Public Health teams have been assessing water quality and septic performance along Vashon’s northwest shoreline. Credit: Public Health — Seattle & King County 

In May 2020, responding to reports of foul odors along certain stretches of Vashon shoreline, Public Health — Seattle & King County (PHSKC) launched the North Colvos Passage Healthy Beach Project. The North Colvos project is PHSKC’s second effort in the last four years to improve water quality along the Vashon shoreline. The first study, from 2018-2020, targeted Outer Quartermaster Harbor, Neill Point and several East Passage beaches. The North Colvos focus area extends from Baldwin Creek (in Fern Cove) north to the ferry terminal. Since September 2020, public health teams have been collecting and crunching data on the septic systems and on the water quality in the natural drainages along that northwest coastline. The results are now in. It’s a good news/bad news situation. I spoke with Meagan Jackson, the PHSKC program supervisor in charge of the North Colvos project, about her team’s findings and about next steps. (My questions appear in green)

Should we be alarmed or relieved by your findings?
“A little of both. In general, we have found very good water quality results. They’re showing that the general status of the area is good. The bigger concern is the status of the septic systems.”

Let’s start with water quality. There are 144  properties in the study area; 33 are vacant. You’ve conducted pollution surveys (with the owners’ permission) on 15 properties, and inspected nearly every septic system. What did you learn?
“[Pollution surveys] identified some minor things: roof drains being directed towards a drain field, which can cause the drainfield to become oversaturated and not treat sewage, and septic tank lids not being secured, which we’re very concerned about. But in general, groundwater drainages that are coming out onto the beach, as well as the creeks and streams and stormwater seem to be of pretty good water quality. 

“Three sites have had higher bacteria levels in the water. Of the three, one had a failing septic system. That has been corrected and the water quality has been improving, which is great. One of the sites, we think, has a septic system that is malfunctioning. We set up a dye test on that property to try to determine exactly what’s going on and see if there’s some smaller fixes we can work on with the property owner so that the wastewater doesn’t flow into a drainage. The third site, we’re still investigating.”

Is it unusual to have trouble pinpointing a cause?
“No, especially for properties like these where there is a lot of water in general and we don’t always know where it’s flowing from. And then most of these properties have septic systems that were put in a very long time ago, like in the 1920s and 1930s, before permits were necessary. So we don’t really know what’s in the ground.”

That’s a good segue to the septic part of the study. How did you gauge performance?
“We required everyone in the focus area to get their system inspected. Niece Pumping Services and some of the other inspectors created high-level sketches showing where the septic systems are located. That’s been a huge improvement in the information we have available, and that property owners can use to protect their systems.”

Who pays for those inspections?
“The property owner. But we offer a rebate for up to $450. And we’ve expanded  eligibility for the inspection rebate. We are now offering [septic inspection] rebates to any shoreline property on Vashon.”

What did the inspections show?
“Some systems are new. They were installed in the last five years and should continue to function for 20-plus years. About 100 systems are providing at least minimal treatment, meaning they’re not introducing any direct pollution. We’re not concerned about how they’re functioning, at least in the short-term. But a lot of those systems are old, and a lot are located right behind bulkheads, so in the long run they will most likely need to be addressed. Nine systems are failing. That’s a 10 percent failure rate [for this beachfront area], which is pretty high.”

How long before some of the “minimal treatment” systems might need to be replaced or upgraded?
“For planning purposes, around five years. About half of the systems that are currently functioning should continue to be inspected and have routine maintenance. That will prolong their life. For the really old systems, we don’t know. They could continue to function for 20 years, or they could fail in the next two months.”

And if they fail or under-perform, we could get untreated sewage on the beach or in the water?
“Yes.”

What’s the plan for those nine failing systems?
“The intermediate goal is reducing sewage overflow. Public Health will get a little more information about the levels of pollution and about water use on those properties. For example, is it just a vacation home, or do people live there consistently? Then we’ll work with the owners to develop a plan that protects public health and water quality, and is the best option for the property owner. We recognize that this can be a stressful thing to deal with, and we do have some financial assistance programs that these properties would be eligible for. Long term, we are really trying to look holistically at how systems are functioning, how old they are, etc. We don’t want to make people replace systems when there could be a cheaper option.”

Cost aside, what are the options for the North Colvos waterfront properties, which are pretty space-constrained?
“[One option] is using subsurface drip lines in the drainfield. It’s very similar to what people would use for irrigation. The great thing about these drip lines is that you can install them closer together, so there’s a smaller footprint necessary for the drainfield. And they can be installed on steeper slopes, which is very helpful for shoreline areas like this one. They are slightly more expensive, but not significantly. Maybe 5-15 percent more.”

Drip lines have a smaller diameter. Doesn’t that effect performance?
“[With drip systems] we require an additional tank that adds a very intensive treatment before the effluent gets to the drainfield. That tank will usually have a fan, which adds oxygen to the wastewater, or sometimes membrane filters. These systems are able to achieve a very high level of treatment, the same level as the Brightwater Treatment Plant [in Snohomish County].”

Other options for property owners in the study area?
“A community septic system like the one at Spring Beach (see map) is probably the best solution for a couple of places in the focus area. Public Health is going to pay for a wastewater engineer to analyze the data we’ve collected so far and determine whether community systems are feasible in some of these areas where there are several systems failing, or where a couple are failing and many more will most likely have issues in the next couple of years. [Feasibility] will depend on what the property owners want, if there is land nearby for a larger drainfield, and the cost of a community septic system compared to doing individual replacements.”

The North Colvos Project officially ends in April 2023. Then what?
“For water quality, we will provide our results to the state Department of Health (DOH) and they’ll take over routine monitoring of the shoreline and of the marine water quality. [Septic] is still up in the air. We may continue to monitor [septic status] for the next couple of years and, if nothing else, continue to work with the property owners who have issues with their systems to make sure those get fixed.” 

So property owners could call your team for help or advice?
“Yup. We are happy to talk to people, because it’s always better to prevent failures rather than have to deal with sewage backing up into your house.Call our On-site Sewage System (OSS) Program at 206-477-8177.”

What would you like to see happen going forward?
“Continue some high level monitoring of water quality and septic status in the North Colvos  area, work with DOH to determine what actions are necessary to upgrade water quality, and then take those actions. But a lot depends on whether we can get additional grant funding.”

Are Healthy Beach projects planned for other Vashon shorelines?
“Yes. Mid-Colvos Passage, Dockton and Neill Point-Tahlequah area.”

Any final thoughts?
“We have been very thankful for how the property owners have responded—getting their systems inspected, taking advantage of the rebate. There are definitely issues with the systems, but we expected that. Addressing septic issues sometimes takes a long time. But things are moving forward very well.”