Wednesday, December 17, 2014

Tacoma Smelter Plume: What's under the new grass at Vassault Park in Tacoma?

By Jill Reitz, Cleanup Outreach Coordinator, Toxics Cleanup Program

Over the past few months, you may have noticed orange fences, trucks, new dirt, and new grass at Vassault Park in Tacoma. Ecology has been cleaning up soil contamination at playfields in the park as part of the ongoing work to clean up arsenic and lead. These toxic metals were carried by the wind from the former Asarco copper smelter and contaminated soil over a large area of Puget Sound.

1. Contractors prepare the site for digging.

The Soil Safety Program provides free soil sampling and cleanup for play areas at schools, childcares, parks and camps. Vassault Park is the largest cleanup in the program, at eight acres. Cleanup happened quickly, driven by the need to plant and establish grass before the winter weather.

2. Contractors remove the top 6 to 12 inches of soil.
Over the years, Metro Parks Tacoma has also experienced drainage issues in the playfields at the park. Both Ecology and Metro Parks were glad to break ground this summer on this $2.1 million joint project to replace soils and fix the drainage problems.


How did Ecology clean up the 8 acres of soil in just a few months?

To give you an idea of how we completed the cleanup work, here's what happened from June to November 2014:

3. Contractors replace the soil with clean soil.
1) In June 2014, contractors did the following to prepare the site for digging:
  • Installed a chain link fence and high-visibility orange fence around the playfields. The fences marked the closed areas and kept park visitors out of the construction zones.
  • Brought equipment to the site and set up a staging area. 
  • Posted signs to inform park visitors of the construction schedule for the park.
4. Metro Parks Tacoma fixes past drainage issues.
2) From July to mid-August, contractors dug up the top 6 to 12 inches of contaminated soil and hauled it to a landfill. Since the cleanup spanned 8 acres, the contractors removed the soil one quadrant at a time. This photo shows the park after excavation and before new soil was backfilled.

3) Next, the contractors began backfilling the excavated areas with new soil. The top soil they used for the playfields was a mix of sand and compost. This mix is best for sports fields because it helps with drainage and is easy to maintain.

They also created a slight slope from the center out to the edges of the fields. The purpose of this is to drain water off the fields during the wet season.

4) To fix past drainage problems, Metro Parks Tacoma coordinated improvements on the east side of the playfield. After backfilling the topsoil, they excavated trenches and installed a network of drainage pipes every five feet. These pipes are buried 12 inches deep to avoid accidental damage.

5. Landscapers restore the lawn and playfields.
5) Finally, landscapers restored the lawn throughout the park. To make sure there's good grass coverage for sports, they completed the following steps:
  • Drill seeding the lawn, a process that uses a small tractor that tows a planter to plant individual seeds to a shallow depth in the topsoil. This process provides an even seed distribution and thicker grass layer.
  • Installing sod around the sprinkler heads and in drainage swells.
  • Watering and fertilizing the new lawn.

Final steps through May 2015

  • Fences will remain up around the new grass until May 2015. Grass roots need time to establish before visitors can start using the playfields again.
  • Grand Opening Celebration! Ecology and Metro Parks Tacoma are plannng to host a grand opening of the park in early summer 2015. More information coming soon!

Questions about the cleanup?

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