Town of Nantucket Capacity, Management, Operations, and Maintenance (CMOM) Program
The Nantucket Sewer Department (NSD) operates two collection systems, totaling approximately 70 miles of gravity sewers, that convey wastewater to two separate treatment plants on the island. Due to a sanitary sewer overflow (SSO) that impacted waters of the United States, the EPA and MassDEP issued an Administrative Order on Consent that required NSD to create and implement a Capacity, Management, Operations, and Maintenance (CMOM) program to mitigate the risk of future SSOs.
The Hazen team developed the CMOM program from the ground up, which included developing a CMOM Program Manual, performing an infiltration and inflow study, developing a hydraulic model to assess system capacity, assisting with closed circuit television inspections of collection system assets, and developing rehabilitation recommendations for pipes and manholes.
Hazen worked closely with the NSD to develop a thorough Program Manual that documented protocols and organization of the department, while concurrently working with a third-party contractor to perform the condition assessment of approximately 100,000 linear feet of pipe and all associated manholes. To streamline this process, Hazen employed the use of several technology applications to minimize data transfer and provide real-time information on progress and results to the client.
An ESRI framework was established early on, and ArcGIS online was employed for monitoring CCTV progress and tracking recommendations for sewer infrastructure repair/replacement. Access to this mobile application, along with the use of Collector and Survey 1/2/3 applications, allowed the Town, Contractor and the Hazen team to stay coordinated in real time throughout the project. In addition, a Microsoft Power BI dashboard was developed to distill all the work being performed in the field into a digestible, dynamic interface showing work progress and recommendations.
A Power BI report on manholes and our recommendations for rehab and replacement.
A snapshot of the Power BI report for CCTV progress. The pie charts show discrepancies between existing GIS and the CCTV data. The gauge on the right shows that 95,913 feet of pipe were inspected (out of the total 37,0877 feet of pipe) as of the reporting date.
After performing CCTV inspections, the contractor would upload all videos and reports to a Bentley’s ProjectWise, a data storage platform. The contractor, Hazen, and client all had access to this application and could view videos and reports in near-real time. The use of ProjectWise and GIS eliminated the need for exchanges of hard drives and cumbersome spreadsheets, while providing real-time data access to the client.
After performing the condition assessment of the first 100,000 linear feet, Hazen was contracted to create design documents based on the initial rehabilitation recommendations. Hazen developed three construction contracts to address the various type of recommendations. The two primary categories consisted of trenchless (CIPP, short liners) and open cut excavations for full length pipe replacement. The first of these three contracts will focus on trenchless rehabilitation and was bid in February 2020.
The next phase will be to finalize design of the two open cut contracts, as well as continue to update the Program Manual as more information becomes available and changes take place within the NSD.
Project Outcomes and Benefits
- Data was made available to client in real-time.
- Modern technology applications selected eliminated the use of cumbersome spreadsheets and hard drives.
- Many structural defects were identified, and the design of their repairs has been completed.
- Developed a strong CMOM program to satisfy the initial conditions of the AOC.
- Results of this program will allow the NSD to continue to provide excellent service, mitigate SSOs, and will allow the NSD to complete their obligations to the EPA and MassDEP under the AOC.
