Wetland Delineation & Rating

Wetland delineations establishes the existence (location) and physical limits (size) of a wetland for purposes of federal, state, and local regulations.

A wetland rating establishes the protection standards and buffers depending on your county or city.

Our team of wetland biologists are prepared to work in a variety of locations in the Puget Sound and understand your properties specific regulatory requirements. Our goal is to understand the needs of your specific property and jurisdiction and facilitate a quick approval through accurate biological assessments.

Peninsula Environmental conducts delineations and ratings in a variety of wetland habitat types: tidal salt, freshwater, seasonal, riparian woodlands, vernal pools, marshes, meadows, seasonal forest wetlands, man-made, agricultural, and ponds.

Our Wetland Delineation and Rating Services Includes

Documentation and Regulation Permits

Here at Peninsula Environmental Group our team utilizes current regulation methods to document wetlands of all kinds, and produce a precise declaration. Our experienced consultants can also assist with designing thoughtful, multi-functional, mitigation and restoration plans to enhance the landscape, and quality of your property, all while satisfying regulatory requirements. We can help with permit application, all the way through completion of the construction project.


Clean Water Act Section 401 & 404

Section 404 of the Clean Water Act authorizes the US Army Corps of Engineers (USACE) to regulate the discharge of dredged or fill material into the waters of the United States, including wetlands, streams, and other waters. To define the location, size, and quality of waters of the United States, the USACE established a delineation protocol. A delineation is required for all projects that involve potential impacts to waters of the United States.

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How do we perform a Wetland Delineation?

In order to determine if wet area meets the qualifications for a wetland, a wetland professional assesses three main components. These three components are the basis for a wetland delineation. The plant community, the soils, and the hydrology of the site. Each of these aspects has many facets but can be summarized as follows.

Vegetation – Certain plants have adapted to better handle the stress of frequent saturation or inundation (ponding). The presence and abundance of these hydrophytic (water-loving) plants can help determine where an area shifts from wetland to upland.

Soils – When soils are inundated for extended periods of time there are various processes that occur and leave behind evidence of the water’s influence. By digging soil pits we can look for these indicators and determine if they match known types of wetland soils (hydric soils). These soil pits can also provide insight to the site history, through features like plow pans, old lake beds, or disturbed soils.

Hydrology – As water moves across our landscape it leaves signs of its passing. This can be as apparent as surface water, or as subtle as buttressed tree roots and raised ant hills. By examining the way water interacts with an area we can determine if it is present long enough to qualify for wetland status.

skunk cabbage growing in wetlands.

Why are wetlands protected?

Wetlands provide many crucial functions and services to our urban and natural areas. Wetlands improve water quality through slowing of water, settling of sediment, and sequestration of pollutants. They recharge aquifers (wells) through water retention and infiltration, and reduce flood severity by providing storage and desynchronizing peak flows. They also provide critical habitat for many priority species, such that we often write habitat management plans that involve wetlands.

Washington Wetlands are a complex and diverse type of ecosystem that can be found all across the landscape, from coastal lagoons to pristine bogs to stormwater detention ponds. The common characteristics are that they support a unique set of conditions and provide important functions to the environment and society. Historically wetlands have experienced heavy losses, a similar fate to many of our old growth forests and other environmentally sensitive areas. While growing as a nation, wetlands were generally seen as areas to be filled to make way for buildings and agriculture, or sources of pestilence to be drained to reduce insect populations. Wetland losses vary greatly by state, but it is estimated that the United States has lost about 1/3rd of the nation’s wetlands.