We’ve been warned in the past that the Soapstone Valley Trail is endangered due to steady erosion of the stream banks. The erosion accelerates whenever we have a major storm event, and the storms have not decreased in frequency or impact since that warning in 2014.
Take last Tuesday’s powerful deluge, so powerful that the resulting DC-area flooding made The New York Times.
In the Soapstone Valley, most of the impact was seen near the end of the stream by Broad Branch Road. A pile of deposited sediment and rocks dramatically changed the contours of the stream bed.
There were clear signs the stream had jumped its bank – mowing down plants…
…and depositing tree debris against the culvert and the guardrail on Broad Branch Road.
The problem is largely man-made – too much stormwater flowing over too many hard surfaces and into the valley. One solution may be man-made as well – a stream rehabilitation like that done at the Broad Branch and Linnean Streams in 2014.
After the sanitary sewer pipes are relined and manholes are restored, the next phase of DC Water’s Soapstone sewer rehabilitation project is to protect these “assets,” as they are described in the environmental assessment. The methods described include rebuilding the stream bed to cover and protect the sewer system. Could the work also have the positive impact of slowing the destructive speed and volume of stormwater, and reducing sediment and pollution?
It does seem so. One appendix of the EA states that a purpose of the project is “[to] meet the regulatory requirements of the District’s MS4 permit [from the EPA, allowing storm sewers to discharge directly into streams and rivers], including moderating stormwater volumes and velocities, reducing erosion, and filtering pollutants by groundwater infiltration.” (See the Statement of Findings, page 4)
Another appendix states: “The effects of the stormwater outfall rehabilitation and asset protection would restore the stream to improved conditions relative to existing conditions.” (Mitigation Summary, page 3)
The project’s largest asset protection site is adjacent to the storm sewer outfall (F-117) at Connecticut Avenue and Albemarle Street.
To view the original image and other maps of the project area, download Appendix B of the environmental assessment here.
Most of the stormwater flowing into Soapstone Creek pours through this outfall after being collected from a 314-acre area west, south and north of this outfall. DC Water wants to cut back the exposed section of pipe by 30 to 50 feet. The “repaired and rehabilitated outfall would then discharge onto a proposed rock cascade structure, leading to an existing plunge pool downstream of the cascade.”
Could DC Water be considering some of the same techniques that the District Department of Energy and the Environment used at Broad Branch and Linnean Streams?
“Yes, slowing flows and stabilizing stream banks through techniques such as raising the stream bed and [installing] rocky pools, both mentioned in the EA, would be appropriate in Soapstone Valley,” Steve Saari, the head of the Watershed Protection Division at DOEE, told me. DOEE is involved with this project because of the MS4 permit.
“This can create benefits to fish and wildlife while reducing erosive forces that undermine stream banks and sewer assets.”
Keith Underwood and his construction firm Underwood and Associates specialize in stream restoration, and if you have visited the Broad Branch daylighting and Linnean restoration sites, you have seen his award-winning handywork. More recently he finished a project at Muddy Creek in Maryland, which faced similar conditions to those in Soapstone Valley. The Smithsonian Environmental Research Center found significant sediment and pollution reduction at the Maryland site.
“Raising the stream bed to create a wetland area with a series of regenerative pools, like those at Broad Branch and Linnean Streams, would be good techniques to use in the Soapstone sewer rehabilitation project to slow the water, and reduce sediment and pollution,” he told me. “DC Water, with the National Park Service, have a great opportunity to restore an ecosystem, replenish the life in and around the stream and establish an even more beautiful and natural parkland.”
We, the neighbors who surround Soapstone Valley and consider it a valuable community asset, need to make our voices heard. We have until August 2nd to comment on the Soapstone sewer project environmental assessment. Let’s tell DC Water, NPS and DOEE that we want them to use this opportunity to rehabilitate the stream as well. Doing so will not only protect DC Water assets, but also improve the health of Soapstone Creek and reduce flood damage downstream at Broad Branch Road.
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