Tibbetts Creek diversion into May Creek Basin





  • Determine whether water from Tibbetts Creek was diverted circa 1960 into May Creek Basin


  • Utilize pre- and post-1970s survey, LIDAR, aerial and potentially other data to determine whether water (and, if so, how much) was diverted from Tibbetts Creek into the May Creek Basin. Rumor is a driveway was constructed in a quarry where the two creeks originate that caused the diversion.
  • If water was diverted, the project will not assume what action might be taken, although it can make recommendations. Options certainly include rediverting the water back into Tibbetts Creek but May Creek Basin residents may prefer to keep the additional water coming into May Creek for agriculture or recreation.


  • May Creek Basin Plan (PDF)

Current project document (Word) (PDF)

May Creek Basin

May Creek runs for approximately 7 miles with the north fork originating in Cougar Mountain and the south fork coming from the plateau east of Renton.

The creek topography can be divided into three sections rougly equal in length. The upper third are the headwaters, the middle third is a flat basin, and the lower third falls through a canyon and eventually runs into Lake washington.

The headwaters of May Creek and Tibbetts Creek on Cougar Mountain run close and cut across a quarry. Rumor has it that in the 1960s, the quarry built a road that resulted in water that originally ran into Tibbetts Creek was diverted into May Creek.

For close to 50 years, the middle portion of May Creek Basin has been plagued by seasonal flooding increasing in duration and intensity. A diversion of water into the May Creek Basin was obviously of concern to May Valley residents and, as a result, correcting the diversion was included in the May Creek Basin Plan.