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Rehabilitate the El Portal Wastewater Treatment Plant
Yosemite National Park » Rehabilitate the El Portal Wastewater Treatment Plant » Document List
The existing El Portal Wastewater Treatment Plant (WWTP) is located within the Yosemite National Park (YNP) Administrative Area in El Portal, CA, approximately 1.6 miles west-southwest of El Portal. The facility serves both the YNP Administrative Area and Yosemite Valley and is the only wastewater service for both areas. Both service areas contain essential facilities that serve YNP visitors, employees, and businesses. The El Portal community has a population of about 700 permanent employee residents, which increases in the summer with seasonal employees. Yosemite Valley is the largest developed district in the park and receives approximately 4 million visitors per year.
Constructed in 1974, the facility consists of aging and deteriorated equipment. The plant has no redundancy in many of the processes, making a failure in any component potentially catastrophic. A 200,000 gallon sewage spill has occurred at the Facility, resulting in unintended discharge of wastewater into the Wild and Scenic Merced River. Since 2000, the park has reported 23 sanitary sewer overflows (SSOs) on the system due to plant and sewer system capacity issues. The park has been diligent in efforts to replace leaking sewer lines, reducing facility inflows to approximately 200,000 gallons per day (gpd) and 600,000 gpd in winter and summer months, respectively. Because of the wide variations of seasonal flows; the lack of automated process control schemes, pumps and controls that are oversized, plant operators are unable to adjust pumping rates and adapt the operation to the various treatment process needs efficiently. This results in increased chemical and energy use, as well as additional labor hours. When completed, the improvements will rehabilitate and upgrade much of the obsolete treatment equipment in the plant, as well as provide redundancy, automation, reliability, energy efficiency elements. The park estimates that the implementation of equipment replacement of deteriorated equipment and proposed energy efficient equipment will save the park $297,671 annually, or 1.5 KW/YR.
The proposed rehabilitation of the facility will involve constructing new and rehabilitating existing structures within the fenced compound of the current facility with the goal of addressing current deficiencies and ensuring reliable operation for the next 50 years. Personnel and vehicle access around the site will remain approximately the same as it exists currently. The project would ensure the reliable and proper functioning of a wastewater treatment plant that is already in place, in use, and being maintained. The proposed project will ensure support of the current level of facilities and conveniences for both visitors and employees and support the imminent restoration projects, currently under design, implementing the Merced River Plan (MRP), and meeting expected changes in regulations.
YNP has conducted a number of design and treatment strategy workshops. The selected proposed treatment strategy (Alternative 3 Option 2) consists of a new conventional activated sludge (CAS) secondary treatment process, rehabilitated existing tertiary treatment process, aerobic digestion, and rehabilitated existing centrifuge dewatering. YNP is in the process of finalizing the design of the rehabilitated facility and is preparing a Categorical Exclusion package for the action.
PUBLIC ANNOUNCEMENT OF DRAFT FLOODPLAIN STATEMENT OF FINDINGS FOR PUBLIC REVIEW:
The NPS has prepared a draft Floodplain Statement of Findings (FSOF) for the El Portal Wastewater Treatment Plant rehabilitation project. This action is subject to the provisions of Executive Orders (EO) 11988 and 13690 (Floodplain Management) because the action constitutes a Class II Action and is located within the 500-year floodplain. The purpose of the FSOF is to review the proposed project in sufficient detail to provide an accurate and complete description of the flood hazards and risks associated with the action, describe the effects on floodplain values from the proposed action, and evaluate mitigation measures to ensure the action complies with EOs 11988 and 13690 and Director's Order 77-2.
The public may review this draft FSOF and provide comments regarding its contents and findings over a thirty-day public comment period that will begin on October 4, 2022. The draft FSOF may be accessed and written comments may be submitted at the National Park Service Planning, Environment, and Public Comment webpage for this Site.
Constructed in 1974, the facility consists of aging and deteriorated equipment. The plant has no redundancy in many of the processes, making a failure in any component potentially catastrophic. A 200,000 gallon sewage spill has occurred at the Facility, resulting in unintended discharge of wastewater into the Wild and Scenic Merced River. Since 2000, the park has reported 23 sanitary sewer overflows (SSOs) on the system due to plant and sewer system capacity issues. The park has been diligent in efforts to replace leaking sewer lines, reducing facility inflows to approximately 200,000 gallons per day (gpd) and 600,000 gpd in winter and summer months, respectively. Because of the wide variations of seasonal flows; the lack of automated process control schemes, pumps and controls that are oversized, plant operators are unable to adjust pumping rates and adapt the operation to the various treatment process needs efficiently. This results in increased chemical and energy use, as well as additional labor hours. When completed, the improvements will rehabilitate and upgrade much of the obsolete treatment equipment in the plant, as well as provide redundancy, automation, reliability, energy efficiency elements. The park estimates that the implementation of equipment replacement of deteriorated equipment and proposed energy efficient equipment will save the park $297,671 annually, or 1.5 KW/YR.
The proposed rehabilitation of the facility will involve constructing new and rehabilitating existing structures within the fenced compound of the current facility with the goal of addressing current deficiencies and ensuring reliable operation for the next 50 years. Personnel and vehicle access around the site will remain approximately the same as it exists currently. The project would ensure the reliable and proper functioning of a wastewater treatment plant that is already in place, in use, and being maintained. The proposed project will ensure support of the current level of facilities and conveniences for both visitors and employees and support the imminent restoration projects, currently under design, implementing the Merced River Plan (MRP), and meeting expected changes in regulations.
YNP has conducted a number of design and treatment strategy workshops. The selected proposed treatment strategy (Alternative 3 Option 2) consists of a new conventional activated sludge (CAS) secondary treatment process, rehabilitated existing tertiary treatment process, aerobic digestion, and rehabilitated existing centrifuge dewatering. YNP is in the process of finalizing the design of the rehabilitated facility and is preparing a Categorical Exclusion package for the action.
PUBLIC ANNOUNCEMENT OF DRAFT FLOODPLAIN STATEMENT OF FINDINGS FOR PUBLIC REVIEW:
The NPS has prepared a draft Floodplain Statement of Findings (FSOF) for the El Portal Wastewater Treatment Plant rehabilitation project. This action is subject to the provisions of Executive Orders (EO) 11988 and 13690 (Floodplain Management) because the action constitutes a Class II Action and is located within the 500-year floodplain. The purpose of the FSOF is to review the proposed project in sufficient detail to provide an accurate and complete description of the flood hazards and risks associated with the action, describe the effects on floodplain values from the proposed action, and evaluate mitigation measures to ensure the action complies with EOs 11988 and 13690 and Director's Order 77-2.
The public may review this draft FSOF and provide comments regarding its contents and findings over a thirty-day public comment period that will begin on October 4, 2022. The draft FSOF may be accessed and written comments may be submitted at the National Park Service Planning, Environment, and Public Comment webpage for this Site.