Ingenuity Stops Sewer Seep Into Chinquapin Run
Thursday Aug 3rd, 2017
An improvised fix to a nearly 100-year-old sewer pipe system that had been seeping into Chinquapin Run has been successfully keeping that urban waterway cleaner, years ahead of a scheduled long-term solution.
Routine methods of repairing the 21-inch sewer interceptor had proven insufficient, and sewage continued to leak from the pipe. But a little ingenuity has provided a secure, albeit temporary, fix until a planned replacement main can be built.
In March of last year, inspectors with the Baltimore City Department of Public Works (DPW) discovered that sewage was seeping into Chinquapin Run in North Baltimore, a tributary of Herring Run, from the 21-inch sewer interceptor that runs near the stream along the 1500 block of Hartsdale Road.
Old, failing construction
The sewer was already scheduled to be abandoned and replaced with a new pipe in a different location. It had been built in the 1920s using three-feet sections of clay pipe held together by oakum (tar-soaked fiber rope). That means every 3 feet a joint presented an opportunity for sewage to seep out. Worse, the sewer interceptor also has an 8-inch underdrain pipe, which was originally installed to keep groundwater away from the pipe during its construction, but then had the unintended effect of moving sewage away from the leak and into the stream.
DPW attempted to repair the pipe by re-lining one segment of it. While that prevented sewage from seeping out from that segment of the pipe, the lining work did not solve the entirety of the problem. Crews could not determine exactly which joint or pipe segment was leaking. The location of the pipe, in a wooded area along a stream, also presented challenges for inspection and repair efforts.
Though the Maryland Department of the Environment initially agreed to allow the City to abate the leak through the long-scheduled replacement project, DPW engineers continued to explore options to address the leak.
Instead of focusing on the pipe, DPW engineers took another look at the underdrain. This May, crews executed a plan to re-route the underdrain so it emptied into a nearby sewer manhole instead of the stream. That kept the sewage in the sewer system, where it is carried to the wastewater treatment plant, instead of continuing to release into the stream.
Since May, regular dye testing and bacteria and ammonia sampling confirmed that sewage has stopped seeping into Chinquapin Run. The Maryland Department of the Environment has acknowledged the success of this fix.
This is not a long-term solution, and DPW is proceeding with plans to re-route the sewer main by building a new interceptor. This is part of a comprehensive $23.5 million sewer main construction project was advertised in May, and is expected to be complete by the end of 2019. The project includes stabilizing the stream so that it can continue to be an asset to the community and Baltimore’s waterways.