One of my favorite responsibilities during my academic career at Pitt has been coordinating the Civil Engineering Department’s Senior Design Project program. In this program each Senior, in his/her last semester, is required to participate as part of a multi-discipline team in a challenging “near-real-world” design project.
This semester two of our seven teams performed major projects relevant to the Bridgeville area – remediation of flash flooding in the McLaughlin Run watershed and expansion of the Bridgeville Area Historical Center History Center. The quality of their work on these two projects was impressive.
The June 20, 2018 McLaughlin Run flood, which covered Baldwin Street with eight feet of water, was the focus of the first team’s efforts. It is well known that flooding in this watershed has been aggravated in recent years by commercial and residential development; the key to understanding its consequences was the development of a mathematical hydrologic model of it.
This they did using the Army Corps of Engineers HEC-HMS software package. It provided them with the capability of predicting the volume of storm-water runoff in McLaughlin Run for any arbitrary combination of rainfall intensity and duration. Separately they were able to calculate the carrying capacity of the channel at any point, including the six places where it passes under bridges or through culverts in Bridgeville.
Their study confirmed that the high density short duration event (two and a half inches of rainfall in an hour in June) produces a more severe flood than the longer, bigger event (seven and a half inches in three days in September). It predicted a maximum flow rate of about 1,500 cfs (cubic feet per second), very close to the theoretical carrying capacity of the channel under the bridges if they were clear of debris. For comparison, flow in Chartiers Creek averages about 200 cfs between storms; it peaked at 8,000 cfs on June 20.
In recent years new developments have been required to make provision for temporary storage of surplus runoff to minimize the impact of heavy storms. This is typically done with retention ponds or buried storage tanks. Unfortunately, this occurred much too late for the McLaughlin Run watershed; South Hills Village and Upper St. Clair High School are two examples of unrestricted runoff that contribute greatly to the floods on Baldwin Street.
The team concluded that this is a watershed problem that is magnified on Baldwin Street. A proper long-term solution would be the installation of a series of retention ponds scattered along the length of McLaughlin Run. They estimated that the volume of water in the Baldwin Street neighborhood was about fifteen Acre-feet; half a dozen one acre retention ponds would be sufficient to contain that volume.
This would require cooperation by all three communities in the watershed, a highly unlikely event. Consequently the team decided that they should focus their efforts on solutions that were within the control of Bridgeville Borough.
These include improvement of the McLaughlin Run channel within the borough limits, the addition of trash racks to keep debris from plugging the passageway through the bridges and culverts, and the necessary modifications to make the baseball field in McLaughlin Run Park function as a detention pond.
In addition, they studied a different problem, the discharge of polluted AMD (abandoned mine drainage) water into the creek. Their recommendation was that it be piped separately to a passive remediation site in the old Chartiers Creek channel, much as a previous team had proposed for the Scrubgrass Run AMD site in Scott Township.
As part of their investigation of the problem, the team attended a meeting of the Bridgeville Planning Commission at which a representative of an environmental services company recommended condemning all the properties in the Baldwin Street neighborhood, demolishing them, and converting the area into a massive detention pond, a recommendation obviously unacceptable to a group of competent engineers.
The short-term plans to remediate the problem that were presented by Borough Manager Lori Collins were generally similar to the team’s recommendations. Her report of early discussions with Upper St. Clair and Bethel Park also suggested the proper long-term solutions might eventually be implemented, permitting the Baldwin Street neighborhood to survive and prosper.
Recently the Bridgeville Area Historical Society began preliminary discussions with a representative of a beneficial foundation regarding a proposed expansion of the History Center to house a permanent exhibit dedicated to George Washington’s seven visits to Western Pennsylvania in the eighteenth century.
The foundation’s response to a letter suggesting this possibility was the request that the Society prepare a formal proposal, complete with a tentative design, estimate of cost, and construction plan.
The preparation of this detailed information was a perfect project idea for one of our teams. The five students who formed the team attacked the problem enthusiastically and did a fine job of producing the necessary documents.
Their starting point was an architect’s concept drawing of an extension to the north wall of the existing Center. Their job was to convert this general concept into reality – “bricks and mortar” is the popular expression; “studs and nails” would be more appropriate for this case.
A conventional Senior Design project team would have confined its efforts to the detailed design of the new building – member sizes and locations, methods of connecting them, etc. – and estimating its cost. This the team did quite professionally.
However, they elected to function as an overall design and construction company and to modify the concept design to reflect the Society’s wishes and to explore a number of non-technical issues. They visited the Center on numerous occasions to interview Society members and even attended a meeting of the Society’s Expansion Committee and Board of Directors to obtain a first-hand knowledge of their aspirations.
The concept drawing included a basement under the expansion, with an external stairwell leading to it, providing well needed storage space for the Society. After hearing serious concerns about problems with transient vagrants, the design was changed to include an internal stairway.
ADA (Americans with Disabilities Act) considerations and requirements to follow historical preservation guidelines (the Center is an Historical Landmark) also significantly affected the design. An unexpected discovery of a gasoline monitoring station that must be relocated added to the cost of the project.
Their final product was a full-fledged bid package containing sufficient information for a potential construction firm to provide a proper price for performing the necessary work. It includes a full set of design drawings, a bill of materials, and a description of the work to be performed. In addition, they provided the Society with a detailed estimate of the cost of the construction, including allowances for acquisition of property, relocating the monitoring station, and tying into storm sewer system.
As a result of their work the Expansion Committee is properly equipped to evaluate this proposal and make a recommendation to the Board of Directors. My personal opinion is that this is indeed a worthwhile project that would provide a meaningful asset to the historical community in Western Pennsylvania. It has a reasonable chance of being seriously considered by the foundation. Implementing the project requires a major commitment by the Society to maintain and staff it, a commitment of which we octogenarians cannot be a part.
This was my last term as coordinator of the Senior Design Project program; I was pleased with the performance of the seven teams and especially the two who implemented the Bridgeville projects.