Wildcat WRP Capacity

Wildcat Hill WRP aerial shot

Objective 2: Address Wildcat Hill Water Reclamation Plant Bio Solids Capacity

Relevant Standards

  • Uninterrupted wastewater and reclaimed water services
  • Adequate collection, treatment, and disposal capacity for current and future customers
  • Maintain wet-weather capacity in compliance with regulatory requirements
  • Efficient and cost-effective approach to maintaining assets, data-driven decision making
  • Comply with current regulations and prepare for future regulations


In 2008, the Division upgraded the Wildcat Hill Water Reclamation Plant’s filtration systems to produce Class A+ reclaimed water. At that time, it was decided not to add additional digester or hydraulic capacity to save costs. Digesters treat the solids in wastewater and provide the means to create Class B Sludge, which can be applied locally on City owned land. It was decided at that time not to increase the hydraulic capacity of the Wildcat Facility.


  • The treatment plant has reached its capacity with respect to processing solids.
  • The amount of water arriving at the plant has reduced over time due to various factors, including water conservation, which means the wastewater is more concentrated, changing plant optimization parameters.
  • There is no redundancy in the plant with respect to many processes, including solids processing.
  • Failure of the current digesters would force the City to send sludge to the landfill, increasing costs by approximately $240,000 per year.

Timing Concerns

The timeline for planning, designing, and constructing a new digestor is 2024, with additional flow diversion to Rio de Flag WRP. Barring measures to buy more time, this process needs to start now to ensure adequate future capacity and avoid compliance issues with the Arizona Department of Environmental Quality

 Screenshot 2022-04-11 120320

Water Services Strategic Plan 20252020 Accomplishments
Objective 2: Address Wildcat Hill Water Reclamation Plant CapacityReporting Period:                January-June 2020Reporting Period:          July-December 2020
 Specific ResponsesChampion & TEAMAccomplishmentsAccomplishments Next Steps
Look for options to buy time by increasing the effective capacity of the current digestersEngineering Manager, Water Reclamation  ManagerPreparing draft scope of work for 2 New Digesters to increase capacity  at WCHRSOQ for Design services has been completed and provided to Purchasing Department for solicitation of bid.. Mac McNamara is Engineering is the City Project Manager delivering this project. PM still needs to go to Council for Award of Design Contract.Design to begin in next 6 months.  
Continuing assessing plant risks (points of failure and time to repair the failure) and implementing mitigation measures to increase reliabilityWater Reclamation ManagerReplaced primary weir supports and grit lines at RDF WRPCompleted constructing bypass line at headworks to primary system in December 2020This work has been completed.
Perform a cost/benefit analysis on providing redundancy in filtration or solids processing
Issued PO to Carollo for Sewer flow measurement at RDF. Awaiting return of normal sewer flows in system. Currently down 1 MGD due to Covid 19.This work is on hold
Review conservation goals, projected growth, and future reclaimed water demands to develop the optimum plant parameters and timing for plant upgradesWater Reclamation ManagerReclaimed Water Master plan in progress In progressWorking with a consultant on this project