Working With Wetlands. A Civil Engineer’s Advice for Navigating Wetlands on Your Site

Civil Associate Principal Keith Kruger (P.E., LEED AP, Assoc. DBIA) often finds himself educating clients about the impacts a wetland can have on a development. He breaks them down here, and shares some common practices and key advice on behalf of the Coughlin Porter Lundeen civil group.

Call it what you like: a marsh, a bog, or a swamp – wetlands are a reality in our region, and an important piece of a healthy ecosystem. According to the State of Washington’s Department of Ecology, “wetlands cover approximately 938,000 acres in Washington state, about 2% of the state’s total land area.” And they’re essential, as they “protect water quality, reduce flooding, provide aquifer recharge for drinking water and other uses, and provide critical habitat for fish and wildlife.”

Protected at almost every governmental level, wetlands can make owners and developers (understandably!) wary. The designs that most often face wetland challenges are campus projects. Schools and corporate campuses that require lots of space have the potential to have wetlands on their site, particularly in rural areas. While this is especially true for new developments (as the land that’s available is usually available because it’s on wetlands), we encounter it often on many existing school and campus settings too.

As engineers who work almost exclusively in the Pacific Northwest, we’re extremely familiar with wetlands and our portfolio includes dozens of the most challenging and complex projects in the region. With 30 years of experience, we partner with owners and developers to navigate this unique project aspect. This includes two of the largest tech company campus projects in the history of the area, which required extensive modeling, permitting, and design work. Our team has a long history of successfully negotiating winning solutions for our clients and the environment.

It’s difficult to confirm if a wetland is truly present until working with specialists. Typically, one of the first steps is to bring a critical areas consultant, wetland specialist, and/or biologist on board. There’s a very large spectrum of what a wetland can look like, and these specialists will define how it’s classified. Even before results are presented by a specialist, our team assists owners with potential options and likely requirements based on available public information. In many cases, this review is completed even before the decision is made to purchase the land and/or any specialists are hired.

As civil engineers, our role is ultimately to look at wetland classifications and characteristics through the lens of the stormwater code: What does this mean for limitations (or opportunities!) to the site? What core permits do we need to consider? How can we marry stormwater management with the design and site vision? How can we help our partners navigate this tricky element without sacrificing options or taking on additional risk?

Let’s say you get the news, or the available information indicates, there is indeed a wetland on or downstream of your site. According to the Ecology Manual, this means your site requires special evaluation and design to mitigate a wetland. The team will need to confirm that any impacts to wetlands are minimized and mitigated. Below are our top three recommendations to achieve this requirement and keep the design vision on track.

1. Get Your Team in the Room Early!

Engaging your team early is something we preach often at Coughlin Porter Lundeen. It should be in our lobby! “The earlier we’re in the room, the better!” We are experts at pre-evaluation. And the pre-evaluation process matters enormously for projects navigating wetlands. We often start long before the decision is made to buy the land, before any survey is completed, and before any fees are spent on hiring experts.

Often, once owners acquire a piece of land, the tendency is to hire a surveyor and perhaps a wetland consultant. Next, they’ll engage an architect. It’s typical for owners to avoid engaging too many professionals early in the process. This is often done in the name of cost savings, but in reality, the opposite can be true. We want to advise owners and developers against falling into that trap. It’s critical to get your site team in a room early, and will likely create a smoother project process and experience, support an expedited timeline, and potentially achieve cost savings along the way!

As civil engineers, we’ll look at many things in this early phase. We’ll review the findings of the wetland specialists (and in some cases, challenge them!). We’ll begin building a plan for core permits, help the owner and architects understand options and risks, answer key questions, and begin to understand the design, entitlement, and related site impacts. Involved early, we’ll be better able to dovetail this long process into the overall timeline, allowing these to run in parallel. This minimizes risk and maximizes value to the client.

Even if you have experience developing with wetlands, it’s important to remember that one size does not fit all. Standards are constantly evolving, and what may have worked a few years ago may be impossible to be replicated, and new solutions and possibilities are always emerging.

2. Understand the Possibilities

An important part of our role is walking alongside clients as the project comes to life and helping them understand options, requirements, and details that they may not be experts in.

This means helping clients and their teams address everything they need to in order to entitle and construct their project in the way they envision. Whether global tech companies, developers, health care organizations, or education clients, we help them understand how their development could be impacted by the presence of wetlands, how to minimize or avoid that risk, and how to hopefully turn the challenge into a positive outcome.

If wetlands are found onsite, the discovery can dictate how a development shapes up – building locations, necessary grades, easements, building setbacks. Even if there aren’t protected wetlands, we may have to create a stormwater mitigation plan, ideally developed as early as possible.

In extreme cases, if a wetland is identified on a site, there could be a mandated long period of observation, potentially a year or more, in which the team will have to observe how the wetland behaves. Your team won’t be idle though! We’ll continue moving forward, approximating what we think that result of the observation period will be. The team will design around the range of assumptions, so when the observation period is complete, we can quickly confirm design, edit, and submit.

3. Seize the Silver Lining

The best projects, no matter the site or market, are the ones that leverage what the site and program present, using what the location offers and celebrating what makes a project or space special.

When it comes to wetlands, we’ve had the opportunity to partner with some incredible clients who have made the best of their site, turning this potentially undesirable element into something hugely beneficial. “Silver linings” range from immersive educational nature environments on school campuses, to unique, cost-saving water treatment solutions. These projects have achieved the balance of protecting the sensitive natural areas, while creating memorable, beautiful, and functional final projects.

Timberline Middle School. Redmond, Washington. © Benjamin Benschneider All Rights Reserved

Timberline Middle School

Built to serve 900 students, this 21-acre project maximized preexisting clearings to nestle a brand new middle school (including parking areas and drive aisles, pedestrian plazas, and athletic fields) into a heavily wooded site. While the site itself was partially cleared, significant effort was made throughout design to limit the school’s environmental impact – aiming to create an organic building embedded in the forest.

This dedication to preserving the school’s surrounding environment extended to the site’s prominent wetlands. This unique site is part of an Urban Planned Development (UPD) within King County that had its own set of development requirements. The UPD includes an undisturbed King County wetland/wildlife corridor. The school embraced the setting as a unique teaching element, and learning labs and stacks are all oriented toward the wetland/wildlife corridor.

The design of Timberline Middle School centered around the themes of Connection, Value, and Challenge – aiming to deliver an environment that resulted in Future Ready students, as outlined by the District’s 2020 Guiding Principles.

Tambark Creek Elementary School, Courtesy of Dykeman

Tambark Creek Elementary School

The new 78,000 SF, two-story K-5 school accommodates 550 students in a V-shaped footprint, with the main entry and shared spaces located where the two learning neighborhood wings form a hub. The central courtyard and protected wetlands area is embraced for outdoor learning and to support the school’s STEM curriculum. As part of the 30-acre site master plan, the team included planning for the future high school on the easternmost 20 acres, including drainage, utility extensions, grading, access roads, and frontage improvements with long-term development strategies in mind.

Existing vegetation in middle of site had to be saved. The school’s clean building runoff is directed to trenches, which lead to the wetland. This maintains natural flows within the wetland and “recharges” it. Walking paths around buffer around perimeter, transforming the wetlands into a teaching opportunities to students.

The project site contained a Category III wetland with a habitat score of 6. The school district was interested in maintaining the hydrology of the wetland in conjunction with other site programming needs, and design criteria for higher category wetland standards were met to the maximum extent feasible. Specific wetland criterion set by the Snohomish County Drainage Manual were met by providing flow control via dispersion trenches within the wetland’s buffer, and by using a continuous simulation hydraulic model to match the average monthly influent volumes from post-development to pre-development within 15%.

Non-pollution generating surfaces from the school site were routed to the wetland too. Through iterations of the analysis, the proposed areas of the project site that were directed to the wetland include reverse sloped sidewalks, landscape areas around the building, the wetland buffer itself, a portion of the elementary school’s roof, and additional upstream undeveloped wooded area. This maintains natural flows within the wetland and “recharges” it. Walking paths were carefully placed around the wetland’s perimeter buffer, transforming the wetlands into teaching opportunities for students and the community.

Longacres Campus Redevelopment

The 158-acre site in Renton is the renowned former Longacres horse racing track. Currently in the master planning stages with the owner, Unico, and the city, this unique project sits in a valuable urban area.

Originally planned in the 90s, we’re working with the development team to reimagine this area, taking it from a standard, suburban office park to a vibrant, live-work community. This will allow the public, the employees, and the residents of this site enjoy this amenity while making it better and more robust than ever before.

The team is also working to preserve the function and health of the site’s resources, as well as the downstream creek it supports.

Redmond Tech Campus

The downstream wetlands at this site have been enhanced and monitored since the early 90s and were a primary concern of the city as well as the client. Working closely with the design and environmental consulting team early in the planning stages, we strategized with the city the best way to support their planned improvements in the basin. Drainage patterns were reconfigured, which supported and improved the health of these well-developed wetlands. Not only did the drainage revisions save the client money and construction time, but it preserved developable area for the future.