A draft plan to improve the environmental quality of the Bear Creek Basin area has been completed and makes several recommendations.
The basin encompasses 26 square miles, 200 miles of road and 10,000 households and stretches east from Redmond and Woodinville.
The results of the study show conditions, on the whole, to be improving somewhat but many issues still exist.
Bacteria levels in streams, lakes and wetlands are higher than they should be, streams are becoming warmer with less usable cover that hurts fish, in-stream salmon habitat is degraded, flash stream flows scour riverbeds of salmon spawns, riparian zones are being lost and stormwater facilities are outdated and inadequate.
Wetland loss is also a constant concern.
The basin’s native salmon populations have been substantially harmed over the last four decades due to increased regional growth.
In 1983, there were an estimated 550 naturally-spawning chinook salmon in the north Lake Washington region, which hit a low point of 33 in 1996 and again in 2011, a previous Reporter article found.
The study found water temperatures have been increasing between .3 to .6 degrees Celsius every decade, which has lead to decreasing dissolved oxygen that harms salmon.
Fecal coliform bacteria levels often exceed the standards set by Washington state as being safe for humans and temperatures are too high for fish.
There were some positive findings, which include fewer nutrients for algae that can result in toxic blooms and few instances of toxic levels of metals.
Warmer water in streams is due to a number of causes, including stormwater that quickly runs off of roads, parking lots and roofs and into streams during storms.
One inch of rainfall generates 748 gallons of runoff for a 1,000-square-foot roof, and 27,000 gallons of stormwater run off comes from a 1-acre parking lot.
This contributes to flash swells, which can scour fish eggs from the bottom of streams, as well as wash toxins from roads into fish habitats.
Puget Sound tributaries are home to a wide variety of fish, including chinook, sockeye, coho, kokanee, coastal cutthroat and steelhead salmon.
Warmer water is due to the loss of riparian zones as well, which are the areas next to streams with overhanging trees and shrubs.
These plants help filter the water, provide shade and offer shelter for juvenile salmon.
The report included a breakdown of land use in the Bear Creek Basin, which included 40 percent forest, 26 percent developed and 25 percent developed open space.
Only 5 percent of the area was wetlands.
The study suggested ways to restore habitat over the next decade.
These included updating more than 80 percent of stormwater infrastructure to modern standards.
Infrastructure includes pipes, ditches, ponds and underground water tanks and vaults.
Other strategies are building gravity wells, which siphon water in and treat it by filtration through soil.
Community-based options include promoting the use of rain gardens, which collect stormwater and filter it through native plants and spongy soil.
Permeable pavement allows stormwater to seep into the ground instead of running off.
Salmon habitat such as replanting riparian zones, restoring wetlands and connecting floodplains and wetlands with streams was also recommended.
The report said residents can get involved by using less outdoor chemicals, planting native vegetation, using a rain garden and by maintaining their vehicles and septic tanks.
The estimated cost of the strategy includes $51 million to upgrade and build new stormwater infrastructure, $4.7 million to restore habitat and wetlands, $4.2 million for programs and studies and $21.7 million for land acquisition.
The study was produced by Redmond, Woodinville, the state Department of Transportation and King and Snohomish counties.
Public comment on the draft plan runs through March 21 and it is expected to be submitted to the Department of Ecology by April 4.