Freshwater Water Quality

Freshwater Environment

About this indicator: King County's Freshwater Water Quality Index is derived from two main groupings of results describing the conditions of lakes and rivers & streams. Wetland conditions do not factor into the index at this time because of inadequate data. Our weighting system applies 65 percent to lakes, 30 percent to rivers and streams, and 5 percent to groundwater toward the overall freshwater water quality. Within the lakes index, our weighting system applies 70 percent to large lakes and 30 percent to small lakes toward the overall lakes indicator.

Status: Overall below standard, though with some areas of lesser concern.

Influencing factors: The impacts of development, landowner practices in areas close to the shoreline and pollutants are the dominant drivers determining the health of freshwater bodies in King County. Less forest cover and increases in impervious surfaces result in higher stream temperatures and more urban runoff. Phosphorus from blended stormwater and wastewater that bypasses the treatment process during significant storm events, failing septic systems, pet wastes and water bird droppings reduce dissolved oxygen levels and increase water temperatures.

What you can do:

• Properly dispose of unused pharmaceuticals, harmful chemicals and paints, instead of pouring them down the drain or allowing them to run off on the ground.
• Minimize the use of fertilizers and pesticides by practicing natural yard care.
• Wash your car on the grass or gravel instead of on the street or driveway, or take it to a car wash.
• Properly dispose of or manage pet and livestock wastes.

More information about King County's Freshwater Lakes and Streams is available by continuing below for these measures:

• Phosphorus in Large Lakes
• Fecal Bacteria at Large Lakes Non-Swimming Beaches (ambient)
• Phosphorus in Small Lakes
• Streams Water Quality Index
• Nitrates in Groundwater on Vashon-Maury Islands

---

Phosphorus in Large Lakes

About this measure: The people of King County have made significant investments in water quality improvement and protection to lakes Washington, Sammamish and Union beginning with the diversion of wastewater effluent out of Lake Washington and Lake Sammamish in 1968.

Water quality improvements continue with efforts to:

• Reduce the discharge of combined sewer overflows
• Improve King County's wastewater treatment system (including construction of Brightwater treatment facility)
• Expand effluent reuse programs

These gains in water quality are constantly threatened by increasing amounts of phosphorus entering the watersheds as a result of increased development.

Status: Lake water quality results vary annually, depending on the climate and biological interactions that combine to create unique annual conditions in each lake. For example, the 1994-2007 results for Lakes Sammamish and Washington show phosphorus concentrations fluctuated between low to moderate threshold from year to year, indicating water quality varies from good to moderate with low potential for nuisance algal blooms. Lake Union typically has phosphorus concentrations within the moderate water quality range, with the exception of 2007. In 2007 high phosphorus levels put Lake Union in the poor water quality range.

Lake Sammamish is the only one of the three lakes with a management plan and designated water quality goals. The plan calls for an annual volume weighted total phosphorus concentration (VWTP) of 22 µg/L or less. Both the north and south lake stations met this goal in 2007 with a VWTP of 19 µg/L and 18 µg/L, respectively.

Influencing factors: In this region, phosphorus is most often the nutrient that promotes algal growth. The more phosphorus that can be stopped from entering lakes, the less chance that a potentially toxic cyanobacteria bloom will occur. Phosphorus can be managed through well-designed drainage systems, maintenance of sewer infrastructure, changing homeowner and business behaviors (to use no phosphorus fertilizers on lawns), education and incentives, and replacing watershed septic systems with sewers.

Existing DNRP response: King County will continue to monitor these lakes as part of its ongoing, Major Lakes Ambient Monitoring Program. This program is designed to track how lakes respond over time to various activities and inputs from the watersheds through influent streams, lake nutrient cycles, ecological interactions, and seasonal or year-to-year variability in weather. The goal of 100 percent of the three major lakes being within the range of moderate to low risk of potential algal blooms was met in lakes Sammamish and Washington, but was not met in Lake Union due to high phosphorus concentrations. If the lakes begin to show serious deterioration in terms of their beneficial uses, actions will be taken to further investigate causes and plans will be made.

Priority new actions: Continual changes to data analysis and Web site reporting will provide current and accessible information for the management of these resources.

---

Fecal Bacteria at Large Lakes Non-Swimming Beaches (ambient)

About this indicator: The presence of fecal bacteria in waterbodies indicates potential contamination with the fecal material from humans, birds or other animals. Fecal coliform bacteria is not a perfect indicator of sewage pollution because it can come from household or farm animals, wildlife, as well as untreated wastewater effluent and failing septic systems.

Although these bacteria are usually not harmful, they often co-occur with disease-causing pathogens, so their presence at high levels indicates an increased probability that people are at risk of becoming sick if they come into contact with the water. The lake standard for fecal coliform bacteria addresses human safety due to direct contact with the water from activities such as swimming and wading. Sites used for this indicator are located in both mid-lake (open water) and nearshore locations in King County's three largest lakes — Washington, Sammamish and Union. This environmental indicator is based on data collected at the routine monitoring sites and does not include sampling done in conjunction with emergency sewer overflow events.

Status: Even though this measure uses a standard that is exceptionally difficult to attain, 100 percent of the Lake Sammamish stations, 85 percent of Lake Washington stations, and 60 percent of Lake Union stations have achieved the lake standard for fecal coliform bacteria. Lake Washington showed a decrease in samples meeting the standard from 2006, due to two high concentrations at station 0829 in addition to two high values measured at station 4903. Lake Union also showed a decrease due to high concentrations measured at stations 0512 and 0518.

Influencing factors: Six of the 11 samples that had fecal coliform greater than 100 CFU were the result of unusual storm conditions with the highest bacteria concentrations collected directly after record rainfall swept through the region the first week of January 2007. Lower percentages are attributed to the influence of combined sewer overflow (stations 4903, 0512, 0518) and stormwater outfalls into the lake. There are no CSO's that discharge into Lake Sammamish, five that discharge into Lake Washington and seven that discharge into the much smaller Lake Union. Additionally, the City of Seattle has 38 CSO's that discharge along the west side of Lake Washington and into Lake Union and the Ship Canal.

Existing DNRP response: DNRP will continue its extensive monitoring efforts to detect existing and potential problems with the stormwater and wastewater treatment system. In addition, King County's Combined Sewer Overflow (CSO) program is employing various ways to control CSO's including controlling pollution at its sources, optimizing flow management, monitoring and modeling flows in the system and constructing CSO control facilities. To protect public health, King County has scheduled to control CSO's, beginning with construction of CSO control projects along Puget Sound beaches (2010-2011) and the east end of the Lake Washington Ship Canal (2015). The final phase of projects will be built along the Duwamish River (2017-2027) and the west end of the Ship Canal (2029-2030).

Priority new actions: King County expects to build about 20 Combined Sewage Overflow control projects during the next 30 years.

---

Phosphorus in Small Lakes

About this indicator: DNRP's goal is to maintain all beneficial uses of county lakes. In this region, high concentrations of the nutrient phosphorus are often correlated with increased algal growth. Thus, if the amount of phosphorus entering lakes is controlled or reduced, algal blooms are likely to decrease. Algal blooms are a nuisance because they can cause scum to form on the lake's surface and occasionally give a foul odor and taste to the water. When a bloom dies off it can also deplete the oxygen levels available to other aquatic life. In rare circumstances, algal blooms can become toxic.

Phosphorus concentrations in lake water as an indicator assess the potential for nuisance or toxic algal blooms that impact lakes, facilitating allocation of limited county resources toward restoring lakes with indications of serious degradation. This indicator uses summer phosphorus concentrations converted to Trophic State Indicators (TSI-TP) to assess conditions. Trophic State Indicators relate phosphorus to the amount of algae that the lake can support. Values below 50 have low or moderate potential for nuisance algae blooms; values above 50 have a higher potential.

Status: This indicator incorporates data from 31 of the lakes monitored by King County. Slightly more than 80 percent of the lakes have good water quality with low potential for nuisance algal blooms.

Influencing factors: Lake water quality varies annually and is affected by many site-specific factors. Phosphorus can be managed through drainage system design, improved sewer service, and encouraging homeowners through education and incentives to use best management practices. Although large amounts of algae may relate to changes in conditions, this increased presence may not always reduce beneficial uses. However, a trend in a particular lake toward increased TSI-TP over time is probably due to changes in the watershed and cannot be discounted.

Existing DNRP response: We continue to monitor the managed lakes and implement elements of the Lake Management Plans under county jurisdiction, with community support, as funds become available.

Priority new actions: Lake management plans will be considered if any other county lakes begin to show serious deterioration in terms of beneficial uses. Monitoring data will be available online beginning in mid-2007.

---

Streams Water Quality Index

About this indicator: King County's Water Quality Index integrates key factors into a single number that can be compared over time and across locations. This index is based on the Oregon Water Quality Index and work done by the Washington Department of Ecology. From 2000 through 2007, 56 sites in the Lake Washington and Green-Duwamish drainage basins were sampled monthly for temperature, pH, fecal coliform bacteria, dissolved oxygen, turbidity, total suspended solids, and nutrients (phosphorus and nitrogen) relative to state standards and guidelines.

Status: Of the total sampled stream sites, 45 percent were considered moderate to high water quality, and 55 percent were rated to be of high concern. All sites rated of high concern were impacted in part by excessive nitrogen and/or phosphorus. In addition almost all high concern sites were affected by high fecal coliform bacteria (97 percent), low dissolved oxygen (74 percent), high temperatures (58 percent), and high-suspended solids/turbidity (32 percent).

Influencing factors: Overall stream water quality in King County is impacted by increased development in our region — primarily stormwater runoff. In 2006-07, cumulative rainfall was well above average compared to historical values, in part due to a very wet November and December.

Stormwater, combined sewer overflows (CSO's), waterfowl and pet wastes are the most likely sources of bacteria in urban streams. Poor livestock manure management and failing septic systems can be a potential source of bacteria in agricultural and suburban areas. In wetlands, wildlife excrement and stagnant water conditions can lead to elevated bacteria counts. High phosphorus concentrations are found in fecal material and elevated concentrations are often linked to similar sources as bacteria. In addition, elevated phosphorus concentrations are linked to areas undergoing development.

Low dissolved oxygen concentrations can be associated with low flows, wetlands, high temperatures (colder water holds more oxygen), and high levels of organic matter (bacteria use up oxygen in the process of decomposing).

Existing DNRP response: King County is responsible for preserving water quality and preventing and repairing damage to its waterways and water bodies. Attention is given to high concern sites to improve water quality. This can involve properly maintaining facilities, constructing or engineering solutions, identifying where or how pollutants are entering the stream, and/or educating adjacent property owners about the impacts of pesticides and fertilizers on streams.

Priority new actions: Results from King County's Water Quality Index highlight the need for a comprehensive and coordinated approach to resolving in-stream flow management, since lower summer flows and increased stormwater runoff inflate every water quality measurement of the index. King County will work with the Puget Sound Partnership to advocate a coordinated effort in the planning at a regional scale.

---

Nitrates in Groundwater on Vashon-Maury Islands

	Nitrates in Groundwater on Vashon-Maury Islands 2007 Findings

About this indicator: King County has been tracking groundwater quality on Vashon-Maury Island since 2001. Nitrate is used to track groundwater quality because it is a good indicator of changes caused by human activities, such as land-use development. King County's goal is to ensure high water quality through effective land-use and on-site septic regulations.

The groundwater quality indicator uses a nitrate index, defined as the maximum concentration of the annual sampling results divided by the maximum contaminant level (MCL) of Nitrate (10 mg/L). This method yields one number. The closer this index gets to 1 (or over 1) the greater concern. The nitrate index has been less than 0.5 since 2003.

Status: Of the 19 well/spring sites monitored, all have tested below the drinking water standard (Maximum Contaminant Level, MCL of 10 mg/L) and all have less than 5 mg per liter of nitrate present. Less than half the sites tested have seen above average nitrate increases since testing began.

Influencing factors: Poor drainage systems, improperly maintained septic systems and improper fertilizer use can increase nitrate levels.

Existing DNRP response: King County plans to continue monitoring Vashon's wells and springs annually for nitrate concentrations.

Priority new actions: Additional locations have been sought to increase our understanding of island aquifers. King County intends to produce Vashon-Maury Island-wide water table, contour maps with seasonal variability that will be reported every year.

Back to top