Monday, August 10, 2015

Suburban Stormwater Tour: The Good, the Bad, and the Ugly

Los Angeles River East
The Pennypack Trust is partnered with four other watershed organizations in the Philadelphia suburbs in a consortium that is working to improve water quality and reduce stormwater quantity in the Delaware River.  Our consortium works in the Philadelphia suburbs, but the William Penn Foundation who spearheaded this work is funding seven similar consortia throughout the huge watershed.  Our consortium is tasked specifically with reducing stormwater, while the consortia working in less-developed parts of the basin are working to reduce agricultural impacts and to preserve open space.  The entire basin-wide project is called the Delaware River Watershed Initiative.

Our work has been going on for 1-1/2 years now, and the staff of the foundation requested a tour of sites where the foundation's support has been used to implement stormwater management projects in the field.  On Thursday, August 6, the watershed organizations' and foundation's staff members gathered for a day-long bus tour of four sites scattered throughout the Philadelphia suburbs.    

First stop was at a private residence in Haverford, Delaware County where a rain garden had been installed.  This rain garden was one of about 20 rain gardens that are being installed in prominent locations where neighbors and passers-by can become familiar with using a rain gardens to capture and infiltrate stormwater running off impervious surfaces instead of allowing it to pour directly into storm drains.
Publicity in the front yard
The rain garden, planted in May
Homeowner (blue shorts) and project consultants (right)
Second stop was a detention basin created to manage the stormwater for a 40-unit subdivision in Whitpain Township, Montgomery County.  While the basin was larger than needed to manage the stormwater generated by the subdivision, the basin was poorly designed and actually did almost nothing to detain stormwater.  The municipality has committed to modifying the basin by reducing the diameter of the discharge pipe (thus trapping and holding the stormwater for longer periods of time), creating islands, peninsulas, and pools within the basin to create habitat, and planting native vegetation throughout.
On the berm above the basin (about 10 feet deep)
Temple University hydrologist Lora Toran explaining testing equipment to monitor project effectiveness
After lunch, we toured a municipal sports complex in Horsham, Montgomery County where stormwater sheets off playing fields.  (Turf sheds water almost as effectively as asphalt.)  At this location, the municipality intends to create deep, rock-filled swales planted with native grasses or plastic igloo-like underground voids that will allow rainwater running off the fields an opportunity to soak into the ground rather than run off to the adjacent creek.
Water from the playing fields (right) and parking lot pours into this swale, then directly into a creek
Grass swale will be replaced with a rock-filled infiltration trench
Later in the afternoon, we stopped at one of the most challenging and intractable sites imaginable; we wanted to show the foundation staff members just what our organizations have to deal with in the developed suburbs.  Here in Abington, Montgomery County, the headwaters of Sandy Run drain a fully-developed residential and retail neighborhood.  Because the watershed has so much impervious surface (e.g., driveways, rooftops, lawns, and roads), very little rain water soaks into the ground, so the stream has almost no baseflow during dry periods.  However, when it rains, Sandy Run turns into a raging torrent because all of the imperious surfaces shed water directly to the creek.  Unfortunately, this neighborhood is densely developed, so the stream channel is located in residents' backyards and there's nothing that can be done to widen the channel or create stormwater detention.  Instead, Abington confined the creek to a concrete channel reminiscent of the infamous Los Angeles River to sluice the water downstream as quickly and "safely" as possible. 
Concrete confines
During Hurricane Floyd, two people living downstream of this channel drowned in their basement when the water rose up in a flash and flooded the house.  So much for safety.
Stormwater management is a difficult problem to address.  It took us literally centuries to for our urbanized watersheds to become like are in today.  Let's hope it doesn't take as long to correct the mistakes of the past.