Maximizing the Use of Existing Infrastructure to Minimize Environmental Impacts

The Monterey Bay is an ecologically diverse wonder. With extensive kelp forests and underwater canyons, it hosts hundreds of species of marine mammals, seabirds, shorebirds, fish, invertebrates, and algae. It is a designated National Marine Sanctuary, and contains four State Marine Conservation Areas (Soquel Canyon, Portuguese Ledge, Pacific Grove Marine Gardens, and Edward F. Ricketts) and two State Marine Reserves (Lovers Point and Asilomar). Despite these myriad designations and corresponding environmental protections, much of the urban runoff to the Monterey Bay area enters the bay untreated. A new project is aiming to change that: the Monterey-Pacific Grove Area of Special Biological Significance Stormwater Management Project. The project, which responds to the designation of a portion of the Monterey Bay as an Area of Special Biological Significance (ASBS), was selected from 22 alternatives after nearly of decade of planning, engineering, and analysis. Through adaptive reuse of existing infrastructure, the project will achieve water-quality benefits while minimizing secondary environmental effects.

Area of Special Biological Significance
In the mid-1970s, the State Water Resources Control Board (SWRCB) designated 34 areas on the coast of California as “ocean areas requiring protection of species or biological communities to the extent that alteration of natural water quality is undesirable” (SWRCB Resolution No. 2012-0012). The Pacific Grove ASBS is 3.2 miles of coastline adjacent to the city of Pacific Grove. This ASBS lies entirely within the Monterey Bay National Marine Sanctuary and overlaps with the Pacific Grove Marine Gardens State Marine Conservation Area and Lovers Point State Marine Reserve. The Pacific Grove ASBS receives runoff from a 950-acre watershed that includes portions of the New Monterey District in the city of Monterey and approximately half of the city of Pacific Grove.

The primary goal of the Monterey-Pacific Grove ASBS Stormwater Management Project is to improve stormwater quality discharged into the Pacific Grove ASBS by meeting a set of requirements adopted by the SWRCB. On March 20, 2012, the SWRCB adopted the “General Exception and Special Protections for the California Ocean Plan Waste Discharge Prohibition for Stormwater and Nonpoint Source Discharges” into any of the 34 ASBS (or “Special Protections”). These Special Protections require, among other conditions, the assurance that wet- and dry-weather flows do not alter “natural water quality” and the complete elimination of non-stormwater (e.g., dry-weather) urban discharges into each ASBS. If water monitoring finds that the natural water quality of the receiving water (in this case, the Monterey Bay) is already degraded by stormwater discharges, the Special Protections require that pollutant loads be reduced by 90% during wet-weather conditions.

The water-quality parameters that define “natural water quality,” as well as impacts from existing stormwater discharges into the Pacific Grove ASBS, are currently unknown. The cities of Pacific Grove and Monterey belong to a 10-party Central Coast Regional ASBS Monitoring Program that is undertaking a two-year water-quality monitoring effort to gather additional information to assess the Special Protections compliance requirements. If water-quality monitoring within the Pacific Grove ASBS determines that the natural water quality is degraded, target pollutants and reduction goals will be determined. If implemented, the project would satisfy the ASBS Special Protections requirements and protect natural water quality if found to be degraded.

Selecting a Project
The process of identifying a project that could capture and treat runoff from within the Pacific Grove ASBS watershed began in 2006, before the adoption of the Special Protections requirements. At that time, the city of Monterey obtained a Proposition 50 grant from the California Department of Water Resources to analyze a suite of options to address regulatory restrictions under consideration by the SWRCB for stormwater discharges to the Pacific Grove ASBS. The 2006 study, conducted by MACTEC Engineering and Consulting Inc., identified 22 alternative projects, including local projects that would collect and treat runoff in Pacific Grove before it is discharged to the Monterey Bay, regional projects that would pump runoff to the Regional Wastewater Treatment Plant in nearby Marina, and other potential project alternatives.

In January 2013, the city of Monterey retained Fall Creek Engineering Inc. to complete a feasibility study to refine and select a preferred alternative from the extensive list of projects identified by MACTEC, develop preliminary project plans, complete environmental review in compliance with the California Environmental Quality Act (to be conducted by Rincon Consultants Inc.), and prepare a work plan for future grant applications.

Several meetings with key stakeholders were held to revisit and refine the various project alternatives. In addition to the cities of Monterey and Pacific Grove, whose runoff enters the Pacific Grove ASBS via 23 12-inch-diameter or greater outfalls, key stakeholders include the California American Water Company, who owns the David Avenue Reservoir (an area utilized by the proposed project, as discussed below); the Monterey Regional Water Pollution Control Agency (MRWPCA), whose existing treatment plant in Marina, approximately 9 miles north of the watershed, will receive a portion of the runoff; and the New Monterey District neighborhood representatives, whose viewsheds include the David Avenue Reservoir component of the project. After review and screening of the 22 alternatives identified in the 2006 MACTEC study, six project alternatives were identified.

A screening analysis of the six project alternatives was completed in May 2013 to identify a preferred and an alternate project. The screening analysis compared the six project alternatives based on 16 criteria, the most critical being:

  • Water-quality benefits (or ability to meet ASBS requirements)
  • Impact to regional water treatment plant capacity
  • Ability to achieve multiple benefits
  • Access to potential funding opportunities

Other criteria included permitting requirements and challenges, anticipated environmental impacts, and stakeholder involvement and support. This initial screening identified a preferred project that would involve treating both dry- and wet-weather flows from Pacific Grove and New Monterey at a new stormwater treatment system constructed at the site of the retired Pacific Grove Wastewater Treatment Plant (PGWTP), at Point Pinos in Pacific Grove. An alternate project was also selected, which would treat both dry- and wet-weather flows at the MRWPCA Regional Wastewater Treatment Plant in Marina. Both projects would include water storage in the currently empty David Avenue Reservoir, formerly used for water supply storage.

A project alternative that consisted entirely of low impact development (LID) practices alone was not considered. LID is a stormwater management strategy concerned with maintaining or restoring natural hydrologic functions to protect water quality, manage stormwater runoff, achieve natural resource protection objectives, and fulfill environmental regulatory requirements. Due to the magnitude of flows that need to be managed to protect the Pacific Grove ASBS, LID practices alone were not considered as a feasible management approach. However, LID strategies and practices were considered throughout the project selection and design process, and the proposed project would result in a multitude of benefits associated with typical LID applications, specifically a reduction in peak stormwater flows and a desynchronization of rainfall and associated runoff that will more closely resemble predevelopment conditions.

As the project team further developed the two alternative project concepts, a hybrid project between the two was identified and considered environmentally superior and more cost effective. This hybrid project—the Monterey-Pacific Grove Area of Special Biological Significance Stormwater Management Project—was environmentally and economically superior primarily because of its adaptive reuse of existing infrastructure.

Reusing Infrastructure
A key component of the selected project is its reuse of existing infrastructure. Runoff from 87 acres within the city of Monterey (at the highest point of the watershed) would be directed into the currently unused David Avenue Reservoir. This reservoir, constructed in 1882, historically retained 56 acre-feet of water. In 1989, the reservoir ceased operation, and it was drained in 1998. The site is currently owned by the California American Water Company.

The project includes retrofit of the David Avenue Reservoir to capture runoff from the portion of the ASBS watershed within the city of Monterey. Improvements would include a new connection to the Monterey storm drain collection system, construction of a new forebay and inlet structure, installation of a multilayer geomembrane liner system, and a new outlet connection to the Pacific Grove storm drain collection system. After construction, the newly restored reservoir would have an estimated water storage capacity of 49.15 acre-feet, which includes storage provided by the new forebay. A minimum reservoir level would be maintained for aesthetic purposes and vegetation stability. Water in excess of this minimum would be released into the city of Pacific Grove storm drain system, where a combination of gravity flow and pumps would convey the runoff north to a new stormwater treatment plant at Point Pinos in Pacific Grove.

The existing storm drain system would be enhanced with approximately 11,860 linear feet of storm drain conveyance pipeline (3,860 feet of new pipeline and 8,000 feet of relining an existing abandoned sewer force main), two underground stormwater equalization and storage facilities, and four new stormwater pump stations. The two underground storage facilities in Pacific Grove—located near the Robert Down Elementary School and at the intersection of Caledonia Street and Pacific Avenue—would have the capacity to store up to 240,000 gallons and 320,000 gallons of stormwater, respectively. These storage systems would serve to delay and reduce peak flows and provide a source of water for irrigation of the school’s sports field, landscaping at a pocket park, and irrigation of the Pacific Grove Municipal Golf Links. Stormwater and dry-weather flows from approximately 751 acres of the ASBS watershed (or 77%) would be conveyed through this system of existing and upgraded infrastructure.

Runoff from the remaining 222 acres of the watershed would be captured using an existing dry-weather diversion system in Pacific Grove and conveyed to the MRWPCA Regional Wastewater Treatment Plant in Marina. Upgrades would be made to the existing system to increase its capacity and allow additional conveyance of wet weather flows, including installation of new pumps at three existing pump stations and replacement of existing 4-inch storm drains with 8-inch lines.

Infrastructure reuse would also occur at the bottom of the system, at the site of the retired PGWTP. Although the PGWTP began operation in January 1956 with an operational wastewater treatment capacity of 2 million gallons per day and discharged treated wastewater to the Pacific Ocean, this plant was decommissioned in 1980. Since then, wastewater from the city of Pacific Grove has been treated at the MRWPCA Regional Wastewater Treatment Plant. The retired PGWTP site is now used by the city of Pacific Grove as a corporation yard for staging maintenance activities on the adjacent Pacific Grove Golf Links. Two aboveground circular tank structures remain onsite, including a clarifier/administrative office and a sludge digester.

An integral part of the project would be construction of a new stormwater treatment facility within a small portion of the retired PGWTP site. This new facility would be capable of handling stormwater flows of up to 1,500 gallons per minute. The system improvements would include a flow control structure and a stormwater treatment system that would provide screening, equalization, multistage filtration, and disinfection with redundancy incorporated to allow single tanks to be taken offline for maintenance purposes. A new equalization basin on the western perimeter of the PGWTP site would manage flows into the treatment system. Treated water would be stored in one of the existing refurbished storage tanks for reuse or discharged into the nearby Crespi Pond before entering the Monterey Bay through an existing outfall.

In addition to constructing new treatment facilities at the former PGWTP site, this component of the project has the potential to coexist with another planned infrastructure project, the Pacific Grove Local Water Project (PGLWP). The PGLWP, which is currently in the planning stages, would include a variety of infrastructure improvements intended to create a new year-round supply of non-potable water for irrigation of the Pacific Grove Golf Links, El Carmelo Cemetery, and other users. The project includes a variety of infrastructure improvements, including the construction of a Satellite Recycled Water Treatment Plant at the former PGWTP site. Colocation of the PGLWP and the Monterey-Pacific Grove ASBS Stormwater Management Project’s stormwater treatment facility would occur on the PGWTP site. Additional synergies can occur between the two projects; with shared disinfection facilities and operation and maintenance staff, treated urban runoff can be blended with the recycled water to maximize available water for irrigation.

In total, the Monterey-Pacific Grove ASBS Stormwater Management Project would rehabilitate a former water supply reservoir, reuse the site of a former wastewater treatment facility, upgrade an existing dry-weather diversion system, reline 8,000 feet of abandoned sewer line, and use existing storm drains, pump stations, and an existing outfall. By maximizing the use of existing infrastructure, the project minimizes construction of new facilities, thereby reducing costs and resulting effects on the environment.

Maximizing Benefits
To achieve the purpose of improving water quality entering the Pacific Grove ASBS, the proposed project would capture the majority of runoff from within the ASBS watershed and treat it prior to discharge into the Monterey Bay. The improved water quality of the bay—as habitat to myriad protected marine species—is a direct benefit of the project.

As a secondary but important benefit, the project would involve the creation of a new source of non-potable water for irrigation. In the short term, the possibility exists for the captured dry- and wet-weather flows to irrigate the sports fields at the Robert Down Elementary School, landscaping at a pocket park near Caledonia Street and Pacific Avenue, and the Pacific Grove Golf Links and El Carmelo Cemetery, located near the retired PGWTP site. The availability of a new water source (captured runoff) could offset all the existing potable water demand at the Elementary School and Pocket Park and provide approximately 4 acre-feet per year of water for golf course irrigation. This benefit, which is already substantial given the Monterey Peninsula’s existing water supply constraints, is made even more critical amid California’s current drought crisis.

Additional benefits of the project would be achieved through the restoration of the David Avenue Reservoir. The reservoir is visible from nearby residences, and replacing the existing materials storage yard with an open water pond would provide a new scenic resource to those residents. Further, although the reservoir currently houses an intermittent wetland—which would be removed to accommodate the reservoir retrofit—the open water and planned vegetation would provide additional habitat for a variety of plant and animal species, including the threatened California red-legged frog.

One of the new stormwater conveyance pipelines (along Pine Avenue in Pacific Grove) was strategically located to coincide with future improvements on a Safe Routes to Schools project and Green Street LID retrofit. The Green Street improvements can be connected to the proposed stormwater conveyance pipeline and would provide additional stormwater quality benefits for the ASBS. It is anticipated that a Pine Avenue Master Plan would provide a cohesive plan for how these three projects can not only be strategically phased but also physically interwoven to maximize their individual impacts.

Minimizing Environmental Effects
In addition to the multiple benefits of the project listed -previously, using available existing infrastructure allows the environmental impacts of the project to remain relatively benign, as evidenced in the project’s environmental impact report (EIR).

Under the California Environmental Quality Act (CEQA), environmental effects are categorized into five categories of impacts: beneficial, no impact, less than significant, significant but mitigable, or significant and unavoidable. Impacts are assessed against “significance thresholds,” which are criteria adopted by the CEQA lead agency (in this case, the city of Pacific Grove) or other resource agencies. If an impact does not meet or exceed the significance threshold, it is considered to have a less than significant impact (or potentially no impact). If an impact exceeds the threshold, mitigation measures are identified to reduce the impact. When an impact cannot be reduced to below the significance threshold level, even with implementation of prescribed mitigation measures, it is determined to be significant and unavoidable. This is the most severe level of environmental impact that can be identified in an EIR.

The EIR prepared for the Monterey-Pacific Grove ASBS Stormwater Management Project assessed a variety of environmental effects, such as aesthetics, biological resources, hydrology and water quality, and transportation. Despite the size of the proposed project and the myriad environmental issue areas analyzed in the EIR, the EIR did not identify any significant and unavoidable impacts. Of the 38 separate impacts identified, the majority (23, or about 60%) were less than significant and did not require mitigation. Of those impacts requiring mitigation, many related only to the construction phase. For example, construction-generated noise impacts would be reduced through the limitation of construction hours, the location of staging areas away from nearby residences, baffling construction equipment, and other noise-attenuating techniques. Construction-generated traffic would be mitigated through preparation and implementation of temporary traffic handling plans, which would include provisions for handling bike and pedestrian traffic, as well as ensuring access to neighboring facilities and residences during construction. For these and other impacts analyzed in the EIR, operational impacts of the project would be nonexistent.

Project Status
The project’s EIR was certified by the city of Pacific Grove on June 18, 2014, and by the city of Monterey on August 5, 2014. Results of the Central Coast Regional ASBS Monitoring Program will provide critical information to assess if the proposed project should be implemented to comply with the SWRCB’s water-quality requirements to protect the ASBS. The monitoring results will indicate if the proposed project needs to be modified and will also inform the stormwater treatment plant design. In addition, the monitoring efforts will evaluate potential stormwater impacts in the mixing zone as related to freshwater and stormwater pollutants. Results of this monitoring effort will likely be delayed due to California’s drought.

Along with developing institutional agreements, a comprehensive funding strategy will be needed for each of the sub-projects because it is unlikely that all the sub-projects would be implemented simultaneously. A successful funding strategy would consider local, state, and federal sources and if implemented would greatly enhance each of the cities’ mandates of successfully managing stormwater runoff in the ASBS watershed.

About the Author

Megan Jones and Emily Corwin

Megan Jones, MPP, is a senior program manager with Rincon Consultants Inc. in Monterey, CA.

Emily Corwin is a senior associate engineer with Fall Creek Engineering Inc. in Santa Cruz, CA.

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