In December 2002, the Covington Water District invested in the development of additional water supply when it entered into a partnership agreement with the cities of Tacoma and Kent and Lakehaven Utility District. Covington’s investment in Tacoma’s Second Supply Project or SSP was imperative if the district was to lift the water moratorium imposed because growth was exceeding the capacity of the district’s own groundwater supply sources.
Tacoma Public Utilities also entered into an agreement with the Army Corps of Engineers to expand the use of Howard Hansen Dam to include storage for water supply. The storage previous to the January 2003 corps agreement was solely for storm water flood control. Tacoma Public Utilities was interested and willing to expand the modification of Howard Hansen project into a regional partnership venture for water supply.
In January 2006 the Environmental Protection Agency enacted the Long Term 2 Enhanced Surface Water Treatment Rule or LT2. The LT2 requirement adds further public health protection against cryptosporidium, requires all open reservoirs be covered and sets an April 2014 deadline to meet the requirements. Cryptosporidium is a one-celled parasite, similar to giardia, which can cause severe gastro-intestinal illness. It is one of the most frequent causes of waterborne disease among humans in the United States.
Tacoma and its partners have studied the feasible options, estimated costs and rate impacts, involved many public outreach opportunities with stakeholders and selected the best option for long term treatment of the Green River. Consulting services lead by HDR Engineering, with support from CH2MHill, have assisted staff in the multi-step evaluation process.
Following the evaluation and review, the elected officials of all four partners support and recommend filtration treatment for the Green River supply. Filtration is recommended for these reasons.
- • Filtration will provide regulatory compliance with all known requirements, providing the greatest level of regulatory certainty for the future.
- • Filtration will provide substantial improvement to water quality, reducing the “yellow water” caused by iron, manganese and other naturally occurring organic materials in the water, reducing the byproducts of disinfection that form, allowing reduced usage of chlorine, and dramatically reducing the introduction of silt and sand into the water system.
- • Filtration will improve the reliability and yield of the Green River supply, allowing better utilization of the second supply project for the partners.
- • Filtration will provide Tacoma the capability to respond to the changes in water quality and supply caused by corps operations at Howard Hansen Dam.
Ultraviolet light disinfection was an option considered by the team and would have been less costly, at least in the short-term. However, its limitations in addressing turbidity (sediment in the water) and the uncertainty that EPA would not require additional treatment, such as filtration, in the future pointed the final recommendation toward filtration.
Filtration will have an impact to the rates of Covington’s customers. The original development project cost the district 19.4 percent of the project, or $42 million; the additional filtration is estimated to cost the district $23 million and the district will issue long-term revenue bonds to meet its obligations. Residential customers will likely see the following increases for each of the next five years:
• $3-4 per month ($ 6–8 per 2 month billing period) indoor use and
• $6–7 per month ($12 – 14 per 2-month billing period) irrigation and outdoor use.
The decision to meet the federal treatment regulations with filtration was a challenging one because of the cost and rate impacts. The SSP partners looked for the optimal long-term and cost-effective answer to meet the expectation of water supply reliability and certainty of meeting current and future federal requirements.
