Case Study · Water Systems
One terminal, two treatment systems.
At the Port of Portland’s Terminal 4, storm water management pairs manufactured treatment structures with natural features. Hardware handles the spill-prone zones; bioswales and riparian buffers slow, cool, and filter runoff before it reaches the Willamette.
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Client
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Port of Portland
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Facility
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Terminal 4
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Practice
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Water Systems
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Approach
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Structural + natural hybrid
The Short Version
Match the treatment to the runoff.
No single BMP fits a whole terminal. T4’s storm water design assigns each surface the treatment its runoff actually needs: manufactured structures where oil and sediment concentrate, vegetated features where space allows water to slow down and cool off.
The structural side
Trucking areas and paved cargo surfaces generate runoff loaded with sediment, oil, and grease. That water moves through staged hardware: catch basins that let particulates settle before discharge, geotextile inserts that trap sediment and absorb oil at the inlet, and oil-water separators where automotive and hydraulic fluid spills are expected. None of it works without scheduled cleanout. A catch basin that never gets cleaned stops being treatment and becomes storage.
The natural side
Where the site plan allows, vegetated features take over. Bioswales slow the flow, drop sediment, and cool the water, which matters because warm discharge disrupts the shallow-water habitat along the bank. Riparian buffer plantings of native grasses, shrubs, and trees stabilize the riverbank, shade the watercourse, and strip pollutants from sheet flow before it arrives. The same features double as open space on a working industrial site.
What we can and cannot claim
The value of T4 as a case study is the pairing, not a headline number. The record documents which features were built and why each was chosen for its zone. It does not include long-term discharge monitoring data we can publish, so we will not invent a percentage. The honest claim is narrower: combining structural and natural BMPs let a constrained, active terminal treat its runoff without giving up working ground, and the same zoning logic transfers to other waterfront facilities.
Natural storm water systems do treatment work and aesthetic work at the same time. The limit is space, and terminals that master-plan for green buffers early rarely regret it.
TDG Water Practice, natural systems overview
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