The State of Edmonds Waters

Introduction and Overview.

Edmonds is surrounded by water. It falls on us; it runs beside us through streams and gutters, and beneath our feet into puddles and lakes and Puget Sound. It is vital and useful, beautiful, sometimes dangerous, and we cannot take it for granted. A better understanding of water quality, quantity and the condition of aquatic habitat will, I hope, raise awareness, promote discussion of water management issues and help generate solutions.

This discussion of stormwater runoff is the first of a series of articles on the state of Edmonds’ waters, including streams, wetlands, the estuary, and marine waters. Subsequent topics will address:

• The state of Edmonds’ streams, including flows, contamination, erosion, and fish blockages;

• The state of the marine waters off Edmonds; and

• The Edmonds Marsh and Estuary including issues, history, and opportunities; and

• Possible solutions to improve our aquatic resources, and how to finance the necessary improvements for stormwater management and habitat restoration.

Stormwater affects the quality of all our waters and will feature in each of these.

Stormwater and Water Quality

“Stormwater” is rainfall that runs off impervious surfaces. Stormwater is the largest source of pollutants to Puget Sound and to our streams.

When Edmonds was covered with old-growth forests there was less runoff. Only 70% of the water dropped by clouds actually reaches the ground; the rest stays on trees and evaporates. In the natural environment, roughly half of the rainfall that reaches the ground infiltrates shallow soils and slowly flows through the soils to streams. The remainder reaches deep soils and recharges aquifers. Large storms may drop more water than can be absorbed resulting in surface runoff into streams or wetlands but they are infrequent events, occurring less than once every two years.

As forests are removed and replaced with roads, parking lots, and roof tops, stormwater runoff increases significantly and the impact on our streams is devastating. Peak flows occur more often, eroding stream banks and causing channels to become wider and shallower. Small gravel and salmon eggs are washed away by these higher volumes of fast-moving water and the gravel is replaced with sand and silt. Between storms the widened streams are shallower and unable to support fish populations.

Stormwater from impervious surfaces introduces pollutants that harm salmon and the insects they eat. Pollutants, many from vehicles and pavement wear, include:

• Zinc (toxic) from tire wear

• Copper (toxic) from brake linings

• 6ppd-q (toxic) from tire wear

• Oil and grease

• Detergents from motor oil and residential use

• Phosphorous from motor oil and fertilizers

• Silt from channel erosion

• Pesticides (insects, weeds, rats)

• Bacteria from pets and improper sewer connections

• Phthalates (mimic female hormones) from plastics and cosmetics

• Bark from landscaping

• Trash

• Sand, silt and salt from treating roads during snow events

• Silt from construction sites

• Micro-plastics

Studies show that as density increases from one house every five acres to one house every two acres there are significant declines in the diversity of species, in the numbers of salmon, and in the insects that young salmon eat. These populations continue to decline as we increase the density of urban development and, if the impact is ignored, valuable species like salmon can be destroyed.

Houses and roads are essential to our way of life, and our population is growing. Urban development is ongoing. However, we can reduce our impact, through thoughtful approaches to building that preserve and protect habitat.

In the next article will explain the conditions of Edmonds’ streams in more detail.