The Forester Creek Improvement Project ($36 million), completed in November 2007, has widened and realigned 1.2 miles of the creek to withstand a 100-year-flood level. Riparian and wetlands habitat has been restored. The project had to be finished before the California Department of Transportation could extend State Route 52 to intersect with State Route 67, linking La Jolla with Santee.

Widening and revegetating a channel to control flooding and improve water quality

By Joseph S. Smith, Gary Yagade, and Mark Sullivan

Forester Creek was once an unremarkable—though occasionally flood-prone—waterway running through the quiet city of Santee, northeast of San Diego, CA. It has since become the focus of the city’s largest capital improvement project, as well as one of the top 25 California Highway Projects according to McGraw-Hill’s 2006 California Construction.  

The $36 million Forester Creek Improvement Project, completed in November 2007, has resulted in the creek being widened and realigned to withstand a 100-year flood level and has facilitated the restoration of riparian and wetlands habitat, making it a model for future creek restoration projects in the San Diego area. Work on the 1.2-mile-long segment of the creek began in January 2006 and had to be finished before the California Department of Transportation (Caltrans) could complete the final segment of State Route 52 to intersect with State Route 67, linking La Jolla with Santee.

Widening Forester Creek involved extensive excavation and relocation of five separate sewer systems, water lines, and numerous dry utilities, as well as bridge demolition and construction. Final landscaping with native plants and trees, as well as a linear park with paths, has transformed the area. After a long struggle and a lot of hard work, Santee can now look forward to renewing plans for sustainable development along the channel.

A Growing City
Located in San Diego County, Santee is 17 miles northeast of the city of San Diego, well within commuting distance. It is a suburban, family-based community with a population of more than 55,000. Almost half of the land around Santee is undeveloped, and the city wants to grow with a focus on sustainable development. A 104-acre corporate campus within a 700-acre town center (master-planned for mixed use) is currently being developed, and a 2,600-acre site has been designated for a master-planned residential community.

One of the factors spurring Santee’s growth is its proximity to major transportation routes. Two interstate highways bypass the city on opposite sides: State Route 52 (which intersects with SR-125) to the west and State Route 67 to the east. Mission Gorge Road, a major arterial running east to west, bisects downtown Santee, connecting SR-52 and SR-67. Mission Gorge is heavily traveled, especially during commuter hours.

While it looked benign in the dry season, Forester Creek frequently overtopped its banks during seasonal storms, flooding nearby surface roads and depressing property values. It was also an eyesore, a magnet for vagrancy, often overgrown with non-native plants, and a conduit of polluted water.

The final phase of Forester Creek restoration included landscaping with native plants and trees along pedestrian and bicycle paths. The restoration is so well received by Santee citizens, regional water agencies, and environmentalists that the project has become a model for others in San Diego County.

Southeast of Santee is the larger city of El Cajon. Forester Creek flows northwest through a concrete-lined channel in El Cajon into Santee, where it skirts the downtown, meandering along commercial and residential areas before it flows into the San Diego River northwest of the town. The San Diego River then travels south and west and eventually drains to the Pacific Ocean.

Before the improvement project, Forester Creek was, to some degree, an eyesore: a dumping spot for trash, a magnet for vagrancy, and overgrown with giant arundo (Arundo donax), an aggressive, grassy plant that can grow up to 30 feet tall, displacing native vegetation and fueling fire in the dry summer months.

Before the project began, the water quality in Forester Creek was poor. A baseline water-quality survey revealed fairly low levels of dissolved oxygen and high levels of phosphorous and fecal coliform from sewage, homeless encampments, and wildlife. Forester Creek was not a healthy waterway.

For years the city had wanted to develop the area along the channel but couldn’t because the adjacent floodplain is subject to flooding. The creek had been identified by the Federal Emergency Management Agency (FEMA) as a Special Flood Hazard Area with a 10-year flood level, which meant it had a chance of flooding at least once every 10 years. That was enough to require costly flood insurance, which prohibited development and depressed property values along the creek.

According to Julie Procopio, principal civil engineer with the City of Santee, “Forester Creek threatened to overtop its banks with almost every significant storm we had. Before the improvement project began, the creek’s capacity was actually less than a 10-year flood.” The last major flood occurred in January and February 1995, when 6 inches to 3 feet of water overtopped the channel, causing evacuation of 20 homes. Surface streets were flooded, and traffic had to be rerouted off Mission Gorge Road. Even the sheriff’s office was waterlogged. Multiple property damage claims were filed with the city.

 “When Mission Gorge Road flooded in the past, it was particularly hazardous because it is a major arterial road designated as a safety route out of the city in the event of a regional catastrophe,” says Procopio. “If the road were flooded during a citywide evacuation, it would truly be a calamitous situation.”

Though various solutions had been suggested to deal with the flooding, action had to be taken in 2002 when Caltrans was planning to build an extension of SR-52, linking it directly with SR-67 on Santee’s eastern boundary. The northern edge of Forester Creek would border the new highway extension, and the flooding had to be contained to a 100-year level.

Concrete Lined Versus Wetlands
In 1976, the County of San Diego initially considered construction of a concrete channel, once the preferred choice because it enabled easy repair, shorter bridge spans, and better control of flooding near roads and freeways. However, the concrete channel and additional development constructed upstream of Santee in neighboring El Cajon had resulted in increased flooding and pollution of Forester Creek in Santee, as well as further downstream where the creek discharged into the San Diego River.

When natural wetland and riparian processes are replaced by concrete, water flows at accelerated speed. Trash and waste move downstream more rapidly and are then quickly deposited once the concrete channel ends. Trash paired with rapidly moving water off the El Cajon channel hindered the natural filtering process of Forester Creek’s remaining wetland in Santee and increased the risk of flooding, in addition to negatively impacting wildlife habitat and water quality.

The City of Santee and its consultants prepared an environmental impact report (EIR) for the project. The work included a survey of the creek area and development of a GIS database used to estimate the project’s impact to wetland habitat. The EIR quantified the extent of the existing wetlands, freshwater marsh, and scrubs and the quality of the vegetation. “The findings revealed the area to be of low urban quality,” says Procopio, adding, “We’ll do a similar study and analysis in 2012, five years after the creek is restored. We expect a significant difference by then.”

The EIR process resulted in four alternatives that were presented to the city, including a concrete-lined option, an unlined option, and two other options for restoring the wetlands and excavating the channel banks. The city’s first choice was to line the lower one-third of the creek channel with concrete and vegetate the remaining two-thirds, which would have allowed for full mitigation of wetland impacts while minimizing traffic disruptions due to bridge construction. However, the San Diego Regional Water Quality Control Board, along with environmental groups, wanted a solution that was unlined and friendlier to the natural surroundings.

In 2003, the City of Santee and the Federal Highway Administration (FHWA) decided to eliminate the concrete portion and to widen and revegetate the full 1.2-mile channel, even though it added $10 million to the project cost. A significant percentage of this additional $10 million was needed to lengthen the Mission Gorge Bridge to twice its size to accommodate the widening of the channel. The city also planned to construct a new bridge at Olive Lane, which would connect residential neighborhoods on either side of the creek.

The flood control project area extended 1.2 miles along the creek from Prospect Avenue (upstream) to Mission Gorge Road (downstream). To accommodate stormwater flows, the width of the channel needed to be three times greater (approximately 200 feet) in size, though width varied along the meandering path of the creek. The creek channel depth of 10 to 15 feet remained unchanged throughout the project, as did the slope of the creek.

The overall cost of the project has totaled roughly $36 million ($23 million for construction and $13 million for right-of-way acquisition and design), making it the largest capital improvement project in the history of Santee. The project was funded through six major sources: $10.2 million from the FHWA, $6.8 million through TransNet (a San Diego County half-cent sales tax passed by voters in November 2004), $5 million from a state water bond included in the passage of Proposition 13, $3 million from the San Diego Regional Water Quality Control Board, $3 million from the County of San Diego, and $3 million from the City of Santee Developer Mitigation funds paid to the city for drainage fees.

 “It was expensive, but we knew the city would benefit in so many ways by widening and restoring the creek channel,” Procopio says.

A Construction Challenge
In 2005, the City of Santee hired PBS&J to provide full construction inspection and contract management services for the Forester Creek restoration project. Archer Western Contractors was awarded the construction contract. PBS&J and Archer Western faced two very major challenges: excavating and relocating wet and dry utilities along the channel, and lengthening a six-lane bridge on a major arterial road used daily by more than 50,000 vehicles.

A four-slab bridge was built at Olive Lane, which links a residential area of Santee to the city center. The bridge, located at the midpoint of the creek, serves as conduit for utility lines buried under bridge sidewalk and along barriers. The bridge was completed and opened in May 2007.

Utilities.Repositioning utilities from locations along the existing creek banks and creek bed to positions farther out along the widened banks was a colossal undertaking. Water and sewer pipelines, as well as electric, gas, telephone, and cable utilities lines owned by roughly 10 different providers, converged within and adjacent to the channel at Mission Gorge Road and had to be relocated in sequence in order to keep services up and running for each line. The job of sequencing and relocating the utilities was so complex that it took approximately nine months to complete the process before work on the Mission Gorge Road ridge could be initiated. Exploratory excavations were performed to verify the location of existing utilities and the suitability of designed alignments. At times, conflicts discovered in the field required planned alignments to be redesigned before construction could progress.

Relocated water and sewer utilities included approximately 3,500 linear feet of 36-inch vitrified clay sewer pipe for the City of El Cajon and 3,800 linear feet of 21-inch to 24-inch PVC sewer for the Padre Dam Municipal Water District (MWD). An additional 3,000 linear feet of smaller potable-water, recycled-water, and sanitary sewer pipelines were installed, ranging in size from 8 inches to 16 inches in diameter. In order to maintain sewer service, approximately five major pumped sewer flow diversions and temporary pipelines were used to bypass sewer flows during construction. Temporary high-density polyethylene pipelines were also used to maintain water service during various phases of the construction.

A 36-inch steel waterline owned by the Padre Dam MWD was relocated and upsized to 48 inches. The relocation work was especially challenging because it occurred within and adjacent to the heavily traveled Mission Gorge Road, where traffic had to be maintained at all times to minimize the impact to the approximately 50,000 daily commuters using the thoroughfare. The alignment for the waterline crossed under a number of existing utilities, including 3-inch and 4-inch high-pressure gas lines, a 42-inch sewer, a 16-inch reclaimed-water pipeline, and other existing utilities. To accomplish the task, excavation depths approached 20 feet in some locations and required beam and plate shoring to support the adjacent roadway improvements.

A portion of the El Cajon sewer was installed underneath Mission Gorge Road by implementing a jack-and-bore construction technique. A tunnel was auger-drilled, and steel casing was jacked under the road to facilitate the crossing and to maintain traffic service. A second jack-and-bore operation was used to install a 42-inch PVC sewer for the County of San Diego. This sewer crossed directly underneath the Forester Creek channel at the downstream spillway. The jack-and-bore method was selected for this portion of the work to protect the existing concrete spillway already in place.

In total, 17 storm drainage systems have outlets that feed into Forester Creek along the project alignment. To incorporate these outlets into the project, approximately 3,000 linear feet of reinforced concrete storm drain pipe and associated improvements were constructed. Storm drain pipelines range in size from 18 to 54 inches.

Nonstop coordination was required with numerous municipal agencies and dry utility companies, including the Padre Dam MWD, the City of El Cajon, the County of San Diego, SBC, Cox Communications, San Diego Gas & Electric, Level 3 Communications, the San Diego Regional Water Quality Control Board, Caltrans, the San Diego County Sheriff, and adjacent business owners and residents.

Bridges.PBS&J and Archer Western’s second challenge was to lengthen the existing Mission Gorge Road Bridge (six lanes wide—three lanes in each direction) to accommodate the widened portion of the Forester Creek channel. The bridge construction had to be performed while maintaining continuous traffic service to the 50,000 commuters who use Mission Gorge Road on a daily basis. Until Caltrans completes the SR-52 extension project in October 2011, drivers will have to exit SR-52 where it ends on the western side of Santee and then drive across Mission Gorge Road and the bridge to connect with SR-67 on the east side of the city.

Given the volume of heavy traffic, the bridge had to be lengthened in three phases to allow a minimum of two lanes of traffic to remain open in each direction. Bridge construction began in September 2006 and was completed in September 2007, much to the relief of commuters.

Another bridge was demolished and a new four-slab bridge built at Olive Lane, which effectively links a residential area of Santee to the city center. The bridge also serves as conduit for many of the utility lines. During the relocation process, dry utilities were temporarily routed overhead on the bridge while crews built permanent conduits underneath the bridge sidewalks and along the bridge barriers. Recycled-water lines now run along the bridge barriers as well. The Olive Lane Bridge was completed and opened in May 2007.

To widen the creek, water was diverted from one side of the channel to the other by digging a second channel that ran parallel to the length of the creek. More than five separate sewer systems had to be excavated and repositioned along the channel banks.

Widening the Channel
One major focus of the Forester Creek project was to permanently slow the speed of the water discharging from the El Cajon concrete-lined channel (upstream of the project), where it was traveling up to 20 feet per second (fps). The goal was to have water flowing at roughly 3 fps through Santee. A reduced flow rate was necessary not only to manage construction conditions but also, and more importantly, to reduce long-term erosion and allow for the natural desilting and filtering process to occur through the restored wetlands area.

The decision to construct a natural channel in lieu of a concrete channel meant that the existing Forester Creek channel would need to be significantly wider. Because the existing upstream channel within the City of El Cajon had already been constructed with concrete years ago, upstream water velocity and energy had to be dissipated. To accomplish this goal, a 100-meter-long riprap energy dissipater was constructed to slow down and spread out high-velocity stormwater.

A series of riprap check dams was constructed within the channel to help control erosion during construction. The check dams were built using small boulders, 1 to 3 feet in diameter, placed roughly in a horseshoe shape. Archer Western Construction also diverted low-flow creek water to pump wells, where the water was filtered with 0.75-inch rock and filter fabric before being pumped through active construction areas to downstream discharge points. Throughout the project, the City of Santee monitored and sampled water quality to check turbidity and sediment levels within the creek.

The flows in Forester Creek are typically heavy during winter storms but light during the dry summer months. To widen the creek, water was diverted from one side of the channel to the other by digging a second channel that ran parallel to the length of the creek. The constructed channel shifted from side to side depending on where crews were working to widen the channel. To control erosion, bonded fiber matrix—emulsified wood chips and other material—was sprayed to help hold the new banks in place. Luckily, the 2006–2007 winter rains and other seasonal storms were relatively light, which enabled more control of the creek flow.

The excavation process to recover buried utilities and widen the banks of Forester Creek yielded approximately 350,000 cubic yards of fill that Caltrans will be using to build SR-52 overpass embankments.

Going Native
The final stage of the project included construction of a network of pedestrian and bicycle paths weaving along the channel. A small linear park with picnic tables was created along the path to invite visitors to stop and enjoy views that include native plants and trees throughout the area. Creek banks have been planted with coastal sage scrub and southern willow scrub, which attract a variety of bird life, including gnat-catchers, terns, and cliff swallows. The paths and park area have been planted with more than 400 trees, including sycamores, coastal live oaks, and toyans.

 “The City of Santee will provide a five-year maintenance and monitoring program while the new plants become established,” says Procopio, “although we expect they will soon be able to thrive on their own with help from normal rainfall and the underlying groundwater.”

Everybody Wins
“We began the project with three goals in mind: to increase stormwater capacity in the creek to a 100-year flood protection level, to invigorate development of the area and save local residents and business from the need for costly FEMA-mandated flood insurance, and to restore the creek’s habitat while improving water quality,” says Procopio. “We’re confident that all three goals have been met.”

Before the project began, FEMA reviewed the hydraulic analysis for the floodplain area along the creek and provided the city with a conditional letter of map revision. Upon project completion, FEMA will update its Special Hazard Area maps, and citizens whose property is officially out of the floodplain will no longer be required to purchase flood insurance. The channel has now been widened to a 100-year-flood level with capacity to move 13,000 cubic feet of water per second. Overflow during seasonal storms will become part of the city’s history.

 “We expect the new Forester Creek to be a community asset in the heart of city, connecting retail and residential neighborhoods. Underutilized commercial property can now be developed, which will make Santee’s economy more robust,” says Procopio, who added that no residentially zoned land along the creek is earmarked for redevelopment.

It is also expected that the creek’s water quality will greatly improve. A trash collector has been installed at the El Cajon border where the unlined channel begins so that refuse can be removed before entering the Santee creek area. As native plants oxygenate the water and slower flows decrease turbidity, there is an opportunity for pollutants to be removed from the water through natural processes in the wetland. Pollutants such as hydrocarbons, metals, nutrients, and fecal coliform can be reduced. The creek’s water quality and various biological indicators will be closely monitored over the next five years to measure the improvement in water quality and wetland habitat as a result of the restoration of the creek.

The restoration of Forester Creek has already won an award from the Association of Environmental Professionals for Outstanding Environmental Solution in recognition of a unique and technically advanced design/construction project to reduce or avoid adverse environmental effects. The restoration has been so well received by Santee citizens, regional water agencies, and environmentalists that the project has become a model for others in San Diego County. Says Procopio, “We think the Forester Creek Improvement Project proves that a city can benefit economically while protecting the environment and enhancing the natural aesthetics of the community. And that’s smart planning.”

Acknowledgements
Julie Procopio, Principal Civil Engineer, City of Santee
Helen Perry, Stormwater Program Manager, City of Santee

Joseph S. Smith, P.E., CCM, is PBS&J’s division manager for construction services based in San Diego, CA. Gary Yagade is a project manager in PBS&J’s San Diego office. Mark Sullivan, P.E., formerly with PBS&J, is president of MJS Construction in San Diego.

SW January/February 2008

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