Border Environment Cooperation Commission

Improvement to Wastewater Collection and Treatment System for

Puerto Palomas, Chihuahua

 

Environmental Information

 

General Criteria

Human Health and Environment

Technical Feasibility

Financial Feasibility

Public Participation

Sustainable Development

 

 

I. General Criteria

 

1.     Type of Project.  The project consists of rehabilitation and expansion of the wastewater collection system and the construction of a wastewater treatment plant.

2.     Location of Project.  Puerto Palomas is located in the northeast part of the State of Chihuahua, in the Municipality of Ascension. The community is bordered on the North by Columbus, Luna County , New Mexico.  The project is located within the 100 km border region as defined by the La Paz agreement. The 1999 population of Puerto Palomas is approximately 7,200 people, and is expected to reach 14,800 people by the year 2020.  To determine the population a historical growth rate of 4.64% was used and reduced to 3% by the end of the planning horizon.  The location of the city is shown in the following map:


3. Description of Project and Tasks. 

The project consists of improvements to the existing wastewater system in two phases.  The first phase will meet existing demands through 2012 for the collection system and 2010 for the treatment system and the second phase for both systems through 2020.  In both phases, wastewater service coverage will be maintained equivalent to the water service coverage.  A summary of the various components of the project are listed below:

Phase I

1.      Wastewater collection, 1st Phase:

·        Install 40,647 m (133,322 ft) of sewer pipes.

·        Install 3,004 m (9,853 ft) of lines at the Lerdo, Galeana, Guerrero and J. Rosas subcollectors.

·        Install 5,371 m (17,617 ft) of lines at the Mexico, Progreso and Lerdo collectors.

·        Install a 732 m (2,401 ft) gravity interceptor

·        Install an 778 m (2,552 ft) forcemain

·        Build 544 manholes and backdrop boxes.

·        Lift station

·         2,856 sewer hookups; 1,400 immediately

2.      Wastewater Treatment, 1st Phase

·        Construction of a lagoon system with 25 lps (396 gpm) installed capacity.

3.      Institutional Development of the Utility

·        Improvement to the billing system

·        Rate study and implementation

·        Update to User List

·        Water Conservation Program

·        Energy Conservation Program

·        Administrative Improvements to the Utility

Phase II

1.      Wastewater collection, Second Phase:

·        Rehabilitation of the wastewater collection system and lift station

·        Rehabilitation and expansion of the sewer pipes

·        800 sewer hookups.

2.      Wastewater treatment, Second Phase

·        Construction of an additional 9 lps (143 gpm) module for a total installed capacity of 34 lps (539 gpm).

3.      Institutional Development

·        Actions similar to the first phase

It is important to note that part of the system is already constructed or under construction.  Since 1996, the Mexican government has increased the sewer coverage from 25% to 40%, constructed the lift station, interceptor and forcemain, constructed a portion of the collectors and is constructing a portion of the wastewater treatment plant.  It must be noted that, as of the end of 1999 only 26% of the total population was connected to the sewer system.

Wastewater treatment consists of a natural system that includes the construction of two treatment trains, each with a primary or anaerobic lagoon, a facultative lagoon, and a wetland.  The treated effluent will have a quality of 30 mg/l of total suspended solids, 30 mg/l of biochemical oxygen demand, and 1000 mpu of fecal coliforms.  This will be used to irrigate 6 hectares (14.8 acres) of tree farms, since there is no receiving body or nearby agriculture.  Any additional outflow will flow into a dry river bed. The tree farm is located within the project site.  Additionally, the treatment plant site of 10 hectares (24.71 acres) will be situated within an “Ejido” and the required agreement with the “Ejidatarios” for use of the site has been completed. 

Figures 1 and 2 illustrate graphically the project.

Figures 1:  Wastewater Treatment System


 

 


Figure 2:  Proposed Wastewater Collection System


4.  Compliance with international Treaties and Agreements.  The project complies with the rights and obligations established in applicable treaties and agreements

II. Human Health and the Environment

 

1.  Human Health and Environment.  The community of Palomas does not have adequate sewage collection and treatment.  Currently wastewater collected is not treated and disposed of in an open-air disposal site.  Additionally, only 40% of the population has sewer available and as of the end of 1999 only 26% are connected.  The remaining population has septic tanks and latrines, which leads to the infiltration of raw sewage into the aquifer.  According to the study “Water Quality on the U.S.-Mexico Border:  An Assessment of the Mimbres Basin Aquifer and Region Surrounding Columbus, New Mexico USA and Puerto Palomas, Chihuahua, Mexico done by Southwest Center for Environmental Research and Policy (SCERP) concluded that there is evidence of groundwater contamination by nitrates associated to wastewater infiltration.  This results in the existence of a source of contamination to the environmental, an immediate health threat to the community such as the occurrence of water borne diseases. . 

The implementation of the project will resolve the human health and environment problems associated with inadequate collection and wastewater treatment, which Puerto Palomas currently experiences. 

2.  Environmental Assessment .   As required by the Mexican Law for Ecological and Environmental Protection, an Environmental Impact Statement (EIS) of the project was completed and presented to the State of Chihuahua Ecology Secretariat,  for review and approval.  A favorable finding was issued by Ecology Secretariat on December 1,1999.

To comply with the environmental requirements for solicitation of BEIF, additional environmental information to complement the Mexican EIS was developed.  The EIS and additional information was sent to the United States Environmental Protection Act (USEPA) for review and initiation of the NEPA (National Environmental Policy Act) process.  A FONSI was emitted on May 27, 2000 by USEPA and the NEPA process has concluded.

4.      Compliance with Environmental and Cultural Resources Law and Regulations. All of the relevant documents have been presented and reviewed.  According to the favorable finding by the Ecology Division of the State of Chihuahua and the list of protected areas provided by the National Institute of Ecology (INE), the project does not affect any ecological reserve or habitat, or protected species.  Additionally, the National Institute of Anthropology and History emitted a finding on November 10, 1999 indicating that the project will not affect historically or anthropologically significant areas. 

 

III. Technical Feasibility

 

1.      Appropriate Technology. A water and wastewater master plan was completed in 1997 for the project through the BECC technical assistance program.  The state of Chihuahua has completed final design of Phase I of the project for the wastewater collection system and the wastewater treatment plant.  Development of the wastewater collection and treatment final design has meet the criteria established in the Master Plan developed with technical assistance provided by the BECC. The planning period is for a 20-year horizon and divided into two implementation phases. Three wastewater treatment alternatives were analyzed: two lagoon systems and activated sludge package plant. The criterion used to select the best treatment alternative was a combination of ease of operation, lowest initial investment and lowest operation and maintenance cost during the planning period.  Additionally, the discharge permit has already been obtained and the site secured for the plant.

Final design was developed by the Government of the State of Chihuahua through the Junta Central de Agua y Saneamiento (JCAS), are based on the design criteria by C.N.A.  and JCAS and comply with the applicable official norms established by C.N.A., I.N.E. (National Institute of Ecology), and Health Department in each case . Through the BECC's Technical Assistance program, a consultant was hired to perform a technical review of these studies and final designs for the purpose of validating or improving the design.  This resulted in two reports: A Comprehensive Review of the Conceptual Design and Assumptions, July 7, 1999, and A Comprehensive Review of the Final Design, August 9, 1999.  These reports recommended some minor adjustments to the project, which have been incorporated.  Additionally, the population projections have been validated by C.N.A.

 

2.      Operation and Maintenance Plan.  A complete restructuring of the water utility is recommended.  Within this context development of operations, procedures, and administrative manuals is considered.  A funding component is also included.

3.      Compliance with applicable design norms and regulations. The project is in compliance with applicable design standards and regulations.  Additionally, C.N.A has validated all documents including final design.

 

IV. Financial Feasibility and Project Management

 

1.      Financial Feasibility. 

The project costs for the various components of the project are the following:

 

Cost of the Project to Improve the  Wastewater Collection and Treatment Systems and strengthen the Utility

 

TOTAL

1st Phase

2nd Phase

Wastewater collection

$33’705,504

$26’775,342

$6’930,162

Wastewater treatment

$10’906,452

$7’907,231

$2’999,221

Utility

$3,600,000

$1’800,000

$1’800,000

TOTAL

$48’211,956

$36’482,573

$11’729,383

Costs in pesos. December 1999 (includes taxes)

 

Of this total budget, approximately $11’821,061 have been expended. Phase I of the project initiated construction in 1996 and continues to date with funds from the Mexican government.  The construction to date includes primarily the interceptor and forcemain, lift station, a portion of the sewer and hookups, and a portion of the wastewater treatment plant.

The recommended financial structure for the first phase is summarized in the table below.  Since a portion of phase I has been constructed more accurate unit costs have been established.  Additionally, since final design has been completed on the first phase of the project, the quantities of materials needed are better defined.

 

Financial Structure for the First Phase

Source

Type

Amount

MX$

% of Phase I Project Cost

Mexican Government

Grant

$17’329,222

47.5%

USEPA

BEIF- Grant

$17’329,222

47.5%

NADB

Credit

$1’824,129

5.0%

TOTAL

 

$36’482,573

100%

 

2.      Rate Model:  The current rate structure is a fixed fee depending on the level of service.   The table below summarizes for 1999 and 2000 the rate structure for and number of users in each category.   There are four domestic rates, A through D, and nine commercial rates, E through M.  Categories A through C are for water service without sewer.  Category D is for water and sewer service.  The remaining commercial rates depend on the type of business and estimated consumption.  All of the commercial rates have sewer included.  Additionally, since there is no micrometering or macrometering the cost per cubic meter is based on an assumed average consumption of 300 liters/person/day (75 gals/person/day) for domestic consumption and 2,387 liters/connection/day (597 gals/connection/day) for commercial consumption.

 

Current 1999 and 2000 Rate Structure

Category

Number of Users

Monthly Fee

Cost/Cubic Meter

 

1999

2000