**Notice of Availability of the Final Supplemental Environmental Impact
Statement for the Interim Operation of the International Boundary and
Water Commission International Wastewater Treatment Plant**

The Draft Supplemental Environmental Impact Statement (SEIS) for Interim
Operation of the International Wastewater Treatment Plant (IWTP) was
prepared by the U.S. Environmental Protection Agency (EPA) and the
International Boundary and Water Commission, U.S. Section (USIBWC). Its=
availability for review was noticed in the *Federal Register* on
September 6, 1996. Written comments were received through October 21,
1996. A public hearing to receive comments to the Draft SEIS was held at
Southwest High School in Imperial Beach, California on October 7, 1996.

EPA and USIBWC have reviewed and considered the oral and written
comments submitted for the Draft SEIS. EPA and USIBWC have concluded,
based upon this review, that no additional alternatives need to be
considered with respect to the proposed project and that no substantive
new analysis or major revisions to the Draft SEIS are necessary. The
Final SEIS consists of copies of the letters of comment received, with
responses; a transcript of the public hearing; an errata sheet and
attachments to the Draft SEIS.

The Final SEIS will be available for public review and comment from
December 6, 1996 to January 4, 1997. Copies of the Final SEIS are
available at San Diego main library and the Chula Vista, Imperial Beach,
Otay Mesa and San Ysidro branch libraries. Comments on the Final SEIS or
requests for additional copies of the Final SEIS, Draft SEIS, or
attachments may be addressed to:

Ms. Elizabeth Borowiec,

EPA Region IX, WTR-4,

75 Hawthorne Street,

San Francisco, CA 94105,

\(415\) 744-1165; or

Mr. Charles Fischer, USIBWC,

San Ysidro Office,

2225 Dairy Mart Road,

San Ysidro, CA (619) 662-7600.

The EPA and USIBWC will prepare a Record of Decision for the Interim
Operation of the IWTP following the close of the public review period
for the Final SEIS.

**TABLE OF CONTENTS**

**1.1 Introduction 1**

**1.2 Comments Received and Responses 3**

**1.3 Public Hearing 161**

**1.4 Errata 224**

**1.5 Attachments 225**

**Introduction**

The Draft Supplemental Environmental Impact Statement (SEIS) for Interim
Operation of the International Wastewater Treatment Plant (IWTP) was
prepared by the U.S. Environmental Protection Agency (EPA) and the
International Boundary and Water Commission, U.S. Section (USIBWC). Its
availability for review was noticed in the *Federal Register* and the
*San Diego Union Tribune* on September 6, 1996. Written comments were
received through October 21, 1996. A public hearing to receive comments
to the Draft SEIS was held at Southwest High School in Imperial Beach,
California, on October 7, 1996.

EPA and USIBWC have reviewed and considered the oral and written
comments submitted for the Draft SEIS. EPA and USIBWC have concluded,
based upon this review, that no additional alternatives need to be
considered with respect to the proposed project and that no substantive
new analysis or major revisions to the Draft SEIS are necessary.

Comments were received from the Surfrider Foundation that questioned the
methodologies used in preparing the modeling and analysis of the effects
of discharge of untreated sewage or treated effluent to the ocean
shoreline in Mexico and through the South Bay Ocean Outfall, which was
prepared by Parsons Engineering Science as a technical study for the
SEIS. The technical study was a key analytic component of the SEIS and
was made available under separate cover to interested parties during the
review period. The Surfrider comments suggest that the modeling could
not have been conducted as presented, based upon deficiencies in the
base data and analytic models used, that the study was a Atechnical
fraud,@ and that previous current studies had indicated that there were
no northerly trending currents along the shoreline south of the
international border.

EPA, USIBWC, the State Water Quality Control Board, and the City of San
Diego had reviewed the methodologies used by Parsons Engineering Science
prior to release of the Draft SEIS. The technical study was also
independently reviewed for the National Marine Fisheries Service during
the public review period. EPA also contacted the author of one of the
analytic models used in the study whose use was questioned by Surfriders
for clarification.

After consideration of the challenges made to the adequacy of the
Parsons Engi­neering Science study by the Surfrider Foundation, EPA and
USIBWC have found that their comments were based upon misunderstanding
of the data and methodologies used in the study and that the Parsons
Engineering Science study is technically sound and appropriate in scope
to evaluate the effects of the alternatives considered in the SEIS.
Specific responses to the alleged deficiencies are provided in the
responses to comments from the Surfrider Foundation.

The Final SEIS consists of copies of the letters of comment received,
with responses. A transcript of the public hearing comments is provided.
An errata sheet listing changes that should be made to the Draft SEIS
for the Final SEIS is also provided. Finally, several attach­ments
providing clarification to issues raised in the letters of comment are
provided.

The Final SEIS will be available for public review and comment from
Decem­ber 6, 1996 to January 6, 1997. Com­ments on the Final SEIS or
requests for additional copies of the Final SEIS, Draft SEIS, or
attachments may be addressed to:

Ms. Elizabeth Borowiec, EPA Region IX, Water Management Division, 75
Hawthorne Street, San Francisco, CA 94105, (415) 744-1165; or to Mr.
Charles Fisher, USIBWC, San Ysidro Office, 2225 Dairy Mart Road, San
Ysidro, CA (619) 662-7600.

The EPA and USIBWC will prepare a Record of Decision for the Interim
Opera­tion of the IWTP following the close of the public review period
for the Final SEIS.

**Comments Received and Responses**

Comments to the Draft SEIS were received from the following agencies,
organi­zations, and individuals:

United States Department of Commerce, National Oceanic and Atmospheric
Administration, National Marine Fisheries Service (NMFS)

United States Department of the Interior, Fish and Wildlife Service
(USFWS)

United States Department of Health and Human Services, National Center
for Environmental Health

Tijuana River National Estuarine Research Reserve, California Department
of Parks and Recreation (CDPR)

County of San Diego Department of Environmental Health (DEH)

City of Imperial Beach, California

City of Coronado

City of San Diego Metropolitan Wastewater Department (MWWD)

Tia Juana Valley County Water District

Otay Water District

San Diego Audubon Society

Citizens Against Recreational Eviction (CARE)

Citizens Revolting Against Pollution

Environmental Health Coalition

Lev D. Rozman, Ph.D.

San Diego-Tijuana Sister Cities Society

Save Our Bay, Inc.

San Diego Chapter of the Sierra Club

Christopher Teng

Surfrider Foundation

The letters of comment are provided with numbers corresponding to
comments responded to. The responses follow each letter.

**United States Department of Commerce, National Oceanic and Atmospheric
Administration, National Marine Fisheries Service (NMFS)**

Comment acknowledged. USIBWC/EPA will continue to work with Mexico with
respect to impacts to the marine environment from discharges to the
marine environment.

The commentor is correct. The SEIS evaluated each alternative as a stand
alone solution for comparative purposes. The preferred alternative would
install detention basins to avoid discharges of treated effluent to the
river, which would otherwise occur if Alternative 2 were carried through
to the year 2001.

The intent of the document was to use Amay@ when there was some
uncertainty about future conditions. It was not intended to mislead the
reader.

NMFS concurs with the conclusion of the SEIS and supports the discharge
through the SBOO over other alternatives.

The statement in the SEIS is intended to advise readers that if
conditions change, such as a more rapid increase in flows from Mexico
being received prior to the completion of the ocean outfall, discharges
to the Tijuana River could result. These discharges would be
unavoidable, as no other discharge option would be available.
USIBWC/EPA=s best estimate is that this circumstance would not occur.

The commentor is correct; the Draft SEIS is in error. There is the
potential for 0.7 mgd of flows during the wet weather season in the year
2000, as shown in Table 3 of Appendix A.

USIBWC/EPA is currently having a headworks analysis completed which will
identify the maximum concentrations of constituent pollutants in sewage
influent that could be treated and discharged to ocean plan standards
through the SBOO. This information will be given to Mexico to help to
focus the industrial discharge source reduction program to address
constituents of immediate concern, including PAHs.

It is anticipated that a detailed monitoring program will be required by
the NPDES permit issued by the RWQCB; the permit will be available prior
to issuance of the ROD for the project.

**United States Department of the Interior, Fish and Wildlife Service
(USFWS)**

The USFWS supports the SEIS preferred Alternative 6, phased alternative.

The use of the South Bay Land Outfall has been considered by USIBWC but
has not been evaluated as preferable to construction of the temporary
earthen detention basins for various technical reasons. These include
requirements for additional conveyance lines to discharge stored
effluent to the emergency connection, need for an additional temporary
pumping station, concerns regarding safety of the workers constructing
the SBOO tunnel adjacent to the SBLO if it is used for effluent storage
and a failure of the pipe or seal occurs and sediment buildup in the
SBLO from detention and settling of solids in the effluent.

Continued use of the emergency connection after the SBOO is completed
would reduce impacts from discharges in Mexico. However, the emergency
connection may not be available on a long-term basis due to constraints
in system capacities in the south San Diego sewers.

Although the preferred alternative is not anticipated to result in
discharges of treated effluent to the Tijuana River, the RWQCB will set
monitoring requirements for any discharges of treated effluent to the
Tijuana River, which will include sediments. If such discharges are to
occur on a regular basis, EPA and USIBWC will consult with the USFWS,
the Tijuana River National Estuarine Research Reserve, and California
Department of Fish and Game with respect to monitoring of the effects of
the discharge on plants and wildlife.

The USIBWC will consult with the County Department of Environmental
Health and the USFWS regarding appropriate vector controls if the
discharge of treated effluent results in ponding of waters in the river
valley.

USIBWC is actively pursuing an industrial pretreatment and source
reduction program with Mexico.

The EPA and USIBWC are preparing a second Supplemental EIS to consider
alternatives to activated sludge. The secondary treatment processes will
be evaluated with respect to effectiveness at reducing these and other
constituents of concern. Reduction through industrial pretreatment and
source control is also being pursued currently.

USIBWC and EPA are willing to provide technical guidance to Mexico in
their design of a new pumping and conveyance system in Mexico; however,
the development of this facility will be under the jurisdiction of
Mexico.

**United States Department of Health and Human Services, National Center
for Environmental Health**

The National Center for Environmental Health supports the ultimate
construction of the South Bay Ocean Outfall and recognizes that the
proposed interim phased approach (Alternative 6) is the most logical
approach.

**Tijuana River National Estuarine Research Reserve, California
Department of Parks and Recreation (CDPR)**

CDPR opposes any alternative that discharges freshwater effluents into
the Tijuana River. It is the intent of the preferred alternative to
avoid such discharges.

CDPR opposes the chlorination of effluents and requests that the limits
of total residual chlorine be given for river water. Disinfection of any
effluent discharged to the river is not proposed. A probable standard of
no trace residual chlorine in any effluent discharged to the river would
be imposed by the RWQCB in its compliance order.

CDPR is concerned that exotic plant invasion (primarily *Arundo donax*)
in the riparian channel should be addressed in the draft. The major
source for exotic plant invasion is wet weather storm flows which the
proposed action will not change. Dry weather flows probably do not carry
significant quantities of exotic plants in the river, though if
established they may be maintained by year-round flows in the river. The
proposed action would reduce any effects of dry weather flows on
invasive species in the river.

CDPR feels that impacts to the benthic communities and fish are
underestimated in Section 2.2.2.4 and that the potential trapping of
flows by tides are not addressed in Section 4.4.2. The SEIS considers
the potential impacts to the river, estuary, and nearshore coastal areas
from dry weather discharges of treated effluent or untreated sewage as
significant impacts. The specific topics are addressed in Appendix B of
the SEIS.

Comment acknowledged. CDPR points out that the succession of events
outlined in Section 2.2.1.4 is tenuous at best. They believe polluted
flows decrease insect diversity and excess nutrients favor monocultures
dominated by weedy species.

CDPR feels that Section 4.5.1.1 of the SEIS inadequately describes
impacts to the plankton community. They are concerned about excess
nutrients in the outfall causing plankton blooms. Eutrophication due to
excess nutrients is identified as a significant impact of discharge to
the river and estuary in the SEIS Sections 4.4.3 and 4.4.4). Effects to
plankton communities from SBOO discharge was considered in the SEIS
under Marine Biology (Section 4.5.5.1) and in the ocean discharge
modeling. Adverse impacts are not anticipated.

**County of San Diego Department of Environmental Health (DEH)**

In the event that discharges must be made to the Tijuana River,
Department of Envi­ron­mental Health recommends that raw sewage should be
treated before discharge.

Once the SBOO is on line, the DEH recommends that the peak flow capacity
of IWTP (up to 75 mgd) be used with ocean discharge rather than allowing
any discharges of raw sewage to the river.

DEH supports and encourages construction and use of the return to sender
pump station and conveyance system. The City advocates the construction
and operation of a new Mexican conveyance system. EPA and USIBWC are
providing funding and technical assistance to Commission Estatl de
Servicios Publicos de Tijuana (CESPT), who will sponsor construction of
the system through Border Environment Cooperation Commission (BECC).

The SEIS includes a requirement to submit a vector control plan to DEH
prior to implementation of any of the alternatives.

Discharges to the river would occur if the capacity of the emergency
connection is exceeded. The required detention to equalize flows for
maximum use of the emergency connection is approximately 5.5 million
gallons. While the SBLO has a greater storage capacity, there would be
no way to discharge the excess effluent other than to the river. Use of
the SBLO would entail additional risks to workers constructing the SBOO
if a failure were to occur, would require the design and construction of
additional pumping and conveyance to discharge from SBLO to the
emergency connection and may result in a build up of sediments from the
effluent in the SBLO. For these reasons, detention basins in the IWTP
site is preferred.

Disinfection is not considered feasible for interim discharges because
dechlorination to achieve removal of residual chlorine in the effluent
is not feasible. Other methods of disinfection would have to be designed
and constructed but would only be needed for the period prior to
discharge through the SBOO. The SBOO discharge is not anticipated to
require disinfection.

Page 37, 1.1.4.4. The average daily flow of 174 mgd is increased to a
peak of 333 mgd using a 1.9:1 peaking factor. The siphon of the outfall
cannot be cleaned, as such, but has been designed to minimize the
accumulation of sediments.

The ocean and shoreline modeling studies used variable T~90~ rates to
account for differences in temperature, light transmissivity, and
salinity during a daily cycle, and assumed non-disinfected primary
effluent.

All references to the San Diego County Department of Health Services
should be changed in the Final SEIS to County of San Diego=s Department
of Environmental Health.

**City of Imperial Beach, California**

The City of Imperial Beach supports the full construction of the IWTP
and its operation as a secondary treatment facility as soon as possible
but for the interim period it supports the phased operation of the IWTP
as described in Alternative 6 of the SEIS. The City opposes any
discharges to the Tijuana River but also acknowledges that they could
occur. The City also supports the continued use of the emergency
connection, construction of a parallel conveyance system in Mexico, and
implementation of an industrial pretreatment program in Mexico.

USIBWC has notification procedures in existence for spills of sewage
into the Tijuana River. This notification will continue after the IWTP
becomes operational. The NPDES permit and compliance order to be issued
by the RWQCB includes a monitoring program that should provide the City
of Imperial Beach and other jurisdictions and agencies with updated
information and timely notification of spills or discharges to the river
and coastline.

**City of Coronado**

The City supports Alternative 6.

The City strongly advocates for the addition of secondary treatment at
the IWTP.

The EPA and USIBWC agree that implementation of the IWTP and SBOO will
not solve the City=s problem of dealing with wet weather seasonal beach
contamination from Tijuana=s sewage.

The City advocates the construction and operation of a new Mexican
conveyance system. EPA and USIBWC are providing funding and technical
assistance to CESPT, who will sponsor construction of the system through
BECC.

**City of San Diego Metropolitan Wastewater Department (MWWD)**

Disinfection of treated effluent discharged to the river is not proposed
or considered feasible, due to the lack of dechlorination facilities for
the effluent if it were discharged to the river and the adverse
consequences of trace residual chlorine.

MWWD supports the construction of a Mexican parallel conveyance system
and industrial pretreatment program. EPA and USIBWC are providing
funding and technical assistance to CESPT, who will sponsor construction
of the system through BECC.

Interim operation alternatives other than discharge to SBOO assume some
use of the connection to the Metropolitan Sewerage System; it should not
be assumed that current capacities (13 mgd) will always be available.
MWWD and USIBWC must establish policies and procedures for its use
during the period of interim operation. EPA and USIBWC accepts MWWD=s
recommendation for close coordination of flow capacity in the emergency
connection. As noted above, disinfection of effluent that may be
discharged to the river is not proposed.

Changes to the City=s NPDES permit for discharges at Point Loma are not
proposed by EPA or USIBWC as part of the interim operation of the IWTP.
The City has been accepting flows from Mexico since the 1960s and the
flows are less than 7 percent of the total flows received. This issue is
within the oversight responsibility of the RWQCB, who permits the
discharge from Point Loma.

MWWD recommends the development of operating procedures (especially
washing of sides) to control odors if the earthen detention basin
alternative is constructed. The Draft SEIS proposes odor controls for
the detention basins, as needed, to control nuisance odors, including
covering of the basins, if required. Washing down of the sides of the
basins will be evaluated as an additional odor control practice.

USIBWC will consult with MWWD regarding operating procedures of the
detention basin. They are especially concerned that the diurnal wet
weather flow may not drop off sufficiently fast to allow the combined
flow from both the treatment process train and the detention basin to
remain below 13 mgd and to be discharged to the emergency connection.

MWWD recommends that the NPDES permit for SBOO discharge should include
an ocean monitoring program at least as stringent as that which exists
for the Point Loma Wastewater Treatment Plant. This monitoring has
already been agreed to and will be included in the NPDES permit issued
by the RWQCB. Also, the USIBWC should be required to notify City of
Imperial Beach officials of spills or plant overflows.

Minute No. 270 specified that Mexico construct, operate, and maintain a
sanitary wastewater treatment and disposal facility for the city of
Tijuana at a site known as San Antonio de los Buenos to prevent
discharges of untreated sanitary and industrial wastewater across the
international boundary in the San Diego-Tijuana area. The design
specified that the plant be constructed in two modules designed to treat
an average discharge in the range of 17 to 25 mgd. The first module of
this facility was completed by Mexico and is in operation today. The
second module called for in Minute No. 270 was subsequently deleted by
agreements of the two governments in Minute No. 283, which called for
the construction of the international wastewater treatment plant, the
first module capable of treating an average daily flow of 25 mgd.

Module No. 1 at San Antonio de los Buenos is operating at 17 mgd.
However, due to the fact that the IWTP and ocean outfall have not been
completed, Mexico has continued to take flows to San Antonio de los
Buenos that exceed the capacity of the plant. Flows over the 17 mgd
design capacity of the San Antonio de los Buenos are being discharged
untreated to the surf. This action by Mexico to continue to convey all
flows up to the capacity of their conveyance system to San Antonio de
los Buenos has prevented these discharges from crossing the
international boundary into the United States. This system is overloaded
during the peak hours of the day. These peak flows are presently
diverted to the City of San Diego=s Point Loma Treatment Plant via the
emergency connection.

It is recognized that a pretreatment program for industrial discharges
to the IWTP is critical for the successful operation of the plant and
the ability of the plant to produce an effluent that will meet the
California Ocean Plan Standards. The IBWC and EPA are actually working
with the Mexican government to develop and institute such a program.
This program plans to utilize the services attended by the City of San
Diego in the utilization of laboratory services, training protocols, and
other appropriate technical services.

The federal agencies recognize that it is in the best interest of the
local community to periodically report on the status of the program to
the cognizant agencies in the San Diego region. Future agreements
between the two governments that could impact the operation of
facilities identified in Minute Nos. 270 and 283 will receive proper
review in the context of complying with the requirements of the minutes.

**Tia Juana Valley County Water District**

The District strongly supports Alternative 6 of the SEIS and encourages
the quick completion and operation of the SBOO, the IWTP with detention
basin and connection to the City of San Diego Point Loma Treatment
Plant, and the completion of a new conveyance system in Mexico.

The District considers the parallel pumping and conveyance facilities in
Mexico the most critical portion of the proposed project and should be
started as quickly as possible. EPA and USIBWC are providing funding and
technical assistance to CESPT, who will sponsor construction of the
system through BECC.

The District reluctantly supports the construction of the interim
detention basins and urges that the basins be covered to avoid nuisance
odors.

The District strongly recommends that the United States and Mexico
develop and implement an effective sewage pretreatment program prior to
the IWTP accepting untreated effluent.

**Otay Water District**

Comment in support of the project is acknowledged.

**San Diego Audubon Society**

The Audubon Society opposes any discharges of untreated or primary
treated sewage from the IWTP into the Tijuana River. The primary reasons
for opposition is that discharge flows would encourage excessive growth
of inappropriate vegetation, a change in the salinity of the estuary,
and nutrient loading. It is not the intent of the project to discharge
to the river; the preferred alternative would be least likely of any of
the alternatives to result in discharges during 1997 and 1998.

The Audubon Society supports use of the emergency connector,
construction of the parallel conveyance, requiring industrial
pretreatment of point source polluters in Mexico, and the construction
of detention ponds for flow equalization.

It is the Society=s opinion that the predicted growth rate for Tijuana
sewage (4.8 5 per annum) is unrealistically low and that the phased
approach is too slow. The growth rate was based upon the best available
estimates at the time the flow projections were developed. If the
preferred alternative is selected, development of additional facilities
will proceed as quickly as possible.

If the preferred alternative is selected and the flow estimates are
correct, no discharges from the IWTP to the river or estuary would occur
and mitigation would not be required. If some discharges do result, the
affected areas will be monitored, as indicated in the SEIS and according
to a monitoring program included in the RWQCB=s compliance order. The
monitoring will provide data on the changes that have resulted from the
discharges. The EPA and USIBWC will then coordinate with the resource
agencies as to appropriate mitigation for impacts from the discharges.

**Citizens Against Recreational Eviction (CARE)**

CARE supports the phased operation Alternative 6 of the SEIS and the
construction of a parallel conveyance system in Mexico as a stand-alone
project. EPA and USIBWC are providing funding and technical assistance
to CESPT, who will sponsor construction of the system through BECC. CARE
urges the implementation of an industrial source control program in
Mexico and that planning for expansion of the IWTP stay ahead of
potential future needs.

CARE notes that in the future, if Mexico asserts its rights to the IWTP
effluent, the parallel conveyance system could be used to return the
effluent to Mexico for reuse.

CARE argues for partial construction of the planned future primary
sedimentation basins within the IWTP site as an alternative to
excavating earthen detention basins, as described for Alternative 3 and
Alternative 6. This suggestion is made as a potential cost savings
measure. CARE notes there are additional areas within the site where the
detention facilities could be sited and built to provide a greater
holding capacity which could be used in future for flow equalization
within the IWTP. CARE notes, after observations of an equalization basin
at an existing treatment works, several potential benefits including
lack of objectionable odors, vectors and cleanliness. USIBWC is
evaluating these suggestions with respect to current and future need,
and construction and operations cost savings.

**Citizens Revolting Against Pollution**

The comment supports the construction and operation of the IWTP.

The comment supports Alternative 3 of the SEIS, emphasizing that no
effluent, treated or untreated, should be discharged to the river.

The comment recommends covering the proposed interim detention basin and
that the area be returned to its original grade after its use.

**Environmental Health Coalition**

It is agreed that both domestic and industrial wastewaters have grown
and are part of the overall problem being addressed. IBWC Minute No. 283
addresses explicitly both domestic and industrial wastewaters. The FEIS
and SEIS included consideration of toxic constituents in its
characterization of wastewater and modeling of the effects of effluent
discharges.

Sewage discharges entering the U.S. have occurred during the past two
years, although the chronic dry weather flows experienced in previous
years have not occurred.

Comment noted, urban discharges refers more to non-point source
discharges but could include persistent, bioaccumulative industrial
toxics.

Comment noted; these have been added to the listing.

These facilities have been referred to as Adefensive measures@ in past
documents, including the Water Quality Act of 1987, which authorized the
project.

Growth is certainly a major factor in estimating future sewage flows.
However, as noted in the SEIS, Tijuana is not fully sewered; its
existing pumping, conveyance and treatment capacity would not be
adequate to serve existing residents and industry if fully sewered.

The San Antonio de los Buenos facility was designed as a secondary
treatment works as identified in Minute No. 270. There is no monitoring
data available for the plant effluent. The treated effluent is required
to meet Mexican standards for discharge to national waters (appended to
the SEIS) and U.S. standards at the international border, as specified
in Minute No. 283.

Although chlorination and dechlorination facilities are part of the IWTP
design, it is anticipated that chlorination of the effluent will not be
necessary based on the results of the ocean modeling for both secondary
and advanced primary discharge through the SBOO. The dechlorination
facilities would not be available for the interim discharge prior to the
completion of SBOO. As discussed in the SEIS, chlorination of the
effluent for discharge other than to SBOO would probably not be feasible
due to impacts to the river and estuary associated with trace residual
chlorine. Chlorination/dechlorination of effluent to be discharged
through the SBOO would only be undertaken if needed to meet bacterial
standards in receiving waters. It will be considered further if
monitoring data of actual IWTP discharges indicates a need for
disinfection.

The 1994 FEIS ROD would not be violated. The ROD stated that no
discharge other than secondary effluent through the outfall would occur
until additional environmental review had taken place. The SEIS provides
the additional environmental review required by the ROD.

The proposed action seeks to avoid any discharges to the Tijuana River.
Discharge to the river is addressed because under certain flow
conditions it could occur if the IWTP is operated prior to completion of
SBOO. The preferred Alternative 6, which includes using detention basins
to store treated effluent for off-peak discharge to the emergency
connection prior to completion of the SBOO, should avoid any discharges
to the river. Creating a larger temporary storage facility at the
Imperial Beach Naval facility would require additional conveyance
pipelines to be constructed, without additional benefit. Closing the
base is not an available option to the EPA/USIBWC.

The Regional Water Quality Control Board will be the permitting agency
for any discharges from the IWTP and will set requirements for
mitigation if any discharges to the river occur. EPA and USIBWC will be
responsible for ensuring that required mitigation is implemented.

The commentor is incorrect. Construction at the IWTP is not ongoing on a
24-hour-a-day schedule; it is being completed on a normal workday
schedule. Portions of the SBOO construction are on a 24-hour schedule,
due to construction requirements for tunneling. Construction of the
detention basins cannot begin until a ROD is signed for the SEIS.

Alternatives 3 and 6 maximize use of the emergency connection during the
interim period. As discussed in the SEIS, the emergency connection was
not intended to be a permanent facility and its future availability will
be constrained by sewage generated in the U.S.

Bioaccumulation of metals other than mercury (e.g., lead) in fish is
addressed in Appendix C of the SEIS; lead in the effluent is not
considered a potential human health risk as levels do not appear to
increase in fish up the food chain.

Section 2.2.1.5 does not state that discharges in Mexico do not flow
northward. The effects of discharges in Mexico were modeled for the SEIS
and are discussed in Section 4.2, including periods with northward
current transport.

Table S-1 provides a summary of adverse impacts for each alternative.

The daily flow of sewage that can be sent via the emergency connection
is limited by diurnal peaking factors, as is explained in the SEIS.
Under Alternative 2, the IWTP is initially providing additional storage
of two million gallons that would otherwise exceed the hourly flow
capacity of the emergency connection and flow to the Tijuana River. The
statements made at the scoping sessions summarized on page 320 refer to
operating efficiency and not treatment performance. Treating 10 mgd is
more efficient and economical with respect to plant operations, but
flows less than 10 mgd can be treated fully.

The SEIS outlines the anticipated flows to the river from increases in
sewage given the existing facilities in Mexico and proposed new
facilities in the U.S. If circumstances change, such as the annual
increases in flow from Mexico are greater than forecast, a failure of
facilities occurs in Mexico, or there is otherwise a reduction in the
flows Mexico handles with its system, then additional flows could occur
in the Tijuana River.

No, for January 1997. Table 2.3 provides estimates through 2001.

The SEIS provides flow estimates that will go to the IWTP. The IWTP does
not have to have a minimum of 10 mgd of flow to provide advanced primary
treatment.

Costs for utilizing the emergency connection are based upon a flat rate
per mgd of sewage. Costs for treatment at the IWTP are variable, with
the unit cost per mgd decreasing as the volume of sewage treated
increases.

As explained above, the IWTP can treat flows less than 10 mgd.

The discussion on page 211 indicates that even though there would be a
reduction in discharges of untreated sewage at the shoreline in Mexico,
there would still be concern for coliform levels for treated effluent
discharges. For coliforms, primary treatment only reduces coliform
levels by approximately 20 percent. Therefore, there is little
difference in health risks from bacterial pathogens between the
discharge of untreated sewage or primary treated effluent.

The SBOO is scheduled to be operational in June 1998 and the Final SEIS
text on page 82 is revised.

The data requested on industrial discharges in Mexico is not available
at this time. Minute No. 283, the 1994 FEIS, and ROD for the project
have recognized the need for pretreatment and source reduction for
industrial dischargers in Mexico and current steps to implement and
expand the Mexican program are described in the SEIS in Section
1.3.1.10. USIBWC is conducting a headworks analysis to identify effluent
limitations for industrial wastewaters directed to the IWTP.

The purpose of the project is to avoid discharge of dry weather sewage
or IWTP effluent to the river and estuary. It is anticipated that with
selection of the preferred alternative, no discharges of treated
effluent from the IWTP to the river or estuary would occur. There are
uncertainties, however, and the SEIS seeks to disclose the potential
effects if discharges do occur. The RWQCB will require monitoring of the
river and estuary if discharges should occur so that the effects of the
discharges can be measured. The responsible resource agencies have been
consulted during the scoping of the project and have reviewed the SEIS.
No specific mitigation for the contingency if discharges do occur has
been recommended at this time. EPA and USIBWC will reopen consultation
with the agencies if discharges to the river become unavoidable.

For purposes of comparison of the alternatives, including using the SBOO
for discharge of effluent, each alternative was evaluated as a
stand-alone alternative through the planning horizon period of 2001. If
SBOO were not used for discharge, there could be discharges to the river
between 1998 and 2001 for several of the alternatives.

Effluent concentrations were estimated by the IWTP design engineering
consultant, Malcolm Pirnie Engineers. Effluent concentrations were not
provided for certain constituents for a variety of reasons, including
lack of influent concentration data or specific treatment efficiencies.
The IWTP will be test operated for several months once completed, at
which time additional data will be available.

Covering the basins to reduce nuisance odor impacts is included as
potential mitigation for the detention basins in the SEIS.

EPA and USIBWC recognize that monitoring is not mitigation. However,
monitoring to assess whether there are impacts from river discharges and
to what extent the river or estuary habitats are impacted is a necessary
precondition to providing appropriate mitigation.

We are sorry for the inconvenience; these omissions were a reproduction
error in some copies. The Minutes were appended to the 1994 FEIS and
USIBWC can make full copies available upon request.

This is a typographical error in the original memo; Mr. Gold is a City
of San Diego attorney.

By agreement, Mexico will be responsible for the disposition of sludge,
which for the interim operations period will go to the Tijuana landfill
in Mexico. As the landfill is not in a north-draining canyon to the
Tijuana River, no impacts to the U.S. are anticipated.

The SEIS discusses the prior international agreements with Mexico, U.S.
environmental laws, and Executive Orders, and summarizes environmental
laws of Mexico. Air emissions from the IWTP operation were assessed in
the 1994 SEIS and have been subject to additional review by the APCD in
issuing permits to construct and operate.

**Lev D. Rozman, Ph.D.**

The commentor suggests that more evaluation be done in order to optimize
the location of the outfall terminus with respect to initial dilution
and subsequent mixing. The type of effort described was completed early
on in the project (1990) and led to the determination of the length of
the outfall and its discharge location. It was found that a 14,100 foot
long outfall would be sufficient to meet regulatory standards. In view
of the potential for re-entrainment in the area, Engineering Science
(the outfall designer) investigated the effects of the currents on
initial dilution and determined that a longer outfall would be needed to
meet the intent of the standards. This issue was presented in the 1994
FEIS for the project. It is possible that other sites might exhibit
higher diffusivities than the selected location; however, the location
must satisfy several other criteria, including conditions of poor
circulation or prevailing conditions during periods of unfavorable water
movements. In evaluating the performance of the outfall with computer
modeling, Engineering Science used conservative values for diffusivity
for the South Bay, resulting in lower estimates of the total dilution
that may actually be achieved.

**San Diego-Tijuana Sister Cities Society**

Comment in support of the parallel conveyance in Mexico is acknowledged.
EPA and USIBWC are providing funding and technical assistance to CESPT,
who will sponsor construction of the system through BECC.

**Save Our Bay, Inc.**

Rainfall data and river flow data are available, but EPA or USIBWC do
not have any studies that correlate rainfall events and flows in the
river reaching the shoreline. The FEIS and SEIS discussions of hydrology
provide evidence of the variability in river flows (annual median 659
acre-feet; annual average 33,000 acre-feet and annual maximum of 586,000
acre-feet). The wet weather flows typically occur December through
March, which is also the period when most rainfall is received. The
frequency and severity of storms as well as the annual total rainfall
all contribute to river flows and flow volumes. The Tijuana River
watershed includes three reservoirs, and portions of the river in urban
Tijuana have been channelized, which are complicating factors. The goal
of the IWTP is to minimize the potential for dry weather flows of sewage
contaminating the U.S. Unfortunately, conditions that would allow runoff
in the Tijuana River to be contaminated with sewage still exist and the
potential for wet weather contamination of beaches will continue.

The FEIS and SEIS both indicated that wet weather flows in the Tijuana
River would not be intercepted and could be contaminated with sewage.

SBOO is an acronym for South Bay Ocean Outfall.

Apparently there were no flows in the river at the time. The flow
estimates are forecasts based upon conservative estimates of various
factors contributing to sewage in Mexico. They were developed to
evaluate the various alternatives under consideration.

The State Water Resources Control Board provided funding to the City of
San Diego for the SBLO. The Regional Water Quality Control Board is
responsible for the permitting of any discharges. Both agencies serve on
the policy and technical oversight committees for this project.

The potential for discharges in Mexico impacting U.S. waters was modeled
for the SEIS and is discussed in Chapter 4.2. The body contact standards
for U.S. waters have the potential to be out of compliance June-August
and during November, according to the modeling.

See response to comment #3.

Sewage from western Tijuana was estimated at approximately 10 percent of
the sewage generated in eastern and central Tijuana. Sewage from Playas
de Tijuana does not flow into the U.S. Spills from the canyon areas west
of pump station one have varied in size over the years.

Wet weather and storm flows refer to periods when the Tijuana River has
runoff flows. Dry weather flows refers to periods when flows occur in
the river that are not related to rainfall or fresh water releases of
water from reservoirs in the watershed.

The IWTP has a peaking factor of 3:1 so hourly flow rates in excess of 1
million gallon can be accommodated.

Comment noted; the word maximum should be deleted from the text.

Comment noted; the syntax in the SEIS text is confusing.

The planning horizon year of 2001 is used to account for the completion
of the SBOO and the re-evaluation and completion of secondary treatment
process components for the IWTP.

There have been dry weather discharges of sewage to the river during
1996, although they fortunately have not met the forecast volumes
estimated in the EPA/USIBWC flow memo.

Although Mexico has made a number of improvements to prevent sewage from
entering the river, conditions still exist which would make it likely
that wet weather season river runoff entering the U.S. would be
contaminated with sewage. Mexico has planned additional improvements to
the Tijuana River which will reduce the likelihood of sewage
contamination. The flow memo forecasts address the potential for dry
season contamination.

SBOO is still scheduled to be completed in 1998.

No modeling of the frequency of wet weather flows in the Tijuana River
was conducted for the SEIS.

**San Diego Chapter of the Sierra Club**

The Sierra Club expresses concerns that any discharges to the Tijuana
River would have adverse impacts on the environment. This conclusion is
consistent with the SEIS analysis. The Sierra Club supports only the
Areturn to sender@ and Aemergency connection@ alternatives offered in
the SEIS. It should be noted that the preferred alternative would
utilize the emergency connection and additional pumping and conveyance
facilities in Mexico if they are available to avoid discharges to the
Tijuana River until SBOO is available.

The EPA and USIBWC have been working with the appropriate parties since
1994 to create a Areturn to sender@ connection to transport IWTP
effluent to the Punta Banderas facility for discharge with other Tijuana
sewage flows. The Areturn to sender@ option could be used to
transport-treated effluent for reclamation and reuse in Tijuana as well
as untreated sewage. Federal agencies are concerned about impacts to
U.S. waters if additional facilities are used to transport and discharge
untreated sewage to the shoreline in Mexico. These facilities would have
to be agreed to and operated by Mexico, and cannot be assured by actions
by U.S. agencies.

The IWTP effluent is not the equivalent of Point Loma effluent.
According to the NPDES permit application to the RWQCB, BOD levels (204
mg/l vs. 273 mg/l at Point Loma) and suspended solids (88 mg/l vs. 289
mg/l at Point Loma) are substantially less; other constituents vary.

Comment noted. This is acknowledged in the SEIS.

The preferred alternative in the SEIS seeks to avoid discharge of
effluent to the Tijuana River. The SEIS discusses recent actions by the
sponsoring federal agencies to assist Mexico in the development of an
industrial pretreatment and source reduction program. Development of
this program is under the jurisdiction of Mexico according to its laws.

Chlorination and dechlorination of the IWTP effluent is not proposed,
although it could be done in the future to disinfect effluent discharged
through the SBOO. Potential effects to the environment from trace
residuals from chlorination are addressed in Section 4.1.1.3 of the
SEIS.

Discharge to the Tijuana River is possible under the preferred
alternative, although all reasonable measures to avoid the discharges
will be taken.. Discharges of untreated sewage or treated effluent could
occur if the capacity of the emergency connection is exceeded prior to
SBOO being completed. This would be more likely to occur if no action is
taken.

EPA and IBWC have been pursuing the implementation of the Areturn to
sender@ facilities with the appropriate agencies in Mexico. EPA and
USIBWC have made funding and technical assistance available to CEPT, who
will sponsor the project through BECC.

Effluent from the IWTP would not be chlorinated prior to discharge to
the river. The effluent from the IWTP discharged to SBOO is not proposed
to be chlorinated unless it is necessary to achieve a reduction in
pathogens. Provision has been made for this as a contingency and the
RWQCB will require monitoring of the discharge through the NPDES permit.
The EPA and USIBWC do not want to commit to this decision until the IWTP
has been test operated.

It is the intent of the proposed project (preferred alternative) to
avoid any discharge to the Tijuana River; however, because flow
projections are only estimates, the possibility exists that Mexican
flows will exceed the discharge capacity before the SBOO facilities are
available. If that occurs, discharge of either untreated sewage or
treated effluent into the Tijuana River will be unavoidable. The SEIS
acknowledges that the discharge would not be consistent with the federal
Clean Water Act. It may meet State Ocean Plan requirements, however.

Additional studies and assessments of Mexican sewage flows for heavy
metals and other toxics will be conducted once the IWTP is operated.
Both influent and effluent will be monitored.

Whatever flow conditions prevail, sewage flows that exceed the capacity
of the Mexican system and the emergency connection would be discharged
to the Tijuana River as either untreated sewage or advanced primary
treated effluent.

**Christopher Teng**

The cost of construction and operations and maintenance specified in
Minute No. 270 is the obligation of the Mexican government. Mexico is to
operate the San Antonio de los Buenos treatment facility in such a
manner that the quality of the coastal receiving wastes at the
international boundary comply with the water quality criteria
established for primary contact recreation uses. Monitoring of the surf
conditions at the international boundary is performed for this U.S.
section of the IBWC and this data is available to the public.

Mexico will participate in the cost of constructing and operation and
maintenance of the IWTP in accordance with provisions in Minute No. 283.
Specifically, this cost contribution will be in the negotiated amount of
what it would have cost Mexico to build a 25 mgd secondary treatment
plant at the Rio El Alamar that would have produced an effluent that
meets Mexican standards for discharge to rivers and streams.
Additionally, Mexico will participate in the annual operation and
maintenance cost in an amount equivalent to what it would have cost
Mexico to operate a 25 mgd treatment facility at the Rio El Alamar. The
construction, operation, and maintenance at the outfall for ocean
disposal is at the sole expense of the United States.

Monitoring of the discharge from the IWTP will be in compliance with the
NPDES permit issued to the IBWC from the RWQCB and will be available to
the public.

The funding for Avarious environmental cooperation mechanisms@ (page 30
of the SEIS) to meet required pretreatment of industrial discharges in
Mexico is not specifically identified. The Department of Ecology, Baja,
California, Mexico; EPA; USIBWC; SWRCB; and the City of San Diego are
assisting U.S. cooperative actions under various grant programs.

Peak flows in excess of 100 mgd would flow untreated to the Tijuana
River. The emergency connection to Point Loma is the only discharge
option other than the Tijuana River.

The time frame for implementing various secondary treatment options will
be assessed in the Alternatives to Activated Sludge Supplemental EIS.

Section 1.6 of the SEIS acknowledges that Tijuana=s sewer improvements
are an Aunknown factor@ in evaluating the potential impacts of the
proposed interim operation of the IWTP. The EPA/USIBWC continue to
communicate on a regular basis with Mexican officials regarding sewerage
improvements on both sides of the border.

The commentor is correct and this inconsistency is acknowledged in the
SEIS.

The least Bell=s vireo is migratory but breeds in southern California=s
freshwater riparian habitats. The proposed capture of dry weather,
periodic sewage flows, will not adversely affect this habitat. This
issue was considered in the Biological Assessment and 1994 FEIS prepared
for the construction of the IWTP and SBOO.

Page 155, Section 3.4.5 of the SEIS addresses estuarine biology and not
terrestrial biology where the least Bell=s vireo is discussed. Please
see page 146, Section 3.3.3 of the SEIS.

**Surfrider Foundation**

The intent of the project is to keep untreated sewage out of the Tijuana
River, not to discharge treated effluent to the river. The IWTP would
treat those flows that cannot be handled by Mexico. Mexico has agreed,
to the best of their ability, to retain sewage flows at their current
levels until the SBOO is built (see Attach­ment 1); and the City of San
Diego has agreed to continue to accept sewage through the emergency
connection. The flow projections used for the SEIS (Appendix A) are
based upon these agreements, and 1995 flow measurements and a 4.8
percent annual growth rate. Based on the estimated flows, the preferred
alternative would avoid discharges of untreated sewage or treated IWTP
effluent to the Tijuana River in the U.S. during the dry weather season.
If the following were to occur: (a) sewage flows in Mexico increase
sooner than expected; or (b) Mexico reduces the volume of sewage it
retains in its existing system; or (c) failures occur in the pumping or
conveyance system in Mexico; then untreated sewage would enter the U.S.
via Stewart=s drain or other locations. If the IWTP is operated, flows
that otherwise would enter the river untreated could be treated at the
IWTP prior to discharge. There is no basis to assume that the volume of
flows from Mexico would be different with or without the IWTP.

The Final EIS and ROD for the project disclosed that interim operation
of the IWTP as an advanced primary treatment plant may occur prior to
the SBOO or secondary treatment facilities being available. However,
this could not occur unless additional environmental documentation were
performed. This SEIS satisfies that requirement. This NEPA process was
agreed to by Surfriders in a Settlement Decree (San Diego Chapter of the
Sierra Club et al. vs. International Boundary and Water Commission,
United States Section et al.) (see Attach­ment 2) and Surfriders and all
the other parties participating in the settlement was aware of the
approach prior to release of the SEIS.

Criticisms of the modeling performed by Parsons Engineering Science are
responded to in more detail below. At the request of the Surfrider
Foundation, EPA solicited an independent review of the modeling. It was
reviewed by A. J. Mearns for the National Oceanographic and Atmospheric
Administration (NOAA); his review comments are attached to NOAA=s letter
of comment to the SEIS. It was also reviewed by EPA, USIBWC, U.S. Army
Corps of Engineers, the State Water Resources Control Board, and City of
San Diego. EPA and USIBWC support the modeling as a reasonable and
technically valid approach to assessing environmental impacts of the
interim operation of the IWTP. EPA and USIBWC do not concur that the
1988 TOES supports the assumption that there are no, or rarely,
northward flows from the shoreline discharge point in Mexico. The 1988
TOES found that upcoast (north-trending) currents predominate about 27
percent of the time. There is also evidence of north-trending currents
from satellite imagery data and bacteriological sampling along the
shoreline both in Mexico and the U.S. It should also be noted that
Minute 270 was predicated upon protecting U.S. waters from discharges of
effluent or sewage in Mexico along the coastline.

IBWC is a binational commission empowered by both governments to address
border issues. Collaboration with the Mexican section of IBWC has been
ongoing throughout the project. EPA and USIBWC acknowledge the
difficulties in sharing information between the two countries; and have
and will continue to take steps to improve communication. EPA and USIBWC
support the CALBECC (with the Direccion General de Ecologia and
Secretaria de Asentamietos Humanos y Obras Publicas for Baja, California
and the Commission Estatl de Servicios Publicos de Tijuana) and other
initiatives. The operations minute is identified as a needed agreement
to be negotiated with Mexico in the SEIS, and will be completed before
the IWTP is operated.

As a statement of purpose and need, many technical details contained in
other sections of the document (e.g., Chapter 2) are not presented in
this section of the SEIS.

The commentor=s reference to the EPA, USIBWC, and SWRCB investigative
team or its findings is unclear to those agencies. Real time recording
meters are being installed by IBWC and more closely monitored data will
be available in the future.

All the assumptions regarding flows in Mexico are stated in the Flow
Memorandum, Appendix A to the SEIS.

The flows through the conveyance canal and treated at San Antonio de los
Buenos are based upon estimates by Mexico, the USIBWC and Minute No.
283. These estimates were confirmed by a representative of CESPT in
1996.

The commenter is incorrect, there is ample evidence of northerly
nearshore currents at the shoreline discharge point in Mexico based upon
the TOES I and II current studies, satellite imagery data, and
bacteriological concentration data as is summarized in the Parsons
Engineering Science shoreline discharge model study. EPA and USIBWC have
not been able to confirm the accuracy of the reference to a 0.06 percent
probability in the TOES study. If treated effluent were discharged to
the Tijuana River, there would certainly be significant impacts to the
river, estuary, and nearshore coastal areas.

That the project addresses the problem of dry weather flows is stated
throughout the SEIS. It is clearly stated that wet weather river flows
would not be intercepted. If contaminated with sewage, these flows would
continue to affect the river valley, estuary, and coastal areas.

As indicated in the SEIS, Mexico has agreed to continue to convey and
treat sewage at current levels until the SBOO is completed. Given this
assumption, flows of 25 mgd will not be discharged to the river valley.
See response to comment #1. If operating the plant would result in the
need to treat and discharge sewage to the Tijuana River that Mexico is
currently able to convey and treat, there would be a negative impact.
However, the SEIS does not address this scenario since it would be
inconsistent with existing agreements.

Both the FEIS and SEIS include summaries of the past problems with
border sewage contamination, and the numerous treaties, minutes,
declarations, and agreements made in response.

Point Loma, as a primary treatment works with ocean discharge was
permitted by the state of California, along with treatment works at
Encina, San Elijo, and Goleta.

The characterization of IWTP effluent as equivalent to Point Loma
influent is misleading. According to data presented to the RWQCB for the
IWTP NPDES permit, the IWTP effluent will have reduced levels of BOD5
(204 mg/l vs. 273 mg/l at Point Loma) and suspended solids (88 mg/l vs.
289 mg/l at Point Loma) compared with levels of Point Loma influent.

The Interim Operation proposal would not import sewage from Tijuana.
Mexico has agreed to continue to handle the current volume of flows
until SBOO is operational. Only flows from Tijuana that would otherwise
enter the U.S. untreated and flow through the Tijuana River would be
treated at the IWTP until the SBOO is operational. There is no basis for
assuming that the IWTP would treat 25 mgd of sewage once it is
operational. The IWTP has a design capacity of 25 mgd. Because sewage
flows vary diurnally, a peaking factor of 3:1 (75 mgd hourly flow
equivalent) was provided to accommodate peak hourly flows. Mexico
generates approximately 42 mgd of sewage currently; which is expected to
rise to approximately 51 mgd on the highest flow days by the year 2001.
The scenario of the IWTP taking 75 mgd from Tijuana is not realistic.

Potential limitations on the future availability of the emergency
connection are explained in the SEIS. The City has indicated its
willingness to continue to accept sewage from Mexico to avoid discharge
to the river as long as it has capacity in its conveyance system.

IWTP effluent will not be equivalent to Point Loma influent. Modeling
conducted for the SEIS indicates that non-disinfected IWTP effluent
discharged through the SBOO has a very low probability of impacting any
beaches or recreational areas near the coastline. Discharge of treated
effluent to the river would represent a health risk, however.

The Final EIS and ROD for the project disclosed that Interim Operation
of the IWTP as an advanced primary treatment plant may occur prior to
the SBOO or secondary treatment facilities being available. However,
this could not occur unless additional environmental documentation were
performed. This SEIS satisfies that requirement. Secondary treatment
options are currently being evaluated and will be addressed in a
subsequent SEIS, along with the alternative of continued operation as an
advanced primary treatment works. Surfriders agreed to this approach in
a settlement agreement with the EPA prior to release of the SEIS. No
decision has been made by EPA or USIBWC to operate the IWTP as an
advanced primary treatment works for a term longer than five years, the
interim operation planning horizon.

Pond-based treatment is not a reasonable alternative to the interim
operation of the IWTP considered in the SEIS and the panel study results
are not relevant to the decisions being made. Pond-based treatment
systems will be evaluated in the Alternatives to Activated Sludge SEIS
which is in preparation. Detention basins discussed in the Interim
Operations SEIS would be temporary (cycled daily) storage basins for
flow equalization to the emergency connection and would not function as
treatment ponds. The current interim operations SEIS does not eliminate
any secondary treatment options that would otherwise be considered,
including ponds, activated sludge, or other means.

EPA/USIBWC used the most up to date flow information available to them
at the time the forecasts were made (data were collected in Mexico in
1995 from the collection system with the cooperation of Mexico). They
are consistent with previous estimates, although there is a range of
variation. The prior FEIS discussed a range of future flow estimates and
their basis.

The No Action alternative would result in significant environmental
pollution and human health risk; and the resulting water quality in the
river would violate federal and state water quality standards. Since
there would be no authorized discharge, there would be no possibility of
enforcement of water quality standards. The SEIS indicates that the
discharge of less than secondary treated effluent is not authorized by
the federal Clean Water Act. Discharge of advanced primary effluent to
the Tijuana River would not meet Basin Plan objectives for surface- or
groundwaters. Discharge of advanced primary effluent through the SBOO
may or may not meet the California Ocean Plan (the modeling indicates
PAHs and HCH limits may be exceeded). The No Action alternative would
not minimize public health and environmental impacts relative to other
alternatives under consideration.

Section 1.3.1 of the SEIS does not discuss the capacities of the Mexican
system. Minute No. 270 states that the peak capacity of the force main
is 62 mgd. The reliable peak capacity of Pump Station One is
approximately 36 mgd and the effective capacity of the conveyance canal
is approximately 48 mgd. Note that the conveyance canal has to carry
additional flows from western Tijuana in addition to flows from Pump
Station One. The flow memo is based on these capacities.

A detention basin is not intended to provide treatment and would be
filled and emptied within a daily cycle to provide flow equalization for
discharge through the emergency connection. They are not equivalent in
function to treatment ponds. The size of the detention basins are based
upon the daily volume needed to maximize use of the emergency
connection, estimated at 5.5 million gallons. The basins have been sized
and sited to minimize pumping requirements and allow gravity flow to the
emergency connection. Feasibility studies are being conducted for use of
treatment ponds for long-term use and will be considered in a
Supplemental EIS.

The commentor is correct; treated effluent would not meet health
standards for discharge to the river. The discharge modeling suggests
that health standards would be met for the SBOO discharge, however. The
1,000 minimum probaby number (mpn) coliforms standard is not applied at
the point of discharge. It applies at the 30 feet water depths or within
1,000 feet of the shoreline or nearshore recreation areas. Bacterial die
off and dilution of the effluent would reduce concentrations below the
standard. It is not agreed treatment will increase mass loading of
coliforms or suspended solids to the environment relative to untreated
effluent, as only equivalent volumes would be discharged.

Mexico chose a capacity of 50 mgd to match the capacity of their current
force main and conveyance canal capacities. The EPA and USIBWC support
the construction of a parallel pumping and conveyance system in Mexico
to reduce the risks of failure of the Mexican system causing adverse
consequences in the U.S. Mexico has stated its opposition to such a
system being used in lieu of the SBOO, however. Its ultimate
construction and operation is at the discretion of Mexico.

Effluent dispersion for the SBOO has been modeled for both secondary and
advanced primary effluent based upon samples of Tijuana sewage without
an industrial pretreatment program. The concerns raised about a counter
current gyre dumping effluent back to beaches in Imperial Beach and
Coronado is not supported by the ocean discharge modeling in the 1994
FEIS and current SEIS.

The ocean discharge modeling has shown that discharge through the SBOO
would have the least impact on the environment and threat to public
health. The model results will be verifiable through the NPDES permit
monitoring program that will be required by the RWQCB for the discharge.

The preferred Interim IWTP operation evaluated in the SEIS would allow
advanced primary operation of the plant through the year 2001 with
discharge through the emergency connection. The phased alternative would
initially utilize the detention capabilities of some of the primary
treatment facilities to provide additional flow equalization and limited
treatment (screening, degritting, and settling) of about 2 million
gallons prior to discharge to the emergency connection. Once the
5.5-million-gallon detention basins were constructed, the IWTP would be
operated with discharge through the emergency connection to its maximum
of 13 mgd. Flow volumes would be as shown in Table 2-3 through 1997 and
Table 2-4 for 1998, and Table 2-6 to the year 2001. Costs for discharge
to the emergency connection are a fixed unit cost per million gallons of
sewage. Costs to operate the IWTP have both a fixed operational cost and
a variable cost for chemicals and energy usage.

Once the SBOO is on-line no additional discharge capacity is needed to
supplement the SBOO. It has been designed for up to 174 mgd average, 333
mgd peak flows. These flow volumes are not needed for interim IWTP
operation; but are valuable as a facilities improvement for the
discharge system for reliability.

Again, Mexico construction of additional pumping and conveyance in
Mexico is at the discretion of Mexico. While EPA and USIBWC have been in
active negotiations, they cannot unilaterally construct these
facilities. CESPT has only recently agreed to sponsor the construction
of the facilities through the BECC, with funding and technical support
from USIBWC and EPA.

The preferred alternative maximizes use of Mexico=s existing facilities
and the emergency connection until SBOO is available. It is expected
that no discharge to the river would result. Discharge of treated
effluent with respect to the Clean Water Act, State Ocean Plan, and
Basin Plan are discussed in the SEIS. EPA and USIBWC believe that it
best meets project=s stated purpose.

The consideration of interim operation of the IWTP prior to secondary
treatment processes or the SBOO was disclosed in the 1994 SEIS and the
SEIS process and alternatives considered was agreed to in the settlement
agreement by Surfriders.

Mexico has taken the position that additional pumping and conveyance
facilities are not acceptable as an alternative to the SBOO. This
alternative is not available to EPA and USIBWC.

Section 4.2 of the SEIS details the effects of SBOO discharge. There are
less adverse impacts to U.S. waters from the SBOO discharge than the
discharge of untreated sewage to the shoreline in Mexico.

The commentor is correct, discharge of secondary effluent through the
SBOO with industrial pretreatment or source reduction in Mexico is the
preferred alternative, as indicated in the 1994 EIS and ROD for the
project. Secondary treatment options for the IWTP will be evaluated in
an SEIS, as agreed to by Surfriders. However, in the interim period the
decision to be made is whether No Action is preferable to operating the
IWTP as an advanced primary plant. In that case, discharge through SBOO
is preferable to other discharge options, and avoiding discharge to the
river of effluent from the IWTP is imperative.

EPA and USIBWC disagree with two fundamental assumptions made by
Surfriders in their amendments to Table S-1: that the IWTP would
immediately treat and discharge 25 mgd to 75 mgd of sewage from Tijuana
and that no evaluation of the effects of discharge through the SBOO is
available. The flow estimates prepared by EPA and USIBWC are considered
the best available forecasts. For reasons explained in response #1, EPA
and USIBWC reject the assumption that 25 mgd flow would be directed to
the IWTP. The entire volume of Tijuana sewage that would be generated
through the year 2001 is not forecast to exceed 52 mgd, even during wet
weather high flow days; the 75 mgd figure could only occur as a peak
hourly flow rate. Discharge through the SBOO has been demonstrated
through detailed modeling to be superior to shoreline or river discharge
(Chapters 4.1 and 4.2 of the SEIS). By Surfrider=s own analysis, the No
Action alternative has significant unavoidable adverse impacts under
each issue except Geology. EPA and USIBWC do not find that No Action is
an environmentally superior alternative.

EPA and USIBWC do not agree with the commentor=s statements regarding
flows.

Minute No. 270 outlined improvements to Pump Station One which included
providing a 62 mgd peak capacity, with 34 mgd average capacity. However,
as designed and built, the pump station currently has a peak capacity of
50 mgd with all four pumps operating. As stated in the SEIS, one pump is
used as a backup. The reliable peak operating capacity with three pumps
is approximately 36 mgd.

As indicated in section 2.1.1.1 of the SEIS, although the conveyance
canal has a peak design capacity of 62 mgd, because of accumulations of
debris in the canal and siphons and the lack of opportunities to perform
regular maintenance, the usable capacity of the canal is estimated at 48
mgd.

This section of the SEIS clearly states that the activated sludge
portion of the IWTP A. . . has been designed, but construction has been
postponed until an additional SEIS has been finalized.@ All other major
elements of the IWTP are either completed or currently under
construction.

The SEIS does not state that the flows cannot be disinfected, but that
chlorination/dechlorination may not allow the flows to meet standards
for trace residual chlorine. Dechlorination of effluent at the IWTP
would require additional facilities as well.

The supplemental EA was circulated for public and agency review, and is
referenced in the SEIS (U.S. Army Corps of Engineers 1996). Bacterial
levels for treated effluent and their transport and fate if discharged
to the shoreline in Mexico or through SBOO were modeled for the SEIS.
Adverse effects from chlorination were also identified.

Please see attached letter from Commissioner Solis of the Mexican
Section USIBWC (Attachment 1). Mexico will continue to convey a total of
approximately 42-45 mgd to San Antonio de los Buenos, of which 17 mgd
will be treated and the remainder discharged to the ocean untreated.
Pump Station One peak design capacity is 50 mgd, with an approximately
36 mgd reliable peak capacity. Peak design capacity of the conveyance
canal is 62 mgd, but due to debris accumulation, the effective capacity
is estimated at 48 mgd.

It is standard convention to express flow rates in millions of gallons
per day (mgd). However, peak hourly flows are not sustained for a
24-hour period. A peak flow rate of 73.4 mgd is equivalent to
approximately 3 million gallons per hour; 91.8 mgd peak flow is
approximately 3.8 million gallons per hour. Total throughput through the
system is expressed as the average flow in mgd, and takes into account
the predicted peak and low flows throughout the day.

These considerations relating to treatment ponds are outside the scope
of the Interim Operations SEIS.

There is ample evidence to support the basic findings of the EPA/IWBC
flow memo. The Mexican section of IBWC has reviewed the flow memo.
Mexico=s estimate of the current capacity of the San Antonio de los
Buenos treatment works is 17 mgd. It is estimated that by the year 2001
total flows to the plant would reach 39.9 mgd such that 22.9 mgd of raw
sewage would bypass the treatment works and be discharged directly to
the shoreline. The effects of shoreline discharge in Mexico to U.S.
waters are included in the modeling for the SEIS.

The SEIS characterizes the current setting as untreated flows to the
Tijuana River estimated to average 1.1 mgd in 1996 and are expected to
reach 5.6 mgd average by the year 2001.

The SEIS does not state that the peak capacity of Pump Station One is 62
mgd nor 48 mgd. The peak capacity of Pump Station One is 50 mgd with all
four pumps operating. However, only three pumps operate resulting in a
peak reliable capacity of approximately 36 mgd; the fourth pump being
reserved as a backup in the event of equipment failure. Pump stations in
the U.S. would also be rated this way, with one pump held as a reserve.

Alternative 3 in the SEIS incorporates a detention basin for flow
equalization and storage during interim operation. The use of ponds for
secondary treatment, including the results of previous studies, is
currently under evaluation and will be addressed in a second SEIS.

Comment acknowledged. If these data were available at the time the SEIS
was prepared, they would have been included in the Draft.

The final Construction and Operations Minute has not been finalized at
this time; it will be finalized before the plant is operated.

Yes, it will reduce the potential for discharge to the river and
estuary.

Yes.

No, as discussed in the SEIS.

The modeling results of discharge through SBOO indicates that the
effluent may not meet two criteria pollutant concentration at the zone
of initial dilution.

Yes.

Not applicable.

Because interim operation limits the amount of untreated sewage
discharged to the river, yes.

Majority of commentors to the SEIS support the preferred alternative
(i.e., USFWS, NMFS, Center for Disease Control, City of San Diego, City
of Imperial Beach, City of Coronado, Tijuana Valley County Water
District, Citizens Revolting Against Pollution, Citizens Against
Recreational Eviction).

No response required.

No response required.

Surfriders are a party to the settlement agreement which laid out the
scope of the supplemental SEISs that are being prepared for the project.

Congress authorized this with the original funding for the project.

The RWQCB will make this determination.

The concentration is 1.6 x 10^8^ total coliform MPN/100 ml. The State
Health Standards referenced are for the shoreline at 30 feet water depth
or within 1,000 feet of the shoreline or coastal recreation area. Taking
into account bacterial die off and dilution, the effluent is expected to
meet the standard.

As coliform bacteria are subject to relatively rapid die off, (a 90
percent reduction in 4 hours) mass loading of coliforms is not
considered to be as critical as the diurnal changes in the rate of
reduction, which was analyzed in the discharge modeling for SBOO and
coastal waters.

The difference between a primary or secondary effluent discharge to
receiving waters is not whether a discharge occurs or its volume; but
the constituent concentrations of the discharge. The effects of
discharge to the river, estuary, or ocean was considered in the SEIS,
whether the effects should be considered direct or indirect effects.

EPA and USIBWC disagree for reasons stated in response to #1.

To the extent that discharges in Mexico adversely affect U.S. waters,
shoreline discharges are relevant to the purpose and need and goals of
the action. Modeling of the transport of discharges in Mexico conducted
for the project and historical records of coliforms at the international
border indicate that such discharges are relevant.

The IWTP will not discharge 25 to 75 mgd.

Effects to riparian habitat and wildlife are considered in Section 4.3
of the SEIS.

This and other hydrographs in Chapter 2 were prepared by Boyle
Engineering who are technical advisors to the project. Flows are based
upon best available information. The SEIS clearly states the assumptions
for the flow analysis and Mexico=s current system capacities. The
conveyance canal is labeled on Figure 2-1.

See response #72.

See response #72.

A comparison of the relative pollutant loadings between each of the
alternatives is discussed for each alternative in Section 2.2
AComparison of Alternatives@ of the SEIS. While it is obvious that 25
mgd of treated effluent would have greater mass loadings than 1 mgd of
untreated effluent, it is irrelevant to evaluating the alternatives in
the SEIS.

Basing a comparison of IWTP effluent with Point Loma influent on the
basis of BOD alone is misleading. BOD would be somewhat lower than Point
Loma effluent, suspended solids substantially lower. Other constituents
vary with treatment efficiencies.

The SEIS acknowledges adverse health impacts from coliforms for
discharges of advanced primary effluent to the river and coastline.

The SEIS does address nutrient loading and eutrophication in its impacts
to the river and estuary in its assessment of terrestrial, estuarine,
and marine biology (Sections 4.3-4.6) and finds the impacts significant.

As noted above, discharges to the shoreline in Mexico may effect U.S.
waters, which is relevant to the purpose and need and goals of the
action.

A functional capacity of 36.6 mgd is used for pump station one for
reasons cited in the SEIS. See response #72.

Mexico does not utilize all four pumps at one time, as explained in the
text of the SEIS. See response #72.

The IWTP would provide 2 mgd of flow equalization to assist in
preventing flows of sewage to the river, as explained in the SEIS.

A functional capacity of 36.6 mgd is used for pump station one for
reasons cited in the SEIS.

A HEC model of the discharges was provided in the SEIS and discussed
under hydrology and estuarine biology (Sections 4.1 and 4.4). No
significant impacts to the hydrology of the river would result from
flows of 1.1 mgd to 5.6 mgd. Flows of 25 mgd are not expected. The SEIS
identifies adverse consequences to water quality.

For reasons noted above, 25 mgd to 75 mgd discharges are not anticipated
and were not evaluated for the SEIS.

For discharge to the Tijuana River, effluent from the IWTP could be
chlorinated but not dechlorinated. At comparable volumes, the discharge
of treated effluent would result in less mass loading than raw sewage.
EPA and USIBWC do not agree that IWTP effluent is roughly equivalent to
Point Loma influent.

Flows of 25 to 75 mgd are not anticipated. Mass loadings from treated
effluent would be somewhat reduced relative to discharges of untreated
sewage, as the flows would be equivalent.

A discussion of chlorination/dechlorination is provided in Section
4.1.1.3 of the SEIS. Alternative 2 will result in less pollutant loading
to the river and estuary than would the No Action alternative. It would
not meet body contact standards, as acknowledged in the SEIS.

If the same volumes of flow are compared, the mass loadings for treated
effluent are less but not below a level to eliminate ecological and
human health and safety concerns. However, it has been repeatedly
expressed by the public that taking action by treating sewage that would
otherwise be discharged to the river would be a positive step.

BOD, solids, and other constituents have been lowered through detention
in an odor controlled environment and ferric chloride has been added to
reduce hydrogen sulfide emissions. That odors may still be objectionable
is agreed.

EPA and USIBWC do not agree with the comment and based upon the SEIS
conclude that Alternative 2 is preferable to No Action, although it is
not the preferred alternative.

EPA and USIBWC cannot confirm the northward drift probability figure
cited in the comment as accurately reflecting the conclusions of the
1988 TOES. Based upon the current modeling, untreated discharges in
Mexico appear to have adverse consequences for waters in the U.S.

The commentor is incorrect; there is no undisclosed Amaximization@ for
the pumping or conveyance capacities in Mexico.

As noted above, the sizing of the detention basin is based upon its
functioning as a flow equalization for the emergency connection. If
sized above this use, treated effluent would be stored in the basins,
which is undesirable.

As noted above, there is no basis to anticipate flows of 25 mgd to the
IWTP on a regular basis.

The SEIS discloses that effluent from the IWTP would not meet health or
safety standards if discharged to the river.

IWTP effluent is not equivalent to raw sewage. Riparian habitats in the
valley have been exposed to continuous years with dry weather sewage
flows prior to 1992. The effects of these discharges were considered in
the 1994 EIS. It does not appear that dry weather sewage flows adversely
impact riparian habitat.

Alternative 3 will not result in discharge of 25 to 75 mgd to the river.
The claimed potential impacts are not realistic.

This comment misstates the analysis presented in Sections 4.1.1 and
4.1.2 of the SEIS. Adverse impacts are identified in these sections.
Effects of discharge to the shoreline in Mexico to marine biota cannot
readily be quantified, but are qualitatively assessed as adverse.

The comment is inaccurate. The effects of discharge of sewage to the
shoreline in Mexico has been modeled for the SEIS by Parsons Engineering
Science.

There is no basis for assuming 25 to 75 mgd would be flushed through the
Tijuana Estuary from the project.

Total pollutant loadings would be reduced under Alternative 2 relative
to the No Action alternative.

Primary treated effluent has a lower BOD and total solids content than
untreated raw sewage and, therefore, will have a lower odor D/T value
than raw sewage. However, these values have not been quantified.
Additionally, Alternative 2 will result in lower discharges to the river
than the No Action alternative. The SEIS discloses that treated effluent
discharged to the river will not meet coliform standards.

Under Alternative 3, there would only be discharges to the river under
high flow conditions in the years 2000 and 2001. The SEIS concludes that
discharge of primary treated effluent would not be consistent with the
federal and state water quality plans and policies.

Mexico has chosen these capacities, consistent with its existing
facilities. They would be temporary in the sense of their use for
interim discharge considered in the SEIS.

The new pumping and conveyance facilities will not be operational until
1998; discharges of untreated sewage could occur before then. A AReturn
to Sender@ alternative was considered in the 1994 EIS for the IWTP and
SBOO. These alternatives result in discharge of untreated sewage to the
shoreline in Mexico, which may adversely impact U.S. waters. Mexico will
not agree to use of the new pumping and conveyance system as a
substitute for the SBOO.

AMixed flows@ refers to untreated sewage and San Antonio de los Buenos
effluent discharged at the same point to the shoreline. There is not a
significant difference in the two flows relative to coliform
concentrations, and this was considered in the shoreline discharge
modeling. The purpose of the IBWC Minutes and the project is to reduce
impacts to U.S. waters, which shoreline discharges in Mexico could
result in.

The commentor is incorrect; there would be discharges to the river prior
to the completion of the new conveyance system if the IWTP is not
operated.

See response #72.

However, IWTP effluent is preferable to untreated sewage if it is
discharged to the shoreline in Mexico.

EPA/USIBWC cannot confirm the 0.06 percent probability figure.

The dilution stated is an order of magnitude estimate.

Impacts to marine environment and biota are presented in Section 4.5 of
the SEIS, based upon modeling by Parsons Engineering Science.

See comment numbers 110-113.

Statement is based upon the results of the shoreline discharge modeling.
The chlorination is recent change in operations at the facility. Data
has not been made available as to the effectiveness of the chlorination
at San Antonio de los Buenos.

Section 4.2 of the SEIS presents the shoreline discharge modeling
results.

Mexico has the rights to the effluent from the IWTP per Minute No. 283.
As a discharge to a national water, the Mexican federal standards apply,
which were appended to the SEIS. Compliance with the appropriate laws is
Mexico=s responsibility.

The 75 mgd flow rate is the reliable peaking factor for the IWTP, not a
flow figure for IWTP interim operation. Operating the IWTP at 25 mgd is
included in Minute No. 283 and will be formalized in the Operations and
Maintenance Minute.

This is discussed in Section 4.2 of the SEIS.

While a waiver from secondary treatment standards was authorized by
congress in the enabling legislation for the project, no decision will
be made until the Alternatives to Activated Sludge Supplemental EIS has
been completed.

The alternatives considered in the SEIS and the environmental process
was formalized in the settlement agreement agreed to by Surfriders
(Attachment 2).

As discharges to the shoreline in Mexico may result in impacts to U.S.
waters, there is no conflict in the purpose and goals.

Table 3.1-2 was developed as an example to show mass loads of various
pollutants based on sampling results at a given flow rate. The actual
flow rate varies on a daily basis, but as indicated in the SEIS is
expected to average 1.1 mgd in 1996 for the No Action alternative. Mass
loadings at flow rates other than 10 mgd can be determined simply by
multiplying the indicated mass loads by the ratio of the flow rates.

Table 3.1-2 presents the results of samples taken in the Tijuana River;
Table 3.1-3 presents the results of samples taken from the sewage stream
at Pump Station One.

As part of the Interim Operation SEIS, one of the alternatives
considered was the construction of a new pump station and conveyance
pipeline for discharge in Mexico near the San Antonio de Los Buenos
Treatment Plant in Mexico. In order to accurately assess the impacts of
short-term discharge of unchlorinated primary treated effluent to the
surf zone near the San Antonio plant, Parsons Engineering Science was
requested by EPA/USIBWC to develop a computer model, later known as the
Shore Discharge Model, to illustrate the migration of treated effluent
discharged in Mexico and its possible impacts to the U.S. coastline.

The commentor is suggesting that there is no evidence of northerly
moving currents which could transport the discharge near San Antonio de
Los Buenos. However, the existence of northerly currents along the surf
zone is amply documented by the abundant bacterial samples taken over
the years by different agencies, including sampling conducted by the
IBWC, the City of San Diego, and San Diego County Department of
Environmental Health. The sampling demonstrates that at certain times of
the year the bacterial plume discharged from the wastewater treatment
plant near Punta Banderas diminishes in concentration as it travels
northward. In addition, current monitoring (metering) carried out for
the TOES I and II studies also substantiates the presence of
north-moving currents along the nearshore zone near the international
border. The 1988 TOES study found northerly currents trending upcoast 27
percent of the time, including the nearshore zone (Attachment 3).

Parsons Engineering Science contacted Dr. O=Reilly when wave data, not
current data discussed above, obtained from the 1986 TOES study model
was found not to be suitable as input to the Shore Discharge Model.
Parsons was concerned that the wave data available from the TOES study
was not representative of the waves in the general area. Parsons
contacted Dr. O=Reilly to enlist his services in providing the required
wave data to be used as input to the shoreline discharge model. In his
conversation with Parsons, Dr. O=Reilly did express some concerns about
the quality of the bathymetric data available for the extreme southern
portion of the area to be modeled, as well as possible limitations on
the data available for the waves in the area. Modifying the available
bathymetry would have required a substantial amount of time in view of
his current work at U.C. Berkeley, and his existing commitments with the
state of California.

Parsons Engineering Science then contacted Pacific Weather Analysis to
assist Parsons with this effort. Pacific Weather Analysis was able to
obtain the necessary data for two locations: one at the border between
the U.S. and Mexico and a second approximately midway between the border
and the discharge near Punta Banderas. Parsons informed Pacific Weather
Analysis of Dr. O=Reilly=s concerns. They concluded that because of the
location of the stations, the known deficiencies in the bathymetry data
base would not affect the predicted wave data because the modeled waves
reaching the specific sites would propagate through the area with
sufficient overall bathymetric information. In total, Parsons obtained
from Pacific Weather Analysis the follow information:

a\) Twenty years of hindcast wave records in southern California which
classified sources of the wave and fetch characteristics;

b\) A Monte Carlo simulation developed by Noble Consultants in order to
generate an annual wave climate by season given the probabilities of
each wave pattern obtained; and

c\) A modification of directional wave spectra in deep water to select
shallow water sites, utilizing the O=Reilly-Guza spectral wave
refraction model from Nicholas Graham of Scripps. (More information
regarding the services provided by Pacific Weather Analysis is included
as Attachment 4 to the Response to Comments.)

Finally, in a conversation with EPA on November 20, 1996, Dr. O=Reilly
indicated that the O=Reilly-Guza spectral wave refraction model used did
transform the wave heights and that Dr. Nicolas Graham at Scripps
Institute of Oceanography was authorized to use the model.

In order to develop the Shore Discharge Model, typical wave and current
conditions had to be developed only using available data in order to
meet the schedule and practical constraints of the preparation of the
SEIS. The wave data available to match current data was not considered
suitable and Parsons Engineering Science had to obtain wave data for a
different time period.

However, not obtaining wave and current data from the same time period
was not considered critical for the development of the Shore Discharge
Model. In general, wave and current characteristics are virtually
unrelated and act independently of each other. Furthermore, because of
variability in the wave and current characteristics, there is an
advantage in using a much larger (representing 20 years) data base which
could result in a more representative sample.

The scope of the description of the SDM model included in the report was
designed to inform the lay reader about the general approach of the
model, the most important assumption and approximations, and the sources
of the data used to drive the model. In general, the key computational
algorithms was found in the article by Press et al. (1992). The model
does contain the elements referred to by Dr. Jenkins except there is no
nested grid, nor is there any reference to a nested grid in the report.
The equations used to qualify the relationship between the wave
characteristics and the wave-induced advective transport model
parameters were obtained by estimates from Inman et al. (1968).
Calculations of the wastewater transport and concentrations in this area
were obtained from Jirka (1990) as the oceanic eddy diffusivities for
the offshore region were estimated from characteristic=s cross-shore
length scales of the wastefield and the work of Okubo (1974).
Wave-induced eddy diffusivities at the boundary of the surf zone were
computed by Jirka (1990).

In order to test the Shore Discharge Model, the report provided a
comparison between bacterial concentrations predicted by the model with
various historical sampling events at several monitoring stations
obtained by the IBWC, City of San Diego, and San Diego County Health
Department at stations between the Punta Banderas discharge area and
northern San Diego.

One factor considered in the Shore Discharge Model was the presence of
rip currents as part of the overall ocean characterization. The modeling
of rip currents was significant since it illustrates the cross-shore
transport between the surf zone and the off shore zone, as well as
illustrates the movement between the transition zone and the surf zone.
Rip currents are observed to both migrate or remain stationary. Rip
currents are typically found between the surf zone and outer transition
zones. Their effects are computed in terms of volume fluxes. The rip
current speed was shown in Figure N-1 of the Ocean Modeling Report. The
speed was determined by the computational model contained in Inman et
al. (1968) combined with information about the actual rip current area.

Furthermore, a fixed rip current length was selected for the model. The
length of each rip current was chosen to be comparable to the average
rip current spacing as described in Inman et al. (1968) and the average
wave conditions. Sensitivity studies carried out with the model
indicated that variations in the rip current parameters had relatively
small effects on the concentrations predicted far upcoast from the point
of discharge. This characteristic supports the use of fixed length rip
currents.

As stated in the above comments, a Surf Discharge Model was developed to
examine the impacts of a short-term ocean discharge of unchlorinated
advanced primary treated effluent from a discharge near Punta Banderas.
A three-dimensional model as referenced by the commentor would not be
capable of predicting accurately the coastal mixing and transport
occurring in the surf, since the primary driving mechanism for this area
is waves. A second ocean modeling was also conducted by Parsons
Engineering Science to examine the short-term discharge from the South
Bay Ocean Outfall three miles in the Pacific Ocean. For this modeling
effort, a three-dimensional model was considered.

Dr. Ralph T. Cheng of the U.S.G.S. in Menlo Park and Dr. Vincenzo
Casulli, of the University of Trento in Italy, the developer of the most
recent three-dimensional model, as well as Dr. Craig Swanson of Applied
Science Associates of Rhode Island, the developer of a Princeton model,
were contacted about the modeling for the interim discharge of advanced
primary effluent through the South Bay Ocean Outfall. After several
conference calls between Parsons Engineering Science and the individual
three-dimensional modelors, it was concluded that with the time
constraints of the SEIS and input data available, only qualitative
results could be expected.

Parsons Engineering Science proceeded to model four ocean layers for the
discharge, obtaining a discrete quasi-three-dimensional representation
of the water quality in the area.

EPA and USIBWC have reviewed the Parsons Engineering Science Modeling
study, have received independent agency review of the study, and have
consulted with some of the principals cited in the Surfrider=s letter of
comment. EPA and USIBWC believe that the study is technically sound and
appropriate as a model to approximate the effects of ocean discharge
through SBOO and shoreline discharge in Mexico for the Interim
Operations SEIS. EPA and USIBWC find that the objections raised are
based upon misinformation about the Parsons Engineering Science study
and the federal agencies do not agree with the comments by Surfriders
Foundation.

See response #131.

Table 4.1-1 was not based upon the Parsons Engineering Science modeling
study; it was based upon estimates from Malcolm Pirnie Engineers, as
cited in the table.

**Public Hearing**

A noticed public hearing was held at Southwest High School on October 7,
1996 for which a transcript of questions, comments, and responses by the
federal agencies is provided. As portions of the hearing were conducted
as a question and answer format with the sponsoring federal agencies,
and that any substantive issues raised were responded to at the hearing,
no additional specific responses to the transcript are provided. Most
speakers at the public hearing also provided written versions which are
responded to in the letters of comment.

**Errata**

The following changes to the Draft SEIS are made for the Final SEIS:

Section 1.3.2.2, page xiv, paragraph 5, should be changed to read:

The outfall is designed to carry an ~~maximum~~ average daily flow of
174 mgd . . . .

Section 1.4, page xv, paragraph 1 should be revised as follows:

EPA and USIBWC are considering operating the IWTP as an advanced primary
treatment works prior to the completion of the ocean outfall and the
secondary treatment process trains to minimize the risk of discharges of
raw sewage ~~or treated effluent~~ into the Tijuana River.

Figure 1-5 The scale shown is in miles, not feet.

Section 2.2.3, page 81, paragraph 3; Section 4.1.4.1 page 210, Paragraph
2; Section 4.2.5, page 231, paragraph 2; Section 4.5.3, page 275,
paragraph 2; modify sentence as follows:

There could be episodic discharges of up to 0.7 mgd (31 lps) and 2.0 mgd
(88 lps) on seasonal high flow days in the years 2000 and 2001 . . . .

Section 1.1.1.5.page 12, paragraph 1; add as indicated:

Manufacturing industries of Tijuana include televisions, computers,
metal products . . . .

Section 1.4.10.1, page xxii, paragraph 2; Section 3.2.1.4, page 140,
Bacterial Contamination, paragraph 2; Section 3.7.2, page 182, paragraph
5; Section 3.7.3.1, page 184, paragraph 1; Section 5.1.1, page 305,
paragraph 1; Section 5.4.1, page 306, paragraph 1:

County Department of Health Services should be changed to County
Department of Environmental Health.

Section 2.2.3.1, page 82, paragraph 1 should be revised as follows:

The discharge of treated effluent to the Tijuana River would not occur
until the year 2000~~1~~, when 0.7 ~~2.0~~ mgd (31 ~~88~~ lps) would be
discharged during seasonal high flow days. If the SBOO becomes
operational by June 1998~~-1999~~ as scheduled, all discharges to the
river of untreated sewage or treated effluent could be avoided.

**Attachments**

1\. Letter from Commissioner J. Arturo Herrera Solis, Commissioner of
the Mexican Section of the IBWC to John M. Bernal, Commissioner, U.S.
Section of the IBWC. This letter recites basic issues with respect to
sewage facilities in Mexico and Mexico=s best disposition to continue to
accept flows through Pump Station One until the SBOO is operational.

2\. Settlement Agreement between the EPA and USIBWC and the San Diego
Chapter of the Sierra Club, Chaparral Green and Surfrider Foundation,
dated July 19, 1995. This Settlement Agree­ment \[Case No. 94-920-J(RBB),
U.S. District Court Southern District of California\] was concluded
after the 1994 Final EIS and Record of Decision was signed for the
project. It outlines the agreed to process for preparing additional NEPA
documentation for the project and the scope of the documents.

3\. Memorandum from Terry Hendricks (11/25/96) with respect to current
meter information collec­ted during the TOES study indicating northerly
transport.

4\. Letter from Pacific Weather Analysis, signed by R. Rea Strange to
Dr. Luciano Meiorin of Parsons Engineering Science, dated November 7,
1996; clarifying data sources and wave records used as input for the
shoreline discharge model.