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Critical Areas Update

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Descriptions of Critical Areas

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What are Critical Areas?

The 1990 Growth Management Act (RCW36.70A) requires our state’s fastest growing cities and counties to write comprehensive plans and development regulations to manage growth and prevent urban sprawl. Local governments that write plans under the Growth Management Act must protect five types of critical areas: important fish and wildlife habitat areas, wetlands, critical aquifer recharge areas, frequently flooded areas; and geologically hazardous areas, (such as bluffs). Thurston County’s critical areas regulations are a response to that law – they regulate how development and redevelopment can safely occur on lands that contain critical areas.

Why was an Update Needed?

A 2003 amendment to the state Growth Management Act requires Thurston County to comprehensively review its Critical Areas Ordinance every seven years to make sure it keeps pace with changes in state law and is achieving the level of protection necessary to maintain the environmental and public benefits of critical areas. The Critical Areas Ordinance was adopted in 1994 and minor amendments have been approved since then; however, a comprehensive update is now necessary.

Updating the critical areas ordinance is also a way to ensure that our regulations “stay local.” If Thurston County fails to protect critical areas – especially certain habitats and species – the state and federal governments may step in and enact stricter requirements, as would be the case if a species is listed under the Federal Endangered Species Act.

Beyond the legal requirements, Thurston County also has a duty to preserve critical areas in order to protect the health and safety of residents and the environment that sustains us all. Click here to view the adopted ordinance.

Important Fish and Wildlife Habitat Areas

salmonThurston County is one of the fastest growing counties in Washington State, and all that growth puts pressure on important wildlife habitat.

Some of our most valuable habitat – “riparian habitat” – is found along water bodies such as rivers, streams and marine shorelines. Riparian habitat refers to the transitional areas between the upland environment and the water. Riparian habitats moderate the temperature of water bodies, help prevent erosion, and provide a home for many types of animals and vegetation. Although riparian areas are located alongside the water, they also provide habitat within the water – trees that fall into the water form sheltered pools where fish can lay eggs. The trees and pools also supply insects and organic materials for the aquatic food chain. More than 90 percent of all wildlife use riparian areas for part or all of their life cycle.

Other types of habitat include marine habitat – such as shellfish beds and spawning areas – and upland wildlife areas such as prairies and native oak trees.

Habitats provide the food, water, nesting/rearing, and cover necessary to support populations of species that are at risk of being lost from Thurston County. If Thurston County fails to protect important habitats and species, the state and federal governments could step in – and possibly impose stricter requirements.

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wetlandWetlands and their buffers act as natural sponges. They help to prevent flooding and erosion by absorbing floodwater and sending it slowly to rivers, streams and aquifers. Wetlands also provide a home for many species of native plants and wildlife.

The plants and soils in wetlands filter out pollutants, such as nitrogen and phosphorous, which are found in household fertilizers and herbicides. This natural cleansing capacity of wetlands can become overtaxed if too much pollution accumulates in the wetland and in the end adversely affect the wildlife it supports. Wetlands include bogs, marshes and swamps. Frequently, their water is visible only in the spring.

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Critical Aquifer Recharge Areas

aquifer rechargeVirtually all of our drinking water comes from groundwater aquifers, which are underground layers of coarse cobbles and gravel that contain space where water collects. Aquifers not only supply our drinking water, they also flow underground to feed rivers, streams and wetlands. “Aquifer recharge areas” are places where water infiltrates into the ground and replenishes the aquifers. As the water seeps into the aquifers, contaminants from aboveground activities can go along for the ride. Toxic substances and fertilizers have already contaminated portions of Thurston County aquifers and water in those areas is no longer suitable for consumption.

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Frequently Flooded Areasflooded area

Thurston County experiences many types of flooding, such as river flooding, where a river breaches its banks, and groundwater flooding, where the water table rises so high it fills low-lying pockets of land. Stream channels may also shift over time and direct water to properties that have traditionally remained dry in recent years. This is referred to as channel migration. Some streams in the county move around quite a bit and have the force to destroy houses and other structures in their way. Of all natural hazards that affect Thurston County, floods are the most common and, on an annual average basis, the most costly.

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Geologically Hazardous Areas

earthquake OlympiaAreas of Thurston County are vulnerable to naturally occurring geologic events such as landslides, lahar flows, and earthquakes. In 1999, heavy rainfalls caused the slope at Carlyon Beach to give way, destroying several homes. A Mount Rainier lahar (debris flow from volcanic activity) could send mudflows down the Nisqually River Valley and sweep away trees and structures in its path. Also, earthquakes can cause severe damage to structures built on unstable soils, such as fill and river deposits.

Thurston County, particularly properties in the City of Olympia, incurred significant damage from the effects of the 2001 Nisqually earthquake.

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