San Luis Rio Colorado, Sonora, Mexico

Wastewater Collection System Expansion to Unserved Areas (Phase III) of San Luis Rio Colorado, Sonora

Status: Completed construction


Residents from the areas Ejido Oriente, Ejido Poniente, Calle-18, Calle-13, Jazmin and Las Flores lacked wastewater collection (WWC) services and rely on latrines, septic tanks without drain fields, or discharge to open drains for their wastewater (WW) disposal. Some of the untreated WW discharges eventually reached surface waters that flowed into the Colorado River  Basin. The Project was referred to as the PIMAAS-3 project.


Eliminate exposure to untreated wastewater and avoid aquifer contamination by providing wastewater collection service to first time users, contributing to the reduction in risk of waterborne diseases and pollution.


The Project consisted of the construction of a WWC system in the unserved areas of Ejido Oriente, Ejido Poniente, Calle-18, Calle-13, Jazmin and Las Flores. Collected WW is now conveyed to the existing WWTP.

Project Financing

Total Project Cost US 7M
NADB Funding US 2.68M - NADB Grant: BEIF
Other Funding Partners CONAGUA
Project Sponsor (OOMAPAS)

Project Photos

Results Measurement

Results are measured upon completion of the project through a closeout process that assesses project performance within 6-12 months after completion, as well as the achievement of the goals and objectives established at the time of project certification and financing approval.


Increase access and use of safe and sanitary wastewater collection services

Reduction of untreated wastewater discharges to water bodies



Increased number of new connections (Target based on full build out; Actual based on existing occupied homes with service)



Quantity of uncollected wastewater discharges eliminated

0.53 MGD



Wastewater new connections


Wastewater collection lines (miles)


Significant project finding(s)

The project included the construction of 9,442 WW access   connections (laterals). With the use of remaining project funds, a new household connections to sewer (HCS) pilot program was implemented; thus, 308 additional HCS were installed. The success of this program led to its use in subsequent projects.