The Kirkland City Council voted unanimously at an Oct. 15 study session to approve a feasibility study for a proposed regional stormwater facility.

Stormwater mitigation had been previously discussed at a July 2 city council meeting, during which staff shared the results of an Altaterra-backed study. The research, which came after the city’s adoption of the 2016 King County surface water design manual (KC manual), found that it would be possible to construct a regional stormwater facility beneath Spinney Homestead Park in the Forbes Creek watershed. The particular area was appealing because the park is about 53 acres without a stormwater facility in place.

If made a reality, the facility would be used as an alternative to site-by-site stormwater mitigation for given short plats. When land is divided into nine or fewer parts for business purposes, it is known as a short plat.

Councilmembers had asked for the study in the first place because of a detail in the KC manual. In the manual, it states that stormwater mitigation is required in smaller-sized short-plat developments. After receiving the results of the study, which would show whether the Spinney Homestead Park facility would be feasible, the council would then be able to see whether it would be achievable to both come up with a design for the facility and work out the details for usage by short plats.

At the Oct. 15 meeting, council was first updated on what study options for the Spinney Homestead Park facility, as well as the development of a mitigation program, would entail.

Two options were discussed. The first, which was recommended by staff before the Oct. 15 meeting, is a three-phased study estimated to cost about $520,000. In the first phase, staff would look at the basic feasibility of installing a facility at the site in question. This would cost about $22,000.

In the second phase, which is estimated to cost about $300,000, staff would collect information that would help inform how design unfolds, as well as get input from the public and prospective developers. About 10 percent of the conceptual design of the project would result.

In the third phase, 30 percent of design would be completed, and the mitigation program itself would be further developed. Phase 3 is likely to cost $520,000, or, as clarified in the agenda item, $220,000 in addition to the 10 percent design cost from Phase 2.

At the end of each phase, staff would update, and then get feedback from council. Option one is preferred by staff, according to the agenda item, because it will help officials know how to prioritize the project by concretely knowing the layout and cost of the proposed facility. It would also better aid the process of pursuing grants and other funding avenues.

The second option would have city officials wait to proceed with the project, and instead include it with the next surface water plan, which will likely be scoped and funded by 2022. The project would then be prioritized against included programs and projects encompassing the surface water facility down the line. While costs would be about the same, more drawbacks were noted by Jenny Gaus of surface water engineering.

“The longer you wait to do this work, the fewer projects might still be left to develop to buy into the facility if you want to use it for mitigation…and your cost estimate wouldn’t be available as soon,” she said.

Gaus added that information on environmental benefits would also be somewhat delayed if to go with option two.

At the Oct. 15 study session, the council voted unanimously to move forward with option one, which necessitated that it approve a resolution that requires the city manager to appropriate $49,000 of Surface water utility operating reserves to the project in question.

The Phase 1 study is set to start in early 2020.

For more information about the project and its background, go to the Oct. 15 council meeting agenda at tinyurl.com/y2gv7h6m.