Stormwater runoff: an impermeable problem

Our built environment has forced the ecosystem to accommodate precipitation in high and fast volumes. The rush of water from pavement and compacted landscape destroys the natural order. It's also a huge source of Puget Sound pollution.
Crosscut archive image.

A street edge alternative project on Second Avenue Northwest in Seattle. (City of Seattle)

Our built environment has forced the ecosystem to accommodate precipitation in high and fast volumes. The rush of water from pavement and compacted landscape destroys the natural order. It's also a huge source of Puget Sound pollution.

It's raining again. Rainwater collects in the hollows of red geranium petals, puddles in the low spots of paved streets and plowed fields. In the country, a stream swollen with runoff flows deeper than it did a day before, foaming where it had barely rippled, its water tinged with brown from a tea of old alder leaves but still clear enough to reveal every rock in its bed. In town, water runs over scraps of paper stuck fast to the pavement, laps the edges of an old plastic lid, while raindrops pock the surfaces of dark puddles. Nearby, a comet of iridescence, a great, prismatic, glistening blob with curving tail, adorns the cracked concrete of a gas station. An hour later the comet is gone, its iridescence moving inexorably toward Puget Sound.

Not surprisingly, surface runoff turns out to be the main source of toxic chemicals in the Sound. ("Runoff called top pollutant in the Sound," screamed the Seattle Post-Intelligencer's lead headline on Saturday, Dec. 1.)

This isn't exactly startling news. In fact, it isn't news at all. Stormwater is the main source of water pollution in Puget Sound, writes John Lombard in his 2006 book, Saving Puget Sound. Stormwater "also affects water quantity, dramatically increasing peak flows and the 'flashiness' of streams ... and decreasing base flows during dry periods." By screwing up the natural flow pattern, it alters the populations and species of plants and critters living in the streams. By flowing off the land in fierce torrents, it gouges out stream beds. And it's expensive. Flooding and landslides like the ones we've seen throughout the Northwest this week cost millions every year. Then there's the cost of trying to control and decontaminate stormwater. "The region probably spends more than $1 billion each year to meet stormwater requirements," Lombard writes.

A 2006 report on "Damages and Costs of Stormwater Runoff in the Puget Sound Region" [160K PDF], prepared by geologist Derek Booth and two University of Washington colleagues, found that "[a]nnual stormwater program budgets ... range from hundreds of thousands to millions of dollars, with typical annual costs of approximately $100/person within a stormwater utility district." Booth and his colleagues reported that the city of Bellingham "has estimated $300,000-$500,000/year in additional funds would be required to keep up with current technologies and population growth beyond the $4.8 million currently budgeted. On a larger scale, Snohomish County identified 220 recommended projects with a total project cost of $85 million (representing a per capita expense of about $130)."

But we're not doing enough. In a generally upbeat conversation about restoring Puget Sound, Gov. Chris Gregoire conceded last spring that "where we're not making good progress is in areas like stormwater." UW professor of earth and space sciences David R. Montgomery wrote in the Seattle Post Intelligencer last March that he was "thrilled to see the rollout of Gov. Chris Gregoire's new 'science-based' Partnership for Puget Sound – until I read beyond the executive summary." Reading further, Montgomery found that "buried on page 43 of Appendix A, was a startling admission by the partnership's own scientific working group: 'The strategies listed are not likely to be sufficient to achieve ecosystem goals.' ... [T]here it is in black and white," Montgomery wrote. "The plan won't work." He went on to criticize "[r]eliance on standards in a storm water runoff manual which itself states 'land development as practiced today is incompatible with the achievement of sustainable ecosystems.'" Last year, he was one of 14 scientists who signed a letter to the partnership arguing that the existing plan wasn't likely to get the job done. He subsequently explained that if clean water laws were actually enforced, the current system would probably deal well enough with pollution – but pollution doesn't pose the main threat to salmon or to the natural systems on which salmon rely. Our fixation on pollution helps mask the real problem: a hydrologic pattern in which rainfall runs off across the paved surface of the land, instead of soaking into soil, then making its way slowly to rivers and streams. In an undisturbed catchment, Derek Booth explains, stormwater can stay in the soil for weeks, or even months. Most of the expensive retention ponds required for new development are designed to hold water for only a day or two. "One is led really inexorably toward ways of storing water in the soil," Booth maintains. Step one may be to "make sure there's still enough of that soil column to store the water. We only make it harder when our development style is to strip the land," he says.

Montgomery said he was "kind of mystified as to why anyone thinks that what we've been doing in the past works." No one did, of course, but no one had any plans for radical change.

In June, another scientist who signed the letter, Tom Holz, said he had heard that the missive "shook the partnership to its core. Partnership staff heard most of the ideas at [a] May 2006 workshop, but they chose to ignore them (or more accurately lose them in their Byzantine process for assessing input). It must have been very inconvenient to have them pop up again. ... Our first encounter with the new partnership ... tells us that they are now either intentionally ignoring the 14-scientist letter (my belief) or are totally clueless (belief of some of the other of the 14). They wish, it seems, to make the default option of the further decline of the Sound without the nasty business of having to say that is what they are doing."

Holz has changed his mind. After Thanksgiving, he said that was "the way I felt all the way up until last week, when I met with [new partnership executive director] David Dicks. He's quite a breath of fresh air." After his conversation with Dicks, Holz says that his June comments "are no longer valid." Rather, "the partnership has demonstrated to my satisfaction that they are not going to hang with the recommendations that came out October 2006." Dicks "is sincere about real change."

Holz recognizes, though, that even with Dicks on board, "it's not going to be a slam dunk." The 14 scientists called for, among other things, a commitment to "low impact development," which might involve green roofs, permeable concrete, minimal disturbance of vegetation, and other steps to preserve - or re-create - a relatively natural pattern of flow. Low-impact development "is such a small step and such an easy thing to do," Holz told the P-I, "why wouldn't we do it as quickly as possible?" The partnership has called only for low impact demonstration projects. "You don't have to be a scientist to recognize how unlikely it is that a few demonstration projects will adequately address the effects of future development," Montgomery wrote.

You don't indeed. But you also don't need much expertise to wonder how the region can possibly deal with the many square miles already covered by asphalt and concrete, roofs and drainage systems that get rainwater out of sight and out of mind as quickly as possible, and even unpaved areas where sod has been rolled out over impervious hardpan.

What to do about that already-built environment? The 14 scientists' letter suggests actually ripping out pavement. "Much existing impervious area is unnecessary and should be removed," it says. What are the chances? A six-year-old Seattle Street Edge Alternative demonstration project shows it can be done. To reduce runoff into nearby Piper Creek, so that surges of stormwater would no longer erode away the creek bed, the city has transformed Second Avenue Northwest, between 117th and 120th streets, into a model of low-impact construction. Above and below the demonstration blocks, Second Avenue is a wide, straight street, resting in a slight trough below the houses on both sides. Parked cars adorn broad strips of gravel or patchy grass that flank the concrete. Conventional gutters carry stormwater along both sides of the street. The pavement is plenty wide enough for SUVs to pass in opposite directions without slowing down.

In the three demonstration blocks the street narrows and winds. Cars pass cautiously on the serpentine pavement, moving over so that their outside wheels rest on the discontinuous paving blocks that replace standard gutters. The parking strips have disappeared. Small, paved cutouts provide on-street parking, but mostly, you see thick shrubbery that conceals small retention ponds. It is much more attractive than blocks to the north and south.

While retrofitting much of the built environment may seem unlikely, Derek Booth insists "that's a postulate. It's not a God-given truth." He points out that urban areas redevelop at a rate of 1 percent to 2 percent a year. Why not insist on low-impact redevelopment? "We've been yakking about [stormwater] for 20 years," he says. It's "painful to think we could be a quarter of the way there." Booth acknowledges that retrofitting to a higher standard would jack up the cost of redevelopment, but he points out that we routinely accept the higher costs associated with other rule changes. "Every time we change the plumbing code or the electrical code," he says, "people pay another $200,000 without batting an eye." But there's a double standard: "Change the stormwater code, and everyone goes ballistic."

Some people worry, or claim to worry, that more environmental requirements will just make housing even less affordable. Of course they will. An extra dollar is an extra dollar, no matter what it buys. But it's hard to figure out just how much environmental regulation adds to housing costs. Best guess is that, as a percentage, it doesn't add much. John Lombard suggests that the efforts to meet those requirements "add $10,000 or more to the average new house, and much more to new commercial development." Holz argues that affordability has become a red herring: that extra $10,000 isn't what makes a $500,000 house unaffordable. Certainly, one might ask if big developers are so concerned about affordable housing, why don't they build some?


About the Authors & Contributors

Daniel Jack Chasan

Daniel Jack Chasan

Daniel Jack Chasan is an author, attorney, and writer of many articles about Northwest environmental issues.