Editor’s note: This article was originally published on Dec. 5 by Vashon Nature Center.
Does Vashon have enough water?
That question is bound to hijack any island conversation about growth, be it building more affordable housing or issuing more water shares. And that’s not a bad thing. The only drinking water we have comes from the precipitation that falls on the island and makes its way into our streams and aquifer system. We are wise to be cautious with such a precious resource.
If we just count raindrops, the forecast looks sunny. Vashon averages about 46 inches of precipitation annually. Experts estimate that the island’s current population (11,055) uses a mere 1.3 percent of that total. But history shows us that having water doesn’t always mean having access to it. Theoretical estimates often bump up against operational realities.
Here are four things to consider when we consider the question of “enough.”
Enough water for what?
This is the obvious follow-up. Do we have enough water to support more homes and businesses? (How many more, and where?) Enough to support more homes and businesses and combat a major wildfire? Enough to support development, contain wildfires, and leave enough water in the ground to satisfy mandated stream flows and keep the saltwater that surrounds us at bay?
Enough to check all those boxes and still satisfy the surge in demand that would result if all current holders of unused water rights decide to exercise them?
Water District 19 (WD19), which services Vashon’s town center, has about 150 customers right now who own but don’t use their water shares. Multiply that 150 customers by the District’s 400 gallons-per-day maximum usage rate for the average single-family home and you get “60,000 gallons a day that we have to put aside,” said Water District 19 general manager, John Martinak.
Could it be that, on paper, we’re already overdrawn?
And let’s not forget the climate change wildcard. Can our water supply sustain us through longer, drier summers and more frequent and heavier downpours, which promise more runoff and less aquifer recharge?
It is true: Homeowners in many parts of the island have sunk private wells that generate the two gallons-per-minute minimum for a single-family household. But the calculus changes dramatically for a large water district supplying hundreds of customers.
Efforts to find wells that can reliably deliver municipal-level volumes (100-plus gallons-per-minute) “have failed,” said Mike Brown, citing historic data on drilling and water production.
Brown is a recently retired professor of Earth and Space Science at the University of Washington, and a member of the Vashon-Maury Island Groundwater Protection Committee. (The Committee is preparing a report on the “enough” question.) He attributes the high failure rate to the “lateral boundaries of the aquifer.”
We are, in short, at the mercy of geology. Which takes us to reality number two:
Finding the water
After enduring eight major glacial advances and retreats, Vashon is a geologic mess. Our sole source aquifer is not one, tidy island-wide layer of saturation. It’s a patchwork of modest, disconnected areas of water-logged dirt. Loose swirls of soggy sands and gravels mingle with dense water-resistant beds of compressed clays and silts. We don’t know the exact extent (those lateral boundaries) or thickness or condition of these various aquifer and aquitard units.
“It’s not a simple layer cake,” said local geologist Steve Bergman about underground Vashon. “Glaciers were deforming stuff, moving stuff, churning it around. The [water-bearing zones] are not homogeneous units of nice happy sand and gravel. They’re interbedded sands and clays and silts and, in some places, channels with coarse gravels. There’s a lot of vertical and lateral variability.”
It’s so much variability that pinpointing pockets of potable water, especially sizable ones, is pretty much a crapshoot.
“Water witch, Ouija Board, Magic 8 Ball, expert advisers, all are equally effective,” said Martinak, about how a Vashon water district, or anyone, for that matter, goes about locating a reliable source of drinking water.
He’s not joking.
“There are people that will dowse, and people that will read well logs like tea leaves and say, ‘Ohhh, if we drill here we’ll hit good water,’” said Martinak. “But I always give the example of my neighbor, who’s got a perfectly fine well. And literally a stone’s throw from it is a King County test well. They drilled 243 feet down and didn’t hit anything.”
Getting the water
Assuming you can find water, reality number three involves getting it. Water District 19 is the island’s largest and most high-profile water provider. In 2022, the district delivered some 100 million gallons to its 1,500 connections, roughly 4,000 residential and commercial customers.
Any zoning changes in its service area could bring more residential and commercial development, putting WD19 at the epicenter of the enough-water debate.
The district draws its supply from surface (Beall and Ellis Creeks) and groundwater (six wells) sources. The groundwater piece, about 40 percent of supply, has always been the trickiest.
WD19 has drilled its share of troubled wells. Its Beall well suffers from high arsenic levels. Well 2, one of the three deep wells in the district’s well field, has seen its gallons-per-minute (gpm) rate fall from 274 gpm in 1990 to 50 gpm today. Three of the district’s other wells show similar declines in productivity.
“These wells are supposed to each be [capable of producing] 200 gpm,” said Martinak, whose team tracks the performance of the district’s well field religiously, and in real-time. “What we’ve figured out from watching is that the entire well field can only sustain about 135 gpm.”
Before he came to WD19, Martinak ran the much smaller Maury Mutual Water Company for many years. In his experience, the only way to determine the true capacity of a well, and of the aquifer it’s drawing from, is to carefully monitor performance over time.
Over-pumping can foul a well by drawing in too many fine-grained particulates. Prolonged over-pumping can deplete a well’s source aquifer.
You can rehab a fouled well with chemicals or good old elbow grease, at least for a while. But an over-pumped aquifer can take decades or longer to recover. Some never do. The island’s Westside Water Association had to limit the use of its Anderson well in 2020 to avoid damaging the source aquifer.
“Once you have disrupted the water-bearing layer, either through overdraw or by drawing too many fines [into a well], you’re never going to return to the original capacity,” said Martinak.
WD19’s current Water System Plan calls for developing a new water source by 2036. Martinak believes the district “should be looking for a new source, or source improvements, now.”
The search won’t be easy, or cheap. WD19 has spent thousands of dollars on drilling and engineering fees over the years in failed attempts to find reliable wells.
Paying for the water
Money is reality number four. Moving water from source to tap is expensive. You need wells, pumps, pipes, people, chemicals and equipment. It all adds up.
Martinak and WD19’s team of two admin staffers and three certified water operators handle the billing and manage the district’s six wells, multiple pump stations, one surface water treatment plant and 37 miles of aging underground pipe. The district plans to replace 6,000 feet of old pipe next year. At $400 per foot, that’s a $2.5 million investment. Loan payments on the pipe replacement will run $160,000 a year for the next 20 years.
And another big-ticket item may be looming. If the state, as expected, lowers its current standard for manganese levels in drinking water, WD19 will need a way to extract excess manganese from its water supply. The Dockton Water Company recently spent $640,000 on a new manganese filtration system. Operating costs eventually get passed along to customers, who rarely rejoice at a rate hike.
What does this all mean and what if anything can, or should islanders do about it? Let’s save that discussion for another time. It’s best to tackle one gnarly question at a time.
So, does Vashon have enough water? The answer depends a lot on whom you ask. In general, water operators are cautious, developers and housing advocates bullish, geologists mixed, and the rest of us confused or clueless.
On paper, the answer is yes. But you can’t drink paper water. So, let’s qualify that yes in this way: We have enough water, for now, and if we can afford to find it, tap it, treat it, and transport it from where it is to where we need it to be.
Mary Bruno, a Vashon-Maury Island Groundwater Protection Committee member, regularly blogs about water issues at vashonnaturecenter.org.
This article has been updated.
This article is part of a series about water and affordable housing on Vashon.
Part 1: Does Vashon have enough water?
