of effluent and prepared conceptual designs for recovery options.

SERVICES

Permitting & Compliance

  • Interfaced extensively with ADWR and ADEQ to negotiate permit conditions, address significant recharge constraints, and satisfy monitoring requirements and associated regulatory limits
  • Prepared permit applications and supporting documentation, including a comprehensive hydrogeologic report and monitoring and contingency plans

Managed Aquifer Recharge

  • Analyzed land use and ownership data to identify potential recharge alternatives and develop a conceptual design for selected alternatives
  • Characterized lithologic conditions and infiltration capacity of near-surface soils via trenching and infiltration testing
  • Characterized hydrogeologic conditions of the vadose zone and regional aquifer via exploration drilling, installation of monitor wells, and analysis of available data from federal and state agencies
  • Compiled a database to evaluate hydrogeologic conditions, surface water flow, infiltration characteristics, and historic groundwater and surface water discharge from the Prescott Active Management Area
  • Prepared groundwater flow models to assess aquifer mounding, storage capacity, area of impact, and discharge impact area
  • Worked closely with the Town’s staff and an engineering consultant to develop a preliminary design for the recharge facilities and to assist with floodplain hydraulic analyses
  • Obtained and assessed groundwater quality data from the monitoring wells and other available sources to characterize pre-recharge conditions and changes to groundwater quality during recharge operations, especially due to nitrate concerns