At a meeting of ANC 3F’s Parks and Watersheds Committee this week, DC Water and contractors gave the most detailed overview to date of the stormwater control and stream restoration aspect of the Soapstone Valley sewer rehabilitation project now getting under way.
As we reported in 2019, the Soapstone stream is badly eroded after decades of pummeling by runoff from stormwater outfalls, and that has further exposed and endangered the 110-year-old sanitary sewer pipes running through the valley.
During the March 8th virtual presentation, Eric Lienhard of consulting firm Hazen and Sawyer went over drawings showing the ways sewer pipes and manholes would be armored against big storm events.
(We will add links to the slides when available. The committee also posted detailed notes from the meeting at anc3f.com.)
Lienhard made several references to 2.2-ton rocks and other structures that would be used to shore up banks and slow the flow of stormwater. The presentation also detailed equipment access points and roads, and how many trees would need to come down at each work site.
In answer to a question from ANC 3F Commissioner Dipa Mehta, Lienhard said no “heritage” trees, with a circumference greater than 100 inches would be cut down. He did not know how many “special” trees, with a 55-inch or greater circumference, would be affected. The design allows for the removal of 235 trees, but Lienhard said it’s likely a smaller number will come down.
Soapstone Park closed on March 7th for the 1.5-year project. The pipe relining aspect of the project, using the hot water cured-in-place pipe method, or CIPP, came up when DC Water was asked when that and the stream reconstruction work will begin. Mark Babbitt, head of engineering for DC Water, explained that given all the changes to the project, they did not know yet. Those changes include switching from steam to hot water CIPP, and starting the relining process at a point downstream instead of upstream. DC Water has been estimating that the relining work will begin this summer. Babbitt said there would be another report on the schedule at ANC 3F’s April 19th meeting.
This project has been on the drawing board for more than a decade, going through through an environmental assessment (compiled for DC Water by Hazen and Sawyer) with a finding of no significant impact from the National Park Service, and many community meetings. DC Water released the first report on the aging Soapstone sewer infrastructure in 2011.