NYCDEP, NYC Assessment of Intercepting Sewers with Grade 5 Pipe Index

Posted on July 17, 2014

Client: New York City Department of Environmental Protection
Location: NYC, New York
Project Period: 2011- 2012
Project Cost: $56,000,000

Project Description

D&B Project Responsibilities

Grade5SewersThe New York City Environmental Protection (NYCEP) is responsible for the operation of the City’s 14 Water Pollution Control Plants (WPCP) located throughout New York City. Pursuant to their State Pollution Discharge Elimination System (SPDES) Permits, 13 of these plants must control wastewater and storm water discharges. Throughout the New York City sewer system, significant lengths of interceptors were identified as having structural defects and could possibly fail within the next 5 years. This project assessed and identified corrective actions to address structural deficiencies and diminished capacity.

D&B reviewed over 40,000 feet of CCTV tape of interceptors in 11 sewersheds throughout the City, and as-built drawings for selected segments of the interceptors in the Port Richmond, Rockaway and Hunts Point service areas. D&B assessed the internal condition based on the procedures detailed in the NASSCO’s Pipeline Assessment and Certification Program (PACP). D&B determined that the common structural defect seen in these sewer segments was corrosion of the sewer fabric above the normal flow level. The defects ranged from surface corrosion to exposed rusted rebar.

dep sewersD&B developed a methodology to rank the segments from “worst” to “least” defects for the purpose of prioritizing rehabilitation/reconstruction actions. D&B’s analysis prioritized 13,500 linear feet of interceptors in the Port Richmond West Interceptor, Rockaway East Interceptor and Hunts Point Interceptor for rehabilitation.

D&B evaluated Sliplining, Cured-in-Place-Pipe (CIPP), Lining with Pipe and In Situ Coating to rehabilitate the interceptors. Other factors taken into consideration when evaluating rehabilitation methods for the interceptors in New York City include the interceptor size, flow, shape, access and location. Based on these factors and the structural defects found, D&B recommended that CIPP for pipe diameters of 48 inches or less and gunite and epoxy coating for the larger pipes.

Based on the recommended rehabilitation methodology D&B developed rehabilitation costs for 30,000 linear feet of interceptors within the 11 sewersheds.

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