1. Yesterday morning’s item about the Wallingford Community Council’s concern that more density would add too much poop to the sewage system—and overwhelm our water supply with combined sewer overflows—got a strong reaction from readers. (Check the lengthy comments thread.) And from the mayor’s office (which is pushing for upzones to facilitate growth by promoting density.)
Basically, they said the community council was full of s—.
(More politely and literally, the mayor's office identified the concern as the "the development/CSO canard.")
For starters, mayor Ed Murray’s spokesman Jeff Reading pointed out that “the city of Seattle’s storm water code says that all new development needs to take care of its storm water onsite through methods such as underground detention or infiltration.”
Storm water is different than poop, you say? True. But raw sewage only makes up 10 percent of the city sewer flows that create the combined sewer overflow problem. 90 percent of the overload, according to Seattle Public Utilities, comes from storm water runoff.
Second, the city is already designing the Ship Canal Water Quality Facility to bring CSOs in Ballard, Fremont and Wallingford into compliance with health standards. “It has been sized to fully control the area’s outfalls,” Reading told me. SPU's project overview explains, "the 2.7-mile, tunnel will capture and temporarily hold more than 15 million gallons of storm water mixed with some sewage that over flows during heavy rains. When the storm passes, overflows will be sent to the existing West Point Wastewater Treatment Plant in Magnolia." SPU estimates that will keep 50 million gallons of overflow out of the Ship Canal, Salmon Bay, and Lake Union every year and prevent the nearly all of the 130 CSOs that hit Ballard, Fremont, and Wallingford every year
Additionally, one reader pointed me to a study which confirms what I call the Green Metropolis Effect—the idea that density actually eases the burden on infrastructure by making infrastructure more efficient. By way of example: it takes less energy to provide heating for 50 families living in a multifamily building than it does to keep the same 50 families warm if they’re all living in a dispersed set of single family homes in a suburban swath.
The findings indicated that "low-density development may not always be the preferred strategy for protecting water resources. Higher densities may better protect water quality - especially at the lot level and watershed scale," the EPA said.
The study found that higher-density scenarios generate less storm water runoff per house at all scales - one acre, lot, and watershed - and time series build-out examples. For the same amount of development, the EPA says, higher-density development produces less runoff and less impervious cover than low-density development.
For a given amount of growth, the agency found, lower-density development impacts more of the watershed. …
dispersed development patterns cost more to serve because of the length of pipe required, pumping costs, and other factors. The literature reviewed shows how large-lot, dispersed development uses more water than smaller lot, higher density development.
This publication concludes with policy options for states, localities, and utilities that directly reduce the cost and demand for water, while indirectly promoting smart growth.
2. The city council's affordable housing and neighborhoods committee is taking up committee chair Tim Burgess's proposal to regulate Airbnb this morning. The key component of the proposal is to cap the number of days that off-site property owners can rent rooms; the proposed cap is 90 days.
Part of Burgess's pitch is that those rentals are hurting the city's housing supply.
Sightline's Dan Bertolet has a timely report this morning that raises questions about Burgess's logic.
The key excerpt:
Airbnb’s data for Seattle show that only 22 percent of “entire homes” listed are rented out 90 days per year or more, amounting to 630 Airbnb units suitable for LTR that the proposed 90-day restriction would impact. The fraction of those 630 units that hosts would convert to LTR depends not only on the financial equation but also on the hosts’ personal priorities. For some hosts, the value of keeping the unit available for family or personal needs will outweigh the loss of rent income. To assess the financial incentive, Airbnb estimated that 296 of its STRs rent for enough days per year to generate more income that could be earned annually from a LTR, based on current Seattle rents.
Six hundred units is less than half of a percent of the total rental units in Seattle, and as Peter Orser, director of the University of Washington’s Runstad Center for Real Estate Studies, noted, it’s unlikely to “make a significant inflationary impact on housing prices.” That said, in the battle against displacement, every additional home matters. However, there are reasons to question whether the proposed restriction would yield even that number of additional LTR units.
The fundamental flaw in the rationale for restrictions is that demand for STRs won’t disappear if the supply of STRs offered through services such as Airbnb is cut back. Where would the unmet demand for STRs go? The prime suspect, of course, is conventional hotels. But here’s the catch: when there is more demand for hotels, more hotels get built. Hotel and apartment developments compete for the same scarce urban land, so more new hotels means fewer new apartments, and fewer apartments means higher rents. If so, then STR restrictions may be a zero-sum game for affordability.
The only reason it wouldn’t be zero-sum is if Airbnb creates its own STR demand—that is, if some Airbnb users would not travel to Seattle if Airbnb didn’t exist. Surprisingly, several studies (here, here , here) have found that the growth of Airbnb has had little impact on hotel revenues, suggesting that Airbnb does in fact expand demand from out-of-town visitors. Because Airbnb tends to offer relatively cheap accommodations, lower-cost hotels are likely to feel any such pinch the most. And it makes sense that Airbnb could entice a handful of casual, low-budget tourists to travel when they otherwise couldn’t afford it.