State Public Services
Commission of Tijuana
Hernando Duran Cabrera
Director General
4057 Federico Benitez Blvd, 20 de
Noviembre, 22430, Tijuana, Baja California
Tel: (664)104 7702
hduran@cespt.gob.mx
Project
Pilot Project on Infiltration with
treated wastewater in the aquifer
Project
Integral
de
of Valle de las Palmas, Tijuana,
B.C.
Contact:
Hector Alejandro Caloca Galindo
Chief of the Office of Analysis and Evaluation
of Hydraulic Systems
State Public Service Commission of Tijuana
Tel: (664) 104 77 00 Ext 1202
alejandro@cespt.gob.mx
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Background:
The municipality of Tijuana is located in the north-western state of Baja California,
Mexico, comprising an area of 1239.49 Km2, 1.57% of the state. Is situated in extreme
geographical coordinates: north 32 º 34 ', south 32 º 04' north latitude east 116 ° 31 'and
west 117 ° 07' west longitude. On the north it borders with the United States of America
on the east with the municipality of Tecate on the south with Ensenada and Rosarito
Beach, on the west by the Pacific Ocean. The state of Baja California and the
municipality of Tijuana in particular, are located in a semi-desert area and therefore
water is scarce. Streams are few and volumes drained through them are small and very
occasional. Annual rainfall is around 204 millimetres, national second lowest. Most of
the Baja California streams and rivers do not exist as such, rather than for short periods
in some years.
The supply sources for the City of Tijuana are, in order of importance, the Colorado
River aqueduct that supplies the dams: El Carrizo and Abelardo L. Rodriguez; and the
wells located along the Tijuana River.
The Abelardo L. Rodriguez Dam is usually empty by the lack of significant rainfall and
only very occasionally for long periods in years, it gets full and can be exploited. Wells
are harvested but the amount extracted is very low for the demand of the city.
Therefore, the best source is the Colorado River, but also very expensive as it is
required to bring water to the City of Mexicali with a pipeline of 147 kilometres and
because of the pumping that have to go through a height of 1.060 metres on the
Rumorosa to finally reach El Carrizo Dam, with the resulting costs of electricity.
Water reuse as a strategy to enhance water efficiency
One of the biggest challenges for cities such as Tijuana, developing at a rapid pace
among all the cities settled along the border of Mexico and the United States, is to
ensure future drinking water supply by rational exploitation of its existing water sources
and reuse of treated wastewater for the benefit of its inhabitants.
The fast-paced urban growth in Tijuana and the lack of local fresh water sources has led
to the construction of works such as the Colorado River-Tijuana Aqueduct, which has
recently increased its capacity by 1.3 m3/s to conduct a total of 5.3 m3/s and the
Abelardo L. Rodriguez dam, whose original purpose was to store water for agricultural
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development in the area currently occupied by the urban sprawl of the city, and today is
used exclusively for drinking water.
One of the main strategies for sustainable water management in the region is
undoubtedly the reuse of treated wastewater in activities where their nature do not
require potable quality, that can reduce significantly the growth trends of first-use water
demand without jeopardising social and economic growth of cities or damaging the
environment and its capacity for regeneration, but on the contrary, the aim is, through
such actions as reuse, the environmental component to be an important factor in the
sustainable use of the resource.
With the construction of the treatment plants: “Arturo Herrera”, with capacity of 460 l/s
and “La Morita” of 254 l/s, the eastern area of Tijuana, it was planned to use part of the
treated wastewater for irrigation in urban green areas of the Tijuana River and Mesa de
Otay, and for the industry. Currently the most important reuse infrastructure to be built is
a line of 18 inches in diameter which starts in the “Arturo Herrera” plant and reaches in
the first stage the Morelos Park, which is expected to consume over 15 litres second.
There are also some small networks in private properties, such as the Country Club
Recreation Centre, with golf course; for irrigation of green area and a nursery in the
“San Antonio de los Buenos” treatment plant; 2 systems in Rosarito Beaches, one
network of 6.768 metres to irrigate 163.2 hectares of green areas on the toll road
Tijuana-Ensenada and another one through a pumping system that takes treated
wastewater to the Grand City Park, however, all these works use only a small amount of
treated wastewater generated in the city, the rest, which is a significant amount go out
the city to eventually reach the sea and therefore, are wasted.
Infiltration Technique for water reuse
In 2007 the State Public Service Commission of Tijuana (CESPT) hired the Mexican
Institute of Water Technology (IMTA) to carry out the geohydrological study of the area
between Rancho Santa Anita, Abelardo L. Rodriguez dam and Valle de las Palmas,
Baja California. IMTA considered that detailed studies should be conducted to
specifically evaluate the indirect reuse potable projects, including a number of necessary
studies such as geohydrological characteristics of the area and regional, sites
favourable for infiltration. The results of this study identified two areas located on the
stream of Valle de las Palmas in "El Dorado" Ranch.
In early 2011 the "Pilot Project on Infiltration with treated wastewater in the aquifer of
Valle de las Palmas in Tijuana, BC" was tendered by National Public Announcement,
and is currently under development.
The objective of the study is to naturally infiltrate 150 m3 of treated wastewater into the
subsoil and analyse its behaviour and reactions with the porous aquifer and when
combined with native water. For this purpose, a structure was built to capture the
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volume to be infiltrated and several observation and monitoring wells to observe the
variations in the static levels of wells and 82 samples will be taken for physic-chemical
characteristics of water.
In order to select the infiltration site, a geological survey was made in an area of
approximately 40 km2 around the sites selected by the IMTA, and with this information
the sites were defined to make 13 electromagnetic transients (EMT) surveys that
provided semi-detailed scale information on the aquifer, followed by a detailed 9 EMT,
with this we were able to determine the geometry of aquifer, thickness and resistivity of
the material and made 3-dimensional sections representing the aquifer and justified the
proposed site for the recharge.
Nine open pits were made at the selected site in order to examine the different materials
present and correlate them with that observed in geophysical surveys.
Location:
The site of artificial recharge of treated water is located in the municipality of Tijuana in
Baja California, in the Valle de las Palmas stream.
Design of infiltration structure and wells drilling
The infiltration system consists of an intake structure or pond of 5x5x1 metres, in which
150 m3 of treated wastewater will poured through pipes from the effluent of the “Arturo
Herrera” treatment plant and the filling will be in such a way that it will always have water
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and infiltration is continuous. The wells constructed around and downstream of the
infiltration structure are spaced strategically and with varying depths to keep record of
the groundwater aquifer at different levels to observe the mixing of treated water and
native water, several of these wells will be instrumented with precise measuring
equipment to define groundwater developments continuously.
During the project, a Design Reference manual on Artificial Recharge System will
develop, which will be useful since it will contain the necessary methodology techniques
and studies; from site selection to construction of an infiltration system and can be
applied elsewhere. It is noteworthy that the study described above is first of its kind, as
there have been no similar studies in the country, in addition to being in accordance with
the NOM-014-CNA-2003 guidelines, which establishes the requirements for artificial
recharge of aquifers with treated wastewater.
Expected results and benefits
The study is achieved through own resources and federal funds that are promoting
projects for water conservation and saving. It is expected that the results are favourable
and a greater refinement of treated wastewater is achieved.
The benefits are evident, in the current project small volumes are considered, but
subsurface infiltrations may be made with larger volumes of treated wastewater, being
able to be extracted downstream of the infiltration site and used as it is traditionally done
in green areas and industry or may be left to increase the volume of the aquifer to be
used as first-use water, with the advantage that would reduce discharges of treated
water to the sea, preventing pollution and thus benefiting the population in general.
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