Clarks Creek Elodea Removal

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Background

The City of Puyallup (City) and Pierce County (County) began elodea control efforts more than 30 years ago. Prior to 2013, the City and County performed mechanical cutting every summer to reduce shoreline flooding associated with dense elodea growth. The cutting reduced creek water levels but the benefits were temporary due to rapid regrowth.

In 2013, the City and County switched to Diver-Assisted Suction Harvesting (DASH) to remove elodea from Clarks Creek. DASH involves uprooting the elodea plants, placing the plant roots and shoots into a suction hose, and using mesh bags to remove the plant material before discharging back into the creek. Based on DASH programs in other locations, it was thought that removing the elodea roots and shoots would lead to a long-term reduction in elodea growth in Clarks Creek.

DASH has removed large amounts of plant material and reduced summer water levels in the creek. However, the annual volumes of elodea removed by DASH do not show a clear downward trend.

Ecology issued the Clarks Creek Sediment and Dissolved Oxygen (DO) TMDL in December 2014. The TMDL study identified elodea as a significant factor in depressed DO concentrations in the creek and called for the City and County to reduce elodea coverage by as much as 75%. The TMDL study noted that the 2013 DASH successfully removed large amounts of plant material but did not specify that DASH must be used to reduce elodea coverage. The TMDL study also issued a requirement for increasing riparian canopy cover (planting) to help suppress elodea growth through shading.

The Clarks DO and sediment TMDL was based on limited data and modeling. The County is performing a TMDL reassessment study to help fill data gaps and recommend TMDL refinements where appropriate. The reassessment monitoring and modeling results to date indicate that dense elodea growth increases daily DO maxima but has little impact on daily DO minima. Moreover, the modeling results suggest that dense elodea growth reduces channel erosion and sediment transport.

The Puyallup Tribe of Indians (PTI) owns and operates a salmon hatchery on Clarks Creek. The hatchery has been in operation for approximately 18 years. The hatchery continuously withdraws ~12 cfs from Clark Creek. Most of the intake water is routed through raceways and rearing ponds within the hatchery before flowing back into the creek. A small portion (about 0.54 cfs, or 200 gpm) of the intake water is treated in a 30-micron drum filter and conveyed to the hatchery’s incubation room.

Emergency Elodea Cutting on Clarks Creek


With the help of Stumpy's Tree Service, the City commenced an emergency cutting of Elodea within City limits beginning October 9 and ended on October 27th, 2023.  

  • This cutting did not extend outside of City boundaries.
  • The crew was in the water for 11 days, and removed approximately 475 cubic yards of Elodea.
  • The Creek levels have dropped over 1.5 feet pre to post cutting and appear to be at average levels for post DASH within City limits.
  • The City plans to cut the Elodea again next year during the 'normal' June/July window.
  • The Puyallup Tribal Hatchery operations appear not to have been effected during the cutting
  • Feel free to reach out to Paul Marrinan by phone or email with any questions.