[All] Update regarding LID

Wed Oct 7 14:47:52 EDT 2009

Hi everyone

I just finished the on line web meeting regarding LID storm water management aka Low Impact Stormwater management. 

Basically, remove the concept of sewers for a moment and picture diverting water by way of discharging water in riparian swales, roof runoff heading into rock water retention areas behind residential units and residential runoff heading through riparian areas into SWM ponds etc.

The end goal is improved "water quality and quantity" without the costs or design limitations of traditional sewers. The big issue is, there is little to no regard for road salt issues, pah's from road or roof runoff etc. There is no data regarding what measures they intend to use for monitoring. No long term data. It's basically an unproven science. Data regarding costs savings is not available at this time. 

The scary example of the day was Calgary where the ground is naturally pervious and surrounds the Bull and Elbow River. They're actually using "PERVIOUS ROADWAYS" thinking this is a good way to SLOW the rates of Total Suspended Solids (TTS) because their current rates are flying off the charts. They had to take action to deal with the TTS because the discharge points are upstream from their intake systems. The down side is their most likely contaminating their own water supply as a result. The method is being used to DELAY the TSS impacts to the river so they can retain the assimilation capacity and allow development to continue as normal. 

Many of the plans were implemented within pre developed areas so options were limited as to what strategies could be used. Green roofs, Rock collection swales, riparian areas were proposed. Much of what they tried to do was heavily contested by area residents who successfully stopped some of the projects because the riparian areas would have reduced parking options.  Calgary is trying to "lead by example" but the residents are not convinced the projects are worth the effort so they're having a rough time getting public support. (Maybe the public understands what point source contamination is)

The entire LID concept was created by stake holders including developers, home builders, municipal officials and certain hydrology firms and it would be fair to state it had a rather pro development bias with little to no public input. 

When I asked Jeff Walker of the Canadian Standards Association about the contamination risks, he stated: It's not a system designed for all places. In some cases it's not appropriate to use this. Limitations should be recognized. For example, it should not be used around wellheads. Permable road coverings should not be used where there are risks such as snow pile ups. It's a system designed to be used where there are "no hazards".

When I asked the Calgary rep, Mr. Paul Fesko, P.Eng if his area has any mandatory studies to assess road salt impacts he stated no. Not that he knows of.  Thanks to that I've got three new grey hairs on my head. 

There appears to be a HUGE need to introduce toxicologists into the discussions of this technology. We seriously need to get these people together with the engineering teams in order to get a reality check on the bona fide risks. If municipalities actually embrace this concept without a reasonable system of monitoring in place our national water supply will seriously be at risk. It's a system designed to mask the toxic impacts by delay. That's it. once the contamination hits, it's contaminated from source to the river.  

The US EPA has a working group. One of the Canadian members of this group is open to public comments regarding the LID system and they can be emailed at:

k_mercer at sympatico.ca

In my view this is a concept in it's infancy. There is no standardized monitoring data, no cost analysis, no way to secure accountability and no data regarding long term impact studies but it's cheap to build. The way I see it, without a  discharge point to monitor the nasty runoff, salt and toxins get buried with little to no chance of detection or accountability. 

On the flip side, I value applying the logic in riparian buffer zones on dirt or country roads. I can see it in regards to roof runoff only if and when the roof and soffit materials are non toxic. I can see it applied in backyards but we should push for a 6 foot wide filter strip on either side of all residential driveways in urban areas and 4 feet off the curb to divert water to discharge through traditional sewers and retention ponds. Folks put the salt in those areas when they clear driveways and plow roads. It would help to reduce chloride infiltration. 

Like Mr. Walker said, this technology should not be used where there's a hazard and I would not want to see this used to justify development over top the recharge under any circumstance.

That's all folks.

Louisette Lanteigne 
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