OLD DUNDAS ROAD SEWAGE PUMPING STATION (HCOO5) WET WEATHER RELIEF MASTER PLAN AND CLASS ENVIRONMENTAL ASSESSMENT STUDY Final Report Prepared for: CITY OF HAMILTON 440 – 77 James Street North Hamilton, ON L8R 2K3 Prepared by: AQUAFOR BEECH LIMITED 260 Skymark Avenue Building 6, Suite 202 Mississauga, ON L4W 5B2 October 15, 2014 Reference: 65420 EXECUTIVE SUMMARY INTRODUCTION Aquafor Beech Limited has been retained by the City of Hamilton to undertake a Master Plan and Class Environmental Assessment (EA) for the Old Dundas Road Sewage Pumping Station. The pumping station was designed and constructed in the 1970’s and services an area of approximately 180 hectares (See Figure ES.1). The area is serviced by a separated sewer system, however field investigations showed that stormwater and groundwater infiltrate into the sanitary sewer system. As a result of the excess infiltration/inflow, the sanitary sewer system and Old Dundas Sewage Pumping Station are unable to convey flows during significant precipitation events. As a result basements in the area have flooded several times in recent years. City records show that basement flooding was reported in 2005, 2006 and 2013. STUDY PURPOSE The study purpose has been defined as follows: Basement flooding occurs within the Old Dundas Road Sewage Pumping Station (HC005) catchment area during some wet weather events. The purpose of this study is to identify the causes of basement flooding and propose remedial measures to mitigate future basement flooding. MUNICIPAL CLASS ENVIRONMENTAL ASSESSMENT (EA) PROCESS The study, which was initiated as a Schedule ‘B’ project, was revised to follow the Master Plan process in order to provide a more logical approach for providing a strategic level of options to better address overall system needs. This study was completed following Approach 2 under the Class Environmental Assessment process and will therefore address Phases 1 and 2 of the EA process for any Schedule ‘B’ projects that are identified and outline additional work that will be required to implement Schedule ‘C’ projects. PHASE 1 – PROBLEM AND OPPORTUNITY DEFINITION Over the years, the City has undertaken routine maintenance on both the sewer systems and pumping station. However, in recent years residents have reported flooding associated with moderate or significant precipitation events. i In summary the primary problem therefore relates to basement flooding. This study will focus on flooding that is related to overloading of the sanitary sewer system and/or the Old Dundas Road Sewage Pumping Station (HC005). The opportunity includes the development of an integrated solution in order that homes within the study area are provided with a level of flood protection (100 year storm) that meets or exceeds that of other areas of the City. PHASE 2 - EVALUATION OF ALTERNATIVE SOLUTIONS Definition of Existing Conditions A variety of information was collected and reviewed in order to define existing conditions. In addition to collecting and reviewing existing information a significant amount of fieldwork was undertaken in order to better define existing conditions. A summary of the field program is provided below: • Closed circuit television work (CCTV) identified priority locations within the sanitary sewer where significant infiltration/inflow of stormwater and/or groundwater into the sewers occurred. • Wet weather inspection of the system identified priority locations within the sanitary sewer where significant infiltration/inflow of stormwater and/or groundwater into the sewers occurred. Smoke testing identified homes or businesses where stormwater from downspouts or catchbasins was directly or indirectly conveyed to the sanitary sewer system. • Flow monitoring identified the magnitude of infiltration/inflow into the sanitary sewer system for different precipitation events. The Mike Urban Hydraulic/Hydrologic model was then used to establish existing conditions and estimate the degree of flooding for different return period storms (2 year through 100 year). A summary of the findings is provided below: • The analysis showed that the flooding was generally limited to low lying areas adjacent to the Old Dundas Road Sewage Pumping Station, primarily along Old Dundas road and Millcreek Court. These areas are low lying and therefore susceptible to flooding. • The analysis also showed that flooding would occur relatively frequently (flooding in low lying areas would occur for the 2 year storm or greater). ii SEWERSHED AREA PUMPING STATION FORCEMAIN (400mm) SANITARY SEWER CITY OF HAMILTON - ANCASTER AREA FIGURE ES-1: PUMPING STATION SERVICED AREA • The cause of flooding is associated with a high amount of infiltration and inflow into the sanitary system that exceeds design standards. Although there is adequate capacity for dry weather flows the infiltration/inflow exceeds the capacity of the sanitary sewer system as well as at the Old Dundas Road Sewage Pumping Station. • For the 100 year storm approximately 400m3 of infiltration/inflow would have to be removed or stored in order to alleviate basement flooding. EVALUATION OF ALTERNATIVES The alternative solutions that were initially developed to address the problem and associated issues were broadly categorized as follows: • Do-nothing • Private property works • Public property works • Inline/offline storage • Increase Capacity of Old Dundas Sewage Pumping Station • Provide an Emergency Overflow The Do-nothing alternative is traditionally carried forward as a benchmark in the Environmental Assessment process. For the purpose of this study the ‘Do-Nothing’ alternative would essentially equate to maintaining status quo. Private property works would include disconnecting roof downspouts and private catchbasins which are likely connected to the sanitary sewer system. These illicit connections were identified during smoke testing of the system. Improving drainage adjacent to homes is also recommended. Public Property works include sealing maintenance hole covers and chambers and replacing or rehabilitating sewer pipes that are structurally unstable or contribute significant infiltration of groundwater into the sanitary sewer system. iii Inline/Offline storage would provide temporary storage to accommodate flows which exceed the capacity of the sanitary sewer system and/or the Old Dundas Road Sewage Pumping Station. Old Dundas Road Sewage Pumping Station works would include measures to increase storage, pump or forcemain capacity. Provision of an emergency overflow would protect homes from basement flooding for storms which exceed the specified level (100 year) of flood protection. Each of the alternatives were then evaluated against a series of criteria which are broadly categorized as follows: • Natural Environment • Economic • Social and Cultural Environment • Technical and Operational SELECTION OF THE PREFERRED ALTERNATIVE A Preferred Alternative was selected based on the evaluation process. As was noted previously, this project was carried out using the Master Plan approach in order to provide a more logical approach for providing a strategic level of options to better address overall system needs. The approach for this study found that several alternatives were required in order to meet the objective of mitigating basement flooding associated with the sanitary sewer system or Old Dundas Road Pumping Station. Based on the evaluation, three alternatives were found to be the most preferred with one alternative assessed as moderately preferred. iv Collectively, implementation of the Private and Public Property works together with Inline/Offline storage along Old Dundas Road will provide a 100 year level of flood protection against basement flooding for the study area. These works should form the core of the preferred alternative. Implementation of an emergency overflow will provide relief to homeowners who would experience flooding during storms which exceed the 100 year level. For this reason this alternative has also been included as part of the preferred alternative solution. Implementation of this alternative will require completion of Phase 3 and 4 of the Environmental Assessment (Schedule ‘C’). The estimated costs for the components are provided in the accompanying table together with the applicable Class Environmental Schedule. Table ES-1: Summary of Preferred Alternative Solution Description Estimated Cost Municipal Class Environmental Assessment Schedule Private Property Works 1 $30,000 Not applicable Public Property Works $300,000 Schedule ‘A’ Inline/Offline Storage $700,000 Schedule ‘A+’ Emergency Overflow $200,000 to $600,000 Schedule ‘C’ Note: 1- Estimated Costs allocated for outreach and education program only. A conceptual design for the inline storage alternative has been completed and is shown in Figure ES.2. Public Consultation Two Public Information Centres (PICs) were held. The first PIC described the study area, defined problems and opportunities as well as a long list of alternatives and evaluation criteria. The second PIC presented the alternative solutions, evaluation criteria and the preliminary preferred solution. A summary of the findings and input is provided in Sections 4.4 and 6.5. v CITY OF HAMILTON - ANCASTER AREA FIGURE ES-2: INLINE STORAGE CONCEPTUAL DESIGN Schedule ‘C’ Requirements Section 7.2.4 of this report illustrates a conceptual design for an overflow from the existing sanitary sewer system to Ancaster Creek. During the course of this study, contact was made with the Ministry of the Environment (MOE) to discuss