Commenter bmorepanic's full post ...

… in response to this Brew story:

“Having been indirectly involved in sewer issues because of living near Herring Run, it’s difficult not to challenge some of the statements in the story.

To the best of my knowledge,the city didn’t examine all of the sewer lines – only those built before some cutoff age. For example, in my neighborhood, they didn’t survey about 200 feet of a line that later needed emergency replacement – even though sanitary sewer leaks were reported and repaired every other year. I was privileged to look at the sewer map for the park which clearly showed what was surveyed and what was not.

Blue Water is a relatively recent combination of a bunch of different watershed organizations – so while it encompasses a lot of territory now, it doesn’t have an institutional memory of events over a few years old – although some individuals know some parts. DPW has a lot of personnel turnover and a lot of outside contractors, so the confusion they sometimes leave in their wake may be unintentional. They also have many layers of maps – most on genuine paper of different ages – showing the sewers with different levels of detail and not all features shown on every map so an engineer needs to read and evaluate an entire stack to figure out what’s down there and where its supposed to be.

The Herring Run and that particular line replacement illustrate two other sewer issues – the official flood maps don’t show the effect of current levels of run-off water and running sanitary sewer lines through streams instead of going over, under or around them has consequences that don’t model well.

The Run rises with storm run off. Most people do not realize that every storm drain exits into any nearby stream. A big thunderstorm can cause the run to rise 4-5 feet where I live within very little time – a few hours at most. It likely rises more, but I have no vantage point that feels safe to use. The run drains the water run off from a wide swath of Northeast Baltimore and some of the county. The Herring Run has little tidal change or storm surge change like those experienced in the bay where the wind whips up the water levels. Then again, looking at the evidence left on the land of past water events, I kinda believe the 100 year flood mark is around 15 feet.

The land beside the run floods when the run rises. In some areas,like the Hall Springs parking lot, this can happen just from an average rainstorm. In larger events but not the ten year type, the run back-floods its feeder streams. Since, the water is gonna go somewhere, it flows over the stream bank and downhill – also towards the run.

The emergency sewer line that was installed used plain manhole covers set level to the ground. So did the many-million-dollar partial main line replacement (causing one or two of those big EWOs). Some of those manhole covers are in land that floods in good sized rains.

The flood water goes into the sanitary sewers through the manholes increasing the load in the sewers. And, of course, the sewer effluent can come out. Because city maps are mostly elevation and tidal-based, they don’t show this type of flooding – so engineers spec the wrong types of manholes or put sewers in the wrong places.

If citizens try to tell them it floods, even when the DPW representatives have good will, the flood map is the only source the engineers rely on. The flood maps show much lower water levels than are actually present and there doesn’t seem to be any way to change them.

When a stream is suddenly carrying that much water so quickly, it’s is capable of carrying a lot – whole trees, iron manhole covers, tumbling pieces of concrete jettisoned from assorted construction – and crashing it into the sanitary sewer pipes still in the run. The debris can rip through “armoring” and damage the pipes or the stacks that lead up to the manholes. This has happened in the Run to both sections that have been recently rebuilt with “waterproof, armored” manhole stacks and to those sewer lines that DPW considers not part of the consent degree.

Another of those EWOs was to re-rebuild some of the waterproof, armored stacks that didn’t even last 5 years. And part of the on-call budget went to an emergency order to fix a newer sewer pipe passing though the run with tall manhole stacks with significant armoring, but not included in the sewer study.

We can do better than this. DPW should “get over it” and work with citizen groups like Blue Water. It would be nice to see more results and less fighting over whether a problem exists.”