On my block in West Chester, last month, workers were boring test holes in the street to discover the best depth for surface water to drain into the subsoil. I said: “But isn’t it all clay down there?” and they said: “No, we are hitting sand and loam at about 5 feet.”
The Borough plans to install, at strategic points, “bumpouts” to absorb storm runoff into garden-like areas and from there into underground holding tanks and into the subsoil. The chief goal is to reduce runoff into streams and consequently reduce erosion and water-borne pollution.
On November 19 I found out more background through a walking tour sponsored by the SE PA Sierra Club in Philadelphia’s “Big Green Block.” My notes from the very interesting tour conducted by Sandy of the Fairmount Water Works show that…
About 60% of Philadelphia has a combined storm and sewage water system, as is common on many older cities. This works fine in dry weather, because in those areas water runoff goes through the sewage processing system and many street pollutants, like drippage from cars and pet wastes, are cleaned out of the water before it goes into the Delaware River. But it is bad in wet weather, when the combined system is overwhelmed and untreated sewage goes into the river from 164 separate overflow points.
Now, along with over 800 other cities, Philadelphia is under federal order to cure the overflow problem. They could do that by separating sewage and storm flow. But that would be extremely expensive and intrusive. So, the city is aiming to cut down on storm runoff into the combined system. This solution has the added benefits of restoring water to underground aquifers, favoring tree growth, and naturally filtering street pollutants.
So as a demonstration project, Philadelphia committed some money, got some grants, and reappropriated a very large, basically abandoned block in Fishtown that had been a rail yard. This fits into the city’s comprehensive Green Waters, Clean Streams plan, now in action for over 5 years.
The Big Green Block now houses the Kensington Creative and Performing Arts High School (the first LEED platinum high school in the whole country), a park for people and one for dogs, a rec center, and facilities specially designed to retain and absorb water: green roofs, playing fields (including underlying geothermal energy fields), rain gardens, tree trenches, a stormwater bumpout, infiltration basins, a rainwater cistern, and porous parking pavement.
The special feature that we notice most readily is the rain gardens, which create pleasant habitats for trees, flowers, grasses, and animals like insects and possibly amphibians and reptiles. Rain gardens, fortunately, are engineered not to hold standing water more than a couple of days, to be sure that they do not breed mosquitoes.
Meanwhile, West Chester is working on its own green infrastructure. You can see a rain garden on Dean St. and a series of catchment basins east of New St. on the WCU campus where Plum Run once flowed (a concern if the proposed new building there diverts additional drainage water into the stream). And demonstration features are planned in the Borough Hall grounds.
The Borough now has a Stream Management Program designed to control rapid runoff, including (as of January) a Stream Protection Fee that impacts property owners (including ones that otherwise are untaxable) in proportion to their amount of impermeable surface or, in other words, the amount of precipitation that potentially flows away without being absorbed. Proceeds will be used to upgrade the aging storm water drainage system and install features like rain gardens and bumpouts.
This is all to the good. Cities like Philadelphia and municipalities like those in Chester County need to be good citizens by reducing runoff, thus improving stream quality and the lives of downstream communities that drink that same water.
Could a Big Green Block be good overall element in the Borough’s still-undeveloped Wyeth property? One can dream….