3 Miles of Pipe Underground

Shaunna J. Watterson and Thomas A. Shuput

Nothing more than a landfill for nearly 30 years, Berkeley's Cesar Chavez Park now has been safely converted into a haven for kite flyers, dog walkers and picnicers.

With its stunning views of the Golden Gate Bridge, San Francisco skyline, Marin highlands and Berkeley hillsides, you might never guess that Berkeley, Calif.'s Cesar Chavez Park was once a landfill. While recreational activities and the park's landscaping compliment the city, the site has been fitted with a landfill gas collection piping system - hidden safely underground - to handle decomposition emissions.

Located in Northern California, the 112-acre Berkeley Landfill site originally consisted of tidal flatlands, which were reclaimed with a levee dike system to dispose of waste away from the public's view, beginning in the late 1950s. However, by 1976, the city council realized that their landfill was filling up. Council members knew they'd have to close their disposal site to meet regulations, but it was "icing on the landfill" when they discovered they could simultaneously create a community asset.

Thus began the Berkeley public works department's five-phase program to develop the North Waterfront Park (initially named North Waterfront Park and renamed in 1994 the Cesar E. Chavez Park, in honor of the famous labor movement leader) and wildlife refuge.

Early Groundwork To close the landfill, the site was divided into five parcels running east to west. As landfilling ceased on each parcel, soil cover was imported so the areas could be covered and re-graded. The amount of import fill (i.e. hilly or flat terrain) determined the final end-use.

Phase one of the site grading and final cover placement was completed in 1981, with the final phase being completed in 1989. A subsurface landfill gas collection system and flare station was installed in 1988 to allow for park development.

Once completely closed, parcels one through four were landscaped and converted into a partially irrigated public park. Phase five (approximately 50 acres) was graded but not landscaped, to allow for native vegetation growth and the wildlife refuge.

SCS Field Services' Long Beach and Modesto, Calif. offices have been providing post-closure operation and maintenance and monitoring services to the site since 1991.

Collecting the Gas Key to the Berkeley landfill closure is its out-of-sight landfill gas collection system. A complex network of more than 16,500 feet of polyvinyl chloride (PVC) piping exists underground to collect landfill gas generated by decomposing refuse and control gas migration. Currently, gas is extracted from 42 vertical extraction wells, ranging from 14 feet to 54 feet deep, which are located throughout the landfill.

The Bay Area Air Quality Management District (BAAQMD) regulates landfill gas control. During closure, the city also was required to monitor and control off-site gas migration to meet California Code of Regulation requirements (CCR Title 27). Subsurface landfill gas migration is under control when methane concentrations are below 5 percent by volume at the property boundary.

The landfill's piping system was designed to control gas coming from Cesar Chavez Park where the majority of landfill gas is generated. The system also controls gas emissions from an area south of Spinnaker Way, which generates less gas, but is adjacent to a hotel complex. Spinnaker Way's high water table and other areas of perched water required a special design to extract the gas. Consequently, 14 trench wells and two horizontal collectors were installed.

Blow and Burn The extraction wells, trench wells and horizontal collectors are connected to an above-ground blower/flare station. Landfill gas is piped to the blower and to the flare, where it can be burned. After treatment, emissions are released into the atmosphere.

The blower system consists of dual blowers that have a rated capacity of 1,000 cubic feet per minute (cfm), which handles the maximum gas flow. The blower is driven through a sheave and belt drive system by a 15-horsepower (hp) motor. A pitot tube also was installed between the blower and flare to measure gas velocities in the header piping.

The flare's pilot system is ignited by a 10-gallon liquid petroleum gas cylinder. An enclosed flare assembly that is 6.5 feet on each side, 35 feet tall and has an 8-inch diameter inlet is used to meet BAAQMD emission requirements. The flare controls combustion and maintains a 1,600-degree Fahrenheit temperature by automatically adjusting air louver actuators powered by electric motors.

Eighteen gas monitoring probes are installed at the site and around the hotel to ensure that landfill gas does not migrate offsite toward adjacent park properties. No additional monitoring probes are located around the site perimeter because much of the former landfill is surrounded by the San Francisco Bay.

The gas collection system is estimated to reduce methane emissions by destroying 10,000 tons of greenhouse gas (GHG) per year, based on 1,000 square cubic feet per minute of gas flow.

A Watchful Eye To ensure the park continues to meet closure regulations, several professional engineering, field operations and maintenance (O&M) programs are in place. For example, the landfill gas collection/control system must operate 24 hours per day, 365 days a year, according to BAAQMD's operating permit. To prevent breakdowns and reduce repair and adjustment time, the landfill's O&M program includes:

- Weekly inspection of landfill gas facilities. Checking of the blower inlet/outlet pressure and temperature; flare inlet gas quality; total gas flow; flare exit gas temperature; and automatic louver position. A leak test of system connectors and components also is performed quarterly.

- Monthly gas collection system testing, including wellhead pressure; header pressure; flow control valve position; percent methane and oxygen; and monitoring well pressure.

- Routine and non-routine maintenance of the gas collection system, including replacing belts twice a year; greasing the motor/blower units twice a year; servicing the flare; shutting down the blower/flare station as necessary; repairing header line breaks; responding to odor complaints; detecting carbon monoxide; and monitoring landfill gas migration to off-site structures.

Additionally, the city monitors the rate at which the site surface settles. Results are correlated with observations of damage to utilities, drainage structures and other site features.

As part of this program, landfill operators maintain two survey control monuments. These reference points verify that the elevation of the top of the levees is consistent with a 100-year high-tide level. The reference points also help indicate differential settlement throughout the former landfill interior. A summary and interpretation of field observations is compiled in a biannual report, which includes recommendations for maintenance or corrective action.

Above ground, potential damage from waves, tidal effects, and/or precipitation is diligently monitored as required by permit conditions, because the landfill site was built on reclaimed tidal flats inside an engineered levee dike system. A low-permeability clay cap covers the refuse, and is topped by varying thickness of soil to provide hilly terrain and promote landscape vegetation for the park. Levees form the perimeter of the site, which is surrounded by the San Francisco Bay.

The final cover and levee inspection program is designed to locate and repair problems that may cause water infiltration and/or landfill gas to escape. While the public park requires relatively little maintenance, the city re-grades localized areas of landfill settlement, as well as repairs drainage structures every few years. Site inspections typically occur in the spring or after a major storm so repairs can be made prior to the next rainy season.

To determine what areas need repair, inspectors look for:

- Significant erosion of surface cover;

- Surface ponding;

- Cracked or eroded levees;

- Blocked or damaged drainage structures;

- Damaged walkways or other site features;

- Leachate seepage; and

- Slope failures.

Protecting the Groundwater To ensure groundwater quality and provide hydraulic gradient and leachate generation information, a network of six groundwater monitoring wells and four leachate monitoring wells were installed. These wells are regularly maintained by:

- Biannually surveying wells and verifying location and elevation;

- Inspecting and evaluating wells for physical damage that might affect data results;

- Measuring groundwater levels quarterly; and

- Collecting and analyzing groundwater samples, as requested by the city.

The site also contains a network of eight observation wells along the inside perimeter of the levees to monitor and evaluate the integrity of the levees, and to detect potential leachate seepage into the Bay. The levee seepage monitoring program includes:

- Biannual surveying wells, verifying their location and elevation;

- Inspecting and evaluating wells for physical damage that might affect data results;

- Maintaining wells; and

- Using continuous recorders for 24 to 48 hours to measure water levels and detect tidal influence.

Surface Water/Infiltration The Surface Water/Infiltration Monitoring program minimizes infiltration of water through the landfill clay cap barrier while providing adequate water to sustain landscape vegetation. This satisfies regulatory requirements, and supports maintenance of the park's landscaping. The city adjusts the irrigation frequency accordingly.

In particular, soil moisture is gauged by using five soil tensiometers and through visual field observations (i.e. saturated cover conditions, condition of vegetation) by park maintenance personnel. This information is reported quarterly, with specific recommendations for adjustments to irrigation schedules and/or any needs for repair or modification to the program.

A quarterly self-monitoring report summarizes site activities from data gathered during the previous three months of monitoring and maintenance. Data analysis and recommendations concerning future studies or corrective actions are included. These reports are submitted to the appropriate regulatory agencies.

End-Use Benefits Overall, the landfill closure, gas collection system and O&M programs help to transform an environmental liability into a public asset, without affecting water quality in the San Francisco Bay.

As part of Berkeley Partners for Parks, the closed landfill facility now consists of open playfields, a perimeter walking trail and bike path, picnic grounds, scenic overlooks, and a wildlife refuge area. In 1998, the Berkeley city council also established a 17-acre area for off-leash dogs.

Kite flying, frisbee throwing, and radio-controlled gliders are popular park activities. And the park's hills and proximity to the Golden Gate area's winds make it a perfect location for the annual Berkeley Kite Festival and West Coast Kite Championships.

Additionally, the city offers a Marina Experience Program adjacent to the landfill. This Program includes the Shorebird Nature Center, an Adventure Playground, educational programs, the Baylit volunteer program, Shoreline Cleanup and the annual Bay Festival. Numerous restaurants and the Berkeley Marina Radisson Hotel are also located adjacent to the Park.

"Long-term planning, continued attention to post-closure responsibilities, and community support and appreciation of these efforts, has allowed for a unique utilization of this closed landfill," says Jack Pajoohandeh, engineering project manager for the city of Berkeley public works department.

Most recently, the city began constructing a bicycle, pedestrian, and disabled access crossing over State Highway 80, which will eventually provide improved access to the Marina facilities and to the park. Construction should be completed in 2001.