The Ripple Effect of a Sewer Diversion Project: A Case Study of the Lady’s Island Sewer Diversion

Last Modified: Jan 31, 2019

Authors:

  • Leon Fanning - Hazen and Sawyer

This presentation will discuss the background and design of the Lady’s Island Sewer Division project for Beaufort-Jasper Water & Sewer Authority (BJWSA). The purpose of this presentation will be to highlight the design considerations and decisions made to allow diversion of flows from the Lady’s Island sewer system to remove load from the existing St. Helena Wastewater Water Treatment Plant (WWTP) to the Port Royal Island Wastewater Reclamation Facility (PRIWRF). The ultimate goal is to capitalize on available effluent disposal capacity of the PRIWRF to assist with St. Helena WWTP operations.

The two sewer systems were isolated physically from one another by the Beaufort River requiring significant improvements to the sewer system to allow conveyance to the adjacent sewer service area. Force main improvements were provided as part of the project to allow conveyance of this flow to the existing service area for ultimate conveyance to the PRIWRF.

The additional flow to the Port Royal system required additional capacity at BJWSA’s SS01 Pump Station. The retrofitted pump station would operate as a regional flow conveyance flows from the Lady’s Island Sewer System as well as flows local to the station. Flows from the SS01 Pump Station manifold into a common force main for conveyance to the PRIWRF. A suction-lift style pump station was selected to provide this service and provide consistent operation to other pump stations within this service area.

Design of the modified SS01 required coordination of several site restrictions. For one, the site was limited to approximately two-tenths of an acre (0.2 ac) and included an existing pump station that required continued operation throughout construction. In addition, the site included critical area that limited facility layout and required significant permitting to allow construction. Additionally, the proximity to critical area posed a great risk of flooding to the site. Provisions were included within the facility to maximize resilience to operations during flood events. Lastly, the site was in a conspicuous location adjacent to numerous property owners requiring the design to account for the general appeal of the area and more importantly, limit noise to adjacent property owners.

For more information, please contact the author at lfanning@hazenandsawyer.com.

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