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Project Update March 1996

This is the second in a series of Project Updates. Its purpose is to update the community on IWTP issues such as progress on construction, upcoming meetings and events, the status of environmental reviews, and other related areas of interest.

Community Briefing Slated

The second in a series of community meetings was held on March 12, 1996 from 6 to 8 p.m. at the Southwest High School Cafeteria, 1685 Hollister Street, in San Diego. The focus of the meeting was to provide an update on the IWTP and also to serve as a scoping meeting for a second Supplemental Environmental Impact Statement (SEIS). The second SEIS will look at alternatives to activated sludge, such as ponds, as a form of secondary treatment.

The first community meeting was held on November 30, 1995 at the Southwest High School. Staff from the Environmental Protection Agency (EPA) gave an update on the status of the Interim Operation SEIS. Bill Ruth from the International Boundary and Water Commission (IBWC) provided a slide show on the construction of the International Wastewater Treatment Plant (IWTP). Bill also discussed how the community is being consulted regarding issues concerning the IWTP. Staff from San Diego Municipal Wastewater Department (MWWD) gave an update on the South Bay Ocean Outfall.

If you are interested in attending the next community meeting and have questions about its location, please contact the EPA Border Office at (619) 235-4769.

SEIS Status

Since the IWTP's advanced primary treatment facilities will be completed before the secondary treatment facilities and the South Bay Ocean Outfall, a Supplemental Environmental Impact Statement (SEIS) is being prepared to examine what should be done with excess sewage flows from Mexico during this interim period of two to five years. Progress has been made on the SEIS, which is formally being called the Interim Operation SEIS. A contract has been awarded to Boyle Engineering to assist in the preparation of the document.

In addition, EPA and the IBWC have completed an analysis of potential sewage flows from Mexico. This analysis estimates the volume of sewage which might be sent from Mexico to the IWTP for treatment once the advanced primary treatment facilities are completed. These estimates were developed now in order to evaluate the viability of each of the SEIS alternatives.

A draft of the SEIS will be released for review in August/ September of 1996. A public meeting will be held to collect public comments during that time. A final decision will be made on the interim operation alternative in December 1996.

As mentioned in the previous article, a second SEIS is being started to address alternatives to activated sludge for completing the IWTP. One alternative is the use of ponds for further treatment of the effluent from the advanced primary facilities. Currently, a technical evaluation of the suitability of ponds for this purpose is underway and will be completed shortly.

A portion of the upcoming community meeting will be dedicated to soliciting the community's input on the possible alternatives to activated sludge, as well as presenting a some of the options we are proposing for consideration. That meeting will be held on March 12 at 6 p.m. at the Southwest High School cafeteria/meeting room, 1685 Hollister St., in San Diego. For more information, please contact the EPA Border Office at (619) 235-4769.

How the IWTP Works

The International Wastewater Treatment Plant (IWTP), a 25 million gallon per day (mgd) facility, is currently being built near the U.S.-Mexico border in San Diego to treat sewage flows from Tijuana. The IWTP will be owned and operated by the U.S. Section of the International Boundary and Water Commission (IBWC). The IWTP is being constructed in phases, with advanced primary facilities being completed before secondary facilities are initiated. Construction of the advanced primary facilities began in June 1995 and are scheduled for completion by January 1997. The advanced primary and secondary treatment processes will remove the great majority of contaminants typically found in domestic wastewater.

Treatment of the wastewater starts at an area called the headworks, where the wastewater is chlorinated to reduce odors. Bar screens are then used to remove large items such as sticks, plastic bags, cans, and rags from the wastewater. These materials are removed since they can damage equipment and clog pipes elsewhere in the treatment plant. From the headworks the wastewater flows to a grit chamber, where the heavier solids, such as sand, cinders and broken glass settle out of the wastewater. The wastewater is then conveyed to primary sedimentation tanks where it is mixed with an iron/polymer solution to make the solids stick together and settle to the bottom for collection. Fats, oils and greases that float to the top are skimmed off.

As currently planned, an activated sludge process will be used to treat the wastewater after primary sedimentation. Activated sludge is a biological process that uses microorganisms to remove dissolved organic matter from the wastewater. At the end of this process, the microorganisms fall to the bottom of the secondary sedimentation tanks and are collected. The treated effluent will be chlorinated, if necessary, to kill disease-causing organisms and dechlorinated to remove potentially toxic chlorine prior to disposal to the Pacific Ocean.

The solids that settle out of the wastewater in the primary and secondary sedimentation tanks are collected at the bottom of the tanks and dried using belt filter presses. The solids are mixed with lime, in a process known as lime stabilization, to prevent decomposition, reduce odors, and disinfect the solids. The stabilized solids, or sludge, will be returned to Mexico in trucks for reuse or final disposal.

Construction Progress

As of March 1996, construction of the IWTP was approximately 40 percent complete. Work on the concrete placement and electrical connections for all major structures is continuing. Foundations and walls have been poured for the processing building, sludge truck loading building, grit chamber, headworks, and primary sedimentation facilities. Installation of an 8 foot incoming pipeline from Mexico, located near Stewart's Drain, is almost completed. Finally, if you visit the site, you will notice that the perimeter fence is nearly complete.

Progress is also being made on other components of the IWTP. Bids were opened in February for soil compaction at the corridor between the IWTP and the South Bay Land Outfall near Dairy Mart Road. This work is being completed in anticipation of construction initiating in July for the pipeline between the outfall and the IWTP. Bids were also opened for the revegetation work at two sites located near Saturn Boulevard and Sunset Avenue. This work is to offset the environmental impacts from the IWTP and the land outfall. In addition, a Notice to Proceed was issued to HPS Plumbing Services to construct a water line from the City of San Diego's public water system located near I-5 to provide potable water to the IWTP.

Meanwhile, the design of the structures that will connect the advanced primary treatment facility to the outfall system was finalized. The design of the administration, laboratory, maintenance and switch gear buildings will also be completed this month. Although the method of secondary treatment for the IWTP is still under study, the design for the activated sludge system selected in the Final Environmental Impact Statement will be completed this month.

Finally, right-of-way acquisition problems at Smuggler's Gulch have been resolved and final design of the interceptor-collection system and pump station is expected to be completed next month. Site selection for the Goat Canyon pump station and dechlorination facility has been finalized and right-of-way acquisition is in progress. This interceptor-collection system will capture surface sewage flows from Goat Canyon and pump the flows to the IWTP.

South Bay Ocean Outfall Update

The City of San Diego Metropolitan Wastewater Department (MWWD) is managing construction of the South Bay Ocean Outfall through a grant from the EPA. The outfall will be jointly utilized by the IWTP and MWWD's South Bay Water Reclamation Plant. Construction of the outfall is underway with marine work scheduled to begin this summer. The outfall is expected to be completed in June of 1998.

MWWD is also moving ahead with planning for the South Bay Water Reclamation Plant to be located adjacent to the IWTP. The City's water reclamation plant, which is partially funded with a grant from EPA, will treat up to seven million gallons per day (mgd) of wastewater from the communities in the South Bay for use in irrigation and landscaping. Planning also continues for related facilities, such as the South Bay Pump Station, and associated pipelines and improvements to the Dairy Mart Road and Bridge. These facilities are being planned and constructed with the assistance of representatives from the local communities who make up the MWWD's South Bay Focus Group. If you would like more information on the outfall, please call the City of San Diego offices at (619) 533-5288.

Printed copies of the following information are available from:

EPA Border Office
Attn: Dave Fege
610 West Ash Street, Suite 703
San Diego, CA 92101

Contact Information

Elizabeth Borowiec (borowiec.elizabeth@epa.gov)

We welcome your comments and questions.

The IWTP Project Update is issued by the U.S. EPA, the U.S. Section of the IBWC and the City of San Diego Metropolitan Wastewater Department.

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