Reusing wastewater for irrigation is not a pipe dream

It looks like Silverdale Water District has found a partner in its quest to turn wastewater into irrigation water, supplying some of the largest water users in Central Kitsap.

The reclaimed water could be used to water ball fields, supply industrial operations, enhance streams and wetlands, and maintain the levels of Island Lake.

Central Kitsap Wastewater Treatment Plant / Kitsap County photo

So far, no financial commitment has been requested from Kitsap County, as I point out in a story in today’s Kitsap Sun. If approved, the partnership between the county and water district would mean that the county will provide the wastewater from the Central Kitsap sewage-treatment plant and possibly allow installation of “purple pipe” alongside new sewer lines to be installed in the next two years. “Purple pipe” is shorthand for the conduit that carries reclaimed water.

Kitsap County is going into the design phase of a new sewer line south of the treatment plant near Brownsville. As proposed, Silverdale would pick up the extra cost of the design to consider installing purple pipe at the same time. Actually, delivery of reclaimed water could be years away, but everyone agrees that now is a good time to install the pipe.

A technical issue is how to lay the purple pipe in conjunction with a sewer line. State rules require a 10-foot separation between a sewer line and any pipe where the water is used for drinking or irrigation – even though irrigation pipes would be marked for non-drinking uses only.

With the 10-foot separation requirement, contractors would either have to dig an extra-wide trench or dig a second trench. Neither option would save the kind of money first envisioned by the piggyback approach, so officials are looking at a couple of other options. One is to seek a waiver that would allow a 5-foot separation, which is likely to be approved. The other is to “double-jacket” the purple pipe – essentially putting the reclaimed water line inside a larger pipe for added protection. With double-jacketing, the reclaimed water line could run right alongside the sewer line.

The bigger issue for county officials could be upgrading the CK treatment plant to produce water pure enough for irrigation and other uses. Silverdale Water District could pay for a new purification unit that picks up where the existing effluent comes out of the plant. Alternatively, Kitsap County could strive for increased purity as part of an overall upgrade of the treatment plant, which is expected to undergo improvements within the next 10 years. It’s a big issue because we could be talking about millions of dollars.

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