Note: This information is provided for reference purposes only. 

Although the information provided here was accurate and current 

when first created, it is now outdated.

Disclaimer: The information in this website is entirely drawn from a 1993 publication, and has not 

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Hillsboro, OR - Jackson Bottom Wetlands Preserve

Introduction

Wetlands Water Source

Putting the Polish on Wetlands for Water 

Quality Management

The Dynamics of a Real-World Experiment 

Enhancement for Wildlife

Education, Research and Passive Recreation

Acknowledgements
Working together for water quality, wildlife habitat, education and passive recreation.

At the south edge of 

Hillsboro, Oregon, lies the 

damp, tranquil sanctuary of 

the Jackson Bottom 

Wetlands Preserve. Nearly 

650 acres of low-lying 

floodplain on the edge of 

the Tualatin River, about 

80 percent of the area is 

classified as wetlands. 

Early mapmakers 

dismissed the damp bottomlands as a “mirey swamp” suitable only for dredging, draining, and farming. 

Over the years, agricultural and sewage disposal practices created a highly degraded landscape of limited 

value for wildlife use, dominated by introduced grasses. 

Since 1979, the Jackson Bottom Steering Committee has been working 

together on an innovative project aimed at changing those conditions 

and transforming this "mirey swamp" into a wildlife and water quality 

"living laboratory." The Steering Committee, made up of a unique 

alliance of economic interests, environmental groups and public 

agencies, spent the first 10 years on efforts directed primarily toward 

improving the area's wildlife habitat and passive recreation values. 

In 1989, the coalition broadened its efforts and began investigating the 

use of natural and constructed wetland systems for water quality 

management as part of the Unified Sewerage Agency's effort to improve 

water quality in the Tualatin River. 

At the Jackson Bottom Wetlands, the Steering Committee has a unique opportunity to manage the 

wetland's multiple goals. Jackson Bottom provides a chance to increase the diversity of resident and 

transient wildlife, improve water quality, provide rich research and educational experiences, offer passive 

and non-consumptive forms of recreation, and attract tourists in an area of rapidly expanding urban 

population. 

The 1989 Jackson Bottom Concept Master Plan clearly outlined the main goals of the Jackson Bottom 

Wetlands Preserve. 
Enhancement for Wildlife:

Attract a more diverse wildlife 

population by expanding and 

restoring the preserve to 

provide food and shelter to a 

variety of birds and animals. 

Water Quality Management:

Develop the Jackson Bottom 

Experimental Wetland to 

investigate the feasibility of 

using wetlands to “polish” 

effluent from a secondary wastewater treatment plant for the 

removal of phosphorus and nitrogen before discharging to the 

water quality-limited Tualatin River. 

Passive Recreation: Provide access to areas of the wetland and 

the Tualatin River for hiking, bird watching, angling and other 

passive natural resource-associated activities. 

Education and Research: Encourage educational use through interpretive signs and displays, 

development of educational materials for schools and groups, providing site tours and assisting 

researchers with research projects. 

The Jackson Bottom Steering Committee

● City of Hillsboro

● Unified Sewerage Agency (USA)

● Oregon Department of Fish and Wildlife

● Greater Hillsboro Chamber of Commerce

● Washington County Soil and Water Conservation District

● Portland Audubon Society

● Friends of Jackson Bottom

● Oregon Graduate Institute

● Washington County Education Service District

● The Wetlands Conservancy

● Portland Bureau of Environmental Services

● Pacific University

● U.S. Fish and Wildlife Service
Wetlands Water Source

Historically, the damp landscape of Jackson Bottom owes its source of water to the regular flooding of 

the Tualatin River. The flooding creates the bottomland wetlands which make up the majority of Jackson 

Bottom. 

Today, water from regular winter flood is 

supplemented in the summer by secondarily treated 

effluent from a nearby Unified Sewerage Agency 

treatment plant. This cleaned wastewater helps to 

maintain the restored wildlife habitat. In return, the 

wetlands filter the effluent before it's returned to the 

river. 

Since 1979, enhancement projects have created and 

restored several types of wetlands once typical in the 

basin. The additional wetland types include deep and 

shallow ponds, wet meadows, riparian wetlands and 

fresh-water marshes. Edging the east side are also 

forested wetlands and upland habitat. 
Putting the Polish on Wetlands for Water Quality Management

Wetlands, ponds and lagoons have long played a role in wastewater treatment. In many areas, partially 

treated wastewater is filtered through wetlands for suspended solids (SS) and biochemical oxygen 

demand (BOD) removal. 

The Jackson Bottom Experimental Wetland (JBEW) is taking this process one step further. Using 

secondarily treated effluent from the Unified Sewerage Agency's (USA) Hillsboro Wastewater Treatment 

Plant, USA's researchers are investigating the use of wetlands to “polish” the wastewater for removal of 

phosphorus and nitrogen. These nutrients are abundant in the effluent of conventional secondary 

treatment plants. This experimental program is part of USA“s comprehensive effort to reduce loads of 

phosphorus and nitrogen entering the water quality-limited Tualatin River. 

Built in the summer of 1988 with operation beginning in 1989, the JBEW occupies about 15 acres on the 

eastern edge of the Jackson Bottom Wetlands Preserve. The Experimental Wetland is actually a series of 

17 parallel cells, each built to contain effluent for varying amounts of time, with different soil types and 

different vegetation patterns. Since July 1989, testing has been conducted to measure the success rates of 

the soils and vegetation to "polish" the effluent. 
Jackson Bottom 

Experimental Wetland

Design and Operational 

Criteria

Cell Design Criteria; 15.6 Acre 

Wetland (17 Parallel Cells)

Cell Size, Capacity Total

Width 18.3 to 22.4 ft .

Length 1250 to 1280 ft .

Depth

46 percent at 1 ft

54 percent at 3 

ft.

.

Surface 

Area

22,000 to 30,600 

sq. ft

0.5 to 0.7 acres

430,600 sq. 

ft

9.9 acres

Water Level0.5 to 2.75 ft .

Volume 254,000 to 

427,000 gal 4.8 mil gal.

Introduced Cattail (Typha 

latifolia) .

.....

Vegetation

Sago pondweed

.....(Potamogeton 

pectinatus)

.

Soil

..... Cove 

Series 5.4 acres .

..... Wapato 

silty loam 6.2 acres .

..... Labish 

mucky clay 3.4 acres .

JBEW Operational 

Parameters

. 1989 1990 1991

Days 77 108 118
Operational Period

July 

25-

Oct 

17

June 

25-

Oct 

10

June 

19-

Oct 

10

Hydraulic cm/d 7.0 4.0 5.5

.......Loading 

Rate in/d 2.8 1.6 2.6

Average 

Flow/cell gpm 30 19 24

Detention Time days 5-10 5-27 4-12

Mass Loading Rates

.......Phosphorus kg/ha/da5.2 3.4 2.4

. lb/ac/da 4.6 3.0 2.1

.......Nitrogen kg/ha/da14.9 7.7 11.0

. lb/ac/da 13.2 6.9 9.8

After three years of testing and extended research on JBEW, interesting results have surfaced . The 

Experimental Wetland is improving the quality of the effluent—it is lower in both phosphorus and 

nitrogen when it leaves the cells. Research has shown, although plants serve important functions in the 

filtering, the soils have proved to be the main elements in binding up the phosphorus, thereby preventing 

it from reaching the nearby Tualatin River. 

Water quality is the focus of the JBEW, but education and wildlife have also benefited from this 

innovative project. The construction of the wetlands has provided food, nesting and rich habitat for many 

wetland species. The Experimental Wetland has also provided valuable educational opportunities for 

teachers, students and researchers from schools and universities throughout the region. 

As research continues to determine how to best meet the state's water quality standards, the Jackson 

Bottom Wetlands Preserve serves as a model for improving water quality and managing multiple goals. 

JBEW Outflow Data, Three 

Year Average

. InfluentEffluent

Biochemical Oxygen 

Demand (mg/L) 5.1 3.0

Chemical Oxygen 

Demand (mg/L) 42 47

Alkalinity (mg/L) 86 126

Total Solids (mg/L) 312 326

Total Dissolved Solids 

(mg/L) 304 316
Total Suspended Solids 

(mg/L) 7.7 9.6

Ammonia-N (mg/L) 8.4 3.0

Total Kjeldahl NitrogenN (mg/L) 11.9 4.8

Nitrate/Nitrite-N (mg/L) 7.3 0.5

Total Phosphorus 6.3 3.8

Soluble Ortho 

Phosphorus-N (mg/L) 5.0 3.0

Chloride (mg/L) 59 66

Enterococcus (#/100 ml)3 75

Chlorophyll a (ug/L) 0.9 28.7

Groundwater Monitoring 

Data

Shallow Wells Within JBEW

. Drinking 

Water Std198919901991

Nitrate/Nitrite 

(mg/L) 10 0.39 0.04 0.02

Chloride 

(mg/L) 250 102 63 49

pH 6.0-9.0 7.2 6.4 6.6
The Dynamics of a Real-World Experiment

Gathering data from a dynamic, realworld experiment presents challenges. 

Variables that can easily be controlled 

in a lab, may be unpredictable in a 

dynamic process. 

JBEW researchers have worked to 

carefully control the variables within 

their reach, yet remain flexible enough 

to adjust for changes in a dynamic 

system. Among the impacts that have 

affected the JBEW are: 

● Non-native vegetation. Planted vegetation (cattails, sago pondweed) struggled to compete with 

the non-native plants (reed canary grass, Lemna, Azola) that dominate much of Jackson Bottom. 

● Phosphate detergent ban.In 1991, a region-wide phosphate detergent ban dramatically reduced 

the concentration of phosphorus in USA's effluent. As a result, the amount of phosphorus entering 

JBEW dropped as did the percent removal. 

● Plant operations. In 1991, the Hillsboro Treatment Plant was no longer able to operate in 

nitrification mode due to a 25 percent increase in service area. This resulted in higher ammonia 

and lower nitrate effluent entering JBEW.

Enhancement for Wildlife

Jackson Bottom is part of a larger Tualatin River wildlife/wetland 

corridor. This rich corridor provides essential stop-over feeding and 

resting spots for migrating waterfowl traveling the Pacific Flyway. It 

is also an important habitat for other species of wildlife. Much of 

this habitat has been lost to agriculture and development. But with 

projects like the Jackson Bottom Wetlands Preserve, crucial links in 

this increasingly fragmented ecosystem are being reconnected, 

enhanced and protected. 

Though degraded by past human practices, Jackson Bottom is 

coming alive with a newly developed diversity thanks to the 

dedicated efforts of Oregon Department of Fish and Wildlife, the 

Friends of Jackson Bottom, Ducks Unlimited and other groups. 

What was once a flat meadow of exotic reed canary grass, with little 

feeding or nesting opportunities for native species of wildlife, is now 

being transformed into a complex patchwork of wetlands and upland 
habitat. The wildlife ponds and marshes created using recycled wastewater are bordered by cattails, reeds 

and rushes, native willows, dogwood, ash and elderberry. This increased diversity of plants provides food 

and shelter for migratory waterfowl, shorebirds and other wetland wildlife. Resident populations now 

include Canada geese, many species of ducks, rails, herons, osprey, bald eagles, nesting red tailed hawks, 

harriers, and several owl species. Larger mammals include rare sightings of deer, elk, mink, beaver, 

coyote and fox. 

Until the habitat has sufficiently recovered, nesting sites are supplemented with floating goose platforms 

and boxes for swallows, bats, wood ducks and kestrels. The enhancement projects offer the opportunity 

to become involved with wildlife agencies and provide rich habitat for wildlife. 
Education, Research and Passive Recreation

From early morning walks in the thick morning fog to 

sophisticated research by soil scientists, there are many 

opportunities to enjoy and learn from this natural resource 

without harming it. 

Research, education and passive recreation activities are a 

major component of the 1989 Jackson Bottom Concept 

Master Plan. Research efforts conducted by the Unified 

Sewerage Agency, the Oregon Graduate Institute and other 

regional colleges and universities are providing answers 

and posing new questions about ecosystems and their role 

in water quality management. 

Education is a top priority, too. Spearheaded by the 

Wetland Coordinator and Friends of Jackson Bottom, 

students and teachers are learning about this astonishing 

natural system through tours and field work. The Friends 

group has developed wetlands curriculum and sponsors a 

variety of events year-round. In 1992, a state grant enabled 

Jackson Bottom to hire a part-time Wetlands Educator to 

coordinate a pilot educational program. 

Trails, viewsites and viewing shelters offer visitors a glimpse into the workings of this rich ecosystem. 

The Kingfisher Marsh Interpretive Trail, designed and built by the Friends group, offers visitors a mile 

long walk through wetland and upland habitat along the rarely seen Tualatin River. Future plans call for 

more trails and improved river access.

For information on the Jackson Bottom Wetlands Preserve and the Jackson Bottom Experimental 

Wetlands, please contact: 
Jackson Bottom 

Wetlands Coordinator

City of Hillsboro

123West Main Street

Hillsboro, OR 97123

(503) 681-6206 

Unified Sewerage 

Agency

155 North First Street

Hillsboro, OR 97124

(503) 648-8621 

Acknowledgments

This publication was funded by the U.S. Environmental Protection Agency. Special thanks to the Unified 

Sewerage Agency of Washington County, City of Hillsboro and Linda Newberry for their contributions. 

Nest photo on page 156 and family photo on page 161 courtesy of Friends of Jackson Bottom. The 

salamander photo on page 157 courtesy of Audubon Society of Portland, Oregon.