by Kevin Dicciani
Nearby residents find plans proposed by the Philadelphia Water Department to address stormwater runoff at the intersection of Norwood and Sunset avenues insufficient and ineffectual over the long run.
The plans were presented at the June 4 meeting of the Chestnut Hill Community Association’s Land, Use, Planning and Zoning Committee’s meeting by Debra McCarty, deputy commissioner of operations for the Philadelphia Water Department, and Patrick Perhosky, a civil engineer with PWD’s ecological restoration group. They said their plans were an attempt to alleviate the issue, which they said came to their attention about in October 2011.
Perhosky said the area receives 14 acres of drainage at the intersection, three of which are impervious. He said at the intersection there is a lack of stormwater infrastructure – no inlets, no curbing, no pipes – and the steep hills surrounding the low-lying area add to the runoff on the crown of the street on Norwood Avenue, where a half-inch rain event can cause about four inches of water to pond.
PWD attempted to fix the issue five years ago, Perhosky said. It tried to improve infiltration at the intersection by adding stone, but he said the construction was either poorly done, the ground was compacted, or over time the stone filled with fine sediment and became clogged.
Perhosky said PWD came up with two preliminary alternatives and a recommended one to address the problem.
The first was to install a system that would convey the stormwater to Bells Mill Road’s sewer, which is already sized to handle the entire area. However, Perhosky said, that plan contained numerous issues. One, the PWD would have to use an existing right of way to build a 30 inch pipe through Norwood-Fontbonne Academy and two private properties.
Within that right of way on the private properties there is already a pool and a building, and Perhosky said they would have to either relocate the right of way or demolish the structures to move forward – both expensive options that would be at the property owner’s expense. Another large issue within that plan is that more flow would be sent to Morris Arboretum, which is already being eroded by stormwater as is.
The second alternative, Perhosky said, was to install another stormwater system – a 15,000 square foot underground stone basin – on Norwood and Sunset avenues that would discharge into a small tributary on a private property adjacent to the culvert at the bridge on Norwood Avenue That plan would double the drainage area in the stream, and PWD does not want to impact downstream users.
To advance with that plan, a regional stormwater management facility would have to be implemented to make sure that the flows are not impacting those downstream users, and PWD would have to obtain a state permit for putting in a new outfall on that private property, as well as going through easement negotiations. The project would cost around $1.1 million dollars.
PWD’s recommended alternative is to deal solely with the ponding issue. Perhosky said the plan, conceptual at this time, would provide surface and subsurface storage at the crown of the road on Norwood Avenue, but would not provide overflow. Instead PWD would use existing conditions, so as to not impact downstream users, and install a rain-garden by retention area on the surface, where underneath a larger stone area would be constructed that would go into the right of way and under Norwood Avenue itself.
For heavy rainfall events, water will pond for 24-48 hours before dissipating. The subsurface, 4-to-5 feet deep, would contain 2-feet of stone, followed by 2-feet of soil media, and above there would be native vegetation, depressed about a foot or so.
The construction of the recommended alternative would occur in stages and take between six and seven months. During that time, depending on which section is being worked on, that road will be impassable. To avoid disrupting the traffic to and from NFA, McCarty said PWD would attempt to do most construction in the summer.
Al Brixler, who’s lived at 8890 Norwood Ave. for 20 years, said that under the recommended plan the area in front of his home will be intermittently flooded and surrounded by a moat because of the 24-48 hour window when the water will pond before infiltration.
McCarty said that at the moment that is the case, but PWD is not “inventing something that doesn’t exist, we’re lessening the frequency that it does exist.”
Brixler said he was hoping the city would devise a plan that would eliminate the moat rather than creating a rain-garden where the moat exists now. Beyond that, he said, anytime there is an overflow of parking at NFA, people are going to park on that rain-garden in front of his home, as they do now, so a plan has to be developed to keep them from parking in that square.
“You have to understand that for 20 years we haven’t had access to the front door of our house,” Brixler said. “And your plan basically creates a permanent obstacle to accessing the front door of my house from Norwood Avenue.”
Moreover, Brixler said he was concerned about the life-expectancy of the proposed alternative since the last project was, by PWD’s own admittance, a “temporary fix.” Perhosky responded by saying that the new plan would be effective for 20 to 25 years, with maintenance, done by the city, occurring at regular intervals.
McCarty said Brixler’s request to eliminate the problem outright was one of PWD’s concerns as well.
“I can’t tell you how many hours we spent trying to figure out a good way to do this,” McCarty said. “It’s a challenging site, and, as Patrick pointed out, to fix all the drainage, without impacting other waterways adversely, which we cannot do, is difficult.”
Another resident of Sunset Avenue asked if there were any plans to combine any of the preliminary alternatives with the recommended plan to solve the issue, such as utilizing the tributary as well as the underground basis.
Perhosky said the size of the footprint PWD was considering, which is larger than what is there now, would maximize the five-year storm, and after that the flows would continue doubling into the tributary. Because of that, they would have to extend the system in both directions and work with private property owners. Additionally, many of the other plans still affect downstream users, cause erosion, and pose a risk to Morris Arboretum, on top of being out of the city’s price range.
“The recommended alternative would be the alternative that we could get done the quickest as well,” Perhosky said. “We’re not saying in the long-term we couldn’t put in a storm sewer, but, to relieve the problems and help out with ponding now, this is the easiest option to implement.”
McCarty said another issue is that Caryl Lane, a private drive, brings a lot of water down onto Sunset Avenue. She said PWD had a consultant examine ways to reduce that volume of water and discovered it would all have to be done by private property owners.
“That’s gone nowhere, apparently,” McCarty said, saying the owners do not get involved as they do not directly benefit by the construction. If a deal could have been reached with those neighbors, McCarty said it “would have reduced some of the volume of water that makes its way to Norwood Avenue.”
One neighbor said that in addition to the problems at the bottom of the street there is still a considerable amount of issues downhill on both Sunset and Norwood avenues and on their properties: There are no culverts, the roads are degrading, the water comes from all directions and washes out across the property. Her wish, she said, was that PWD address this issue for the long-term and cover all of its complexities so as to not only mitigate the small storms but ameliorate the effects of the larger ones.
McCarty said there is stormwater collection along Norwood Avenue, and some of the properties have mended some of the effects of the runoff themselves with culverts. When asked if it was the owner’s responsibility to dig out and fix those culverts, McCarty said, that if they were in the city’s right of way, it would fall into the hands of the Philadelphia Streets Department – if not, it was then up to the property owners themselves.
LUPZ committee member Joyce Lenhardt asked if there was any possibility of installing a stormwater system underneath NFA’s parking lot, if PWD could reach a deal with the school. Perhosky said he believed NFA had a stormwater management facility to deal with private runoff in place already but that PWD would investigate the matter further.
McCarty said PWD would go back to the drawing board, discuss different alternatives with private property owners, including NFA, and see if they could arrive at a solution that covers a majority of the neighbor’s needs.
“As I’ve said a couple times, this is a really challenging location, and we wanted to come up with a solution that meets all of the objectives,” McCarty said. “The alternative that we presented as a preferable option this evening is the one that we think we can do in a reasonable time frame, has the least impact on receiving waters, and will improve the situation. Is it perfect? No, it’s not perfect, but after looking at so many options, this is the one that can be implemented fairly quickly.”
In other news
PWD announced a capital improvement project that would replace water mains throughout Chestnut Hill. Most of the water mains were installed between 1884 and 1907, and PWD needs to replace them every 100-120 years. The project is slated to take place over the course of 250 calendar days.
The areas affected by the construction are: W. Highland Avenue from Seminole Avenue to Navajo Street, Willow Grove Avenue from St. Martins Lane to Seminole Avenue. St. Martins Lane from W. Willow Grove Avenue to W. Highland Avenue, and Seminole Avenue from Rex Avenue to W. Highland Avenue A PWD inspector will be assigned to oversee work along the blocks mentioned.
The anticipated start date is January 2016.