Cover photo:
The A-Mazing Water Garden
at sunset
© Peter Marbach

Their exciting and surprisingly ornamental wetland plant communities perform a vital public service for the residents of Silverton, Oregon. It’s part of their city wastewater treatment process! 

The Oregon Garden Wetlands

by Deborah Hill and Renee Stoops
Photos by Peter Marbach, Renee Stoops and The Oregon Garden
Click to enlarge

The City of Silverton partnered with the Oregon Association of Nurserymen (OAN) to create The Oregon Garden (TOG). In the early 1990s the City failed to meet its National Pollution Discharge Elimination System permit requirements for treated wastewater. An Oregon Department of Environmental Quality Clean Water Act survey of surface waters in Oregon listed the town’s Silver Creek on the 303(d)* list of water bodies not meeting water quality standards for temperature and bacteria problems, caused partly by the influx of City-treated wastewater. Silverton decided to buy land where it could create wastewater wetlands to treat the temperature problem.

Meanwhile, OAN was looking for a site for its planned botanical garden, and approached the City with the partnership idea. A botanical garden needs water for irrigation, and the City’s treated wastewater made a perfect fit. Although not regulated as a treatment process, the wetlands were designed to lower temperature and nutrient load. Water in the wetlands was designated “Waters of the State” so that it could be used for irrigation in our garden. This designation officially makes the wetlands non-fish bearing, warm water refugia.

We finished and dedicated parts of The Garden between 1999 and 2001 following the official July 27, 1997, groundbreaking. The City started pumping treated wastewater to us in May 2000. We continue to grow and expand; in the summer of 2005 we opened our most recent addition, the Lewis and Clark Garden.


The heaviest wastewater load is May-October when about 700,000 – 800,000 gallons a day runs through the terraced ornamental wetlands. November-April yields about half as much wastewater and much more rain.

Water flows through a series of three complexes. First it passes through Complex A consisting of the upper 16 shallow ponds (cells A through O) before pouring into holding tanks for irrigating the gardens. When full, these tanks overflow passively to Complex B (cell Q), a single large pond on the north side of the driveway by Cascade Highway.

Water then flows into Complex C (cell R through cell Y), the last series of eight larger, deeper ponds south of the driveway by the highway. Cell P is the A-Mazing Water Garden which is not connected to the other cells.

We emphasize native plant species in and around all of our ponds, with the A-Mazing Water Garden showcasing hardy and tropical plants favored in home water gardens.

Wetland Research > | Water Quality Research >
Barley Straw Algae Control Research >


* Section 303(d) of the Federal 1972 Clean Water Act requires states to develop a list of limited segments that do not meet water quality standards, and to create action plans to improve water quality for the listed segments. 

Wetland Research > | Water Quality Research >
Barley Straw Algae Control Research >

The Oregon Garden - More Than A Pretty Face!
Gallery of Aquatic Images by Renee Stoops and The Oregon Garden

The Oregon Garden Web Site

WGI ONLINE Journal Table of Contents

Water Gardeners International
Home | Join WGI | Members' Exclusive | Gateway to Water Gardening