Lost Dobson’s Run: Kelly Drive Flood Relief Improvements Explained

[KELLY DRIVE DRAINAGE IMPROVEMENTS]

Last week, when the Inquirer ran a story about a surprisingly massive ($38 million) drainage improvement project that will snarl traffic just below the East Falls bridges, the region let out a collective groan. For something like six months, Kelly Drive will be reduced to two lanes — severely crimping one of the city’s major arteries. What was lost in the hubbub over traffic was an explanation as to why the Scotts Lane/Allegheny Ave. basin needs better drainage and how new impervious surfaces, development, and insufficient stormwater systems built in the early 20th century make this need acute.

[1868 MAP OF FAIRMOUNT PARK SHOWING DOBSON’S RUN]

A topographical survey of the project area reveals that Scotts Lane lies in a groin between the Boulevard and Allegheny Ave. Respectively, these two roads could be considered the west and east rims of a small canyon formed by an historical creek called Dobson’s Run. Scotts Lane’s is roughly 85ft from sea level (Schuylkill: 32ft) at the point where the road intersects Ridge and Allegheny Aves. At Scotts Lane’s lowest point is Sherman Mills, a complex offering residential/commercial/loft space in an adaptively reused textile mill. Scotts then wends its way up the western side of the ravine and crosses the R6 line (114ft) at grade and continues up into East Falls. Parts of the Sherman Mills complex sit in a shallow depression of about 79ft. Just to the northwest, on the opposite side of Scotts, is a new gated development incorporating new units into the fabric of another mill structure [Dobson Mills]. Scour marks along the sides of the lane and the narrow inlets testify to the velocity of the flow down this grade.

[STORM DRAIN, LOWER SCOTTS LANE]

Superficially, it appears that this project is yet another instance where the taxpayers get stuck holding the bag — paying retroactively for incentivized overdevelopment — yet a historical study of the Dobson’s Run watershed tempers this judgment. As Adam Levine has pointed out in his research for the Water Department, as early as the 1880s the city was grappling with residential and industrial pollution in the sluggish creek.  A notorious offender was Dobson’s Yarn Mill which dumped its dye-colored effluvient into creek, staining the Run’s delta at the Schuylkill just north of the Falls railroad bridges. In 1882, the Superintendent of Fairmount Park Russell Thayer anticipated that more and more industrial waste and sewage would find its way into the Run, a creek which above inhabited portions of Falls Village Thayer noted was “pure”. “Unless the necessary Sewage Works are constructed,” he reported to the Fairmount Park Committee on Plans and Improvements, “the pollution of the [Schuylkill] River will be much greater than at present” owing to the fact that “at some distant date the entire territory through which the stream and its tributaries pass will be more or less covered with buildings of various description.” In the rancorous litigation that followed, Dobson hired his own expert who argued that the sewage from residential cesspools polluted the stream more than the yarn dyeing plant.

[1902 PWD MAP SHOWING SEWERIZED DOBSON’S RUN, NOTE PROPOSED DOTTED LINE CONNECTION]

One of Thayer’s recommendations: to “sewerize” Dobson’s Run and lead the combined stormwater/wastewater flow to an intercepting sewer paralleling the Schuylkill was eventually selected. An intercepting sewer is like a paper towel roll placed perpendicular and beneath another roll. During times of low flow, the combined sewage and runoff fall into the interceptor and is processed. During high flow, engineers accept that the interceptor will be overwhelmed and some combined sewage and runoff will pass into watercourses. It was a calculated gamble based on the new science of bacteriology. As Thayer put it: “The surplus at time of freshet may be allowed to empty itself into the Schuylkill directly opposite the mouth of the run without material injury to the water of the River for drinking purposes.” By 1912 Dobson’s Run was effectively sewerized and connected to an interceptor along the Schuylkill.

[SCOTTS LANE ABOVE SHERMAN MILLS]

Lest we get immobilized by thinking that development has invariably caused watershed problems and there’s no way around it, it’s clear that the present runoff problems are a new animal. According to the Deputy Water Commissioner Debra McCarty, its been the development, the parking lots and driveways, the disturbed and hard-packed soil that has caused the runoff to swamp the early 20th century, 8′ Dobson’s Run sewer. To relieve the pressure in the Scotts Lane basin, the new 12.5′ reinforced concrete tunnel will be constructed to the south and west, roughly along the line of Allegheny Ave. Then it will continue under the quietly reposing bodies of Laurel Hill and to an interceptor and new outfall. Presumably, the “scenic overlook” which PWD has bandied about as the sweetener to the deal will be constructed above the new outfall. Should be the an interesting site come heavy rain.

In some ways, this story is all superlatives: biggest tunnel, largest project in recent history, most frustrating logjams imaginable. And this story is drenched in the can-do spirit of water departments and their contractors. But seeing the project through the lens of the Dobson’s yarn mill, a sort of Groundhog Day-esque scene emerges of city obsequiousness to the needs of private enterprises. For the revenue-generating Water Department, arguably the “least disfunctional” of all city departments, hopefully $38 million isn’t a lot of money to pay to whisk water away from the parking lots of the hip new residential incarnation of Dobson’s Mill.

[FOR MORE SEWER MAPS, CHECK OUT ADAM LEVINE’S SITE http://www.phillyh2o.org/]