Part of the aging sewer system that carries waste away from area homes and businesses flows through the national park in our backyard – Soapstone Valley.
Erosion by storm water, which DC Water separately carries to the park, has exposed sewer pipes and manholes originally buried under stones and soil. DC Water wants to rehabilitate its sewage pipes, leaving them inside the park. As a first step, it needs the National Park Service to issue a draft environmental assessment for public comment.
Both agencies want to avoid catastrophic failure of those exposed sewer pipes in the park. But the Park Service had feared that DC Water’s preference would remove too many trees while failing to remove sewage odors escaping from manholes.
After four years of discussions between these two agencies, during which DC Water made community presentations in 2013, DC Water agreed to prepare a new alternative proposal to reroute sewage flow outside the park, as requested by the Park Service. This alternative, according to DC Water’s version, would require the addition of pumping stations and a permanent road across the park.
This alternative had not been presented in the 2013 community forums, so DC Water wanted to give the community an informal heads up. It asked ANC 3F to host last week’s meeting, which was attended by Ward 3 Council member Mary Cheh, neighbors, DC Water and District Department of the Environment personnel, Nick Bartolomeo of the National Park Service and community activists.
With 3F Commissioner Mary Beth Ray presiding, Will Elledge of DC Water, backed by engineer Bisrat Abebe and consulting engineer Eric Lienhard, talked about DC Water’s version of a new “rerouting” alternative. They also offered some comparisons with DC Water’s preferred course of relining all the pipes in the park, explained a small, non-catastrophic leak DC Water is repairing, and touched on pollution of Soapstone Creek which is now under investigation.
DC Water projected 44 slides during its presentation, which were provided to Forest Hills Connection the next day.
DC Water expects that a draft Environmental Assessment with two alternatives may be issued by the National Park Service for public comment in January 2016, after the two agencies agree on details of those alternatives. Responding to a question, Mr. Elledge said he did not expect construction to begin before 2017.
Why DC Water is concerned about the Valley
DC Water (DCW) operates more than a mile of sanitary sewer pipes and related manholes in Soapstone Valley. Some are on National Park Service land. More are on District Department of Transportation (DDOT) rights of way – paved and unpaved. Most are more than 100 years old. Originally buried, many such “assets” – as DC Water refers to them – are now exposed, carved out by rain water which rushes over paved streets and buildings into DCW storm sewer pipes and discharges into Soapstone Valley.
DCW fears both small leaks of sewage from old pipes and catastrophic releases in case exposed assets collapse. It therefore proposes a construction project to line the insides of pipes, using a technology called CIPP, which stands for “cured-in-place pipe,” and to protect and cover its exposed assets.
The National Park Service requested the rerouting alternative because it is concerned about the risk of sewage leaks, sewage smells from manholes which lining the pipes would not solve, and tree losses. NPS also questions whether a sanitary sewage system is compatible with a protected national park.
Both alternatives call for stream restoration to protect exposed pipes and manholes. Restoration would replace soil and stones lost to erosion, cover exposed pipes and manholes, and raise the bed and banks of the creek. DC Water tells me they would also place new stepping-stone boulders in the creek at trail crossings.
Asked about the longevity of a stream restoration, Mr. Elledge said DCW vegetation planting contracts carry a one-year warranty, so the contractor would have to replant any vegetation wiped out by storm water. The Park Service’s Bartolomeo said NPS might condition any permit on a five-year warranty. The questioner had asked about erosion wearing away soil and stones as well, but they did not address this or the probable useful life of stream restorations.
Where the storm water and sewage come from
The storm water DCW sends into Soapstone Valley comes from a large area.
DCW collects sanitary (i.e. household and business) sewage from roughly the same area and transports it in pipes by gravity flow to Soapstone Valley, and from there to trunk sanitary sewer lines. Most of that sanitary sewage enters the park from the western end.
About 70 percent flows into the Park via a 38-foot deep manhole on Albemarle Street, east of Connecticut Avenue and west of the Soapstone Valley Trail. It’s marked with a “1” the slide below.
DCW lists a DDOT public alley between Park Connecticut at 4411 Connecticut Avenue and Park Van Ness at 4455 Connecticut as the number “2” entry for sanitary sewage collected from those buildings plus others up and down and across the avenue. Other, lesser entry points are to the east of “1” and “2.”
Soapstone Creek water pollution investigation and emergency measures
In this part of the District, storm water and sewage from homes and businesses flow into separate pipes. They are not supposed to mix. DCW is investigating possible mixing (also called “cross connection”) into some storm water pipes because of smells and analysis of samples from Soapstone Creek at the western end of the Park, using iterative dye tests.
The District Department of the Environment (DDOE) is also investigating.
In early July, DCW identified a possible small leak from a sanitary sewer just east of Audubon Terrace NW near Linnean Avenue, and confirmed with a dye test that leaked sewage flowed under and into a corrugated pipe.
DCW took emergency measures. It stopped that small leak with a temporary, manhole-to-manhole pump and bypass. It plans a long-term fix by means of lining a few hundred feet of pipe – the same CIPP technology it proposes to implement on a larger scale. Neighbors can get a sense of what is involved if they walk by DCW’s emergency fix at Audubon Terrace this week.
Advances in CIPP technology
DC Water’s preference is to line the pipes using the CIPP technology, which has advanced in just the two years since the agency first presented the option to this community in 2013. It is now possible to winch liner material longer distances, so fewer staging areas would be needed. Also, the useful life of CIPP liners may well exceed the estimated 50 years, though experience will tell. And when CIPP liners wear out, DCW now understands it will be possible to install a replacement CIPP lining inside, unlike DCW’s view two years ago.
DC Water’s version of a rerouting alternative requested by the Park Service would also use CIPP lining for a long stretch of 18-inch diameter pipe between the east end of Audubon Terrace and Broad Branch Road.
The new rerouting alternative that would pave a road inside Soapstone Valley
DCW presented a rerouting alternative which it explained in three parts.
Part 1 would remove sewage that enters the park via Albemarle Street or Connecticut Avenue and reroute it via new gravity flow sewers under Connecticut Avenue, Albemarle Street, Soapstone Valley Trail and Audubon Terrace. This would entail laying about 3,280 linear feet of new sewers and would discontinue use of about 527 linear feet of sanitary sewage pipe in the park (marked on Figure 5 map as four yellow X’s between numbers “1” and “2”).
The Connecticut Avenue stretch would flow northward by gravity from the DDOT public alley between 4455 and 4411 Connecticut to Albemarle Street, where it would connect to an existing gravity-flow pipe. It would probably go under the street, in tunnels carved out by small remotely-operated boring machines to minimize impacts on adjacent properties. However, DC Water explained to me after the meeting that a staging shaft in the northbound parking lane would take that lane out of evening rush hour service while the work is done. This new sewer would replace Connecticut Avenue pipe that now takes sewage southward past the apartment building now under construction at 4455 Connecticut (I recall workers discovered a collapsed segment of that pipe) and then eastward under a DDOT public alley into the park.
A new Albemarle Street stretch would flow eastward by gravity from today’s principal point of park entry, a 38-foot-deep manhole, to the head of Soapstone Valley Trail and from there to new sewer pipes under the trail and Audubon Terrace. DCW concludes that new Audubon Terrace sewer should be larger diameter and deeper than the existing sewer to maintain proper gravity flows and that open cut (rather than trenchless) construction would be appropriate there as well as under the trail. That would impact adjacent residents, raising questions of how long they might be deprived of parking and other access and how effective might be any mitigation measures that DCW offered.
DC Water told me Part 2 would remove sewage that enters the park from the Park Connecticut, which has apartments above and below street level at 4411 Connecticut Avenue, which today delivers all its sanitary sewage to DCW at the bottom of DDOT’s public alley right of way at the edge of the park. DCW would discontinue use of the sewage line that runs under the DDOT public alley into the park.
DC Water decided a pumping station would be necessary here to force all of that building’s sewage up through 100 feet of pressurized pipe called a force main to a manhole on Connecticut Avenue.
This pumping station, referred to in the presentation as Pump Station No. 1, would be built in the space between 4411 and 4455 Connecticut – east of and below where vehicles enter and leave the two garages. Pumping would be electrically driven. Consulting engineer Eric Lienhard thought it would be quieter than a pump WMATA uses to transport deep groundwater from its Metrorail tracks into the park. DC Water’s Will Elledge said the pumping station would have to comply with environmental regulations, possibly including sound shielding. In case of electric power interruption, the pump station would have a back-up diesel generator.
DCW said the pumping station would require daily inspection and service visits and would thus require the construction of a permanent paved access road across Soapstone Park from Audubon Terrace. The concrete road would cross the creek, impact trees, and require access through national park land. DCW would use that road for a work truck to inspect the pump station daily, an occasional fuel truck to restock the back-up generator’s supply, and vehicles for any major maintenance that might become necessary.
My impression is that a paved access road poses more significant impacts than noise or odors. But there may be another way. Neighboring 4455 Connecticut, now under construction, will also have residential units below Connecticut Avenue. According to its construction plans and my own conversations with the developer, Park Van Ness will pump its own sewage to street level.
DC Water advised me after the meeting that it had not investigated whether plumbing and mechanical retrofits, possibly akin to what is being built at 4455 Connecticut, could be installed at 4411 Connecticut to lift sewage from below-grade units. It would be more difficult to retrofit an existing building with people living in it, and might not be possible. However, so long as 4411 Connecticut’s management operated and serviced pumping from its property, DCW would not need to operate, maintain or service that activity and would not need an access road. The National Park Service could ask DC Water to examine such possibilities.
Part 2 would eliminate a modest amount of sewage flow but discontinue use of 1,138 linear of pipe – up to the point where sewage DC Water picks up at Van Ness East condominium complex enters the main pipeline.
There, DCW has assumed it would have to build, maintain, and service another pump station and force main on condominium land to deliver the sewage to its Van Ness Street main. Part 3 would do that via Pump Station No. 2 and 1,200 feet of force main. As a result, DCW would discontinue using another 1,154 linear feet in the park.
What about the trees?
Tree loss has concerned NPS and many neighbors from the outset. DCW has worked to revise and refine its plans to reduce such losses in any event. It may do more. For purposes of comparing two alternatives, however, DCW separated trees on park land from total trees impacted by both alternatives, including those on DDOT “and other” land. DCW also showed trees “trimmed” as well as those removed. Neither the meeting nor slides explained why tree “trimming” is of concern.
My summary follows, indicating differences:
DCW’s preferred alternative remains CIPP lining and asset protection measures in the western part of the Soapstone Valley (as currently refined) rather than rerouting outside the park.
Next step: The draft Environmental Assessment
DCW and NPS are finishing a draft environmental assessment (EA) now targeted for public review and comments around January 2016. It would include aspects of the project that got little attention at the community forum – or were not addressed at all. For example, DCW may well have to remove an unknown number of trees to repair an area where a culvert discharges the buried portion of Soapstone Creek and storm water into the Soapstone Valley (The creek is piped beginning at southeast corner of Woodrow Wilson High School property west of Nebraska Avenue.).
DCW also plans repairs to nearby slopes to address acute erosion, and it plans measures at the western end of park to slow down creek flow even though project does not attempt to reduce storm water flow into the park). How much effect will such measures have on storm water scouring?
Such aspects could be explored in the draft EA, if NPS and DCW so agree. I urge them to do so.
If you have ideas for inclusion in or questions you would like to have answered in the draft environmental assessment DCW is preparing on behalf of NPS, contact Emanuel.Briggs@dcwater.com. DC Water would welcome your input.
If you would like an answer sooner, please comment below and we will try to provide the answers here. DC Water has helped us understand its 44 slides for this article. A follow up article may also be in order.