Influent Bar Screen Design and Construction Administration

The Lower Perkiomen Valley Regional Sewer Authority’s 14.25 million gallons per day (MGD) wastewater treatment plant (WWTP) in Oaks, Montgomery County had a problem.   The existing channel grinders at the headworks of the plant, in the influent pumping station building, were not providing sufficient reduction of raw influent solids.   Long, thin strips of rags were getting through the grinders and clogging up equipment and impacting downstream treatment processes at the WWTP.

G&A designed the solution.  

The existing four (4) channel grinders are currently being replaced with two (2) mechanically cleaned, fine bar screens.  The project preconstruction meeting was recently held in February and construction will soon begin and continue during 2016.

The project consists of alternating demolition and installation of the new bar screens (to maintain plant operations), construction of a new bar screen building, and associated site work.  G&A based our design of the new bar screens on the FlexRake® Model manufactured by Duperon, Inc. of Saginaw, MI.   The Duperon bar screens will more efficiently remove objects from the plant’s influent flows, such as rags, as compared to the existing channel grinders from the plant’s influent flows and project downstream treatment processes. The Duperon equipment was selected for its ability to remove objects from influent flows to the WWTP, as well as its durability.  

Please take a few minutes to watch a YouTube View on how the Duperon FlexRake® Bar Screens Work:  https://www.youtube.com/watch?v=YM8AY2uRGvo

Duperon FlexRake

To accommodate the new bar screens, G&A designed a new bar screen building with associated dewatering of screened material, collection of the screened material for disposal, and reworked site grading and drainage in order to expand the existing access road for new truck traffic.   Each component of the project had to match with existing conditions at the influent pump station building, both in terms of functionality and operation, while also visually matching the existing building.     

Since the new bar screen building is to be constructed on top of the existing concrete roof slab, almost 36 feet above the influent channels below, G&A subcontracted a geophysical survey using ground penetrating radar technology to locate rebar and electrical conduits in the existing roof slab and the concrete beams beneath the roof slab.  This allowed avoidance of existing features in the design of the proposed building wall dowels and connections to the existing roof slab.

Gilmore_Oaks_P1 - GEOPHYSICAL

The project also involved G&A’s Structural, Land Design, and Construction Observation Departments, and highlights G&A’s ability to design solutions for existing wastewater infrastructure, which will become increasingly necessary as sewage collection and treatment systems continue to age.  

The project team included the following:  

Water/Wastewater Department – William Dingman, P.E., Hyon Duk Shin, P.E., Matthew Bailor, E.I.T., CHMM, and Zachary Johnson, E.I.T.
Structural Department – Roman Jastrzebski, P.E. and Surinderjit Kler
Land Design Department – Sharon Dotts, P.E., CPESC
Construction Observation – Bill Pierce
Electrical Engineer – Tangibl, LLC
Geophysical Survey – TPI Environmental, Inc.

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