In order to ensure that tap water is safe to drink, the United States Environmental Protection Agency (USEPA) and the California Department of Health Services (DHS) prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. The District’s source water has consistently met all primary drinking water standards established by USEPA and DHS for the protection of public health. The source water has been classified by DHS as groundwater, which is important with respect to regulations that a water system must follow to ensure water quality.
The only water quality issue occasionally encountered by HBMWD is with respect to turbidity. Turbidity results from dispersed solids in the water such as silt, clay, or other organic or inorganic matter. Generally, turbidity in the Ranney Well source water is very low and meets the turbidity standards set by DHS. However, during or following severe winter storm events, turbidity in the source water may rise beyond the standards set by DHS. Turbidity itself is not a health concern. However, in the late 1990’s an extremely heavy “El Nino” rainy season caused a prolonged series of storms that raised turbidity in the source water to such a level that DHS became concerned it may interfere with the disinfection process, and therefore, could pose a threat to public health. In 1997, DHS directed all of the Public Water Systems in the Humboldt Bay area (HBMWD and its wholesale Municipal Customers) to address the wintertime turbidity issue and to meet the turbidity standards established by DHS.
Turbidity Reduction Facility
HBMWD initiated a process with its seven Municipal Customers to determine the most cost effective way to meet the State’s requirement. As part of this process, HBMWD hired Kennedy/Jenks Consultants to evaluate the Ranney Well source water, conduct a pilot plant study, and based upon the findings, to design a regional Turbidity Reduction Facility (TRF). Kennedy/Jenks recommended a facility based on an “in-line gravity filter” process (described to the right) as the most cost effective solution.
The TRF consists of a Rapid Mix Station, Filter Building, Chemical Building, Backwash Pump Station, Washwater Recovery Basins, and Sludge Drying Beds. The TRF design capacity is 14 million gallons per day (MGD) in the wintertime and 21 MGD summertime. The TRF cost approximately $10 million to construct, which was financed by a zero-interest Safe Drinking Water State Revolving Fund Loan. The TRF now operates during the winter storm season to reduce higher turbidities in accordance with the State’s standards.
And on to our Customers …
Following treatment - chlorination year-round and turbidity reduction in the winter - the finished drinking water flows through two storage tanks and then into a regional distribution system. This treatment and distribution system reliably serves high quality drinking water throughout the greater Humboldt Bay area.