3.8.5 El Dorado Regional Park
Project Description
El Dorado Regional Park, owned by the City of Long Beach, is 500 acres
of open space in a densely developed urban area. It is a long stretch of
open land running along a concrete-lined section of the river. The park is a
well-established urban recreation area, bordered by the river, Coyote Creek,
and the 605 Freeway. The City and the RMC have partnered to develop a
new Master Plan for the park, which will include new treatment wetlands,
replacing exotic plants with natives, and creating new riparian habitats.
An alternative vision includes returning this reach of the river to a more
natural state with a soft bottom.
In a parallel process, the County of Orange is working with the U.S. Army
Corps of Engineers on the Coyote and Carbon Creeks Watershed Management
Plan, which includes the El Dorado Regional Park. That study will
help determine the feasibility of elements of this project.
Opportunity
The park is at the confluence of the San Gabriel River and Coyote Creek,
on land that was originally part of the floodplain. When the river and creek
were channelized, the rich alluvial soils were perfect for farming. In the
early 1950s, the City of Long Beach had the foresight to buy 500 acres of
that farmland for a regional park to preserve open space. The farmland is
long gone. The park is now surrounded by dense urban environments, the
freeway -- and two miles of the river. However, there is little connection
between the park and the river: berms block views of the river from the
park and SCE power lines run all along the river, precluding access except
at two points.
The park is divided into four sections. The southernmost section, called
South of Willow, is six City-owned acres of mostly undeveloped open
space. Between that land and the river is 12 acres of SCE right-of-way.
The area has been heavily disturbed through extensive construction and
maintenance activities associated with the Wastewater Reclamation Plant
(WRP) and the new Water Replenishment District groundwater injection
facility -- injecting water into the coastal basin to prevent saltwater
intrusion. There is very little native habitat and minimal wildlife.
Area 1, just north of that site, includes the well-used El Dorado Nature
Center, visited by more than 130,000 people a year. It offers natural trails
and two lakes joined by a stream that meanders through forested areas
and fields of wildflowers. To birds, the Center is a huge green oasis with
water, cover and food -- it is home to over 50 bird species. There is also a
wide variety of mammals, including coyotes, foxes, squirrels, and raccoons.
However, the area was initially planted with many non-native species that
grow quickly, including pine, eucalyptus and oak. Many of these forested
areas have now reached maturity and are beginning to die off. Grounds at
the Center are overgrown with non-native grasses, and need replanting.
The Nature Center itself has become shopworn and needs updating.
Areas II and III in the northern half of the site, offer a manicured park
setting with common turf and ornamental, non-native trees planted for
shade. These areas have paved trails and four more lakes, some concrete
lined, stocked with fish. Wildlife diversity has dramatically decreased:
mainly gophers and field mice remain, along with ducks, herons, and
egrets on the lakes. During dry months, all the lakes are replenished
with a combination of potable water and well water from the Long Beach
Water Department.
This two-mile stretch of open space along the river presents several
tantalizing, unique opportunities:
- With potable water an increasingly scare resource, the City is interested
in creating a more sustainable lake and creek system. A new treatment
wetland at the northern end of the Park could fully treat a year’s worth
of stormwater runoff from a portion of the surrounding urban areas,
replenishing the lakes and perhaps providing Long Beach TMDL credit
and increasing the amount of potable water for Long Beach residents.
The wetland could also cleanse reclaimed water from the treatment
plant at the south of the park, making it acceptable for replenishing the
lakes. (Landscaped areas are already irrigated with reclaimed water.)
- Working with SCE to create habitat and allow river access in more
places would set a precedent for more partnerships along the
entire river.
- Vegetating with native plant species would increase food and cover,
allowing wildlife to return to the area.
- A constructed wetland adjacent to the river at the south could further
treat water in this reach of the river, which is mainly effluent from the
Los Coyotes Long Beach Water Reclamation Plants. That water currently
flows to the ocean and could be recaptured through a new wetland.
- And, in a visionary alternative scenario, replacing the concrete
bottom and east bank of this reach of the river with a soft bottom
and terraced vegetated bank would widen the river, create valuable
new riparian habitat, integrate the river with the park, and increase
both recreational and educational opportunities.
Challenges
Many other areas along the San Gabriel River are reclaiming unattractive
landscapes and restoring native vegetation, which will vastly improve both
aesthetics and habitat. El Dorado is already "green," although it is
manicured and artificially created in Areas 2 and 3. This project proposes
replacing the exotic and ornamental plants with native vegetation that will
not require as much water and is better for habitat. However, it won’t be
as "green" all year long. Some people may prefer the manicured areas
and may not like the change. Designs should include some of the most
aesthetically pleasing native vegetation and ensure minimal loss of active
recreation space. It will also require some awareness raising to promote
the benefits of native vegetation. The completed El Dorado Nature Center
Master Plan study may have also addressed this issue.
In the LA metropolitan area, it is also unprecedented to remove concrete
channels from a river. These channels were built in the 1960s and 1970s,
continuing four decades of flood control efforts. The community did
not want any more damaging floods and the channel represents a major
psychological and monetary investment. The open area here offers excess
capacity to restore the natural floodplain for the river and it is feasible to
remove the channel and maintain flood protection. But, it will take a major
effort to convince all stakeholders that it is a wise and prudent idea. (Only
the east side of the channel would be removed; the west will remain to
provide flood protection for residential areas.)
A decision about whether to remove the concrete must be made before
designing treatment wetlands in the southern area of the park, to take
into account the larger floodplain that would be required. According to the
2003 State Water Resources Control Board, Section 303(d) list of Water
Quality Limited Segment, the reach of the San Gabriel River adjacent to
the park is considered impaired for algae, with abnormal fish histology and
high coliform counts. That water would benefit from new treatment
wetlands in the southern part of the park.
In addition, SCE power lines that run along the river would need to be
moved further into the park area, away from the floodplain. In some areas
of the country, power lines are placed in wetlands. However, it might be
more feasible to relocate them in the park.
According to City of Long Beach park officials, using reclaimed water
coming directly from the treatment plant is not acceptable for lakes that
are stocked with fish, based on California Department of Fish and Game
standards. Reclaimed water is too high in nutrients like nitrates and
phosphates that might cause algae blooms in a lake. It is too costly for the
Long Beach WRP to remove those nutrients, so treatment would be an
ideal solution. However, that water would first need to be pumped up to
the new north treatment wetlands.
Design Concepts
WETLANDS. The wetland would cover about 6 acres, situated about 10 feet
below the existing grade. Stormwater runoff from the adjacent residential
and commercial areas in Lakewood and the Long Beach Towne Center,
would flow into the northernmost lake. That lake will act like a settling pond.
Sediments like oily sands would settle at the bottom and be removed.
Water then flows into a snaky maze of vegetation within a newly created
wetland, which very effectively cleanses the water. From there, the
cleansed water flows into the second lake.
Reclaimed water would need to be pumped up into the wetland area to be
cleansed of nutrients before flowing into the second lake. During the dry
season, reclaimed water from the Long Beach WRP would supplement
the urban runoff throughout the treatment wetland system to ensure
continuous water flows and help the cleansing process. Water would flow
continuously through the lakes, and back out into the river.
A second wetland, at the south end of the park, would treat stormwater
runoff and the discharge from the Los Coyotes WRP, returning cleansed
water to the river. The habitat areas can be designed to meet the access
requirements of SCE and promote multiple uses on the utility corridor
rights of way. A decision about removing the concrete channel would need
to be made before designing this wetland. The planning and design of
both wetlands would be in coordination with the local mosquito and vector
control agency to reduce mosquito breeding and not create any public
health risk. Long-term maintenance and monitoring will also be developed
as part of the final design.
RESTORED FLOODPLAIN. An alternative vision is replacing the concrete
bottom with a soft bottom and a series of terraces for flood protection.
That is a long-term goal requiring extensive reengineering of the river
corridor. The river here is about 100 feet wide and flows are consistently
between 100 and 150 cfs. The channel capacity now is almost 59,000
cfs, greater than the 100-year flood.
A soft bottom would require increasing the width of the river with its
terraces to 300 feet to provide the same flood control capacity -- in most
places that would require less than 10 percent of the parklands. The
western bank of the San Gabriel River channel and the eastern bank of the
Coyote Creek channel would remain, while the two internal channels would
be removed. This would create about 8.5 acres of riparian habitat, with
willow and cottonwood trees, baccharis and mule fat scrub. It would
provide habitat for the least Bell’s vireo, yellow warbler and yellow-breasted
chat, as well as foraging mudflats and shallow water for native sandpipers,
egrets and herons. It would be an important link for migrating coastal birds.
An engineering study will be needed. This may be integrated into the
U.S. Army Corps of Engineers study. In addition, operators of the water
treatment plant will require assurance that there would be no negative
impact on treatment.
TRAILS. Trail access, signage, artwork and shade trees will improve the trail
experience and emphasize connections to the river. Overlook points and
vistas can highlight the water conservation and water quality aspects of the
wetlands and lakes. The current San Gabriel River Bike Trail runs along
the park, and could be linked through the wetlands area. If the river
becomes soft-bottomed, the terraces could provide soft equestrian trails
as well as decomposed granite and asphalt multi-use trails.
LANDSCAPING. Potential habitat changes include replacing existing
ornamentals with native drought-tolerant plants and re-vegetating land
on the eastern bank with native trees and an understory of gooseberry
and mule fat, which attract flying birds and provide foraging habitat for
shoreline birds. The eucalyptus in the Nature Center area would be
removed and replaced with native trees. The ruderal vegetation adjacent
to the water treatment plant can be replaced with a mosaic of willow trees
and native scrub, including sage scrub that supports declining wildlife
species such as the cactus wren and California gnatcatcher.
Key Components of the Concept Design Study
- Connected system of wetlands and stream corridors, treating
stormwater and reclaimed water
- Potable lake water replaced with treated water
- New habitat areas, replacing exotic plants with native plants
- The river integrated with the park
- Improved, linked trail system with interpretive signage
- Multi-use on the utility right of way
- Potentially removing concrete channels on east side, restoring
the floodplain -- feasibility study required
3.8.6 Lessons Learned
The purpose of the concept design studies was to apply the principal
theme of this Master Plan: the multi-objective approach to river corridor
project planning, designed to respond to the needs and interests of
multiple users. Each study was conceived as an experiment designed to
explore the planning process of simultaneously addressing the goals of
habitat, recreation and open space, along with the pre-existing priorities of
flood protection, water quality and water supply. In this way, the studies
helped measure the benefits and limitations of this multi-objective/
multi-user approach. The lessons learned from the concept design studies
will be useful to other project sponsors as they navigate the challenges
created by integrating seemingly divergent program elements.
A key finding is that the multi-objective approach can only be successfully
applied on a case-by-case basis. There is no "cookie-cutter" design
or formula for success. A successful combination of divergent program
elements is dependent on both the physical setting to which it is applied
and the talent of the planning team whose site designs are created in
response to that setting. In addition, the multi-objective planning
process must also take into account institutional, regulatory, and
political factors that may limit the available options. As a result, what
may work in one setting may have to be significantly modified to be
successful elsewhere, and the multi-objective approach may not work in
all settings. However, a planning team should approach all future project
opportunities from the assumption that a multi-objective approach is
applicable unless the emerging design process should prove otherwise.
This approach represents a significant shift from past planning practices
that began each project with the assumption that it was a single-purpose
endeavor, as multi-objective projects were then seen as the exception
rather than the rule. ...
El Dorado Regional Park (R6.21 and R6.22)
This rare, 497-acre open space opportunity of parkland adjacent to the
river presents a very large and tempting canvas with which to work. How
can one make the best use of this opportunity while recognizing that the
site design must address significant constraints? The planning process led
to a short-term plan to create urban runoff wetlands treatment systems
and a long-term plan to partially restore the floodplain by removing one
side of the concrete channel.
Both visions require hydrology studies to assess their feasibility.
Because long-term plans will affect the treatment wetlands design and
configuration, a decision about whether to restore the floodplain must
be made before planning can begin on the wetlands.
Other observations include:
- The river should be front and center as it passes through all the cities
along its path to the sea; it cannot remain a forgotten, hidden flood
channel. Existing parks and open spaces can be re-oriented to face
the river.
- Many parks along the river have the traditional ornamental landscape
design. This project could be the prototype for a new river park design
model based on native vegetation and river orientation.
- "Thinking big" (e.g., taking out the concrete) may open up other
possibilities that no one would have thought of, even if the initial
concept is not implemented in its pure form.
