Seawater intrusion
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“The proximity of saltwater makes island ground water resources among the most fragile and sensitive systems in nature.”
1978 was a banner year when Dr. Roland Schmidt, a professor at WWU, published The Water Resources of Northern Lummi Island. This was part of sub-area planning efforts by Whatcom County Planning Dept and islanders interested in grappling with balancing zoning, growth and future resources needed to support that growth. It’s interesting to note our permanent households grew by 63% between 1966 and 1978, prompting concerns about how island infrastructure (transportation, electric, water, and sewage) were able to cope with growth in the future. Dr. Schmidt said, “The proximity of saltwater makes island ground water resources among the most fragile and sensitive systems in nature.”
What’s all this talk about intrusion?
Dr. Schmidt went on to say, “the fresh water is constantly moving seaward, ‘leaking out’. If fresh groundwater is also removed by pumping, then unless an equivalent amount of water is returned to the aquifer in the vicinity of the well, the net effect is to lower the water table near the well, and because of reduced head, to raise the level of the saltwater in the ground.”
In other words, overpumping your well may draw saltwater into your water system.
The report offered three observations.
Dependent on wise use, Lummi Island is capable of using groundwater indefinitely as its sole source of water.
Because of the complexity of the island's hydrogeology, some resource management will become necessary.
Residential development raises a potential for groundwater pollution, both from seawater and septic systems.
This graphic illustrates what happens when excess pumping of shallow aquifers creates both a cone of depression (drawing fresh water from around the well) and cone of ascension (drawing fresh water up from the salt water/freshwater buffer area). Over-pumping a single well can also affect neighboring wells in the same aquifer. Once salt water is drawn into a well, it is very difficult to reverse the process, requiring you and your neighbors to pump less and restrict future withdrawals.
What do the studies show?
1978
The Water Resources of Northern Lummi Island (Whatcom County Planning Dept, Robinson & Noble, Dr. Roland Schmidt, et al) examined 39 wells for chlorides (an indicator of seawater intrusion) and discovered that only one well had elevated levels and that well was not being used at the time. That was good news, but Dr. Schmidt cautioned that future populations will have to start “compiling information about the island’s hydrologic system so that long-term data will be available whenever resource management becomes necessary.” Now, over 40 years later, we are that future population.
1991
An article about seawater intrusion in Lummi Island’s The Tome by Sue Blake, funded by a grant from the Dept. of Ecology Centennial Clean Water Fund. Sue noted that two of 21 wells had chloride levels above 250 ppm, warning that “seawater intrusion can cause aesthetic, health, agricultural, and environmental problems for users … and can become a health problem for individuals with a history of heart disease.” Humans aren't the only the only ones to suffer. “Salty water is detrimental to most plants and can have detrimental effects on wetlands and estuaries of coastal environments.”
1994
Lummi Island Groundwater Study (Whatcom County Dept. of Health, Anne Atkeson, and Washington Dept. of Ecology). At that time Lummi Island had a permanent population of 620 persons. There were 559 dwelling units of which 249 were for seasonal visitors. 75 wells were examined with 7 of those with elevated levels of Chlorides above 250 ppm. Two wells were considered ‘medium risk’ (100 - 250 ppm), and another 16 were ‘low risk’ (25 - 100 ppm). Both public and private water wells were included in the study.
2005
The Hydrogeology of Northern Lummi Island by Bill Sullivan. We are grateful for Bill’s tireless investigation of our island for identifying unique aquifers, and assessing each for physical properties, chemical analysis, yields and seawater intrusions. Sullivan confirmed the earlier tests of 80 wells and suggested that “up to 14 additional wells may be experiencing some degree of intrusion, with most being in the sandstone aquifer near the eastern shoreline.”
2006
Northern Lummi Island Hydrogeologic Investigation (Whatcom County Planning, Aspect Consulting). Of 40 wells selected for examination for seawater intrusion, Aspect found 15 wells in six areas where chloride levels were elevated:
Point Migley: two wells of 100 ppm or above.
Northwest Coast: two wells, one north and one south of the Willows Inn, with varying results.
Village Point: two wells with levels above the maximum of 250 ppm within 700 feet of Legoe Bay.
West of Nugent Dr: one well measuring over 100 ppm.
Central East Shoreline (Legoe Bay Rd to Centerview Rd): five wells above background levels completed in bedrock within 1,000 feet of the shoreline with levels exceeding 100 ppm.
Lane Spit: one shallow well completed at sea level exceeding 250 ppm.
Aspect recommended “developing standards and policies that are protective of the groundwater resource” and that, “protective measures could be developed based on limiting further degradation of water quality in areas where impacts are observed.” The Aspect report lists 272 separate wells for information of location and depth, along with numerous maps of well conditions and geologic representations of the island.
2021 ?
There have been no further studies in the 15 years since 2006.
We do know our population has grown nearly 20% since the last study and seasonal housing has increasingly trended to be used as vacation rentals. AirBnB hosts regularly post about the challenge of excessive water use, like here and here.
Our well water for public water systems reveals that chloride testing has decreased significantly. In 2006 there were 92 compliance chloride tests in the preceding 15 years. In the last 15 years there have only been 36 tests done! After reaching out to the Dept. of Ecology, we confirmed that the DOE receives very few tests even though most well water right permits include a requirement to test for chloride in April and August of each year.
Given the trajectory of wells experiencing saltwater intrusion in the past and rising demands, are we sticking our heads in the sand and hoping for the best?
How chloride affects the quality of drinking water
Chloride is a component of salt (sodium chloride) and an indicator of seawater intrusion. Chloride is considered a “secondary contaminant” by the EPA because levels above 250 ppm can affect the aesthetic quality of water making it taste salty, corrode pipes, fixtures, and appliances, and cause high blood pressure.
Chloride distribution map from Northern Lummi Island Hydrogeologic Investigation (2006). Tap image to enlarge.
This 2006 map developed by Aspect Consulting shows where about a third of the wells of northern Lummi Island were located, which formation they draw from (circles are in glacial till, squares are in fractured stone), and to what degree saltwater intrusion was present.
Blue is good. Yellow is marginal, with chloride to 100 ppm. Red is above 250 ppm, indicating that saltwater has taken over and is not usable for drinking water.
There were several areas of concern including Lane Spit, Legoe Bay and along Nugent Road near Beach School. As we have not been gathering data over the last 15 years, those neighborhoods are left to question what changes have been occurring since.
The Salish Sea is intruding
Hat Island
Hat Island treats much of their well water using a reverse osmosis plant. These systems can become quite complex, expensive to build and operate, and raise the cost of drinking water by about $25 per 1,000 gallons just for electricity consumed according to the Hat Island Community Association.
Guemes Island
The Dept.of Ecology warned Skagit County Public Health of the dangers of seawater intrusion for wells on the north side of the Guemes Island, and recommended discouraging the drilling of new wells,” according to a recent article in the Skagit Herald. Some Guemes Islanders have been lobbying Skagit County to allow rainwater catchment to be used as drinking water.
Cattle Point,
San Juan Island
Cattle Point Water District serves about 50 households. About 10 years ago they were forced to abandon six wells due to high chloride levels and build a desalination plant costing about half a million dollars. Once an operator for Cattle Point, Arnie Klaus is now the operator for Hilltop Water Owner’s Association on Lummi Island. Arnie’s experience was that, “operation of this type reverse osmosis plant is quite expensive, requiring large pumps capable of 900 psi to split the water molecule away from the salt.” This costs about seven cents to produce one gallon of water—roughly $112 per month per household! When asked for his advice to Lummi Islanders, Arnie said, “invest in solar energy if you have to go that route.”
Lopez Island
The 1997 USGS report, Is Seawater Intrusion Affecting Ground Water on Lopez Island, Washington? found that 46% of the 185 wells they checked showed levels of chlorides above 100 ppm, and includes a trove of facts, data, and mapping The report concluded, “the small amount of yearly precipitation keeps the Island's ground-water system in a fragile balance between the recharge rates and the ground-water pumping. Increased pumping rates may upset this balance and result in seawater intrusion.”
Island County
In 2005, the Seawater Intrusion Topic Paper studied 379 wells and concluded that 36 wells tested positive for indicators of intrusion, while 101 wells showed inconclusive indicators. This has prompted Island County to take a 3-step approach to monitoring and detection for approving additional wells in areas prone to intrusion. This report is very well documented and worth a look.
This story is on the level
Measuring the level of water in your well compared to sea level is a rough way to predict how many feet of fresh water you have below sea level. Studies show that a static well level (at rest, when not pumping) of at least eight feet above sea level is a good indication that sea water intrusion is unlikely. A static level within eight feet of sea level is a cause for concern. Static levels below sea level are prone for intrusion.
This graphic shows how pumping can draw down static levels below sea level, and draw up the floor of sea water to reach the well intakes if pumped hard enough or long enough.
Private well owners are encouraged to contact us (see author contacts below) to have your static level measured and compare that to the original well log.
Monitoring your own well
The best way to tell if your well is experiencing sea water intrusion is to have it tested for chlorides and conductivity concentrations. Each test costs about $25 at a certified lab. Or if you prefer, Mike Skehan (one of the Water Watcher authors) has a test kit and is glad to test your water if you drop off a sample. Mike can test for chlorides, conductivity, and dissolved solids—all indicators of intrusion. It’s free and confidential. This is not a ‘lab certified’ test, but not a bad way to get an idea of where you stand. Email Mike if you're interested.
Laboratories in Whatcom County
Exact Scientific Services
1355 Pacific Place #101
Ferndale, WA 98248
(360) 733-1205
Edge Analytical Laboratories
805 W. Orchard Drive #4
Bellingham, WA 98225
(888) 725-1212
Need help or advice collecting samples for chloride and other contaminants on Lummi Island? The authors of this article are happy to help.
Background chloride levels around Lummi Island vary from 15 to 30 ppm. Anything above 99 ppm would be cause for concern and maybe warrant a follow up test from a certified lab. Above 250 ppm, your drinking water exceeds the EPA’s secondary maximum contaminant level.
Hey neighbor, pardon our intrusion...
As aquifers serve many wells, sharing that information with neighboring water systems is beneficial. With this, water systems can start a dialog if a well is in jeopardy and work to prevent nearby wells from suffering the same fate. This could start with local Group A and Group B systems serving as collection points for well information in the same aquifer who are willing to share results as patterns emerge.
Fill er up! How to help your aquifer
Limit impervious surfaces like asphalt and concrete driveways and roads. In the 1991 Water Watchers series, Sue Blake advised that “impervious surfaces prevent rainwater from draining directly through the soil.”
Let the forest work like a giant sponge. "There is no better argument for retaining and enhancing our forests than the impacts they have on our freshwater resources," according to our resident Doctor of Forestry, Scott Josiah. Check out his advice in Water Watchers: Understanding Aquifers.
Swales are swell. Ditches discharge water directly to the sea without much chance for absorption. A vegetative swale promotes infiltration by allowing water to slowly drain into the soil.
Don’t pump your well all at once. A flow restrictor will limit the water to a set gallon-per-minute rate. A timer can be used to pace short pumping times throughout the day. This, and an adequate reservoir, may mitigate cone of depression and cone of ascension problems.
Control water usage with meters. How would you know you were speeding without a speedometer? Group A water systems are required to have meters at each customer connection as part of the Washington Dept. of Health Water Use Efficiency Rule. Group B and individual water systems can also monitor usage by at least metering the water pumped from the well, if not at each customer connection. Meters are a key tool in leak detection. Charging a premium for water in the driest months is also an effective way to conserve the aquifer. Learn more from the DOH with Water service meters: An opportunity to focus on residential water use.
Rainwater catchment for gardens. It can be as simple as diverting your roof downspouts into a barrel. Because rainwater is relatively clean it can be stored during the wet months and used later when your plants are thirsty. Just be careful not to connect your rainwater catchment to your drinking water system.
According to the University of Washington’s Climate Impacts Group there is a 50% chance that the sea will rise seven inches by 2050 and two feet by 2100. Below ground the effect is even greater as fresh water is less dense than seawater.
Using the Ghyben-Herzberg principle, a water table that is one foot above sea level extends 40 feet below sea level (a 1-to-40 relation). Increase sea level by seven inches and that difference with the water table is now just five inches. The saltwater transition zone then pushes up leaving less than 17 feet of fresh water (a thirsty water system can quickly deplete that).
So just seven inches of sea level rise may cause salty groundwater to rise 23 feet.
The Ghyben-Herzberg principle. Source: Is Seawater Intrusion Affecting Ground Water on Lopez Island, Washington?
Sea-ing the future
We don’t have powers to tell the future, but we can infer from other coastal areas what may be ahead:
Rising sea level in the coming decades means that the height difference between your water table and sea level will shrink. In our opinion this is the greatest risk to Lummi Island’s groundwater, and one that future Water Watchers will have to address.
Higher populations draw from the same supply. Our recent ferry study predicts higher populations through 2060, justifying a ferry nearly twice as large as the existing one for our future. Will our aquifers be up to the challenge of more of us?
Changing climate will bring changing rainfall patterns. Wetter winters will be an opportunity to capture extra runoff otherwise lost to the sea. Drier summers will extend both drought conditions and the peak water use of the vacation season. We’ve already seen these changes over the last 40 years.
Will we adapt?
We appreciate your viewpoints and feedback on this series. Drop us an email.
Co-Authors
Mike Skehan | email
MANAGER OF RIDGE WATER ASSN, PAST OWNER OF LUMMI WATER WORKS, MGR OF HILLTOP WATER AND SUNSET BEACH WATER, (WATER DISTRIBUTION SPECIALIST, BASIC TREATMENT OPERATOR), RETIRED.
Isaac Colgan | email
WATER TREATMENT PLANT OPERATOR LEVEL 2 AND WATER DISTRIBUTION MANAGER LEVEL 2 FOR , Isle-Aire Beach Association, OWNERS ASSOCIATION OF BEACH CLUB CONDOS, Marine View Estates, SEACREST WATER ASSOCIATION, Salvation Army Camp Lummi, and previously for LUMMI ISLAND SCENIC ESTATES.
Resources referenced in this article
The Hydrogeology of North Lummi Island, 2005 by Bill Sullivan
North Lummi Island Hydrogeologic Investigation, 2006 by Aspect Consulting
Secondary Drinking Water Standards: Guidance for Nuisance Chemicals by EPA
Is Seawater Intrusion Affecting Ground Water on Lopez Island, Washington?, 1997 by USGS
Seawater Intrusion Topic Paper, 2005 by Island County and DOE
Water service meters: An opportunity to focus on residential water use, by Washington DOH
Sea Level Rise Visualization Tools, by University of Washington Climate Impacts Group
