Project Overview
The project consisted of rehabilitation design of approximately 16,930 feet of 18-inch and 36-inch diameter sanitary sewer. The alignment of the sewer runs from the east side of Walled Lake in the City of Walled Lake, around the north and west sides of the lake to the southwest, ending at the Walled Lake-Novi Wastewater Treatment Plant (WLN WWTP) in Novi, Michigan. The sewer owner, Oakland County Water Resources Commissioner (OCWRC) awarded the engineering design project to NTH Consultants, Ltd after reviewing our qualifications and experience with similar projects.
Project Scope
The initial tasks for this project included a review of available historical design information and CCTV inspection videos and reports to understand the existing defect types and locations of sewer deterioration and to prepare prioritized repair recommendations for the observed defects. NTH also made site visits to each manhole along the alignment to determine the existing site conditions, access limitations, traffic patterns, and potential resident and business impacts.
Using the data from the available record drawings, NTH then prepared a set of plan and profile drawings of the sewer. In addition, the existing critical repair defects were shown on the sewer profile based on the findings from the review of the CCTV inspection data.
During development of rehabilitation plans for the observed defects, NTH determined that a spot repair program consisting of chemical grout leak sealing and localized debris removal at tap connections would provide a significant cost and schedule savings for OCWRC when compared to a lining program. NTH is currently in the process of developing Contract Documents including design drawings and specifications and will also assist with permitting, bidding, and construction engineering services as the project progresses.
Client Benefit
NTH reviewed the available data and created a rehabilitation plan consisting of a leak-sealing and spot repair program to extend the service life of the sewer while reducing the construction costs and schedule associated with a traditional lining program. The spot repair alternative approach to rehabilitation design reduced the construction schedule / cost and the community impact by limiting the time spent at each manhole to rehabilitate the sewer.
