USA – California (Arcata) – Constructed Wetland: An Alternative for Wastewater Treatment

The city of Arcata, California was faced with a dilemma: Buy into an expensive regional sewage processing plant to bring their wastewater discharge into Humboldt Bay up to water quality standards, or come up with an acceptable alternative. They embarked on a pioneering journey, using wastewater to create and nourish a wetland where a logging pond and city dump had once been. The wetland provides prime wildlife habitat and recreation for the community at the same time it purifies the water.


The people of Arcata, California, did not think of their sewage as a resource. In fact, like most of us, they did not think about their sewage much at all. But in 1974 they entered a period referred to as the “Wastewater Wars” when the need to reassess that view and assert their community’s control of this “valuable” resource became essential.

Arcata is a small city located on Humboldt Bay, in the coastal redwood country of Northern California. In 1972 new federal legislation required that the water quality of the Bay be improved. Eureka, a larger city 5 miles south was often dumping raw sewage in to the bay, and Arcata’s wastewater treatment plant was not adequately treating their wastewater. The State and regional government proposed a new wastewater treatment plant that would serve this small university town and the other areas on the bay. This would be a very expensive undertaking for Arcata, population 12,600. Also, the sewer pipeline that would follow Highway 101 from McKinleyville on the north, through Arcata to Eureka and then out into the bay itself was a potential nightmare. Ruptures under the bay could make the pollution worse. And it would provide the infrastructure to open up the surrounding area to development.

Arcatans valued the unique character of their university town and their semi-rural setting. They had no desire to be engulfed by strip malls and housing developments. The regional wastewater treatment facility proposal was an engineer’s and developer’s dream. Turning that dream into their own is a story about taking charge of a local resource and tipping it from planned unsustainability to a sustainable, productive force in their community. The outcome was the Arcata Marsh and Wildlife Sanctuary (AMWF), 154 acres of freshwater and saltwater marshes, tidal mudflats and grasslands. It treats and disposes of the city’s sewage while providing a wonderful natural recreational area, and has become an inspiration for other communities throughout the world.

In 1974, before this began, the area where the Arcata Marsh Interpretive Center (AMIC) now stands was surrounded by a derelict lumber mill with a log-filled marsh, cracking concrete and an unkempt landfill, affectionately known as Mt. Trashmore.

Arcata had recently fought a battle to prevent a new federal freeway from bisecting their town and developing the surrounding agricultural lands. Earlier on they had stopped the clear cutting of an adjoining redwood forest, turning it into a community park with hiking trails. It was the first community managed and owned forest in the country. Arcata also boasted the first recycling program in the country.

Despite their history of local environmental activism, taking on the State of California and the Feds was daunting. But there were things about Arcata that made it possible—though it didn’t always seem that way in the midst of the fray. Arcata is the home of Humboldt State University, a campus known for its strong environmental programs. The more conservative surrounding areas see it as home to “kooks, tree huggers and flakes.” Even within Arcata the town-gown split has traditionally mirrored this difference. However, a change in the federal electoral law had recently allowed 18 year olds to vote and the students and young residents used their new found voice to elect a new city council, one that campaigned on protecting the environment and near-by agricultural land. The university also contributed a faculty with incredible expertise and a willingness to share it.

Ironically, the shoreline of Humboldt Bay had not been accessible to the town for many years as it was blocked by the old saw mill, the landfill and the existing sewage treatment plant. Now it is the crown jewel of Arcata, used daily for recreation, birding and gazing by locals and tourists alike.

Committed and courageous leadership is essential to carry a campaign like this through to the end. The Arcata story had many. A trip around the marsh sanctuary introduces some of these leaders.

There is the George Allen Marsh on what was once an abandoned concrete log deck. In 1969 Dr. Allen, a professor of fisheries science at the university, had begun an experimental project intended to find out if Pacific Salmon and cutthroat trout could be raised in ponds with a mixture of partially treated wastewater and seawater. This project was the first to question the conventional paradigm of waste, accustoming Arcatan’s to more elastic thinking about wastewater. In fact, the initial alternative proposal to the regional treatment plant was to use aquaculture based on some of Dr. Allen’s ideas. Though this changed, he remained an important part of the development of the marsh.

Then we come to the Robert Gearheart Marsh, formerly minimally used pastureland. Dr. Gearheart was a professor of environmental engineering at the university. He always saw himself as a biologist first, and an engineer second. Like many of the important leaders in this project, he was willing to take a calculated risk—some would say a huge gamble. What they tried to do had never been done. He knew there was no guarantee his idea of a marsh would work. However, he was a careful scientist and an excellent communicator. His dedication to the vision of the marsh as way for the community to maintain control of its resources and uniqueness kept the torch alive. He feels that one of Arcata’s strongest arguments was that “they were putting back into service 30-40 acres of unused wetland—basically ugly, industrial brownfields that nobody wanted.”

Further on is Dan Hauser Marsh, the first marsh to be treated with wastewater. Dan served on the city council and as mayor from 1974—1982, and then spent 5 years as city manager. He felt the marsh grew out of political and land use issues rather than wastewater treatment. “When Bob Gearheart started explaining what a marsh could do and we began reading stories about what the marsh used to be like,” Dan says, “I fell in love with the idea of marshes.”

“The regional wastewater project was a good idea in theory, but it just didn’t fit Arcata,” according to Hauser. The proposed pipeline would increase pressure to develop the adjacent agricultural land. In fact, in 1974 one of Dan and the new city council’s first acts had been to deny water for development of a newly annexed area pushed through by the old guard. This effectively stopped the project.

Hauser and the council estimated that “The wastewater treatment plant and pipeline would have been the largest energy consumer in the county, costing a bundle to run.” Even the environmental community was not wholly behind the marsh idea. David Joseph, an environmentalist, was the head of the North Coast Regional Water Quality Control Board (RWQCB), the body that was in charge of the proposed regional treatment plant. He was concerned that the city was trying “to get out of something.” Also, at that time Eureka, the larger city down the road, was discharging raw sewage into the bay. He was afraid if the project didn’t go through this wouldn’t stop.

Continuing around the Marsh, Franklin Klopp Lake comes into view. Frank had been a city engineer since 1968, graduating to Director of Public Works. He was an “old guard” engineer and says he didn’t object to the new treatment plant until he got to the last 4 pages of the report and saw the cost. It would mean doubling the sewer rates just to get it going. He had just pushed through a doubling of the rates and had taken quite a bruising. He was not anxious to repeat that. He started listening much more carefully to Bob Gearheart. But he needed to see an actual working example. Words were not enough. They went on a visit to Mountain View, a town on the peninsula south of San Francisco. There they saw “a simulated marsh made up in part of beer cans filled with foam and wood chips processing sewage.” He figured with Arcata’s resources it could work even better. He also gambled that the costs of developing the marsh for sewage treatment would be less than the regional plant. He figured it would have cost Arcata $10 million for their share of the construction of the regional system as opposed to the $5 million they spent. And the annual maintenance cost is about $500,000 instead of $1.5 million.

Today the marsh not only treats all of Arcata City’s municipal sewage and wastewater, it also supports approximately 100 species of plants, 6 species of fish, and a multitude of bird and mammal species that have populated it naturally from the surrounding region, including otters. The marsh lies on the Pacific Flyway, which is the permanent or temporary home to over 200 species of birds. The Aleutian Goose, for example, takes off from the tip of the Aleutian Islands, flies across the Gulf of Alaska, and makes landfall in Humboldt County.

And most important, more than 200,000 people a year get to enjoy the marsh for recreation, birding, or scientific study, and the whole area now has access to the bay. The community support organization, Friends of Arcata Marsh, hosts regular birding tours. Moreover, since 1996 Arcata has hosted the annual 3-day Godwit Days festival, a birding event held at the peak of the spring migration, which features field trips, boating excursions, lectures and other community activities for birders.

The vicissitudes of the political battle that led to the marsh are complex. It came down to the pro-marsh forces being able to prove that the marsh would “enhance” the water quality of the bay, meeting a key legal requirement. We will leave most of the politics aside for now and focus on the marsh itself.

The Setting and Its History

Arcata city, population 16,651, lies on the north-east shore of Humboldt Bay, 280 miles north of San Francisco. It was established in 1850 as a supply port during the gold rush era that precipitated the timber boom which was to follow. Arcata rests in the heart of Northern California’s “redwood county” and is home to Humboldt State University. In 1970, the population was 8,985, and it has risen to 12,850 in 1980 and to 15,197 in 1990. Today it has about 16,381. About half of Arcata’s residents are students at Humboldt State University, and the overwhelming majority of the population (81.3 %) is Caucasian. It is a progressive town in an otherwise conservative region. The decline of the logging and fishing industries has caused the regional economy to flounder economically over the past three decades. Where Arcatans see an unspoiled landscape, small cottage industries and extensive community involvement as ongoing goals, others in the region would like to see industries that bring jobs, convenient shopping and affordable housing so they can stay there.

People have inhabited the region of Humboldt Bay for thousands of years. The indigenous Yurok and Wiyot people settled here because of its abundant resources and easy access to transportation. In those days, the Bay was surrounded by salt marshes, freshwater swampy meadows, and forest. Despite the Wiyot peoples’ presence, the landscape remained relatively unchanged over centuries.

From 1849, however, European explorers arrived and began to settle in the area. The settlers forcibly displaced and sometimes massacred the indigenous communities, so that by 1860 the native population was down to less than 5% of its pre-Europe population. From 1870 the settlers began draining the marshes for agriculture, and built a wharf and California’s first railroad track. The railroad linked dry land and a shipping channel built further out into the Bay that remained functional until the 1920s.

In 1945, two lumber mills operated in the area (one where the Interpretive Center is now located and the other where Allen Marsh is located). There was a log deck for storing lumber. Butcher’s Slough was elongated to make a channel for the mills, and a nine-acre log pond was built. The mills closed down in the late 1960’s as the region’s logging economy began to implode. The mills’ condition further deteriorated over the years as a result of fires and neglect.

In 1964, the area that is now nicknamed “Mount Trashmore” was drained and diked in order to create a 40-acre landfill. Within a decade of the landfill starting operation, the ecosystem deteriorated as the overpopulation of cats and gulls began unraveling the food web, and leachate from the landfill contaminated the Bay. In 1973 the landfill was condemned, shut down, and sealed using mud from the Bay. This raised the question of what to do with the closed landfill,. Suggestions floated included a marina, motor cross area, golf course, baseball field and nature center/marsh restoration area. The City of Arcata finally decided to restore the area to a wetland. This coincided with the time that the federal and State government began strictly regulating wastewater.

The History of Wastewater Treatment in Arcata

Arcata’s former wastewater treatment plant was constructed in the 1940s, when the town’s first sewers were installed. There was only primary treatment of the wastewater, with no chlorination, before it was discharged into the bay. It did not reduce Biological Oxygen Demand (BOD) or remove suspended solids and possible pathogens. Biological Oxygen Demand, a key standard for measuring treated wastewater, is the measure of oxygen required to break down organic materials in water. With untreated (or improperly treated) sewage high organic loads may reduce the amount of oxygen available to sustain fish or other aquatic life.

Fifty-five acres of oxidation ponds were added to the facility in 1958, which raised the level of treatment to secondary standards, followed by chlorination facilities in 1968. De-chlorination facilities were added in 1975. At this time, the State of California was getting tougher on municipalities’ wastewater management policies in response to the Federal Water Pollution Control Act Amendments of 1972, the predecessor of the Clean Water Act.

In April of 1974, the California State Water Resources Control Board (SWRCB) adopted a Comprehensive Basin Plan for the North Coast Region. In a nutshell, the policy regarding discharges into the Bay was that it be “phased out at the earliest practicable date.” However, the Regional Water Quality Control Board could grant exceptions if the discharging municipality could prove that “the wastewater in question would consistently be treated and discharged in such a manner that it would enhance the quality of receiving waters above that which would occur in the absence of the discharge.” This meant that a municipality would somehow have to prove that the wastewater, if discharged into the Bay, would enhance the water quality in the Bay. It was assumed that this would only be feasible if all the municipalities along the bay pooled resources to build a regional treatment plant. No single municipality was large enough to afford a treatment system advanced enough to satisfy these federal regulations.

In response to this plan, a “Joint Powers Agency” was created in 1973 to resolve the issue. The Agency consisted of the municipalities of Eureka, Arcata and McKinleyville in Humboldt County. An engineering firm, Metcalf & Eddy, developed a design for a regional facility that would serve these communities. The facility would be located on the Samoa Peninsula and was estimated to cost $25 million. In 1974, the Humboldt Bay Wastewater Authority (HBWA) was formed. It included the Joint Powers Agency and the McKinleyville and Humboldt Community Services Districts, and was charged with the responsibility of constructing the regional wastewater treatment plant.

The proposed plant would have large interceptors around the perimeter of the bay, with a major line crossing under the water in the region of active navigation. Effluent from the plant would be released offshore into an area of shifting sea bottom and heavy seas during winter storms. The facility would have been capital-and energy-intensive, and no one agency could afford it, so sharing expenses was believed to be the only solution to solving the Bay communities’ collective wastewater problems. However, as plans progressed, the logistical challenges of incorporating all communities as well as the costs–economic, social and ecological–became increasingly apparent. The plan became a hot political issue. A major concern, especially in Arcata, was that the creation of a sewer interceptor line running from McKinleyville to Eureka along Highway 101 would open up agricultural areas to suburban-style sprawl. The resulting strip malls and subdivisions would render the communities indistinct from one another and eliminate the rural character of the area. Another concern was that some of Arcata’s investments, both in the aquaculture project, and in the existing treatment plant, would be lost. For two years, the City Council tried to convince the Regional Water Quality Control Board (RWQCB) and HBWA that there had to be other alternatives to the regional treatment plant.

From the time the Comprehensive Plan was created, Arcata descended into a politically volatile period sometimes referred to as the “wastewater wars.” The main factions split along two lines. The supporters were the development and financial interests, the engineering community consisting of the RWQCB as well as State officials, the bulk of Arcata’s “old-timers,” and environmentalists who feared that if Arcata opted out of the plan, HBWA would collapse and neighboring Eureka would continue to discharge its partially untreated effluent into the Bay. Supporters of the marsh were led by City Councillor Dan Hauser, Humboldt State University environmental engineering professor Bob Gearheart, then-Public Works director Frank Klopp, and Humboldt State University fisheries professor George Allen. Arcata citizens against the project tended to be environmentalists, professors and students, and newcomers who were fleeing other built-up areas further south, all of whom valued Arcata’s natural beauty and historic rural charm.

In 1975, critics of the regional plan formed a coalition called “Citizens for a Sewer Referendum.” They launched a campaign to call for a vote on the project. Their persistence paid off in eventually helping to stall the project. However, it became increasingly clear that if Arcata were to opt out of the plan it would effectively block the regional treatment plant. Other communities in HBWA could not afford to go forward without Arcata. Part of the antagonism towards the Arcata critics of the plan was that as time went on, inflation was rapidly increasing the cost of the project.

At this point, Arcata had to come up with an alternative plan that would not only assure treatment of the sewage, but that would satisfy the “enhancement” requirement in the Comprehensive Basin Plan. The idea to build its own wastewater treatment plant came about in 1976 amidst this divisive controversy. The City began exploring the design of a decentralized system which made use of constructed wetlands. The idea had its origins in the aquaculture work of Dr. George Allen. In 1969, Dr. Allen had begun an experimental project intended to find out if Pacific Salmon and cutthroat trout could be raised in ponds with a mixture of seawater and partially treated wastewater. This type of project challenged the conventional paradigm of waste in two ways. First, it said waste was a valuable resource rather than a harmful, expensive nuisance that had to be disposed of. It also declared that communities themselves—rather than centralized bureaucratic regulatory bodies—could manage this resource if given the freedom to do so. The idea of creating and using a marsh began to grow in the mind of Robert Gearheart, another Humboldt State University professor. Using the fish aquaculture project and a treatment marsh as probable ways to prove “enhancement,” a city task force proposed that the natural processes of a wetland could be harnessed to effectively and efficiently treat municipal wastewater. This was a huge departure from business as usual.

In 1977, the City of Arcata team, consisting of George Allen, Bob Gearheart, Public Works director Frank Klopp and City Councillor Dan Hauser put their proposal to the Regional Water Quality Control Board. They would have a wastewater treatment process that used the existing primary sedimentation facilities, a 22.3 hectare oxidation pond facility, and three new constructed marshes. The effluent from the marsh system would then flow through a 6.9 hectare lake before being discharged into the Bay. The city insisted that this system would not only protect all of the existing beneficial uses of the Bay, but would enrich them and even create new ones such as greater bird habitat and extensive recreational space. They presented this plan at RWQCB meetings and before the SWRCB, as well as to the citizens of Arcata itself. There was much quibbling over whether or not this was the type of enhancement outlined in the regulations. They challenged the Chair of the SWRCB to define exactly what was meant by enhancement. When he could not do it, the marsh supporters were able to prove that ‘enhancement’ of the Bay’ was a meaningless term and legislation was introduced to eliminate this requirement.

Meanwhile, the Coastal Conservancy, a California non-profit organization became involved. The Coastal Conservancy purchases critical coastal habitat and conservation easements and works with communities to restore coastal land. They had been observing the events in Arcata and offered to help fund the wetlands restoration that was part of the three original marshes.

The University and the city formed the Task Force on Wastewater Treatment that created the pilot project Arcata was finally granted permission to undertake. The State Water Resources Control Board funded the 3-year study which began in September of 1979. It experimented with partially treated wastewater and the natural processes of wetland ecosystems. The results of the pilot project promisingly showed that not only could the constructed wetlands effectively treat wastewater, but that it would also enhance the biological productivity of the wetland environment into which wastewater was discharged. At the end of the pilot project in 1983, the Board agreed that the marsh system would indeed “enhance” the beneficial uses of the Bay for scenic enjoyment and educational study, and that a full-scale marsh system would satisfy the requirements of the Basin Plan. As the Task Force’s original leaders emphasized, the plan was a simple, cost-effective application of an appropriate technology.

With the help of the Arcata City Council and political representatives in Sacramento, in 1983 the city received the go-ahead to develop the marsh.

Constructing the Marsh

Sections of Arcata’s old industrial sites by the shore of the bay had concrete where the lumber had been stacked and stored. To create the marshes, they had to break up the concrete. This was done as an activity with the National Guard combat engineers. They came in one Sunday, blew the concrete up, and carried it off. A lot of other residue from the saw mills also had to be taken out.

The section that is now Gearheart Marsh was originally pasture land. Because the terrain was slightly lower than the surrounding area, it had relatively large areas of open water once the water was let in. Marsh plants were allowed to grow in naturally.

When the landfill was closed, a dike was set up around the Bay. Sediment was scooped out and put on top of the landfill to seal it. The current wetlands surround the landfill, but none are on top of it. The landfill has been monitored for seepages of any kind and so far no contaminants have been found to have leached out of it.

The last marsh was “terraformed” to be various depths, deeper in some places, shallower in others. Moving the dirt around to create this “micro-terrain” was done by bulldozer. Differing depths was necessary because if it was kept shallow, the tubers of the sago pondweed would spread everywhere uniformly and undermine the biodiversity needed for the marsh to do its work. Flow in the marsh is faster at the edges of groups of aquatic plants than in the middle.

Vegetation was added to about one third of the last marsh, Hauser Marsh, to provide denser vegetation towards the end of the system. This ensures that the marsh will strip out any remaining solids in the effluent. They used native Hardstem bulrush brought in from a near by fishing lake. This marsh has alternating areas of open water and vegetation. Everyone said they wanted islands but they didn’t work as well as planned and were removed. This was one important lesson they learned about creating a constructed wetland.

Sago pondweed seeds were broadcast into all the deep areas of all the marshes. Ducks love to eat this seed, providing a natural harvest to keep it from taking over. The team learned a lot about planting, often by trial and error. Some of the unsuccessful methods they used included burying the whole plant by the roots and throwing sprigs of the plants into the water. Unfortunately the waterfowl would eat everything immediately. Their greatest success came when they trucked in plants, cut off their tops, but kept a substrate of some of the original soil around the tuber. Previous orders of plants had come with their original dirt stripped away and they were unable to make the transition to the marsh. It takes about two years for the soil encrusted plants to grow to maturity.

A floating plant, Hydrocotyl, can sometimes take over and excessively shade the marsh, so it is periodically harvested. It is then mixed with sludge settled out from the first stage of treatment and used as compost in the Arcata Community Forest.

In 1986, the treatment system was completed and became operational. In the same year, the Coastal Conservancy provided funds to restore Butcher’s Slough which expanded the Sanctuary to its current size. The slough was refigured into a more natural channel, thereby enlarging the saltwater wetlands, and creating another freshwater marsh in a former log pond.

In order to extend the area of the marsh further, 3.15 acres of land on the inland side of the wetland area has been acquired, and a pond has been created there. Aquaculture still continues in parts of the marsh, though the fish are not raised for commercial purposes. However, more than half of the oysters grown in California are produced in a subsection of Humboldt Bay known as Arcata Bay.

The Wastewater Treatment System

All municipal sewage treatment, whether conventional or alternative, is broken down into two main phases. Primary treatment is largely a mechanical process which separates the solids from the liquids, while secondary treatment removes contaminants and pathogens harmful to humans. The AMWS’s primary treatment occurs in the headworks and clarifiers, while the secondary treatment occurs at the oxidation ponds, chlorination basins, treatment marshes and enhancement marshes.

The flow between components occurs through underground tunnels. Water levels in the marsh are not intentionally changed, for example, by adjusting weir levels. Once they are set, they are left to function on their own.

  1. The Headworks. This is the first phase in the treatment of raw sewage. Water is piped underground from Arcata households to the headworks. Here inorganic materials are removed from the water using two Archimedes screw pumps that lift the raw sewage fifteen feet up and pass it through bar screens and grit separators before it enters the clarifiers.
  2. Primary Clarification. The water sits for about four hours in the clarifiers. Two clarifiers (26 feet and 60 feet in diameter) are used for settling out any remaining suspended material that makes it past the headworks. The liquid effluent from the clarification process is sent to the oxidation ponds. The solids that settle out from the clarification process are sent to digesters.
  3. Digesters. The remaining sludge from the clarifiers is pumped to the primary and secondary digesters respectively. Anaerobic microorganisms in the digesters consume the nutrients in the sludge as their food, and produce carbon dioxide, methane and hydrogen sulphide as by-products. The digesters mix the sludge by recirculating methane gas with compressors. The remaining sludge goes onto a sludge drying bed. It is then mixed with yard waste and hydrocotyl, the aquatic plant, and is used to fertilize the soil in the Community Forest.
  4. Oxidation Ponds. These ponds cover an area of 55 acres. They were built in the late 1950’s. They are approximately five feet deep, and are used for settling out smaller solids not removed by primary treatment. The effluent is channeled by underground tunnel into the oxidation ponds to treat it to secondary standards. “Secondary standards” means that at least half of the BOD (biochemical oxygen demand) and suspended solids that remain after primary treatment have been removed. Breakdown of the floating and settling organic matter in the sewage is facilitated by algae growth and microbial/bacteria activities in the ponds. Sunlight is key to this process, because algae produce oxygen through the process of photosynthesis,. Algae also consume nitrogen and phosphorus, two common nutrients found in municipal wastewater. Microbes and bacteria use oxygen produced by the algae to break down and use the nutrients in the waste for their own metabolism. The by-product of this is carbon dioxide, which is then used by the algae to produce more oxygen for the microbes. Mechanical aerators are used in the oxidation ponds as well, to aid the algae in oxygen production.
  5. Treatment Marshes. The treatment marshes reduce the remaining BOD concentrations, dead algae, and other suspended solids that remain in the oxidation pond effluent. There are three treatment marshes, each of which is two acres in area. They are located north of the oxidation ponds. They were created by subdividing the original oxidation ponds. All the marshes were planted with hardstem bulrush. This helps settle out the suspended solids by slowing down the water flow and preventing growth of new algae. The wastewater circulates through a marsh system before it is combined at a pump station and flows into the disinfection facility.
  6. Disinfection. There are two separate stages of disinfection. The first occurs after the effluent passes through the treatment marshes. The second takes place after passing through the enhancement marshes just before its release into Humboldt Bay. Disinfection is necessary to kill any viruses or pathogens present in the water. Technically the second chlorination is unnecessary given the effectiveness of the enhancement marshes, but is required by regulators in order to conform to fecal coliform standards. Ironically, the standards are ‘violated’ only because birds are discharging excrement into the enhancement marshes. Because of the double chlorination, two chlorine contact basins are necessary. The basins are located immediately south of the headworks. Any free chlorine remaining in the final effluent after the 60 minute contact time is removed with sulphur dioxide. After the second chlorination, depending on how much water is coming into the marsh, it is either released into the Bay or sent to the enhancement marshes. Usually it is mixed with water from the enhancement marshes and released into the Bay.
  7. Enhancement Marshes. After the first chlorination process, the effluent flows into the enhancement marshes located northwest of the oxidation ponds. The three marshes, each named after George Allen, Bob Gearheart, and Dan Hauser respectively, cover a total of 31 acres. The flow is controlled through the use of sluice gates and weirs, though the water flow is rarely interfered with. The natural processes occurring in the marshes simultaneously purify the wastewater by removing excess nutrients and ‘feed’ the marsh plants with water high in nitrogen-rich organic matter. Nutrients are taken up by the plants and thus removed from the wastewater. The roots and stems of the plants also clean the water by forming a dense netlike filter that removes large quantities of suspended solids. Algae, fungi, bacteria and micro-organisms attached to the roots of these plants feed on these solids. This nutrient-rich habitat attracts many birds to the sanctuary. It has become an exceptional and cherished place for birders, recreation, research and education. Before discharge into Humboldt Bay, the water returns to the disinfection facility for a second chlorination. In total, all wastewater that enters the system spends about fifty days there from its first contact with the headworks to its release into Humboldt Bay.

Marsh Specifications

  • Design Population: 19,056
  • Average Annual Flow: 2.3 million gallons/day (mgd)
  • Maximum Monthly Flow: 5.9 mgd
  • Peak Flow: 16.5 mgd
  • BOD’s Load: 4100 lbs/day
  • TSS Load: 3400 lbs/day

The Arcata Marsh Interpretive Center

All the work and ingenuity that went into the marsh was rewarded in 1987 when Arcata received the Innovations in Government Award from the Ford Foundation/Harvard University Kennedy School of Government and $100,000 to begin building the Arcata Marsh Interpretive Center. Open to the public since 1993, the Interpretive Center has exhibits on the political, ecological and technical aspects of the marsh. It is staffed by city employees on weekdays and by community volunteers on weekends and holidays. The Friends of the Arcata Marsh offers free educational tours of the AMWS and treatment facility.


Creation of the marsh allowed not only reuse of wastewater but also ecological restoration of industrial, agricultural, and public service land:

  • “Zoning.” An important aspect of the case was that it not only prevented development in the agricultural areas between the communities, but it also restored a degraded waterfront area. Before the marsh, the land consisted of an abandoned lumbermill pond, channelized sloughs, low-quality pasture land, and a sealed landfill.
  • A window to Humboldt Bay. Before the marsh was created, Arcata citizens had no access to its waterfront. After the AMWS, the entire area was opened up. As the disused landfill, “Mount Trashmore,” was on higher ground, it now allows people a broad view of the Bay.
  • Habitat creation. Some 60,000 acres of wetland are lost annually, mainly to draining and reclamation for development and agriculture. Of the remaining 100 million acres, many are severely degraded. Creating the Arcata wetlands not only provided a cost-effective, low-energy, low-maintenance essential service, it also locally reversed the trend of wetland loss.
  • Green city. Arcata City Hall is environmentally active and maintains various other programs including a greenhouse gas reduction plan, solid waste reduction, Open Spaces initiative, pesticide reduction plan, pedestrian/bicycle plan, and community forest.

The Community Forest

Arcata’s Community Forest is comprised of approximately 622 acres of 120+ year old redwood forest obtained in several purchases financed by bond measures over a 50 year period. This acquisition process culminated in the dedication of the Community Forest in 1955.

The forestland was used as a source for the municipal water supply until 1964. Since then it has served many functions including recreation, education, sustainable timber harvesting, and wildlife habitat. It is also an outdoor laboratory for students and ‘citizen scientists’. The forest serves as the headwaters of many of Arcata’s urban streams. The main tree species is California Redwood but Douglas Fir, Grand Fir, Western Hemlock and Sitka are also present.

In 1979, a “Forest Management and Parkland Initiative” ballot measure was passed by Arcatans. Its intent was to create a long-term management program governed by ‘ecological principles’ that would preserve its recreational uses as well as generate revenue for further forest acquisition by carefully harvesting the forest’s timber. This was the nation’s first forest to be certified by the Forest Stewardship Council (FSC) as eligible for the “Smartwood” designation which denotes sustainably harvested wood.

Annual revenue generated by the forest is $500,000-700,000 per year. Trees are generally harvested every other year. Revenues from the sale of timber go into acquisition of land through outright purchase or by granting conservation “easements,” where land owners are paid a fee to sustainably manage a given parcel of land. The focus is on areas contiguous to the forest or otherwise ecologically sensitive habitat. Land acquisition is contingent upon funding, mostly from grants.

Conditions Contributing to Arcata’s Success

  1. Public Works Director Frank Klopp was an “old paradigm engineer” who subscribed to the belief that wastewater had to be disposed of and not utilized, typically through command-and-control and technology. He initially supported the regional wastewater treatment pipeline plan until he saw the cost to Arcata. He realized Arcata would never be able to afford it. This led him to seriously consider the merits of the ‘other side’s’ plans. Through discussions with the marsh’s main proponents and after witnessing a similar project in the San Francisco Bay area, he ‘converted’. He then became a key figure in enlisting buy-in from engineers in the HBWA, SWRCB, and RWQCB as well as the more conservative members of the community in a way that someone outside his profession could not.
  2. There was a reduction in the national voting age in 1971 from 21 years of age to 18. This new political clout among younger people had particular impact in a university town like Arcata.
  3. The change in political climate helped facilitate the “changing of the old political guard,” which brought in a new generation of politically progressive leadership in City Hall.
  4. The city displayed a high level of creativity in finding alternatives to the ‘bust’ that characterized the region’s extraction-based fishing-forestry economy (possibly due to #2 and #3) (see Julie Fulkerson’s and Dan Hauser’s comments below).
  5. The Marsh and the Community Forest became de facto ‘zoning’ initiatives because development could not occur there. This was more effective than any regulation, as the community forest and wetland became physical barriers to development, impregnable to the power or political machinations of the development crowd.
  6. While initial concern over the pipeline was that it would allow development between Arcata and neighboring Eureka and McKinleyville, this bled into other concerns such as the mounting costs and potential liability issues if the pipelines under the Bay were to malfunction or rupture.
  7. The presence of Humboldt State University meant access to cost-effective, often free, technical support, data collection, monitoring and research that continues to this day. This level of scientific and technical knowledge would not have been otherwise affordable to Arcata. Humboldt State is unique in that it has the only program known as “environmental resources engineering,” which integrates fields which have normally been fragmented. It integrates biology, chemistry, physics and ecology. Partly as a result of Bob Gearheart’s involvement with the marsh this program was redesigned so that engineering students, in their formative undergraduate years, get a more comprehensive outlook on the world (see Bob Gearheart’s comments).

Environmental Tipping Point Elements

  1. Positive feedback. The trend in North America towards development that opens up formerly agricultural or virgin land was partially halted by the marsh in two ways: i) The Regional plan with its pipeline following Highway 101 would have provided the infrastructure for easy development of the agricultural land between McKinleyville and Eureka. Creating the marsh prevented the “freeing up” of this land. ii) Creating the marsh efficiently reused disused land which had fallen onto the City because no one wanted it, rather than using new land which would have set in motion the feedback loops in i).
  2. “Nature Doing the Work.” Wetlands are well-known biological filters and perform critical cycling, filtering, purifying, water storage and flood prevention services for free. Using a wetland to treat waste simply takes advantage of natural biological processes occurring in wetlands. The main function of wetlands in wastewater treatment is the uptake or removal of nitrate, ammonium, phosphate, and possibly heavy metals.

A Few of Many Examples of Nature “Doing the Work” in the Marsh:

· The structure of a wetland itself, with its slow flow and shallow depths allow sediments to settle as water passes through it. Also, the slow flow allows long contact times between the water and the surfaces in the wetland, allowing for crucial exchanges to happen at the microbial level.

· Two processes are of particular importance for nitrogen cycling:

1) Dentrification: The conversion of nitrates found in wastewater by bacteria into nitrogen gas through removal of oxygen in the anoxic conditions found in the detrital layers of the wetland.

2) Nitrification: The conversion of ammonium to nitrates (which must happen in oxygen rich regions of the soil, usually near the clumps of vegetation) which can then be converted into nitrogen gas through dentrification.

· Plants, primarily bulrushes, provide a “canopy” of shade over the water which inhibits algae growth, cools the water, slows down its flow, blocks UV rays, reduces the level of evaporation and helps to oxygenate the water through the process of photosynthesis. It also provides the habitat for microorganisms such as beneficial bacteria, on the roots of these plants. These bacteria are beneficial because they consume the suspended solid particles. Floating plants that block light are generally harvested by aquatic birds (although, as stated earlier, periodically they must be harvested if excessive). These floating plants also reduce the level of evaporation.

· The layer of litter on the soil surface of a wetland is known as the “detrital layer.” It is in a generally constant state of slow decomposition by bacteria and other organisms. Generally wetlands have ample detritus because the anaerobic conditions in the wetland slow down decomposition. It offers surface area for decomposers such as fungi and bacteria that nitrify and dentrify (see above). Acinomycetes is one particularly active microorganism that helps to cycle nutrients. Sediments in the oxygen-poor detrital layer also provide conditions for breaking down complex organics (i.e. greases, fats, solvents, fuels). As well, they sequester metals and provide a source of carbon, nitrogen and phosphorus to drive microbial processes.

· Sunlight, through the process of photosynthesis, produces oxygen needed to facilitate the processing of nutrients in the wastewater by microorganisms.

· Single and multi-celled organisms reduce the carbon and organic material and “pass it up the food chain” in the form of insects and birds which then fly away and carry it out of the wetland. Birds also bring in seeds from other areas which foster biodiversity and ensure continued growth of flora.

· Insect larvae and other insects such as beetles consume the solids which settle out of the partially treated wastewater.

3. “Success Breeding Success.” The success and popularity of the marsh gave those in City Hall the freedom to imagine more possibilities for the marsh and other projects. It also has created a stronger base for support of environmentally friendly projects in the town.

4. Replication: Arcata’s story has become a landmark in alternative wastewater treatment. It has attracted interest and visitors nationally and internationally. Bob Gearheart and other key players have traveled to various parts of the world to promote and provide technical support to other communities interested in adopting similar models. They have visited Oaxaca in Mexico, the West Bank, Egypt, Thailand, Indonesia, Palo Alto and Petaluma in California, and some smaller towns in the San Francisco Bay Area. Neighboring McKinleyville and Eureka are creating similar systems, though they are loathe to admit it has anything to do with influence from Arcata. Replication is not always easy to trace. Multiple sources may be consulted. Sometimes communities try and fail, others adopt some aspects of the Arcata model, and still others may not yet have done so, but the ‘seeds’ are lying dormant, needing only a final impetus to start bearing fruit.


  • US EPA et al. “Design Manual: Constructed Wetlands and Aquatic Plant Systems for Municipal Wastewater Treatment.” pp. 27-30.
  • Davis, Luise. “A Handbook of Constructed Wetlands.” USDA-Natural Conservation Service and US EPA, region II. Online link
  • A site visit to Arcata City including a tour of the marsh and interviews with Dr. Robert Gearheart, former Councilor Julie Fulkerson, City Manager Dan Hauser, former Public Works Director Frank Klopp
  • Maria Streshinsky. “From Blighted to Beautiful: Five fabulous makeovers for Mother Earth.” Via Online: The AAA Travellers Companion, November 1999.
  • Jordan, Fred. 1990. “The Wastewater Wars,” in Innovating America, Chapter 8. A Ford Foundation report. Profiles of eight award-winning projects (1986-1988) in the Innovations in State and Local Government awards Program, which is sponsored by the Ford Foundation and administered by the John F. Kennedy School of Government at Harvard University. The awards honor exemplary programs and policies addressing important social and economic problems at the state and local levels.


  • SWRCB: The State Water Resources Control Board
  • RWQCB: The Regional Water Quality Control Board
  • HBWA: Humboldt Bay Wastewater Authority
  • AMIC: Arcata Marsh Interpretive Center
  • AMWS: Arcata Marsh and Wildlife Sanctuary

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