Exposed Soapstone manhole, from the cover of the June 2019 Soapstone Valley Park Sewer Rehabilitation Environmental Assessment
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.
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Green Eyeshades says
It looks like our ANC 3F has essentially thrown in the towel in the struggle against DC Water’s toxic pipe relining methods. At least, that is my impression from the final two paragraphs of this blogpost on DCist:
https://dcist.com/story/22/03/18/soapstone-sewer-rehab-breaks-ground-rock-creek-park/
DCist continues to misunderstand what the Soapstone Valley project is really about. It continues to foment DC Water’s propaganda that the sewer line is the source of the chronic, historic E. coli infestations in Soapstone creek. The E. coli comes primarily from the storm water, not from the old sewer line, which has already been partially repaired along Audobon Terrace.
The sewer pipe re-lining is just a sideshow to the boulders-and-cascades and manhole-armoring heavy lifting involved in raising the creek bed and armoring the floor of the ravine against “extreme events” up to but NOT including hundred-year floods. The boulders-and-cascades and manhole-armoring components of the project would have gone ahead even if no part of the sewer was going to be re-lined.
The notes of the March 8 meeting of ANC 3F’s “trails and watershed” committee reveal that the “watershed” is where the majority of the capital construction will take place:
http://anc3f.com/wp-content/uploads/2022/03/ANC-3F-Parks-and-Watershed-Notes-3.8.22.docx
In my opinion, it is just incidental to the “watershed” construction that the sewer line runs through part of the watershed.
Here are some of the comments recorded in the ANC’s committee notes of the March 8 meeting:
Page one (DC Water engineer): “External Defects focus tonight.” … “specifics of the rehabilitation design … Not meant to protect from a 100 year storm, but reduce the impact of extreme events”
Page two (same engineer): Under “Stream Design Site 1” … “450 linear feet of stream restoration to fix. Riffles, covering sanitary pipes; preserving existing trees; adding boulders for Rock sills and Cross vanes that promote grade control; Cascades at steeper slopes than a riffle. Create pools. Manhole Armoring to shield from major storm events.” Under “Stream Design Site 4” … “re-routed trail; skipping stones for creek crossing; manhole armoring, rock sills; imbricated walls etc to be applied.
Outfall F-140 in this area. Failing Step Pools were installed and DC Water determined that a cascade structure was better for continuing from there. DOEE will be back to fix the failing step pools.”
There are four pages of notes, the discussion of trees seems to be the primary concern on pages three and four.