Sanitary Sewer Collection System
Briar Chapel, Herndon Woods
During the development of the large Briar Chapel residential development in Chatham County (near Chapel Hill), residents in a nearby mature neighborhood (Herndon Woods) were experiencing failing septic systems, and expressed the desire to connect to the sanitary sewer system being constructed to serve the Briar Chapel development. The Briar Chapel developers agreed to provide Herndon Woods with a sanitary sewer collection system for approximately 30 homes, and to treat the sewage at the on-site Briar Chapel Reclamation Facility and discharge it through Briar Chapel’s reclaimed water irrigation system. The connection of the Herndon Woods wastewater to the Briar Chapel wastewater collection and treatment system posed several challenges, including minimizing public nuisance, addressing public concerns, environmental impact and NCDOT coordination, while minimizing capital costs.
In addition to completing the entitlement and initial design and permitting for the Briar Chapel development, along with the associated wastewater infrastructure, McAdams provided the survey, design and permitting for the new Herndon Woods sanitary sewer collection system. The goal of the survey was to obtain accurate topographic information and to accurately locate the residences, property lines, driveways, septic tank locations, significant trees and plantings, existing utilities (water, electric, gas, cable, etc.) and any other existing elements that could impact the design of the proposed sanitary sewer system. As part of this effort, McAdams’ environmental scientists also flagged wetlands and stream buffers and the flagging was located during the field survey.
Prior to beginning detailed design, McAdams participated in several neighborhood meetings to identify and understand concerns that the Herndon Woods residents had in regards to the proposed sanitary sewer system. Since the roads within Herndon Woods were maintained by NCDOT, McAdams met with NCDOT to discuss the alignment of the sanitary sewer collection system within the NCDOT right-of-way and under the pavement. With the field survey information and with an understanding of the resident and NCDOT concerns, McAdams designed a collection system that minimized damage to existing infrastructure, avoided or minimized wetlands and stream buffers, and minimized impacts to landscape features that were valuable to the residents. The collection system was primarily gravity, but during the design process, McAdams determined that by collecting a portion of the neighborhood sewage with a low pressure system, a more cost effective design would result. The final collection system included 15 grinder pump stations, a 180 gpm pump station, and 4,745 linear feet of 2-inch to 8-inch piping to convey the collected sewage to the reclamation facility. McAdams completed the permitting for this collection system as well as the necessary permitting for the minimal wetland and stream buffer impacts. McAdams also provided construction administration services to ensure that the system was installed per the approved plans.