PLWC engagedCrist Engineers, Inc. to provide a preliminary engineering report and final design for improvements to their wastewater treatment plant to include a new headworks facility.

The project involved evaluating decommissioning the existing screen, washer and compactors, and grit removal system and provide new equipment capable of complete redundancy that can screen and remove grit to process and peak flows diverted to the equalization basin. Current configuration did not screen or remove grit for peak flows diverted to the equalization basin.The Crist team evaluated influent SCADA data of depth stage and volume of the equalization basin to determine the historical peak flow of record.

The process peak capacity is 6 MGD. The peak flow wet weather capacity is 36 MGD. The preliminary evaluation included evaluating verticalclimbing screen of various openings and channel requirements to address peak flow conditions. Provisions wereincluded to hydraulically flow 52 MGD to the equalization facility.

Two types of grit systems were evaluated: 1) mechanically inducted vortex, and 2) structured flow vortexwith a target 95% capture of grit >105 micron (140 mesh).The design included a three channel 18 MGD capacity, each and two 18 MGD capacity, each mechanical vortex grit removal units. Process will treat 6 MGD with the balance of the flow that is screened and degritted flowing to the equalization basin.

To abate inflationary and time delivery concerns, the Crist Team assembled equipment procurement contracts for screens, grit removal, slide gates, and yard piping during the NPDES permit review not to delay contractor lead times.