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Recently we have been pressured by some to required developers to include LID features into their subdivisions. However, we have resisted as;

Soil depth is generally shallow – 0.5 to 1.0 m cover over rock

Low slope swales lead to ponding in rear yard swales which owners find unacceptable

LID features located on private property would require maintenance and we do not want to be on private property maintaining the features.

Is anyone familiar with LID? Has it been successful? What is the LID subdivision like 10 years later? What does the maintenance/bylaw staff think of LID?

Paul Knowles P Eng
Town of Carleton Place
Hi Paul,

LID implementation is very much dependant on your underlying soil conditions and if you have a significant amount of bedrock it may not work as ideally as one would want.

CVC (Credit Valley Conservation) and the Region of Peel have some great information available on LID implementation. Unfortunately none of the participating area municipalities in the group have had enough experience with LIDs to comment on how they operate 10 years later, or what Operations and By-Law staff thoughts are.

I would suggest reaching out to CVC for further information.

Andrea Dale
Town of Whitby
In Wasaga Beach, we have been specifying LIDs via roof leader soak away pits and shallow gradient swales with infiltration trench (perforated subdrain and geotextile wrapped clearstone trench under swales less than 1% gradient) for infill lots and in some cases, subdivisions since 1999; I am not aware of issues with these items. Bear in mind however, that we did not look at these as "LIDs" back then, it was simply a requirement because the Town is so flat and in a lot of cases there are / were no roadside drainage systems, so the water simply had nowhere else to go after building infill lots but into the ground. I also note that WB is predominantly sand, so the surface water is able to infiltrate quite easily.

We have also had Site Plan applications use underground storage and infiltration with products like ADS Stormceptor, for which I am also not aware of any long-term issues with these.

One very recent POTL subdivision (roads built in 2016) is the first we have will full LID methods for SWM control. They have stacked storm sewer pipes (solid for conveyance over perforated for exfiltration), reduced gradients and rain gardens. In this example, the roads are private, so maintenance of these new (to us) types of facilities are to be maintained by the condo corp. (Works well as a pilot for us to see how it works long term.) This development had high groundwater table, so the only way these systems worked was they had to raise the whole site upwards of 2.0m with granular 'B' (basically sand) to allow for the exfiltration / infiltration.

I recently took a course on LID through TRCA and CVCA and their message was the forthcoming update to the SWMP Manual from MOECC will require that each ECA application include a water balance calculation to show how groundwater recharge is being maximized. So at the end of the day, we all have to prepare to implement LIDs and it is a good idea to start developer's engineers designing a private system for the Town to monitor how it works.
I thought I would share my province-wide cost analysis for LIDs. This is assuming a retrofit cost of $400,000 per hectare and about 850,000 hectares of 'untreated' urban area in Ontario. This is the municipality-by-municipality breakdown of initial capital costs (on my blog):

http://www.cityfloodmap.com/2016/11/gre ... urban.html

These cost concerns were shared with MOECC in the recent EBR posting for the LID Guidance Manual. Here are costs looked at a difference way considering km of road in each municipality and $1.3M/km for retrofits:

http://www.cityfloodmap.com/2017/03/exp ... cture.html

We are compiling some demonstration project costs and they confirm the overall unit costs. Also in North Markham (a new 1000 hectare block) we are assessing the tax rate impact of LID lifecycle O&M and capital replacement.

If anyone has example LID project costs to share please let me know. Thanks.

Robert Muir
City of Markham
4 posts Page 1 of 1