CSA W204:19 Flood resilient design of new residential communities

CSA W204:19 Flood resilient design of new residential communities. 7 Sanitary sewer design 7.1 Sewer backwater protection Sewer backwater protection shall follow Clause 6.8 of CSA Z800, as well as the following: a) Downspout, foundation drain, and sump pump discharge should not be directed to the sanitary sewers. b) The design of sanitary sewers should include an I/I WWF rate of at least 0.3 L/s/ha in addition to sanitary dry-weather peak flows. c) Sanitary sewers should be designed to operate without surcharge under the design event, as specified by the local jurisdiction. d) Under extreme I/I conditions, the HGL in the sanitary sewer shall be 0.30 m below the underside of footing (USF). Note: When designing for an extreme 100-year return period, 0.5 L/s/ha may be considered (or even higher in areas with high groundwater). 7.2 Hydraulic design of sanitary sewer The hydraulic design of the sanitary sewer system shall follow the same considerations as outlined for the minor system under Clause 6.6.3.1. 7.3 Incomplete sewer infrastructure During the construction of new development phases, measures should be taken to minimize the possibility of excessive flows, for example, from overland runoff, being discharged to downstream sanitary sewers. 7.4 Manhole surface inflows to sanitary sewer The following requirements and recommendations apply: a) Where possible, sanitary sewer manholes should be located outside of sags. b) For any sanitary sewer manholes located in sags, seals shall be used around all joints to reduce inflow into the sanitary sewer system. 8 Wastewater pumping stations 8.1 Wastewater pumping station designs shall include the following: a) The HGL in the sanitary sewer shall be evaluated under the extreme condition event assuming that the station is operating at full capacity. b) In anticipation of a potential catastrophic failure of a wastewater pumping facility, a gravity-based emergency/overflow conduit shall be evaluated as a “last line of protection” against flooding. c) The elevation and hydraulic capacity of emergency overflow connections shall be optimized to minimize the risk of flooding due to sanitary system backup. d) Emergency/overflow conduit connections shall be provided with suitable protection to prevent backflow from the flow receptor into the pumping station. This may consist of backwater valves and/or shut off valving. CSA W204 pdf download.