Drippy roof_Flickr_AndyN.The Washington Department of Ecology has released its draft draft plan for beefing up its low-impact development requirements for controlling polluted stormwater runoff—which is considered the top environmental threat to the Puget Sound and many other Northwest lakes, rivers, and streams. This policy change is a big deal. It’s trying to solve one of the region’s top environmental and health challenges, perhaps second only to climate change and ocean acidification in importance to our area. And what’s approved in the coming months will be on the books for a long time.

The grossly over-simplified, five-second summary of what’s being proposed: rain gardens and porous pavement are in, green roofs are in for commercial projects, water harvesting and reuse is out, and preservation of trees and other native plants—the most sure-fire way to control toxic stormwater runoff—is encouraged, but not strongly enough given its importance.

And the oversimplified summary of responses from those tracking this deal: the enviro community and stormwater experts and engineers are disappointedin the plan, which they say will lead to the continued destruction of our Northwest waterways. They’re not alone. The Puget Sound Partnership, EPA, and NOAA Fisheries Service all call for a stronger plan and faster time frame for getting it implemented in their comments to Ecology. At an August meeting of folks who have been advising Ecology in this process, the City of Seattle called for more aggressive action by the state. At the same meeting, representatives of the building industry and some Western Washington counties said the regulations went too far and would be too tough to comply with.

What’s out now is sort of a “draft of the draft” proposal, which will officially be released by the end of this year. The rules will be part of the updated 2012 stormwater permits, though the deadlines for implementing the changes are pushed out until the end of 2014 and 2015.

The goal of the new policy is to take low-impact development strategies and turn them from quaint oddities to ponder and admire into the standard, business-as-usual approach to building our region’s homes, businesses, roads, parking lots, and communities. Without that sort of serious paradigm shift, water quality and wildlife experts say we’ll be in deep trouble as bugs die, salmon are injured, and waterways become more polluted for humans.

Again, the strategy of LID is to keep the rain where it falls rather than flushing it—along with all the toxics it collects along the way—into the Sound, lakes, and rivers as fast as humanly possible through the use of drains, gutters, and pipes. Instead, by preserving vegetation, and through engineering tricks, the rain soaks into the ground where it falls or the water is captured by plants and in pools where it can evaporate back into the air. The pollution doesn’t go away, but it stays put.

For the sake of this post, I’m focusing on the use of LID at the site-development level, that is, the rules that apply when someone builds a house or apartment or commercial building. The draft proposal also speaks to stormwater management at two higher levels: the government codes establishing road widths, house set backs, gutter construction, and other conventional stormwater infrastructure, as well as at the watershed or basin scale where regional density goals are determined.

So let’s review in more detail which LID strategies Ecology proposes requiring, and when and where at the more micro scale.

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  • Size matters, and so does location

    First, the department’s proposed strategy is to break development into different categories based on size: whether a project is a new development or a redevelopment, whether the project is in rural or urban areas, and how easily a site’s soil absorbs water. Rural and non-rural designations are determined by whether a project is within or outside what’s called an Urban Growth Area. UGAs, as they’re also called, are predetermined areas where growth is supposed to be concentrated so that undeveloped land is preserved for farming, logging, and as natural preserves.

    The most lax scenarios—ones in which there are no requirements for using LID—apply to projects that cover less than 7,000 square feet and less than 2,000 square feet of hard surfaces (for perspective, the minimum lot size in most Seattle neighborhoods is 5,000 square feet). The most extensive use of LID is required for projects that disturb more than 5 acres of land outside of an urban growth area (that is, in a rural area preferred for protection).

    For projects falling between those two extremes, a sliding scale of LID requirements apply.

    Ecology goes “pro-choice”

    Rainy cedar_Flickr_dr tim 1956Provided a project is big enough to warrant LID, and except for the largest projects, a developer has some choices as to how to meet the LID requirements.

    The first option—and the only one that Ecology and stormwater experts agree will actually eliminate the harmful runoff—is called the 65/10/0 rule. It requires that 65 percent of the land is left in native or forested vegetation and that only 10 percent of the project is turned into impervious or non-absorbent surface (conventional roofs, driveways, etc.). Preserving the plants and limiting impervious surfaces is expected to  result in zero runoff. This strategy is also called “full dispersion” (in case you were hoping for some new stormwater jargon to bust out at the next cocktail party).

    The second option is to use all of the LID techniques from a list established by Ecology, with some exceptions.

    The third option is to meet a “hydrologic performance standard” (usually just called the performance standard) through the use of a self-selected set of LID strategies. Despite the name, the performance standard doesn’t actually require someone to go out and measure the amount of runoff coming from a site. Instead, an engineer working with a computer model has to propose a menu of LID techniques to be used for a specific project that will reduce the amount of stormwater to set levels.

    Are we having fun yet? Let’s get into still more detail.

    The LID grocery list

    So let’s say you’re a developer who wants to skip the engineer and computer modeling and throw the whole list of LID techniques at your project and hope that they stick. Here’s what you’re required to do:*

    1. Use on-site stormwater man
      agement, which in
      cludes making sure the soil is deep enough and absorbent enough to soak up some of the water.
    2. For driveways, roads, sidewalks, walkways, patios, etc. use permeable pavement, or lay impermeable pavement with a system to catch the runoff and channel it under the pavement so it can soak into the ground.
    3. Retain native vegetation and minimize impervious surfaces “to the extent feasible.”
    4. Build rain gardens that cover 7.5 percent of a residential development and 4 percent of a commercial development. Rain gardens are not required in areas with less absorbent soil (specifically soil with a “saturated hydraulic conductivity of less than 0.15 inches an hour” for the dozen of you who actually know what that means).
    5. For commercial buildings (and not single family residences), build a green roof or a conventional roof whose runoff is channeled to flow below the parking lot where it can be absorbed. Exemptions can be made to this requirement based on cost.

    The advisory groups chosen to aid Ecology on these proposed rules have pointed out many faults with this mandatory-list approach. They include the apparent ease with which the green roof requirement can be waived, and the failure to require green roofs for residential buildings; the arbitrary size of the rain gardens and the failure to require them on sites with less absorbent soils; the lack of any requirement to retain native vegetation; the failure to include rainwater harvesting in the mandatory list; and the lack of any LID requirements for smaller sites.

    *Footnote: For projects greater than 2,000 square feet of hard surface or more than 7,000 square feet of disturbed area, only requirements 1 and 2 apply; for projects with more than 10,000 square feet of hard surface or more than 3/4 of an acre disturbed but less than 5 acres, all conditions apply, or a developer can opt for the performance standard.

    This section was updated Oct. 14 at 3 p.m. to clarify that rainwater harvesting is not required, as opposed to water reclamation.

    Backhoe_Flickr_Mike tn

    A less than model model*

    In the off chance that these proposed rules and endless caveats haven’t made your head hurt yet, we’ve now come to the performance standard. Grab a couple of aspirin.

    Developers of larger projects are required to meet the performance standard, which is the computer model that determines how much runoff a given project is allowed. Developers of smaller projects can either choose the performance standard, or do everything on the previously described list. Ecology’s preference between the two is that a developer goes with the model, which is supposed to be the more protective route, but that opinion is not shared universally.

    So what the heck is the performance standard? First you estimate how much runoff came from a site in historic, pre-development conditions. For areas deemed “highly urbanized” the model doesn’t consider historic runoff conditions, but rather existing runoff levels as its baseline. Then the standard says that once the new project is completed, the amount of runoff must not exceed a stringent goal. (I’m not going to explain further how these goals are set—they’re confusing as heck and pegged to flow rates. If you want to read more, check out Chapter 2 of Volume III, and Appendices B and C in Volume III of the Stormwater Management Manual for Western Washington.)

    The truth is, I’m not sure it exactly matters whether the goals are set. What’s really important is how well the model can calculate the historic flow and how accurately it can predict the benefits of various LID techniques. These numbers are based on factors such as the soil type, what sort of vegetation is native to the area, the amount of water various LID techniques are expected to absorb, etc. It also includes some on-site measurements of infiltration rates, which is how quickly the soil soaks up water. And by Ecology’s own admission, these numbers are much less than perfect and are in need of updating and adjusting, but the question is whether they’ll have the resources to do so.

    Commenters on the draft plan worry that the model de-emphasizes the conservation of trees and plants in trade for engineering “tricks,” when trees and vegetation may in fact be the single most effective solution. Taken to an extreme, the approach could result in a treeless development paved in porous concrete—and still meet the rules if the stormwater volumes met the calculated goal.

    The staunchest critics say this model is utter hogwash, including made-up numbers that have nothing to do with protecting salmon, streams, and the health Puget Sound. Tom Holz, one of the advisory committee members and a stormwater expert, considers the standard so unlikely to succeed that he recommended that Ecology add a “power of prayer” option, suggesting it has as good a chance of protecting local waterways as this approach.

    *Footnote: This section was updated at 4 p.m. on Oct. 12 after an interview with Ed O’Brien at Ecology, and again at 3 p.m. on Oct. 14 following additional feedback from Ecology regarding requirements for on-site testing of infiltration rates.

    Time keeps on slippin’

    Love or hate these proposed rules for cleaning up and reducing Washington’s polluted stormwater, you won’t legally be affected by them any time soon. That’s because they take effect painfully slowly.

    For reasons that many folks don’t agree with, Ecology decided that the timing for the stormwater rules should match up with an update of the Growth Management Act. The act, also called the GMA, is what sets up the Urban Growth Areas discussed previously.

    The larger jurisdictions within King, Pierce, Snohomish, Clark, Kitsap, Thurston, Whatcom, and Clallam counties (also called Phase I and Phase II jurisdictions) face a Dec. 1, 2014 deadline for implementing whatever rules are finalized by Ecology. Smaller jurisdictions within Island, Skagit, Lewis, Cowlitz, and Grays Harbor counties are under a Dec. 1, 2015 deadline.

    Many feel that this timeline is way too slow.

    Complication caveat

    Even though this post delved into Ecology’s proposal in as much depth as I could bear, it still skipped over some some of the situations and conditions when the requirements go away or are tweaked, such as in cases of unstable slopes or in the most urban settings.

    And as I warned in the beginning this post also didn’t address the two other levels of stormwater regulation: site development standards and basin planning. Basin planning, which deals with Urban Growth Areas, is the section where the conservation of native vegetation gets the most attention, so it’s an area to watch and one that I will tackle in the near future.

    These rules exemplify the tricky line that Ecology is trying to walk. Some stormwater experts would like to see the state set simpler rules, for example requiring that a certain percentage of a development—say 30 percent or 50 percent or more—is kept in native vegetation. It’s clear how to follow and enforce a straight percentage like this. But some governments and builders and developers call for more flexibility in the rules, which forces Ecology to set a range of options. Ironically, these tend also to be the constituents that claim the rules are too complicated.


    Drippy roof photo used from Flickr user AndyN; rain drops on a cedar sprig is from Flickr user dr Tim 1956; backhoe photo from Mike_tn. All photos are used under the Creative Commons license.