Minimum Design Criteria (MDC) Team
8/24/2015
Triangle J COG, Durham
Team Members / Others
Eban Bean
Bradley Bennett
Jonathan Bivens
Tim Clinkscales
Tracy Davis
Boyd Devane
Hunter Freeman
Mike Gallant
Joe Hinton
Marc Houle
Ron Horvath
Bill Hunt
Linda Lewis / Brian Lipscomb
Annette Lucas
Mike MacIntyre
Todd Miller
Cameron Moore
Tom Murray
Robert Patterson
Derek Pielech
Peter Raabe
Joe Faulkner
JD Solomon
Virginia Spillman
Toby Vinson
Rob Weintraub / Julie Ventaloro, NC DEMLR
Sue Homewood, NC DWR
Robert Josey, NC DEMLR
Dan Sams, NC DEMLR
Georgette Scott, NC DEMLR
Ben Brown, City of Raleigh
Rule Readoption Webpage
Annette reviewed DEMLR’s rule readoption webpage that has all existing and proposed rule drafts:
Rule 15A NCAC 2H 1019 (Coastal Counties)
Todd – G.S. 143-214.7 says purpose is to protect surface waters of the state. Might be better to say that instead of minimize impacts.
JD – Is this rule part of the MDC?
Annette – One thing to consider is under the fast-track program, we’re not supposed to issue permits unless you show compliance with the MDC. MDC includes did you design device in accordance with the design storm, for example. To make it clear, we’re calling those requirements MDC as well in addition to the design standards themselves.
JD – Seems like compliance is a gate to getting compliance with MDCs. I don’t know that consolidating coastal rules as an MDC is what was envisioned.
Linda – Our concern was that these folks here didn’t need to be involved in the rulemaking part as opposed to the MDC.
JD – I think it’s good general information for this group, but if it’s not affecting the MDC --
Bradley – We felt that this group had a lot of technical expertise in stormwater. We thought this was a good place for us to get a good draft to bring to the EMC.
JD – I think a general awareness for this group is great, but I don’t think we take an action on this.
Annette – For us, we decided that because Legislature was telling us to do rule readoption and the MDC, we decided to do one big rulemaking. You propose rule to public, receive public comments. If you make changes based on comments, you go through public notice again. We appreciate you all helping us put our best foot forward early in the process. We know this will be one of the more controversial rules.
JD – So noted. Let’s move on.
Annette – Some of our stormwater rules are implemented by the state, and some by the local governments. We’d like to get your comments on applicability of the rule:
Item (b) is new: Existing residential lots within ½ mile and draining to SA waters and propose to add 3,000 square feet or more to existing BUA.
Annette – Now, the threshold is 10,000 square feet. A 3,000 SF addition can have significant water quality impacts.
Mike G – I think it’s a bad idea. Depending on the size lot and what they’re doing on their property. I’m guessing the state won’t want to get into that for residential property. If you’re on a quarter acre lot, that’s a lot of space. If you’re on a half acre lot or 5 acre lot --
Georgette – This is talking about adding 3,000 SF to “existing” BUA. Purpose of 10,000 was it was not covered by anything else. It was under an acre, right? No CAMA majors – the trigger was 10,000. Maybe here you want to say add 3,000 to existing under an acre. Putting a substantial amount of BUA on a very small lot. Point was they had to put in some sort of BMP to handle the BUA. You want to capture those developments where you have concern about large amount of BUA on small lot.
Mike G – How do you – seems like this will be something someone finds out after they build their outbuilding. As someone who is currently building an outbuilding --
Georgette – I think whole purpose of original rule was to capture those who were concreting their entire lot, area already having issues with stormwater. Idea with 3,000 -- you don’t want to get into 500 -- but 3,000 is substantial addition to existing --
Jonathan – A lot of coastal lots are long and narrow. A 10-foot wide driveway – if they decide to pave the existing drive, they end up 100 feet shy of the house with 3,000 feet. If they pave it with asphalt – would it count as impervious?
Georgette – Existing driveway would be considered existing impervious.
Jonathan – If we’re having this discussion here, it could become an issue out there.
JD – If someone comes in and has unimproved driveway, been driving on for 30 years, going to put a garage in, you’re permitting it?
Georgette – They could probably do it under redevelopment.
Linda – If we consider the driveway “existing” --
Mike G – I thought threshold was 24%.
Annette – This item only applies to lots draining to SA waters.
Jonathan – If someone does want to add 300 SF or 500 SF, maybe put a smaller percent to existing applications. That way you don’t have someone tear down a 2-room fishing shack and building a McMansion without getting a permit. I don’t disagree with the intent. I’m fine with putting in 6% additional impact without getting a permit.
Dan Sams – On barrier island, with tiny lots, will we be taking something more from those?
Georgette – You’ve got to protect these SA waters. 10,000 that was in there before was a lot to put on a little lot. 3,000 SF would be a trigger for what they would have to treat. If we say 6%, and say you’ve already got 12%, what would be the trigger?
Jonathan – Putting 6% in, you’re protecting anything less than an acre greater than the 3,000 SF would, plus giving people with bigger lots a little more. This gives you flexibility on bigger lots. Percentage protects smaller and gives you flexibility on the larger.
Annette – How about: Existing residential lots that within ½ mile and draining to SA waters that propose to convert six percent or more of the lot from pervious surface to BUA and this results in a project density greater than 12 percent --
Jonathan – I thought whole point was they could add something minor without getting a permit?
Mike G – What if you’re in a subdivision that is permitted up to 24%?
Georgette – That’s permitted under that permit. This wouldn’t apply.
Annette – We moved provisions that apply to all programs to 2H .1001 – 1(c) says “development activities that have already received a State Stormwater permit or certification where no modification or minor modification was requested.”
Annette – Jonathan, does the proposed change to (2)(b) make sense?
Linda – I’m a little worried about capping it to 12% for existing lots. Most likely, from the get-go, they’re over 12%. I don’t want to penalize them today for what happened years ago when they didn’t need a permit.
Dan Sams – We’re not saying you can’t redevelop to 12%. We’re saying if you go over 12%, you need a permit.
Annette – You get 6% of your lot size for changing pervious to BUA.
Jonathan – If have a 5,000 SF lot, 6% on that lot is virtually nothing. I was a little concerned about the cap. It cuts them off immediately if they’re already exceeding it. If they just want to put a hot tub pad in, all of a sudden they’re in violation.
Georgette – That’s what we don’t want.
Mike G – Do you make it an either/or – either 3,000 SF or the other option?
Jonathan – Then you have people adding 3,000 to 6,000 – no protection on the small lots.
Dan Sams – Frankly, if someone’s building a hot tub pad, that’s a don’t ask, don’t tell situation. We may be creating a problem that doesn’t exist. I added a 12x14 to my house last year, and it wasn’t a problem. We can set here and make issues out of nothing all day.
Mike G – Are we depending on building inspectors to catch these?
Jonathan – If neighbor doesn’t want them doing what they’re doing, they will find some loophole.
Dan Sams – If this says what we need it to say, we might need to stop before we make it worse.
Annette – Jonathan’s point is that 6% of a small lot is still pretty small.
Mike G – You have a guy with a house, builds his garage, sells that. When does that become vested?
Linda – Don’t standards of when you normally vest things apply?
Georgette – I’ve asked them to show me when different sections of building were built. On tax records, it has dates.
Mike G – Say it was after this – I can see a point when someone takes this and makes a federal case out of it.
JD – I don’t think this is “MDC.” This group is not going to endorse it.
Peter – I’m seeing this mainly as a stakeholder commentary.
Bradley – Since we’ve finished MDC process, we haven’t done voting. We’ve just been getting comments.
Georgette – What we learned today is that this needs work.
Item (2)(c) – another new one: Undeveloped lots that are within one-half mile of and draining to SA waters and propose a project density greater than 12 percent.
Mike G – Anything you do on the island requires a CAMA permit now, so it kind of takes it out of your hands.
Linda – That’s something to consider: Why regulate it if CAMA’s already doing it?
Item (4) – Requires projects to comply with general MDC.
Item (5) – Determination of which coastal stormwater program applies depending on classification.
Item (6) – Here’s a summary of the coastal program requirements. Every SA water is either SA-ORW or SA-HQW. We’re not proposing to change 12% low/high density threshold. We do propose to reduce size or storm from 1-year 24-hour, (3.8”) to about 2”. One of reasons for this is there’s not a lot of difference between annual runoff captured between making practice almost twice as big. 1-year 24-hour storm moves you up to only about 97-98 percentile storm. We did increase size of design storm for freshwater ORW in coastal counties from 1.5” to 90th percentile storm.
Jonathan - I don’t know anything about this. Todd’s got it covered. Are B-ORW and C-ORW different things? Shouldn’t that be an “or” not an “and”?
Mike G – Where are we finding the 95th percentile?
Annette – NC State has compiled that for us.
Mike G – Is that information available some place?
Annette – It’s available now in our Storm EZ.
Mike G – Will there be one number for Wilmington, one for Raleigh?
Annette – There will be 30-40 stations. This will increase current 1.5” storm (about 80th percentile) – small increase, but we’re capturing more volume. You get diminishing returns as storm increases at some point. Going from 80th to 90th is a lot more improvement.
Mike G – Wasn’t SA-HQW 24% before?
Linda – Since 2008, it was 12%.
Annette – Within ½ mile and draining to. Todd, did you want to add anything?
Todd – Our concern is overall amount of stormwater that reaches SA waters, so this is a good tradeoff.
Brian L – Not clear that for existing development, this applies only to new development.
Bradley – Definition of redevelopment covers it.
Annette – Also, in rule where we talk about MDC for all projects – we talk about how you deal with existing development, excluding it from calculations. This provision applies to a number of stormwater rules. We put it in one place rather than repeating it. To summarize, only things that are changing is size of design storm (reduce it for SA waters), increase it to a lesser degree for freshwater coastal waters.
For vegetated setbacks, proposing 50 feet or new development; 30 feet for redevelopment.
Item (7) – We want to encourage people to infiltrate in SA waters because virtually any stormwater discharge to SA waters already has bacteria level too high to meet water quality standards. We want to get as much stomwater in the ground as possible. But we also have high water tables. If they’re saturated, you can’t infiltrate well. Our current no discharge policy is confusing. It allows you to have a wet pond. Wet pond effluent is not supposed to be directly discharged to SA waters. Supposed to be place in series with secondary BMP without regard to where water table is.
Linda – Most use vegetated filter as their secondary BMP.
Annette – To encourage folks to think about using non-discharge SCMs -- We have different options: Option a is to do runoff volume match design for 95th percentile event; Option b using non-discharging SCMs.
Mike G – So discharging rate if you have wet pond, drawdown will be too long – would be quite a few days for 1-yr 24-hr storm. You’ll end up with wet pond with very small orifice which is not a good idea. Just meeting pre- and post—I don’t know.
Annette – Professor Hunt proposed this because he says more recent research has shown when you discharge at pre-development rate, prolonging bankfull condition and causing more erosion in the stream.
Mike G – Are you going to waive 2 to 5 days then?
Annette – That’s a good question. For 1-year 24-hr storm, how long do you have to hold that back to match pre- and post-?
Mike G – I try to do it for 50-year event; not same as for 1-year, 24-hour storm.
Joe F – For that you use a larger orifice.
Robert P – I think you should run the numbers and see if it’s even possible.
Jonathan – What we’re trying to do is -- because we’re developing it, we’re trying to put runoff at half of what it was a pre-development?
Annette – Yes. But volume of runoff will be higher because you’ve cut off natural infiltration.
Jonathan – Yes, discharge will be longer. But, likewise, if you’re not increasing the discharge, now you’re trying to cut it in half.
Bradley – Existing rules prohibit the discharge.
Mike G – But we put in the magical vegetated filter and it’s ok.
JD – Do we require a level spreader in that case?
Mike G – Usually before vegetated filter you use a level spreader. If you take a wet pond, storage volume to let it out at pre-development rate, going to increase it a bunch, and you are going to be providing storage equal to what you are now or close to it. I think you’d have to sit down and do the math on a typical pond. Pond for a 20-acre development will be different than for 1-acre. I think it might impact a smaller -- like 3 or 4-acre project -- substantially, where it might not for a big project. How does this affect the lateral infiltration BMP?
Annette – We wanted the verbiage in there about exposing water to filtration – that type of device like you proposed with a berm within the wet pond where water would filter through the berm where water table was high. We also have filtration outlet structures being studied which can reduce bacteria levels in stormwater. We don’t think this language is perfect right now.
Todd – Fundamental requirement still is to protect water quality standards. Question will be asked -- will this discharge meet standards? That was basis for nondischarge language.
Annette – We definitely need to run the numbers. We don’t want to propose something that’s impossible.
Mike G – When I was doing the wet pond study, some argued shouldn’t have drawdown over 2 days – want it lower. You have a problem with vegetation, being ready for next storm. This protects stream for erosion and inundation, but might not be better for bacteria and vector control.
Dan Sams – If water’s not gone in 2 days, you’ll start hearing about mosquitoes.
Annette – I’m hearing very little support for holding peak discharge rate so low. Any other parts of Item (7) you all want to talk about?
Mike G – If you have a small site and peak discharge is 1-2 cfs, keeping it to half of that – If receiving stream is intracoastal waterway, won’t erode bank. But is an issue if receiving water is small stream. I could see where it would be very site specific.
JD – You’re trying to give people an option to discharge – is that what you’re doing? My concern is if we’re not taking into account cumulative effect. How many sites would we have in SA waters that would do this?
Mike G – As written, you’ll push it back to where folks have to do infiltration on site. Then you have water table issue, raising up a lot of sites. You’ll meet considerable resistance outside this group.
Annette – Only where licensed professional provides documentation that infiltration is not possible – is that appropriate, fair?
Mike G – Guy can say I don’t want to spend money to lift up my property 6 inches. When does it become reasonable to do that?
Jonathan – Flip side is you can design discharging device that works on paper, but not in the field. There has to be a practical bottom end where you can’t go any smaller.
Mike G – Must be a sweet spot where if you reduce number of acres --
Jonathan – At bottom end, will only work on paper.
JD – Is there technology that would be better here than an orifice that doesn’t work?
Todd – Pretty clean when it leaches laterally.
Mike G – If Bill is worried about flooding stream, going over bank, you’ll have less bacteria, but there will be longer chance for erosion from volume.
JD – Which is more sediment, more release of --
Peter – You have a good amount of runoff even in natural state because of high water tables. With philosophy of Storm EZ, what is natural hydrology -- maybe natural hydrology doesn’t infiltrate 95th percentile storm.
Mike G – With flat property, water will just pond and sit there for days. Runoff will be low on paper. Having it discharge at half that very small rate, you could end up storing in excess of what we’re storing now.
Peter – Naturally, the drawdown wouldn’t be slower.
Todd – We allow runoff match as one of the options?
Annette – Yes, Option a.
Todd – Is that a better alternative?
Mike G – For residential, it’s a good tool. For commercial with large parking lots, need something else. Chances are if I can make the math work, it’s because I made the math work. Even if you have a 5-acre commercial tract, putting on strip center with parking lot, have a hard time getting – wet pond will be pretty large, larger than you are now. Point below where you get below a certain size with setbacks, you won’t be able to do a higher density development.
Todd – With runoff match, if it’s a wet site, you’re matching already high runoff volumes.
Annette – We can’t require people to do LID, but it’s an option that we encourage. Unfortunately, the approach of filtering stormwater within a wet pond is a developing science right now. We’re not at a place for writing MDC – we’re trying to get there. Bill’s doing some research. He’s also doing research on sand filters within a wet pond. We will run the numbers and see what the impact will be.
Mike G – You have to be careful if someone who owns property, and this rule makes it undevelopable -- will you be accused of a taking?
Dan Sams – We run that risk every time a proposal comes across their desk. If that’s our concern, that’s perpetual with everything we do.
Annette – Any more suggestions for staff as we go back and scratch our heads over this? We’re going to Water Quality Committee on Sept 9 as information item. In November, we will have an action item.
Mike G – Possible to connect this to size of receiving stream channel somehow? If receiving stream has a flow of “x,” and you can show that flow will be large, maybe this not as big a deal as if you have a small branch. Might be a question for Bill. If you’re going into a wetland before you get to a receiving stream --
Peter – If you went with the hydrologic match option -- if that water is able to receive large volumes, you wouldn’t need to worry about that as much.
Mike G – It’s a great option. But if you have a small commercial tract, you’ll be limited. I think you have to be careful if you get people who go with gravel standard and propose a huge gravel parking lot.
Annette – Some things you can control and some things you can’t.