I was particularly interested in the October meeting of the Bridgeville Planning Commission as recorded on the Bridgeville.org website, and continue to be impressed with the power this medium has for connecting the general public with the workings of local government. The combination of clear, easy-to-read slides and individual microphones for each participant provides the viewer with an excellent capability of observing the meeting as if he/she were there in person.
This specific meeting dealt with mitigation of flooding in McLaughlin Run and elimination of the devastation it has caused to the Baldwin Street neighborhood. Mr. John Heyl, representing the borough’s engineering firm, Lennon Smith Souleret, presented the result of an extensive analysis the firm has made of this problem, culminating in the evaluation of several alternatives. It is obvious that Bridgeville made the proper decision when they replaced their previous engineer with Lennon Smith Souleret; this study was certainly an excellent example of professionalism.
Mr. Heyl began by reporting on four small projects already completed or underway that are intended to reduce the severity of future floods – the installation of a new, higher wall along Maple Street; dredging the channel through the Commercial Street culverts; installation of a trash rack and lowering the ballfield to collect debris at the McLaughlin Run Park; and installation of an access ramp and flood gate at Jane Way to facilitate getting equipment into the stream bed. All four projects have been fully funded by grants.
He then presented three options for major projects that would eliminate flooding from a one-hundred-year event. By definition, a one-hundred-year flood is an event that has a one percent probability of being repeated in the same year. NOAA (the National Oceanic and Atmospheric Administration) publishes data for rainstorm intensity and probability for each area; these data are used to predict flood intensity for specific watersheds. Using the data Engineers can determine necessary modifications to permit the stream bed to accept storm water runoff without flooding.
Each option was subdivided into three phases. Phase One covered the stream from the Chartiers Creek back channel upstream to the Commercial Street culvert. Phase Two runs from the culvert to the Baldwin Street bridge. Phase Three runs from that bridge to McLaughlin Run Park. Phases One and Three are common for all three options; Phase Two is the differentiator.
One of the lessons learned from the Engineer’s modelling of the stream is that a large sand bar in the old Chartiers Creek back channel is a major contributor to flooding in Bridgeville’s Lower End. Theoretically, proper operation of flood gates where the old channel leaves the new one should have prevented the sand bar from building up, by flushing out the channel each time Chartiers Creek floods. Instead, its existence prevents McLaughlin Run from entering the channel properly, producing flooding. Removal of this sand bar will help mitigation of flooding in the Phase One area.
Phase One primarily consists of the installation of a soldier pile/lagging levee eleven hundred feet long on the north side of the stream bed. The storm sewer along Carol Avenue will be relocated and valves added to two storm sewer outlets to prevent backflow during high water events. The anticipated cost of this phase is about four million dollars. Mr. Heyl commented that moving this neighborhood out of the FEMA (Federal Emergency Management Agency) flood plain will dramatically reduce flood insurance for its residents.
For Option One, Phase Two is estimated to cost about fifteen million dollars and to require the condemnation of four properties. It includes replacement of the Bower Hill Road and the Baldwin Street bridges with new structures providing sufficient space beneath them to provide the capability of each to handle the one-hundred-year runoff without initiating flooding.
Soldier pile/lagging levees will be installed on both sides of the stream bed, high enough to contain the anticipated flood levels. Bower Hill Road will be completely reconstructed, including the installation of stable subgrade beneath it. The sidewalk along Bower Hill Road will be eliminated, with Baldwin Street becoming an alternate route for pedestrians.
For Option Two, Phase Two is estimated to cost about thirteen million dollars and to require the condemnation of six properties. It proposes converting Baldwin Street into a one-way street terminating in a cul-de-sac, with a pedestrian bridge over the stream replacing the vehicular bridge.
Phase Two for Option Three is unique. It envisions eliminating Bower Hill Road completely, as well as most of the properties on the northeast side of Baldwin Street. The Bower Hill Road and Baldwin Street bridges would be replaced with structures capable of handling the flood water. A round-about would replace the current Baldwin Street/ McLaughlin Run Road intersection. This option is estimated to cost about seventeen million dollars and require the condemnation of thirty-seven properties.
Phase Three consists primarily of the installation of a soldier pile/lagging levee eight hundred feet long on the south side of the stream bed. The anticipated cost of this phase is about two and a half million dollars.
The discussion that followed the presentation covered several topics – funding sources, consideration of a detention basin upstream in Upper St. Clair Township, and responsibility for maintenance of the Chartiers Creek back channel. I was disappointed that the subject of the acid mine drainage that pollutes McLaughlin Run was not included.
Two years ago a Senior Design team I mentored at Pitt studied the specific problem of McLaughlin Run flooding. I am impressed with the similarity between their recommendations and the ones presented in this meeting. Our team failed to recognize the significance of the sand bar in the Chartiers Creek back channel.
It is encouraging to see the high level of professionalism displayed by the Engineer and by the Planning Commission in discussing this recurring situation. The first step to resolving any problem is understanding it; that appears to be well under way.