Wadsworth Well Groundwater Treatment Plant 

Pasadena Water & Power 

Pasadena Water & Power (PWP) delivers water to almost 38,000 households and businesses in Pasadena and to communities in the San Gabriel Valley, California. To continue satisfying customers with high-quality clean water PWP selected the Civiltec team to assist in the design of a new state-of-the-art Wadsworth Well Groundwater Treatment Plant.

A little bit of background on Wadsworth Well, located on the northwest corner of Walnut Street and Vinedo Avenue was turned off in July 2020 due to increased 1,2,3-trichloropropane (TCP). To bring these levels to the acceptable California Water Resources Control Board Division of Drinking Water (DDW) regulations changes to the system needed to be made. The Maximum Contaminant Level (MCL) for 1,2,3-trichloropropane (1,2,3-TCP) of 0.000005 milligrams per liter (mg/L, or five parts per trillion or five ppt). Wadsworth Wells has a production capacity of approximately 1,600 gallons per minute (gpm) and currently delivers production water to the Eastside Collector system. PWP determined the goal of this project is integrating a granular activated carbon (GAC) Ion Exchange (IX) treatment plant to sustain the TCP compounds to below-regulated levels so Wadsworth Well can become operational once again. The treatment plant design included civil, structural, mechanical, and electrical systems updates to facilitate the proper operations of the system.

Overall improvements to the site were created with access to the treatment plant, backwash tank, and other ancillary equipment in mind. The system’s design includes piping from the Wadsworth Well was modified to combine with the lateral constructed from the Eastside Collector System and be aligned to the common manifold that will feed the treatment plant. Treated water is collected in a common manifold and directed to the existing Wadsworth Well discharge piping. Additional piping was installed to facilitate backwash supply and discharge. A slab was designed to support the GAC units, filter units and 50,000-gallon backwash bolted steel tank. To ensure clarification of backwash water a floating decant mechanism was designed to be inside the tank. Clarified water is directed through new drainage facilities that convey the backwash wastewater to a series of infiltration wells. Other elements of the Wadsworth Well project include a new lateral pipeline that extends southerly along Vinedo Avenue from a point of connection with the 20-inch pipeline located in Foothill Boulevard to the Wadsworth site. Installation of the three GAC vessel pairs in lead-lag configuration at the adjacent property to the Wadsworth Well site will allow for proper treatment of TCPs for not only the Wadsworth Well but also the Craig and Woodbury wells and mitigate against any breakthrough concentrations above proper reporting levels. As a result, the treatment plant has a 3,000-gpm capacity. This design presents the benefits of electrical, chemical storage, chemical dosing, chemical analysis, a new stationary emergency generator, and minimal impact development improvements that infiltrate and treat stormwater from the site. Chemical injection points from the existing gaseous chlorine system are realigned to convey chlorine downstream of the treated water system as well and serve as a backup to the newly installed sodium hypochlorite disinfection system.

With Wadsworth Well out of commission, other production options need to be considered. The production from Craig and/or Woodbury wells is to be diverted from the Eastside Collector System so that it may be treated at the GAC plant located at the Wadsworth site. Due to water quality issues, the Monte Vista Well will not be operational soon. With this consideration, hydraulic surge modeling was performed by the Civiltec team to recommend the relocation of an existing 2,550-gallon surge tank at the Monte Vista Well. The surge tank will be relocated to the Criag Well site. Our project team included the project management services of Shem Hawes, PE, project engineers Steven Walker, PE, and Alec Escamilla, PE, structural engineering from Sanjay Verma, PE, and electrical engineering from Heber Torres, PE.