Drinking Water Supply and Treatment

For three school districts in the Sonoma County, PES has provided a variety of services to provide a safe and reliable source of drinking water.

Services have included:

Alternative Groundwater Supply Assessment:

  • Previous drinking water supplies within two school districts contained high levels of iron and manganese. PES assisted the School District in siting and designing two new water-supply wells to provide higher quality drinking water. PES prepared well construction and drilling specifications and provided construction management services during the installation and testing of two approximately 500-foot deep wells. Services provided by PES included the review and evaluation of borehole geophysical logs and drill cutting samples to determine design criteria for the water wells, including the selection of appropriate well-screen intervals and filterpack gradation and placement.

Arsenic Assessment in Groundwater Supply Well:

  • PES performed a hydrogeologic and geochemical investigation of the occurrence of naturally occurring arsenic in groundwater extracted from a 300-foot deep well which provided the sole source of drinking water for the school. PES evaluated local and regional geologic and geochemical data (pH, iron chemistry, and oxidation/reduction conditions) and developed a conceptual model for the arsenic occurrence. Based on this conceptual model, it was determined that the arsenic was a natural constituent of the aquifer formation and was very mobile under the reducing conditions present in the deep well;
  • PES evaluated several engineering alternatives to treat the groundwater and/or provide an alternate source of water. Based on the results of the evaluation, PES assisted the school district in siting, designing, and constructing a new water-supply well to avoid the arsenic-bearing zone of the aquifer and to provide a sufficient quantity of groundwater that achieved state and federal drinking water standards. PES established excellent working relationships with Department of Health Services, Drinking Water Field Operations Branch personnel to gain regulatory acceptance and approval of the selected alternative; and
  • PES also conducted an evaluation of district compliance with State of California Title 22 and Title 17 drinking water regulations and made recommendations to improve compliance and provided training to district staff.

Treatment System Modification to Improve Water Quality:

  • Elevated levels of iron, manganese, and turbidity were present in drinking water supplied by a water-supply well. PES evaluated the characteristics of the water supply and treatment system, determined the necessary system improvements, and selected an ion-exchange/ozonation/tank storage system as the most cost-effective solution to improve water quality and storage. PES prepared a preliminary engineering design, developed costs and assisted with acquisition of State funding.

Lead, Manganese and Odor Reduction:

  • Lead, manganese, and odor were present in drinking water in excess of drinking water standards. PES evaluated the source of these constituents in the water, assessed corrosion control/treatment alternatives and selected ozonation/polyphosphate corrosion inhibitor/tank storage as the preferred alternative. PES developed cost estimates, assisted with the acquisition of state funding and provided construction management oversight.