E. coli Reduction in Storm Sewers – Investigation, Rehabilitation & Monitoring Results

Introduction:
GM BluePlan Engineering Limited (GMBP) was retained by the Town of Niagara-on-the-Lake to complete an investigation in two urban watersheds containing seven storm sewer outfalls with elevated levels of Escherichia Coli (E. coli). The results from the 3-year storm sewer water quality monitoring program are applicable to all municipalities' management of wastewater assets by incorporating condition information and risk management for water protection initiatives. Successful water quality improvement was demonstrated with yearly reduction in E. coli levels ranging from 85-100% at various locations. Project Locations: 1.Site #1 ' Queens Royal Beach storm outfall was flagged by the Niagara River Remedial Action Plan as an Area of Concern (AOC) due to elevated levels of E. coli. GMBP's objective was to reduce the E. coli loading to the catchment through investigation of infrastructure condition on municipal and private property and remedial actions to eliminate and reduce sewage contamination to four storm sewer outlets. The success of this project led to removal of the AOC designation. 2.Site #2 ' Water quality near Garrison Village was monitored from 2010 to 2015 by the Niagara Peninsula Conservation Authority which flagged three stormwater outfalls with high E. coli concentrations. The investigation and rehabilitation process reduced E.coli from 500,000 Human DNA copies/100mL to Below Detection amounts. Project Stakeholders & Objective: Stakeholders included the Ministry of the Environment Conservation and Parks (MECP), Niagara Peninsula Conservation Authority, Environment and Climate Change Canada (ECCC), Public Health, Region of Niagara, and Town of Niagara-on-the-Lake.

GMBP completed the following activities:
1.Developed and implemented a water quality sampling program to understand the existing and post-rehabilitation state of the storm sewer watershed area.
2.Investigated and collected wastewater asset condition information through unique field investigations and existing digital data.
3.Developed a prioritized list of rehabilitation recommendations for infrastructure improvements to reduce E. coli loading to the catchment area.
4.Implemented infrastructure improvements for 'Quick Wins' and short-term recommendations for E. coli reduction and monitored resulting water quality improvement.
5.Developed and implemented prioritized recommendations requiring greater capital budget and implementation time. 6.Provided bi-monthly meetings to convey project progress to all stakeholders. Unique Solutions Implemented: GMBP developed a systematic study approach to identify sources of contamination, sub-catchment areas for improvement, and monitor the subsequent effect of rehabilitation action items.

The following unique solutions were implemented for each project site:
1.Water Quality Sampling using DNA Analysis ' GMBP utilized an innovative water quality grab sample analysis for the storm sewer catchment area. Monitoring was completed bi-weekly for both dry and wet weather conditions. Grab samples underwent a digital PCR analysis which categorized the E. coli to be Gull DNA (Seagulls), Human DNA (sanitary sewer contributions), or Other Animal Source (e.g., horses, racoons, rats, dogs, geese).
2.Prioritizing Assets for Rehabilitation ' GMBP developed an in-house tool (DARRT) to provide a prioritized list of recommended rehabilitation options (open cut, CIPP Liner, Spot Repair, etc.) with estimated costs for each pipe. The DARRT tool uses NASSCO standard PACP or LACP databases to examine every defect to determine each asset's overall condition. This analysis reviews defect type, severity, and proximity across the sanitary and storm systems to assist in identifying high risk areas for water quality degradation in the storm sewers.
3.Unique Field Investigations ' Work included smoke testing, dye testing, investigation during subzero temperatures to identify storm sewer locations with enough heat to emit steam, dry weather flow analysis of the storm sewer network to identify sanitary influence (diurnal flow pattern), and lateral condition assessment from both the mainline and private property. All field inspection results were digitized in GIS and overlaid with CCTV condition inspection data and water quality monitoring results to make data driven decisions for rehabilitation locations and budget prioritization.
4.Improper Connections ' Located and removed improper connections to the storm sewer system which included a wading pool, sanitary lateral and mainline connections.
5.Sanitary and Storm Mainline Rehabilitation ' Work included trenchless technology for sanitary lateral lining completed from the mainline, with open cut for defects which were too large, Ultra-Violet (UV) lining of mainline storm sewers to avoid styrene byproduct to natural watercourses, and manhole structural lining.
6.Fauna Protection ' Inlet and outlet protection of the storm system was implemented using WaStop Check Valves to prevent racoon inundation.
7.Low Impact Development ' GMBP designed and installed a Biofiltration Facility along with Smart Sponge catchbasin inserts which were effective in a 95% reduction in remaining fauna E. coli loading due to runoff from a tourist horse carriage route.

Impact and Future Initiatives:
The success of the project has led to encouragement from MECP to share GMBP's investigation method and findings with other municipalities. Through this process, GMBP has identified: -No regulation for stormwater outfall discharge currently exists in Canada. -No monitoring or sampling required of stormwater outfalls (retroactive approach). -Storm sewer system is typically the first to receive budget cuts. -Storm sewer digital records are typically lacking or incorrect. -Storm sewers are the least likely to have CCTV condition inspection data. -Historical infrastructure practices affecting storm sewer water quality: use of clay material, sanitary assets installed at an elevation above storm assets (risk increase leaking defects), improper connections and no-fill abandoned of historic mainlines which contribute to cross-connection flow between assets.

Closing:
Sewer systems are critical infrastructure and asset management through regular inspection and maintenance will detect issues, improve operational efficiencies, and enable planned improvements before defects result in system failure. Essential to this process is establishing and maintaining accurate records which provide the basis for making data driven decisions and support timely allocation of adequate funding. Storm sewers have a greater risk to discharge human waste directly to natural watercourses if upstream assets are not properly maintained. As the climate changes, with increased likelihood of more frequent and intense rain events, it is imperative that infrastructure is managed effectively to avoid the social, environmental, and economic costs related to water quality degradation. These suggested practices are an investment in system resiliency through inherent improvement of system knowledge, operation, and condition.