»EPA
United States
Environmental Protection
Agency
EPA832-R-93-005e
September 1993
A Natural System for
Wastewater Reclamation
and Resource Enhancement,
. t
Arcata, California
j n
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INTRODUCTION
The constructed wetland system is
the cornerstone of Arcata's urban
watershed renovation program.
This program includes major urban
stream restoration, log pond conversion
to a swamp habitat, pocket wetlands
on critical reaches of urban streams,
and an anadramous wastewater aqua-
culture program to restore critical
commercial recreational and ecological
important populations. The Arcata
project is a demonstration of waste-
water reuse, ecological restoration, and
reuse of industrial, agricultural and
public service land.
Arcata
San
Francisco
Arcata Site Plan
Situated in the heart of the redwood country and along the rocky
shores of the Pacific Northcoast, the City of Arcata is located
on the northeast shore of Humboldt Bay in Northern California,
280 miles north of San Francisco. Arcata, with a population of
approximately 15,000, is a diverse community whose resourcefulness
and integrity has demonstrated that a constructed wetland system
can be a cost efficient and environmentally sound wastewater
treatment solution. In addition to effectively fulfilling wastewater
treatment needs, Arcata's innovative wetland system has provided
an inspiring bay view window to the benefits of integrated wetland
enhancement and wastewater treatment.
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What is the Arcata Marsh
and Wildlife Sanctuary?
Arcata is a small town located on the
north-eastern side of Humboldt Bay,
about 280 miles north of San Francisco.
Humboldt Bay is a focal point where
timber resources and marine resources
cross paths as they struggle to sustain
Humboldt County's economy. Resource
management is a practice that receives
high priority and expert advice in this
scenic niche of the Pacific Northcoast.
Arcata, with a population of approxi-
mately 15,000, is a diverse community
whose resourcefulness and integrity
... a constructed
wetland system can
be a cost efficient
and environmentally
sound wastewater
treatment solution.
has served to lead the city down a
successful path marked by innovative
decisions and maintained by pride.
So, when the city faced making a
change in their wastewater treatment
methods, they demonstrated that a
constructed wetland system can be a
cost efficient and environmentally
sound wastewater treatment solution.
In addition to effectively fulfilling
wastewater treatment needs, Arcata's
innovative wetland system has provided
an inspiring bay view window to the
benefits of integrated wetland enhance-
ment and wastewater treatment.
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Arcata established its
innovative treatment
system as a result of
extensive community
involvement and a series
of political events.
How did the project evolve?
Arcata established its innovative
treatment system as a result of exten-
sive community involvement and a
series of political events. In the early
1970's, Arcata s active wastewater treat-
ment plant discharged unchlorinated
primary effluent into Humboldt Bay.
In 1974 the State of California enacted
a policy which prohibited discharge of
wastewater into bays and estuaries
unless enhancement of the receiving
water was proven. In response to this
policy the local Humboldt Bay Waste-
water Authority proposed the construc-
tion of a state sponsored regional waste-
water treatment plant that would serve
all the communities in the Humboldt
Bay vicinity. The plant was to have
large interceptors around the perimeter
of the bay with a major line crossing
under the bay in the region of active
navigation. The proposed treatment
facility was energy intensive, with signif-
icant operational requirements. Efflu-
ent from the proposed plant was to be
released offshore into an area of shift-
ing sea bottom and heavy seas during
winter storms. As the scale of the
regional treatment plant grew, the costs
and difficulties of incorporating other
communities became apparent
Recognizing the constraints of the
local environment and criteria for
wastewater treatment, the City of
Arcata began exploring the design of a
decentralized system which employed
constructed wetlands. Wastewater aqua-
culture projects at the City of Arcata
started as early as 1969 and had been
successful in raising juvenile Pacific
Salmon and Trout in mixtures of
partially treated wastewater and
seawater. This project demonstrated
that wastewater was a "resource" that
could be reused and not simply to be
viewed as a disposal problem. With
this philosophy a city Task Force on
Wastewater Treatment determined that
the natural processes of a constructed
wetland system could offer the city an
effective and efficient wastewater treat-
ment system. From 1979 to 1982 the
city, and associated proponents of
alternative wastewater treatment,
experimented with partially treated
wastewater and the natural processes
of wetland ecosystems. These experi-
ments demonstrated that constructed
freshwater wetlands could be utilized
to treat Arcata's wastewater and at the
same time enhance the biological
productivity of the wetland environment
into which treated wastewater was
discharged. The Task Force determined
that a constructed wetland system was
extremely cost effective. Moreover, a
successful system offers the city a vital
wetland ecosystem that could be used
for the rearing of salmon and steelhead
as well as offer the community a unique
site for recreation and education.
With the aid of the Arcata City
Council and political representatives in
the state capital, the city received
authorization in 1983 to develop the
constructed wetland system and incor-
porate its use at the original Arcata
Wastewater Treatment Plant. The wet-
land system that exists today was
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completed in 1986. Since that time the
natural ability of marsh plants, soils and
their associated microorganisms has
successfully been utilized to meet the
need for a cost-effective and environ-
mentally sound wastewater treatment
technology that meets federal and state
mandated water quality requirements.
Who cares and what are
the benefits?
At the same time that wetland waste-
water technology has been used to
successfully meet water quality criteria,
it has also aided in restoring a degraded
urban waterfront. Prior to the installa-
tion of its wetland treatment system, the
City of Arcata's waterfront was the site
of an abandoned lumbermill pond,
channelized sloughs, marginal pasture
lands, arid a closed sanitary landfill.
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Today, Arcata's waterfront has been
transformed into 100 acres of fresh-
water and saltwater marshes, brackish
ponds, tidal sloughs and estuaries.
Because of the wetland communities
and wildlife habitats that the waterfront
now supports, the area in its entirety
has come to be known as the Arcata
Marsh and Wildlife Sanctuary
(AMWS.) The AMWS's three freshwa-
ter wetlands are Gearheart, Allen and
Hauser Marshes. They were construc-
ted to receive treated wastewater,
thereby treating the wastewater further
and enhancing the receiving water at
the same time. These enhancement
marshes are a host of aquatic vegetation
that, in association with Klopp Lake
and the adjacent estuaries and ponds,
have further provided an extraordinary
habitat for shorebirds, waterfowl,
raptors and migratory birds.
As a home or rest stop for over 200
species of birds, the AMWS has devel-
oped a reputation as one of the best
birding sites along the Pacific North
Coast. The Redwood Region Audubon
Society uses the site on a regular basis
for its weekly nature walks. For the past
10 years, docents trained by the Society
have explained the role the wetlands
play in attracting birds and mammals,
as well a s their role in managing the
water quality of Humboldt Bay. The
beauty and uniqueness of the AMWS
has served as inspiration to many artists,
whose products range in form from plays
and poems to photographs and paintings.
Arcata has become an international
model of appropriate and successful
wastewater reuse and wetland enhance-
ment technologies. Over 150,000 people
a year use the AMWS for passive
recreation, bird-watching, or scientific
study. Visitors from around the world
have come to Arcata to investigate its
success in wastewater management.
Students of all ages and institutions
use the AMWS for scientific study. In
1987, the City of Arcata was selected
by the Ford Foundation to receive an
award for this wastewater wetlands
project as an innovative local govern-
ment project. This award included a
$100,000 prize to be used to fund the
establishment of the Arcata Marsh
Interpretive Center. The Center
focuses on the historical, biological
and technical aspects of the AMWS,
and attempts to meet the informational
and educational demands of the waste-
water treatment system.
Today, Arcata's
waterfront has been
transformed into
100 acres of freshwater
and saltwater marshes,
brackish ponds, tidal
sloughs and estuaries.
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squitos and
animals
Plants provide canopy over water,
intercept light, inhibit algal growth,
cool water (block UV light), reduce
evaporation, and help oxygenate
water through photosynthesis
Floating plants block light and take up
nutrients (Nitrogen and Phosphorus) and are
harvested by aquatic birds and removed from
system and reduce evaporation
Fish feed on insect larvae and
plankton (Gambuzia)
Detritis and other plants provide
surface area for decomposers (fungi)
and bacteria that nitrify and denitrify
Organisms (single and multi-cell animals)
reduce carbon and organic material and
pass it up the food chain and are
biologically self-governed
Sediments are mostly anerobic and provide conditions for
breaking down complex organics (greases, fats, solvents,
fuels) and also sequester metals, reducing their bioavailability.
Sediments are also a critical biological niche for aquatic
organisms (dragonfly larvae, mosquitos,...)
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Stage in Treatment Plan
_ _ Biochemical
bUD (mg/l) Oxygen Demand
*•»« i ,n Suspended
SS (mg/l) Solids
TIM / /i\ Total
TIN (mg/l) Nitrogen
200
Influent
Primary Treatment Oxidation Pond Treatment Marshes Enhancement Marsh
200
Arcata s present wastewater treat-
ment plant consists of seven
basic components. These are
the headworks, primary clarification,
solids handling, oxidation pond, treat-
ment marshes, enhancement marshes
and disinfection. Each one of these
components will be detailed as follows.
Headworks: The "headworks" compo-
nent of Arcata's wastewater treatment
plant is the first phase in the treatment
of raw sewage and consists of technolo-
gies aimed at removing inorganic
materials from the raw sewage. The
technologies include two screw pumps
that lift the sewage fifteen feet and pass
it through bar screens, a parshall flume
(for flow measurement) and grit
separators before it enters the clarifiers.
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Primary Clarification: Two clarifiers
are used to settle out any remaining
suspended material that passes through
the headworks. The liquid form of
sewage that results from clarification
flows to the oxidation ponds, complet-
ing primary treatment. The solids that
settle out in the clarifiers are pumped
to the digesters.
Sludge Pumping and
Stabilization/Cogeneration: The sludge
from the clarifiers is pumped first to
the primary digester and then the
secondary digester. The digesters mix
the sludge by recirculating methane gas
with compressors. The digestors were
designed in conjunction with a methane
recovery and cogeneration system. The
cogeneration component is designed
burn the methane gas and utilize the
heat to aid in the digestion process.
Oxidation Pond: The oxidation ponds
efficiently remove approximately
50 percent of the BOD and suspended
solids that remain after primary treat-
ment. Long detention times and natural
processes (see diagram showing plant
and animal roles) accomplish these
reductions.
Treatment Marshes: The treatment
marshes reduce the levels of suspended
solids and BOD concentrations that
remain in the oxidation pond effluent.
The three, two-acre treatment marshes
in operation are located north of the
oxidation ponds. They were created
by subdividing the previous oxidation
ponds. All treatment marshes were
planted with hardstem bulrush (Scirpus
acutus), a freshwater marsh plant native
to the Humboldt Bay area. This plant's
effectiveness as a treatment species was
shown by Marsh Pilot Project data. The
treatment marsh's effluent is combined
at a pump station where it is pumped
to the disinfection facility.
Enhancement Marshes: After the first
chlorination, wastewater is directed to
the enhancement marshes, which are
located northwest of the oxidation
ponds. The three enhancement marshes
cover a total of 31 acres. These marshes
are managed to maintain the greatest
diversity of aquatic plant species and to
maintain or improve water quality. Flow
is directed through the enhancement
marshes with sluice gates and wooden
stop-log weirs. After disinfection, the
wastewater flows into George Allen
Marsh, then Robert Gearheart Marsh,
and finally Dan Hauser Marsh. The
effluent from Hauser Marsh is pumped
back to the disinfection facility.
Disinfection: Chlorine gas is used to
disinfect Arcata's waste water before
it is discharged to the enhancement
marshes and again before it is dis-
charged into Humboldt Bay. Because
of this "double™ chlorination" two
chlorine contact basins are necessary.
These basins are built as one unit,
which is located immediately south
of the headworks. Any free chlorine
remaining in the final effluent after
the 60 minute contact time is removed
with sulfur dioxide.
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ARCATA MARSH AND SANCTUARY: POINTS OF INTEREST
1 Robert Gearheart Marsh: Com-
pleted in 1981, this marsh was built
from pastureland and now uses treated
wastewater as the sole water source.
2 George Allen Marsh: Also
completed in 1981, this marsh was
built on an abandoned log deck and
is enhanced with wastewater.
3 Dan Mauser Marsh: The final
marsh to be irrigated with treated
wastewater before returning to the
treatment plant for disinfection and
release into to the bay. This marsh
was a barrow pit for the closure of
the adjacent landfill.
4 Mount Trashmore: This grassy
hill has been reclaimed from a sealed
sanitary landfill that operated during
the 1960'sand70's.
5 Frank Klopp Lake: This brackish
lake was also a barrow pit for the
closure of the landfill and is now a
popular loafing area for shorebirds, a
feeding area for diving birds and river
otters, and a place for artificial-bait-
only sport fishing.
O Treatment Marshes: Three 2.5 acre
constructed wetlands which process
oxidation pond effluent to secondary
standards prior to release to the
Arcata Marsh and Wildlife Sanctuary.
7 Arcata Boat Ramp: The only
concrete boat ramp maintained in
Arcata Bay, this serves as an access
point for sport boating, duck hunting,
and sport shellfish harvesting.
O Wastewater Aquaculture Project:
Fish hatchery and ponds where salmon,
trout and other fish are raised in a
mixture of wastewater and seawater.
9 Marsh Pilot Project: These ten
20' X 200' marsh cells have been used
since 1980 to demonstrate the effec-
tiveness of constructed wetlands to
achieve water quality and habitat goals.
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1O Oxidation Ponds: These 45 acres
of ponds, built in the late 1950's, treat
Arcata's wastewater to secondary
standards.
11 Butcher's Slough: Butcher's
Slough is a restored estuary receiving
feed from Jolly Giant Creek, the
principal watershed in Arcata. A
California Coastal Conservancy
Project returned the estuary to its
original alignment and ecological
value. This slough serves as home
to the Coastal Cutthroat Trout.
12 Butcher's Slough Marsh: An old
log pond restored to provide swamp-
like habitat in the Arcata Marsh and
Wildlife Sanctuary.
•3 Arcata Bay: This bay produces
more than half of the oysters grown
in California and is home to a variety
of other aquatic animals.
14 Headworks Facility: This is the
place where the influent to the treat-
ment system is received.
15 Discharge Point: This is the
point where a mixture of treatment
of marsh effluent and enhancement
marsh effluent is discharged into the
Arcata Bay side of Humboldt Bay.
16 AMWS Interpretive Center:
This is the site where the AMWS
Interpretive Center is built. This center
will attempt to meet the educational
demands of the treatment system.
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SPECIFICATIONS
ACKNOWLEDGMENTS
Design Population 19,056
Average Annual Flow 2.3 mgd
Maximum Monthly Flow 5.9 mgd
Peak Flow 16.5 mgd
BOD's Load 4100 Ibs/day
TSS Load 3400 Ibs/day
Headworks
Mechanically Cleaned
Bar Screens 2 at 5 mgd each
Gravity Grit Removal 144 ft.2
Primary Treatment
2 Primary clarifiers 26 ft. diam./60 ft. diam
Retention time at design flow 3.8 hrs.
Retention time at max. monthly flow 1.4 hrs.
Treatment Marshes
Total area 7.5 acres
Ave. Depth 2 ft.
Total detention time at design flow 1.9 days
Chlorination/Dechlorination
Volume 185,400 gallons
Retention time at design flow 58 min.
Retention time at max. monthly flow 30 min.
3 Enhancement Marshes
Total area 31 acres
Ave. depth 1.5 ft.
Retention time at ave. flow 9 davs
Elected Officials
Lynne Canning
Elizabeth Lee
Bob Ornelas
Sam Pennisi
Victor Schaub—Mayor
City Staff
Frank Klopp—Director of Public Works
Steve Tyler—Deputy Director of Public Works
David Hull—Aquatic Resources Specialist
Supporting Organizations
California Coastal Conservancy
California State Water Resources Control Board
California Coastal Commision
California Department of Fish and Game
Humboldt State University
Redwood Regional Audubon Society
U.S. Environmental Protection Agency
Cover Painting—Jim McVicker
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