Inflow and Infiltration in New Subdivisions: Giving away Capacity we don t have

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1 Inflow and Infiltration in New Subdivisions: Giving away Capacity we don t have Barbara A. Robinson, M.A.Sc., P.Eng. Norton Engineering Inc. nortonengineeringinc@gmail.com

2 Project History This issue was discovered accidentally in the Region of Waterloo (St. Jacobs: Township of Woolwich) during a routine flow monitoring program in 2007 Subsequently, FM was undertaken at three additional sites; all were demonstrating unacceptable levels of I/I Papers were presented at WEAO in 2010 and WEF in Many other jurisdictions reported similar findings Norton Engineering initiated this project in 2015 with funding from Peel, York and ICLR We currently have data on dozens of sites with the same issue

3 Context: What is Allowable I/I in NS? There is no Allowable I/I in New Subdivisions We have two measurements we can apply: Allowable Leak testing of sewers at construction (average): 0.01 L/s/ha (22 L/c/d) Allowable (peak) long term I/I per MOE Guidelines: 0.10 to 0.28 L/s/ha (212 to 593 L/c/d) Sewers are leak tested (and this doesn t always occur) once sewers and laterals to property line are constructed MOE Guidelines are for sizing sewer infrastructure: they are meant to size sewers for their life, e.g. long term I/I

4 Micro-monitoring Required to Identify

5 What should Subdivision Flows Look Like? A nice two hump diurnal pattern. No response to rainfall. Flows at night drop to almost zero.

6 What did we Find? 120 houses: Leaking at P/L

7 More of What we are Finding Nearly 350 L/c/d (Population 3421) NO homes!

8 More of What we are Finding This is at a PS: It runs continually during rain events NO houses! NO houses; 4.5 L/s/ha

9 What are the Causes? These have varied significantly, but we have found: Standard issues on the public side, including offset joints, poor connections at MH, MHs leaking, poor connections at lateral to mainline (not all were identified on CCTV) Rehabilitated sewers leaking again after a few years Poor connection of lateral at property line (different sized pipes, glue that didn t set, offset joints) Stake driven through a lateral Indoor plumbing issues: removal of cleanout caps by builder, plumber or homeowner Drainage of excavations during construction (very common)

10 More of What we are Finding These are brand new sewers

11 More of What we are Finding Most homes built in this drainage area were built in the 2000s

12 It Gets Worse This is incredible: These are brand new sewers D/S of a pumping station Brand New Sewers: Flows at PS (peak shaved!)

13 Potential Costs of I/I (flooding) I/I may costs may include: Treatment costs; lost capacity in trunk sewers; lost opportunity costs (development capacity); administration (staff) costs; insurance claim costs Not included are the risks to homeowners of denial of insurance, increased premiums, and capping of payouts The present value of a single 1 L/s of I/I, over a 40 year life (before scheduled rehabilitation of a sewer), is $1,000,000 (@ $1.50/m3 and 3%), for treatment costs alone

14 What I/I Ranges Look like on a Graph

15 What are the Issues Here? Acceptance Testing of New Sewers takes place once trunk and laterals to property line are constructed, before some problems develop If CCTV is done in the dry, deficiencies are harder to detect When homes are connected the connection is supposed to be checked by City staff, but practically speaking, this doesn t always happen (limited staff) Building Department staff issue Occupancy Permits but aren t necessarily aware of I/I issues Plumbers have been known to disconnect sump pump and positively connect sump to sanitary We don t have an Acceptable I/I in New Subdivisions number

16 Recommendations Communication with Industry: most municipalities do not check for I/I in New Subdivisions; those who do usually find it!! Find a regulator mechanism or framework to allow municipalities to protect themselves from this I/I We are working with MOECC, MMAH, the insurance industry We need to return this risk to the developer, where it belongs