Throughout almost the entire sampling season, our bacteria readings on Almshouse Creek have been well above the EPA threshold for safe swimming (see here). For the past several months, we've been trying to track down the source. Our sampling site is at the top of the creek, and the surrounding area is entirely on sewer. Edgewater Park is at the top of the creek and comprises a significant portion of the drainage area.
Having walked the park a number of times and determined that pet and/or wildlife waste doesn't appear to be a significant problem in the area, we contacted Anne Arundel County Recreation and Park and Department of Public Works (DPW) about coming out to look at the sewer infrastructure in the area. Needless to say, that involved a lot of looking down pipes.
Last week, DPW popped the manholes off several sewer junctions to examine their condition. The photo below shows the gravity pipe coming from the park concession stand (in aquamarine) draining into the main sewer line. A dye test and smoke test seemed to indicate that the pipe was intact and not leaking into the adjacent soils. One problem that this investigation did reveal is that groundwater is leaking into the sewer system from around the pipe collar. This is a problem because it means clean water is getting into the sewer and being treated at the treatment plant, occupying capacity and costing additional money. DPW expects to fix the problem within a month or so.

With the feeder pipe from the concession stand apparently in working order, we scoured the site for other possible bacteria sources. Below is a shot of the filled-to-the-brim grease trap from the concession stand. Though from outward appearances, the tank appeared relatively new, it was quite full, and we've requested that Recreation and Park pump the tank just to rule it out as a possible source.
DPW will be checking one or two other sewer segments in the area, and our bacteria monitoring program continues on, but unfortunately, the mystery remains unsolved. I'll keep you posted on any future revelations here.
Note: Never open a manhole lid and descend into the sewer system yourself. Dangerous gasses can build up in these systems, and because they are often heavier than air, remain there. Suffocation and death could easily occur if one ventured down without the proper breathing equipment.