Wednesday, September 21, 2016

Touring Baltimore stormwater BMP facilities

Sometimes it takes a tour bus and organized presentations to see what is otherwise hidden in plain view. Case in point, the Stormwater 2016 Tour sponsored and organized my the MD chapter of landscape architects and the MD Society of Civil Engineers.

A whole bus full of planners, engineers and landscape architects wanted to see what Baltimore had to offer in terms of bio-retention and stormwater management (best management practices, BMP) in the small scale in the urban setting.
Practitioners have used the term BMP to describe both structural or engineered control devices and systems (e.g. retention ponds) to treat polluted stormwater, as well as operational or or procedural practices.
The objective of those multiple small interventions is not the control of massive storms like the one that ravaged Ellicott City but the control and improvement of the first inch of precipitation. The water washing off roofs and pavement is often the most polluted especially after longer periods of dry weather. It is important to prevent this dirty and frequently heated water from running straight into storm drains leading directly into streams and waterways such as the Inner Harbor. The treatment of subsequent inches of rainfall delivers much less incremental benefit but requires much larger holding areas. Thus most of the facilities on display on the tour were designed for that critical first inch.

It was clear from the facilities and the stories behind them that stormwater management 2.0, the small incremental first inch treatment areas, is still in its infancy. The installations are more demonstration projects than actual solutions. Proof of concept, as disruptive start-ups call that phase.

The examples presented at the tour are shown in the below pictures with a description, explanations and sometimes a critique in the captions.

Klaus Philipsen, FAIA

The stormwater swale at 400 West Pratt Street treats the first inch of the water flowing off the adjacent sidewalk. It doesn't contribute to groundwater recharge thanks to a liner under the soil and sandfilter, apparently required by the city. The project received funds from the Downtown Partnership. Design: JMT, presenter Jon Conner,

breaks in the curb let the sidewalk water flow into the bio retention area. Those pointed flows caused some scoring on the backside. Trees in the planting area are red maple. They are offset to avoid a major stormdrain under this facility

regular curb drains are installed on the backside to take on overflow water in storms that are larger than the facility can handle
Pierces Park  at the Columbus Center is a retrofit of the original Chesapeake grasses installation and is an elaborate kids entertainment and learning area that cost $2.5 million to install in 2011, money that came from a donation. This bio retention area and several smaller ones on the same grounds use no liner but have irrigation to keep the green and lush. The designer was Mahan Rykiel, the presenter Eric Souza of the Waterfront Partnership that helps with the upkeep and maintenance. According to Souza the use by young people "is off the charts".  

The largest bio-retention at the Columbus Center
A smaller bio retention area at the Columbus Center

The Columbus center BMP is fenced off due to heavy usage by kids. Still, soil compaction is an ongoing issue

The 2013 Blue Alley project in Butchers Hill  is a demonstration of making Baltimore's alleys pervious. Nick Lindow of CityScape Engineering presented the project that was executed with support by Bluewater Baltimore. The pavers with large pervious joints are basically the inlet to a sandfilter with underdrain explained DPW representative Rosanna LaPlante who reviews all bioretention submittals in Baltimore City. The project received funding from the National Fish and Wildlife Fund. The complicated set-up in which the job was bid and constructed by DOT led to various problems due to the fact that DOT and its contractor had no experience with stormwater management. In spite of being a demonstration project, there was no monitoring to date, so Lindow said: "Who knows how much it's infiltrating". Monitoring  isjust now beginning for flow rate and volume. A difficulty is that in alleys the private properties go to the center of the alley. To avoid water infiltrating towards houses, there are liners on the sides of the paver area. There was a $900,000 budget including the bump-outs shown below, but the project hasn't been fully accounted so real expense is unknown.

large scale depiction of the paver joints that are supposed to take the water

The "bump-outs" at Butchers Hill are supposed to be traffic calming devices doubling up as BMPs. Ashley Trout of Bluewater Baltimore explained how difficult it is to get agreements with the neighborhood associations regarding maintenance and upkeep and stewardship. 

Keeping pet waste out of bio areas apparently requires Spanish signs

The Butcher Hill bump outs sank too much and need to be replanted and refurbished

One of the sidewals was poured over top of the retention soil instead of a CR 6 stone base, the water finds a shortcut directly to the overflow inlet making water improvement a fantasy that exists only on paper 

The nearby school helps with a special green group of students who love to work on these areas. The plants also attract butterflies and other small animals usually not found in the streetscape

The last stop on the tour was the Library Square at the Patterson Branch of the Pratt Library on Fayette and Linwood Streets, a historic park with 60 mature linden trees.

The park was retrofitted with retention areas. Many of the small plantings did not survive the summer and need replacement under the contractor warranty. Design  BioHabitats for Bluewater Baltimore, design-build Angler Environmental, presenter
Bryan Arvai, Biohabitats. The facilities treat approximately one half acre area. They will do little to mitigate the flooding common for the area when the underground channels of the Harris Creek overflow. because they are not designed for large volumes but the first inch again. The budget is $350,000, a grant from the Department of Natural Resources (DNR). many community groups including the Friends of Library Square were part of the design process.

Traditional brick pavers laid with open joints to absorb rain water.

The Audobon garden across the street from Library Square is not part of a stormwater project but drew a lot of attention from tour participants

The western portion of Library Square which is bifurcated by the underground Harris Creek

The Friends of Library Square meet in the library

Panelists Michael Peny (Angler), Ashely Trout (Bluewater), Steve Allison (Floura Teeter) and Rosanna LaPlante (DPW) discuss the design, implementation and maintenance issue of small urban stormwater facilities at the end of the tour.

Steve Allison stated as his special interest and expertise: "How does the plant take the pollution out of the water?" He also got into the question of the bigger storms which appear to be a result of global warming and dump heavy rains in very short periods. He said: "We talk a lot about the regulation rains but need also talk about big storms. Guidelines must be rewritten to adjust for weather. Burst storm wash everything out", referring to how the fragile first inch of rain facilities are not resilient enough to withstand those storms. He demanded that "In biomass and metabolic horizons we need to create systems that keep themselves in check". Joanne Trach Tongson of Mahan Rykiel who had organized a lot of the event and moderated the panel added: "We need to define soils not only by chemistry and structure but also their biology. "
Aside form such esoteric issues , the opportunity of a green workforce development was also discussed. Today there is a shortage of people that understand how to take care of these facilities and maintain them.

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