Border Environment Cooperation Commission
Construction of
a Wastewater Treatment Plant and Rehabilitation of the Wastewater Collection
System San Luis Río Colorado, Sonora.
Enviromental Information
Financial
Feasibility and Project Management
1.
Type
of Project. The
project consists of the construction of a wastewater treatment plant and
rehabilitation of the wastewater collection system.
2.
Location
of Project. The City of San Luis Río Colorado is located in the
northwestern part of the State of Sonora at an altitude of 45 m [147 ft] above
sea level. The City is bound to the North by the United States of America; to
the West by the Colorado River and the State of Baja California; to the East by
the municipalities of Plutarco Elías Calles and Puerto Peñasco; and to the
South by the State of Baja California and the Sea of Cortez. The
project is located within the 100 km border region as defined by the La Paz agreement.
The current population of San Luis Río Colorado is approximately 180,000
people, and is expected to reach 420,000 people by the year 2018. The location
of the city is shown in the following map:
Description
of Project and Tasks. The
project consists of constructing a wastewater treatment plant with a capacity
of 9.1 mgd (400 l/s); rehabilitation and expansion of an existing pump station,
as well as the addition of a new one; and, rehabilitation and expansion of the wastewater collection system.
The existing wastewater collection system has a
total length of 26,855 meters and provides service to 37 percent of the Citys
service area. The total expansion of the system will be approximately 36,000
meters, to bring coverage of the wastewater collection system to 85
percent.
Compliance
with International Treaties and Agreements. The project complies with existing treaties
established by the International Boundary and Water Commission.
1. Human Health/Environmental Needs. The accelerated growth experienced by San Luis
Río Colorado in the last few years, in addition to the lack of funds has
resulted in a wastewater collection system with insufficient capacity and
efficiency. The insufficient capacity in the wastewater collection system, as
well as leaking and collapsed lines have led to the contamination of
groundwater resources. The lack of funds has led to an incomplete level of
maintenance, which has caused a rapid deterioration of the system.
In
addition, the lack of adequate wastewater treatment facilities has given rise
to the incidence of water-borne diseases. Currently, 37 percent of the
population is connected to a wastewater collection system that discharges
wastewater to the Colorado River, without receiving any treatment, while 63
percent of the population uses septic tanks or cesspools.
2. Environmental Assessment.
As part of the planning process, an environmental assessment (EA) was submitted
to the Environmental Protection Agency (EPA) and is currently under review. In
addition, a Manifestación de Impacto Ambiental was submitted to the
State of Sonora Secretaría de Infraestructura Urbana y Ecología, SIUE
[Department of Urban Infrastructure and Ecology] for their review. SIUE
approved the document and submitted their project authorization on February 18,
2000.
3. Compliance with Ecology and Cultural Laws
and Regulations
As part of the environmental
review process, the Instituto Nacional de Antropología e
Historia, INAH [National Institute for Anthropology and History]
was contacted to determine the existence of cultural and archaeological
resources. The INAH submitted their concurrence for the project on February 9,
2000.
1.
Appropriate
Technology. A water and wastewater Master Plan was
prepared for San Luis Río Colorado. The document identifies the following
priority projects: 1) rehabilitation and expansion of the wastewater collection
system; 2) rehabilitation and construction of a pump station; 3) construction
of a wastewater treatment plant.
WASTEWATER TREATMENT
The design of the wastewater treatment plant was
based on the basic parameters specified under the Mexican Official Norm
NOM-001-ECOL-1996, for discharge of effluent to rivers.
|
Parameter
(in mg/L, unless otherwise noted) |
Monthly
Average |
Daily
Average |
|
Temperature, oC |
40 |
40 |
|
Grease and oils |
15 |
25 |
|
Floating matter |
None |
None |
|
Settleable solids, ml/l |
1 |
2 |
|
TSS |
75 |
125 |
|
BOD |
75 |
150 |
|
Total nitrogen |
40 |
60 |
|
Total phosphorous |
20 |
30 |
|
Arsenic |
0.1 |
0.2 |
|
Cadmium |
0.1 |
0.2 |
|
Cyanides |
1 |
2 |
|
Copper |
4 |
6 |
|
Chromium |
0.5 |
1 |
|
Mercury |
0.005 |
0.01 |
|
Nickel |
2 |
4 |
|
Lead |
0.2 |
0.4 |
|
Zinc |
10 |
20 |
|
Fecal coliform MPN/100ml |
1000 |
2000 |
Several alternatives were evaluated during the
planning process. These include:
1. Stabilization
lagoons [anaerobic, facultative, and maturation lagoons in series]
2. Stabilization
lagoons [facultative and maturation lagoons in series]
3. Rapid
infiltration
4. Overland
flow
5. Slow
infiltration
6. Activated
sludge, conventional process
7. Activated
sludge, extended aeration
The selected alternative will consist of
stabilization lagoons (alternative 1) and will have the following unit
processes:
1. Pretreatment
2. Wastewater
diversion structure
3. Anaerobic
lagoon
4. Facultative
lagoon
5. Maturation
lagoon
6. Splitter
box
7. Disinfection
system
The
treatment capacity of the wastewater treatment plant will be 400 l/s (9.1 mgd)
and will be comprised of two modules of 200 l/s each. The City expects to add
two more 200 l/s modules at a future date to accommodate population growth.
The
stabilization lagoons treatment process was selected for several reasons: 1)
the costs is lower than mechanical processes; 2) operation and maintenance
costs are minimal; 3) the system is capable of receiving large variations in
the influent loads; 4) produces stable sludge. The selected alternative would
require 175 Ha of land. For this purpose, the wastewater treatment site has
been selected in the southern part of the City with a total area of 200 Ha.
No-Action
Alternative. Under this alternative, no wastewater treatment plant
would be implemented and the City would continue discharging untreated
wastewater to the Colorado River. This could worsen environmental conditions in
the area.
The following process train will be used for the
proposed wastewater treatment plant.
WASTEWATER COLLECTION SYSTEM
Several of the
collectors and subcollectors in San Luis Río Colorado, Sonora would be
rehabilitated. Currently, the City has a total of 26,855 meters in sewer lines,
providing service to 37 percent of the population. The project consists of
adding 36,000 meters of wastewater collection lines, cleaning of 104 manholes
and 10,300 meters of the wastewater collection system, replacement of 60
manholes and rehabilitation of an additional 60, removal of roots from 54
manholes and installation of 173 manhole covers
2.
O&M Plan. The
Master Plan identifies the requirements of O&M of
all unit processes, including human resources, the frequency of maintenance and
cost estimates. The O&M plan would be developed once the final design for
the project is completed.
3.
Compliance with applicable design norms and regulations. The technology used for construction of the sewer system and
wastewater treatment plant has been authorized by the Comisión Nacional del
Agua, CNA [National Water Commission].
Financial Feasibility and Project Management
1. Financial Feasibility.
The NADB is currently analyzing the project to
determine its financial feasibility.
This analysis will help determine the contributions for each funding
source, as well as credit and/or grant components, and the final rate
structure.
The table below summarizes the project
construction costs.
|
Estimated
Cost |
|||
|
Concept |
Amount
(US$) |
||
|
|
|
Improvements to the
wastewater collection system |
$7,640,814 |
|
|
|
Pump station and force
main |
$2,202,206 |
|
|
|
Wastewater treatment
plant |
$5,645,755 |
|
|
|
Total |
$15,488,775 |
|
Estimated
Operation and Maintenance Costs (Annual) |
|||
|
Concept |
Amount
(pesos) |
||
|
|
Wastewater collection system |
$42,105 |
|
|
|
Wastewater pump stations |
$131,580 |
|
|
|
Wastewater treatment plant |
$84,210 |
|
|
|
|
Total |
$257,895 |
Based on the analysis
developed by the NADB, the grant and loan amounts for the project were be
determined.
Financial
Structure
|
Source |
Amount (US$) |
% |
|
Local, State and Federal Funds |
$6,525,081 |
42 |
|
NADB BEIF |
$7,744,388 |
50 |
|
NADB Loan |
|
|
|
Operating Agency |
$1,219,307 |
8 |
|
Total |
$15,488,775 |
100% |
2.
Project
Management. The project will be managed by the Organismo
Operador Municipal de Agua Potable, Alcantarillado y Saneamiento, OOMAPAS [Municipal
Operating Agency for Water, and Wastwater Collection and Treatment] As part of
the program, several institutional development strategies will be implemented. The system is expected to operate in a self-sufficient
manner, supporting itself through user fees.
3.
Rate
Model. The proposed fee increase is from
0.80 pesos to 2.40 pesos per cubic meter of water consumed. This rate increase
applies in a period of 4 years.
Comprehensive
Public Participation Plan. The public participation plan (Plan) was submitted
to the BECC for approval last month. The plan includes a press campaign, meetings
with local organizations and neighborhoods. Also, as part of the process, a
survey was conducted to measure public opinion on the project before the
implementation of the public participation plan.
Steering Committee: A steering committee was formed on August 6,
1999 and is in the process of performing the tasks outlined in the public
participation plan. These tasks were completed successfully.
Local Organizations: Several local organizations have taken part
in the Steering Committee for the project. Outreach to other community
organizations was performed as part of the public participation plan.
Public Information: Project materials are available in City Hall and the OOMAPAS (operating
agency) offices.
Public
Meetings:
A public meeting was held on March 1st, 1996, as part of the
ECOBOSQUE project that previously pursued BECC certification. The second meeting is scheduled for April
25, 2000 and the third meeting for May 3, 2000.
Sustainable
Development
1. Definition and Principles. The project complies
with BECCs definition of Sustainable Development: An economic and social
development based on the conservation and protection of the environment and the
rational use of natural resources, but considering current and future needs, as
well as present and future impacts of human activities.
The principles of sustainable development
are satisfied. These include: Human beings are the central point of all
concerns for sustainable development; they have the right to a healthy and
productive life in harmony with nature. The project complies with the
principles objectives, which are to solve human health problems by improving
the potable water system, and decreasing pollution of the environment and
health risks to the population, through sewerage improvements and sanitation.
2. Institutional and Human Capacity
Building. The
investment of approximately $154 million pesos in improvements to the
infrastructure in San Luis Río Colorado, as well as an institutional
development program will have a positive impact on government institutions and
local economy, as well as on the community residents.
3. Conformance with Applicable
Local/Regional Conservation and Development Plans. The rehabilitation of the wastewater collection
system and the construction of a wastewater treatment plant is consistent with
the Citys Urban Development Program.
4. Natural Resource Conservation. The construction of a wastewater treatment plant in
San Luis Río Colorado will prevent the discharge of untreated wastewater to the
Colorado River. Thus it will help preserve precious groundwater resources, as
well as riparian habitats located downstream of the City.
5.
Community
Development. The
construction of approximately $154 million pesos in infrastructure will be the
foundation for the future growth of the community. Without an adequate infrastructure, the city could not sustain
the development of new businesses or the current population growth. The positive impacts related to the project
are short as well as long term.
Water and Wastewater Master Plan prepared by
CIEPSA.
San Luis Rio
Colorado, Sonora Project Certification Document.
San Luis Rio
Colorado, Sonora Public Participation Plan.
San Luis Rio
Colorado, Sonora Final Public Participation Report.
San Luis Rio
Colorado, Sonora Project Survey.
San Luis Rio
Colorado, Sonora Environmental Impact Analysis submitted to Secretaria de
Infraestructura Urbana y Ecologia.
San Luis Rio Colorado,
Sonora Transboundary Impact Analysis prepared by Geo-Marine for BECC and
submitted to the Environmental Protection Agency.
Environmental Assessment of the Effect on San Luis, Arizona by the Proposed Construction of a Wastewater Treatment Plant and Improvements to the Wastewater Collection System for San Luis Rio Colorado, Sonora.