Stormwater management should work with, not against, Smart Growth

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Stormwater management should work with, not against, Smart Growth

by Daniel Nairn • July 8, 2009 10:56 am

Virginia is updating statewide stormwater regulations. A draft is open for public comment until August 21, 2009. Some people are concerned that the stricter caps on nutrient loads, as currently written, will promote low-density development and ultimately hurt the water quality and quantity of runoff in the Chesapeake Bay watershed.

Raining downtown, and that's just fine. Photo by bobtravis.

Here's a simple but realistic hypothetical scenario. Developer A wants to develop 100 dwelling units on 1,000 acres of land, and developer B wants to develop 100 dwelling units on 10 acres of land. Developer A will only need to cover 10% of her large site with impervious surface, while developer B will need to cover 70% of her small site with impervious surface. Developer A assumes that 100% of residents will use an automobile for transportation, while Developer B assumes 50% will primarily walk or use transit. Therefore, Developer A's project will require twice as many parking spaces and approximately twice as much road width in the region, but will accommodate most of the parking off-site.

Under the stormwater regulations being proposed, Developer A will likely score an A+ with a pass to move forward, while Developer B will fail. This is because the standards are determined, site-by-site, on a per acre basis and not a per unit basis. Developer B may have the option of purchasing off-site water quality improvements or implementing a set of BMPs to offset the damage she is incurring, but she takes a hard look at her balance sheet and decides to join developer A as a business partner. What benefited the individual acres of the sites in question clearly was an overall loss for the watershed as a whole.

And considering opportunity costs makes the situation even dicier. What if these developers bypass infill redevelopment of an industrial site for a more compliant and cheaper greenfield development? (Stormwater controls will generally be more expensive for redevelopment than new development). Now you have impervious surfaces in two places, instead of one.

The economic market analysis, conducted for the Department of Conservation and Recreation by a Virginia Tech professor, bears this out in more detail.

Based on this site-by-site method, low density developments would produce less estimated phosphorus runoff than medium or high density areas. Very low density developments (1 dwelling unit per 3 to 5 acres) would unlikely face any water quality control requirements. Yet, on a watershed basis, low-density ("sprawl") development increases dependence on auto transport (thus increasing emissions and roadway impervious surfaces). Highly impervious areas accompanied by dense population settlement can produce net water quality improvements, independent of whether stormwater controls are implemented ... Higher phosphorous control costs in high density developments create financial disincentives that may work at cross purposes with larger watershed objectives.

I'm no hydrologist. Most of the science and bureaucratic mechanisms behind this policy are pretty bewildering, and I don't really have the time to try to figure them out. Furthermore, I thought it might be safe to assume that as glaring a potential problem as this is, somebody in the state offices must be working to sort it out. Then I read this comment from a member of the Technical Advisory Committee that helped craft the policy:

Stormwater management seeks to replicate the water quality and quantity benefits that are provided by a natural, undeveloped landscape. Development that contains more natural landscape (e.g. rural dev.) will consequently find it less costly to comply. This is not a fault of the stormwater management regulation; it is a natural consequence of the hydrologic cycle.

In other words: That's life. Deal with it. He went on,

Stormwater codes should be judged on how well they manage runoff quantity and quality, not how well they do or don't control growth ... Smart growth codes should be judged by how well they control sprawl.

This is where the trouble lies. Sometimes genuinely smart and well-intentioned people err by focusing intently on the piece of the puzzle they have been commissioned to solve, thereby missing the larger system within which their problem is embedded. It's the classic widen-the-freeway-to-reduce-congestion scenario. It may solve the technical problem at hand, but it exacerbates the real problem.

The fact is that stormwater management and Smart Growth have everything to do with each other. Treating them separately and pitting one against the other is a losing game for both water quality and growth of development.

This was demonstrated pretty convincingly by a 2006 EPA report. Here are the three scenarios proposed by the study:

From the U.S. Environmental Protection Agency, Protecting Water Resources with Higher-Density Development.

They put this model to empirical tests and mined numerous other studies to back up their conclusions. Once again, the crux of difference:

The results indicate when runoff is measured by the acre, limiting density does produce less stormwater runoff when compared to the higher-density scenarios. However, when measured by the house, higher densities produce less stormwater runoff.

They show that this is the lapse in logic that lead so many regulatory agencies to assume that sprawl is good for controlling stormwater runoff:

Many communities assume that low-density development automatically protects water resources. This study has shown that this assumption is flawed and that pursuit of low-density development can in fact be counterproductive, contributing to high rates of land conversion and stormwater runoff and missing opportunities to preserve valuable land within watersheds.

And this report focuses exclusively on quantity of water runoff. If you look at the issue of quality and factor in the introduction of pollutants such as motor fuels, de-icing chemicals, vehicular exhaust, lawn fertilizers and pesticides, faulty septic systems, and more into the water supply, the case against promoting low-density development grows and grows.

Let's not strike out on this one.

Crossposted at Discovering Urbanism.

13 comments

Tags: environment, Smart Growth, stormwater, Virginia

Constructive stormwater management proposals emerge in Virginia (Aug 25, 2009)
Slow and steady creates Virginia's Urban Development Areas (Jan 22, 2010)
Virginia tea party opposes less government regulation with anti-Smart Growth, "eco-extremist" hysteria (Feb 5, 2011)
Frontline examines imperiled watersheds and the Arlington solution (Apr 22, 2009)
Will Tysons halfway plan bolster or doom the future city? (May 6, 2010)

Daniel Nairn is a graduate student in Urban and Environmental Planning at the University of Virginia. He works, plays, and studies in Charlottesville. He also blogs at Discovering Urbanism.

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Dammit, Jim, I'm an urban planner, not a hydrologist!

by Dan Miller on Jul 8, 2009 11:57 am • link • report

Great article. Two minor additions. First, greater distances have to be covered by more and wider roads, producing a lot of very polluted runoff. In comparison, urban spaces can compensate withis in-house rainwater catchment and treatment. Constructed wetlands and green roofs go a long way to reducing the load of urban areas, and don't cost that much if it's on a mid-rise building.

by цarьchitect on Jul 8, 2009 12:33 pm • link • report

The problem identified in this post (i.e., putting the impervious surface cart before the environmental horse) is also the reason we could not get Montgomery County to build a complete bike trail next to the ICC.

The original plan called for a hard surface trail along the full length of the roadway, but after approving a six-lane highway the Planning Board concluded that large segments of the trail would have to be detoured to side streets to avoid putting too much impervious surface in the parks. The net effect is that the bike trail has been cut to pieces while the highway runs uninterrupted through Paint Branch and Northwest Branch parks. The net result is that an opportunity to create a high quality east-west route for cyclists in upper Montgomery County has been lost.

Casey

by Casey Anderson on Jul 8, 2009 1:21 pm • link • report

Virgina could consider adopting the stormwater standards adopted by West Virginia. (see:http://www2.wvdep.org/dwwm/stormwater/MS4_docs.htm)

All new development and signifcant redevelopment must manage 1" of stormwater on site through green infrastructure approaches. However, specific land use measures with demonstrated water quality benefit, e.g., redevelopment, high density, mixed use TOD, receive a reduction from that standard. This approach, while not perfect, begins to recognize the environmental performance of some land use strategies.

by Lynn Richards on Jul 8, 2009 1:56 pm • link • report

I like Lynn's suggestion and would add that just as LEED recognizes the difference between Urban and rural buildings so should the stormwater management standards.

It's also possible that a form of mitigation could be used. A dense development could buy some land within a reasonable distance and agree to give it to the county as a 'water refuge' along with a payment to capture lost tax revenue. It would drive up costs of course.

by David C on Jul 8, 2009 4:44 pm • link • report

isn't DC currently in violation of the Clean Water Act and being forced in court to soon do something?

by Tom Coumaris on Jul 8, 2009 5:15 pm • link • report

Once again we see that optimizing a system by individual parts produces a suboptimal outcome. :sigh:

by Chuck Coleman on Jul 8, 2009 8:18 pm • link • report

isn't DC currently in violation of the Clean Water Act and being forced in court to soon do something?

Yes. In most places, storm water is collected and dumped into streams and lakes, with varying levels of effort to mitigate the damage on the receiving waterways. Sewage, however, is collected in a separate system and carried to waste water treatment facilities where the discharge is almost universally cleaner than the receiving body of water. All of the sewage from DC, a substantial amount from suburban Maryland, and some from Northern Virginia go to the Blue Plains plant at the southern tip of DC.

The older parts of Washington have a single sewer system that includes both storm water and sewage, called a combined sewer. Under normal conditions, all the water and other material that gets into the sewers ends up at Blue Plains. When we get heavy rains, however, this system is overloaded, and water spews into the Anacostia, the Potomac, and Rock Creek. As you might hope, this violates the Clean Water Act.

DCWASA has developed a Long Term Control Plan to significantly reduce the number of times the combined sewer system overflows into these streams and the amount of water that overflows. There are two ways to deal with the problem, and the Long Term Control Plan uses both approaches.

The first is to separate the two systems. Because it is very expensive and disruptive, it is only being used in a small area where the sewer systems can be fairly easily separated and the existing storm sewer system can accommodate the additional flow.

The majority of the problem will be handled in a much better, but much more expensive way. DCWASA will be boring huge tunnels underneath the city and diverting the overflow from the streams into these tunnels. When the flows in the sewers return to normal levels, the excess water will be pumped out of the tunnels back into the sewer system, and will be treated at Blue Plains.

This is a multi-year, multi-billion dollar plan, but will result in significantly cleaner discharge into the area streams. DC will be far ahead of neighboring jurisdictions, in that we will be treating a significant amount of our storm water, not just our sewage. In addition, holding the water in the tunnels until the rain stops will help reduce the surges that cause rapid erosion of stream beds.

by Stanton Park on Jul 9, 2009 3:20 pm • link • report

The EPA Smart Growth scenarios A, B & C as shown, may initially show that 'C' produces the best overall result upon initial construction. It turns a blind eye, however, to the long held American cultural view that land not currently occupied by buildings is just land that hasn't been yet developed. What is to prevent a future rezone being filed and approved for the 'C' scenario so that there are now 2 dense developments in the previously hydrologically functional area (which was so only because the developed area was limited to the original footprint?) Who compensates the landowners who are on land that is not allowed to be developed as they previously could? ANd what about yet a third rezone scenario which gets passed because of the virtue of 'density is better than sprawl' or undue economic hardship on the landowner through a property 'taking' without appropriate compensation? The EPA Smart Growth Office has not adequately addressed the fallacy of "density is the solution". They need to work with the EPA Office of Water and integrate LID into Smart Growth concepts. If sheer density was the solution, our Urban Waterways wouldn't be in such dire straits.

by Ann on Jul 9, 2009 10:57 pm • link • report

I used to work at EPA and the "fallacy of density is the solution" is itself a fallacy. Density is not the solution, but only one facet of the solution of interconnected actions on the built and natural environments. Several offices in EPA and many other partners are trying to crack challenges raised. The graphic was created, in part, to debunk the myth that low density development was the solution.

These challenges getting a fuller grip on impacts and figuring out who pays - schools are roads are readily observed and measured, but the interference of slow infiltration over vast areas is not. Perhaps the greatest challenge is getting people to pay for ecological services that have always been "free" until a couple of thousand rezonings ago - getting rid of stormwater, plunking a septic tank in the ground, replenishing groundwater, storing carbon.

The offset issue, that smart growth cannot claim victory until the open space is forever off limits, has appeal. But my hunch is that the offset challenge is the opposite. Land conservation efforts are decades old. Smart growth helps at least buy time to not only raise funds to conserve land, but figure out a way to let people know it's worth doing a lot more of .

by Lisa Nisenson on Jul 10, 2009 5:46 pm • link • report

I really appreciate these comments.

Lisa, I take it that you have extensive experience with this issue. I'd love to hear more about some of the strategies used (or being considered) to pin down the advantages of density in regulatory language. Has anyone ever tried to attach allowable runoff to the number of units (or sq. footage of commercial/office) rather than number of acres in a development? Seems like an elegant approach, but I bet there are some hidden problems to it that I'm not thinking of.

Ann, I don't believe the rest of the land necessarily has to remain undeveloped to capture the water quality advantages of density (although that would be ideal in my opinion). Even if most of development is concentrated in one location and some is spread out, that's better than most spread out and some concentrated. Nor do I think density is the only solution. One of many. I tend to think of this marginally, rather than with absolutes. Although, I agree, the EPA diagram was a simplified picture. If the regulations incentivize marginally less density, I think that's a problem for the watershed.

Also, we can't talk about densities without talking about cars. Probably nothing creates more impervious surfaces or pollutants (except for Ag probably) than automotive infrastructure. Surely if density can allow more alternatives to driving, that's at least one good thing.

by Daniel on Jul 11, 2009 9:10 pm • link • report

One more thing I forgot ...

Maybe one of the reasons urban waterways are as polluted as they are is precisely because of the amount of low-density development already in existence. The parking lots and many of the roads happen to be in urban areas, but they are serving drivers who are living in low-density areas, not so much urban dwellers biking, walking, or taking metro.

by Daniel on Jul 11, 2009 9:16 pm • link • report

A few of the photos you can view by clicking the link below are facilities done by developers in response to Portland, OR's stormwater regs, but most facilities were installed by the city itself.

http://picasaweb.google.com/mvogeldc/T6GreenStreets#

If you download any of these photos, please label them to credit Mary Vogel/PlanGreen. What I am trying to show is that creative designers can infiltrate stormwater in dense development--even infill retrofits. The photos were taken in downtown Portland or adjacent neighborhoods. If you know the transect, some are actually T5, but could work in T6.

I spent some of the 8 years I recently (Aug 07) concluded in DC trying to get DC to require of itself and its public spaces the same thing it requires of private developers re: stormwater. I think they started a few "Green Streets" though I don't know that they are calling them that. Check with DDOT.
Mary Vogel
http://www.plangreen.net

by Mary Vogel on Jul 26, 2009 10:26 pm • link • report