Case Study: Emergency Sewer Force Main Rehabilitation in Valley Forge National Historical Park
Susanne Lockhart, P.E., Senior Project Manager
CH2M (now Jacobs), Philadelphia, PA
Stephen Burgo, Township Engineer
Tredyffrin Township, Berwyn, PA
Tredyffrin Township faced three catastrophic failures of a 30-inch Prestressed Concrete Cylinder Pipe (PCCP), the Wilson Road Sewage Force Main (WRFM), between 2012 and 2014. The second and third failures occurred only 42 days apart affecting a major intersection near Washington’s Headquarters in Valley Forge National Historical Park. The majority of pipe is located within the national park, and the pipe alignment also parallels Valley Creek, which is an exceptional value trout stream. The compromised pipe alignment is also adjacent to Washington’s Headquarters, which is one of the most culturally sensitive and valuable areas of the park.
The stakeholders ranged from regulatory agencies, citizen groups, to the five other communities (Partners) that discharge to the WRFM via the upstream Valley Creek Trunk Sewer (VCTS) interceptor. The Township proactively entered into a voluntary consent decree with the Pennsylvania Department of Environmental Protection (PA DEP) to ensure a solution was reached in a timely manner given the complex stakeholder environment. PA DEP also required the Township to take a regional approach to capacity and facility planning for the future capacity needs of the VCTS service area and document that effort in an Act 537 Supplemental Document that requires adoption by the VCTS Partner communities.
This presentation includes an overview of pipe failure risk reduction actions and field assessment for contributing factors to the pipe failures. The assessment work included pressure monitoring, hydraulic modeling for surge, soils analysis for corrosive soils, and forensic materials testing.
Additionally, we will review the decision process that led the Township to pursue Compressed Fit Lining as the rehabilitation methodology of choice for the Wilson Road Force Main. The goal was to identify a “tried and true” method that was cost competitive, trenchless and preserved or increased capacity within the existing 20-foot easement running through the national park.
A single bypass of the entire force main allowed the Contractor to closed circuit televise (CCTV) the two Schuylkill River siphon crossings. Surprisingly, the downstream siphon was 40% occluded with debris. The inspection identified areas of missing interior mortar and visible corrosion. Rehabilitation of these two siphons has commenced. A critical factor was the existing geometry of the siphons require strategic excavation.
By the close of 2016, the project was complete. This project has been an exercise in working quickly and decisively with commitment from the project team to make this project successful.
Susanne Lockhart is a senior project manager with CH2M (now Jacobs) for the past five years working on a variety of projects from CMMS implementation to conveyance projects. Prior to working for CH2M, Ms. Lockhart worked for county government in Maryland as the lead engineer for Utility Operations for 10 years participating in design, construction, start up and operation of projects from elevated storage tanks to force mains, pumping station upgrades, water and wastewater treatment plant expansions and process upgrades including enhanced nutrient removal using membranes. Ms. Lockhart is licensed in Maryland, Delaware and Pennsylvania and has worked in both public and private sectors on the east and west coasts of the US. Ms. Lockhart’s primary focus is conveyance projects most notably condition assessment and rehabilitation of pipelines.
Experience in the area/subject of your presentation: Recently Ms. Lockhart was the project manager and engineer of record for a complicated, high profile force main rehabilitation in Valley Forge National Park for a municipal client. Ms. Lockhart has worked on numerous conveyance project design, rehabilitation and construction throughout her career.
This seminar does qualify for 1.0 Professional Development Hour (PDH). A Certificate of Attendance will be available on site for AWRA-PMAS members only. The meeting price for non-members who wish to receive a Certificate of Attendance for the PDH is $10.00 ($3.00 for meeting + $7.00 for certificate).
Please note: all lunch orders will close by noon on the day before the presentation. In addition, all lunch orders will need to be paid for online by this time. We are unable to refund the cost of lunch or meeting fees because they are paid ahead of time based on number of registrations. Registration begins at 11:30am with the presentation starting promptly at 12:00pm.