Construction
of a Wastewater Collection System in Gadsden, Arizona;
General Criteria
Human Health and Environment
Technical Feasibility
Financial Feasibility
Community Participation
Sustainable Development
Environmental Assessment and FNSI
1. General Criteria
1.1
Project Type
The Gadsden
Improvement District is proposing the construction of a wastewater collection
system in the community of Gadsden, Arizona. The construction of the wastewater
collection system will address existing human health and environmental problems
caused by failing septic tanks associated to a high groundwater table.
The project is located within the community of Gadsden,
Arizona. Gadsden, an unincorporated area in Yuma County, is located between
Somerton and San Luis, Arizona (see Figure 1). The Town of Gadsden is located
approximately 5 miles north of the U.S.-Mexico border. The elevation of Gadsden is approximately
100 feet above mean sea level.
Figure 1
Location map of Gadsden, Arizona
U.S. Highway 95 is the main route through Gadsden.
Interstate 8 is located 14 miles north of Gadsden. The infrastructure will be located within the Gadsden Improvement
District boundaries and along Highway 95 right-of-way. The septic tanks are
located throughout the project area.
1.3 Project
Description and Work Tasks
There is no existing sewage
collection system within the townsite of Gadsden. The only waste disposal
facilities that exist are on-site disposal units. These consist primarily of
septic tank and leach field systems, although there are a few cesspools. There
are also some open discharges to ditches.
The on-site disposal units are
generally old and many are failing due to age and inadequate maintenance.
Replacement of the failing or failed systems is often not feasible due to a
restricted area and a seasonal high ground water table.
The project consists of
constructing a community-wide gravity sewer system, lift station and a force
main. Wastewater will be pumped approximately four miles to the City of San
Luis, Arizona for treatment. The project also contemplates the construction of
a lift station at Gadsden and a force main for receiving and transporting the
collected wastewater for treatment at the San Luis wastewater treatment plant.
The force main will be constructed along the right-of-way of Highway 95.
Collection
System
The sanitary sewer mains will consist of 8-inch diameter
Polyvinyl Chloride (PVC) pipe (SDR 35). The minimum slope used in the design is
0.5 percent, except at terminal end segments, where a minimum slope of 1
percent is used. The depth of the sewer mains will vary from 5 to approximately
25-feet.
Sewer manholes will be 4-foot diameter made out of concrete
in conformance with Yuma County Standard Number 5-030, and have a protective
liner in conformance with the City of San Luis Standards. Manholes will be
placed at intervals from 300-feet to a maximum of 500-feet in conformance with
Bulletin No. 11 of the Arizona Department of Environmental Quality. The depths
will vary from 6 to 26-feet deep.
House connection sewers will be
4-inch diameter PVC placed at a minimum slope of 1 percent. House connection
sewers, from the sewer main to existing building sewers, will be constructed as
part of the project. The connection sewers will be constructed at shallow
depths relative to the sewer main (3 to 10-feet) and where the main sewer is
excessively deep a vertical riser connection (chimney connection) will be
utilized to avoid an excessively sloped connection. Clean-outs will be provided
in the house connection sewer at bends and connection points with the existing
building sewer. Also, a clean-out will be provided at the street/property line
in conformance with City of San Luis Standards. Existing sewer disposal systems
will be abandoned by pumping out existing septic tanks, breaking up the bottom
of the tank, and then backfilling the tank. The average length of a house
connection sewer for Gadsden has been determined to be approximately 125 feet.
Construction of some of the house connection sewers will be expensive due to
the limited construction space between existing building structures in which
the pipe must run, and the presence of masonry walls, fences, driveways,
landscaping, etc, which must be removed and replaced.
Lift Station and Force main
A force main system consisting
of a single lift station and approximately 19,000-feet of 6-inch force main
will be used to convey collected sewage south to existing sewer facilities of
the City of San Luis. The lift station will be located centrally within Gadsden
and will be a duplex pump system housed in a 5-foot diameter underground basin
having a wet well capacity of approximately 765-gallons. The required discharge
capacity of the pumps is 205-gpm at a total dynamic head of 110-feet. Pumps
will be electrically operated and provided with a secondary power source. The
station will include appropriate lighting, AC power outlet, and fencing. Air
injection will be provided to control odor resulting from anaerobic breakdown
of sewage.
The 6-inch main will consist of
butt-fuse welded high-density polyethylene (HDPE) pipe (DR11). The force main
will be generally located along the side of Highway 95 in a trench having an
average depth of 5-feet. At least two air/vacuum release valves have been
determined necessary for the main. Flushing/clean-out stations, line plug
valves, and air injections systems are proposed at approximate intervals of 2,500-feet.
Each of these systems will be contained in a manhole, except for the air
injection pumps, which will be housed above ground on a pad in a secured
enclosure. The southerly terminal end of the force main will connect to a new
manhole near an existing 18-inch gravity sewer main near the intersection of
County 22nd Street and Highway 95.
The project will be performed
in two phases. Phase I includes construction of the sewer main along Highway
95. Phase II contemplates the construction of sewer laterals, the lift station
and force main to the City of San Luis. Phase I has been completed. The project
sponsor is seeking funding for Phase II of the project, due to a shortfall in
funding from USDA Rural Development.
The town of Gadsden, Arizona
consists of approximately 190 households arranged on a series of streets, both
paved and unpaved, in a predominantly agricultural area. The residences include
both permanent homes as well as a large number of mobile homes. An elementary
school and a few small businesses are also located in the planning area.
There are no records of past
population growth from which to project future growth. Population estimates
from the Yuma County Special Survey of 1996 are 737 residents. Average
occupancy is 4.79 persons per occupied dwelling. Projecting the average
occupancy to the existing 185 dwellings yields a full occupancy of 888 persons.
Four alternatives were
considered to address the septic tank problems in Gadsden: 1) no action; 2)
upgrade, repair, or replacement of existing disposal systems; 3) provide a
community-wide gravity sewer collection system and treatment; and, 4) provide a
community-wide gravity sewer collection system, lift station, and force main.
Alternative 1
The no-action alternative would
provide no new facilities for the community. The households would remain on the
present on-site septic systems and the associated problems would remain. This
alternative was not considered suitable, as it will not reduce the potential
for pollution of ground and surface water.
Alternative 2
This alternative consists of
identifying specific existing on-site systems that are experiencing some degree
of failure or that are incapable of handling the present wastewater loading.
Septic tanks or disposal fields would be replaced with new units that are
correctly designed and installed. Although this alternative may eliminate some
potential for surface water contamination and resulting health concerns from
direct contact, it would not be applicable to many of the smaller lots where
replacement options do not exist. It would also not reduce the potential for
pollution of the ground water.
Alternative 3
The third option considered a
community-wide sewer collection system and the construction of a clay lined
pond system.
Alternative 4
Under this alternative,
wastewater will be pumped approximately 4 miles to the City of San Luis,
Arizona for treatment. This alternative includes providing a complete sewerage
collection system to the entire Gadsden townsite. It also includes a new lift
station at Gadsden and a force main for receiving and transporting the
collected wastewater for treatment at the San Luis wastewater treatment plant.
Within this alternative, two
alternative routes were evaluated for the sewer force main to San Luis. One
route would follow the alignment of U.S. Highway 95 south from Gadsden to Yuma
County 22nd Street where it would connect to the gravity sewer line
from the new San Luis high school. The alternate routing would follow the
alignment of the West Main Canal from Gadsden to a new lift station at the San
Luis wastewater treatment plant. This routing was found to require
significantly higher capital and operating costs than the Highway 95 alignment.
The project site is located
entirely within the United States of America and will not have any affect on
surface water or groundwater in Mexico.
The project will not discharge any waters into Mexico. No international treaties or agreements will
affect this project.
2.1
Human Health and Environmental Need
The
project will significantly reduce the potential for contamination of the
groundwater in the area and eliminate human health hazards associated with a
high groundwater table and failing on-site systems, such as septic tanks, and
cesspools.
The proposed project includes
the construction of a wastewater collection system. An environmental assessment
has been prepared for the project and has been reviewed by EPA. A Finding of No
Significant Impact has been issued for the project and will be under public
comment period until December 1, 2002.
Environmental Laws and Regulations
The NEPA process has been
followed through the preparation of an Environmental Assessment. Consultation
with the Indian tribes, as required under Section 106 of the National Historic
Preservation Act has been followed. Also, consultation with the State Historic
Preservation Office has been completed.
3. Technical Feasibility
Construction
of the wastewater collection system will prevent further overflows of raw
wastewater caused by failing septic tanks in the area. Figure 2 shows the
proposed location of the sewer lines. The wastewater collection lines will be
installed using traditional open trench techniques. The depth of the lines will
vary from 5 to 25-feet deep. All lines will be installed in existing
rights-of-way.
One of the most important tasks
during development of a project is selection of appropriate technology. Selection of the alternatives took into
account the available human and technical resources of the community, as well
as the short and long-term economic impact on the residents. The selected technology is the most cost
effective and has an adequate level of complexity compared to the resources
available, and is flexible enough to adapt to changing conditions within the
community.
The proposed alternatives for
reducing the impacts to human health include the construction of a wastewater
treatment plant in the community of Gadsden, or install a wastewater collection
system and use the City of San Luiss wastewater treatment plant. A no project alternative was also
considered to analyze the effects of continuing operation of the on-site
systems.
The City of San Luis, Arizona
will be responsible for the operation and maintenance of the proposed
infrastructure. The City of San Luis follows their O&M manual for their
system. The same procedures will be followed for the Gadsden wastewater
collection system.
The City of San Luis has
adequate capacity and personnel for operating and maintaining the wastewater
collection system and lift station.
Final design for the project was prepared according to
standard design practices. ADEQ has issued a construction permit for the
wastewater collection system and lift station.
4. Financial Feasibility and Project
Management
4.1 Financial Feasibility
The
financial analysis of the project was performed based on the estimated total
cost of the project and already approved funding sources. The district
has signed a contract with the City of San Luis to pay $17.05 per month per
household for operation and maintenance of the sewer collection system and
treatment in the San Luis wastewater treatment plant. Additionally, a $41,832
assessment will be collected from 186 residences to guarantee payment of the
USDA RD $600,000 loan. This translates to $18.50 per household per month. The
district does not have any personnel, as all monthly fees are collected
directly by the City of San Luis. The estimated costs for the project are
presented in Table 2.
Table 2
Estimated capital costs
|
Proposed
Improvement
|
Estimated Capital Cost ($)
|
|
Phase I: Construction of
sewer lines along Highway 95
|
$958,678
|
|
Phase II: Construction of
sewer main and sewer lines and lift station
|
$4,384,952
|
|
Total
|
$5,343,630
|
One funding options was used to
formulate pro forma financial statements.
This option considers that the shortfall in funding of $1,452,952 will
be paid with a loan. In formulating
the pro-forma financial statements, a 25-year loan period with a 4.5% annual
interest rate compounded annually was assumed.
A 3% annual inflation rate was added to the districts expenditures and
a 1.9% annual growth rate was used to formulate the revenue projections. Since the district does not provide any
service to-date, financial projections begin in the year 2003. In order to
cover debt-service on the $1,452,952 loan, the district would have to make
additional yearly payments of approximately $86,000. This translates to an
additional assessment of $462 per household per year, or an additional $38.50 per
month in addition to the $35.50 monthly fee. The $33.50 paid monthly represents
2.7 per cent of the median household income. Increasing the rate to $74 per
month to cover the additional debt service for the $1,452,952 loan brings the
fee to 5.7 per cent of the median household income.
Data from the private water
company that serves the Gadsden area was requested and was not provided. The
average water bill is approximately $18 per household per month. The financial
model did not include any capital improvements to the water system since the
water company did not make this information available.
Financial
Structure of the project
|
Source
|
Amount (US$)
|
%
|
|
NADB
BEIF-Construction Assistance
|
1,452,952
|
27
|
|
NADB BEIF-Transition
Assistance
|
72,640
|
|
|
USDA Rural
Development (loan)
|
600,000
|
11
|
|
USDA Rural
Development (grant)
|
2,489,240
|
47
|
|
CDBG (grant)
|
801,438
|
15
|
|
Total
|
$5,343,630
|
100%
|
The sewer rates have been
established at $17.05 per household per month. The rates will be paid directly
to the City of San Luis, the operating agency responsible for collection,
treatment, operation and maintenance of the wastewater infrastructure. In
addition to the $17.05 per month, a $222 annual assessment will be charged to
each connection, adding $18.50 per household and bringing the total monthly fee
to $35.55. A total of $72,640 in transition assistance will be applied during
the first seven years to subsidize the user rates. The following table presents
the proposed user fees for the water and wastewater systems.
Table 4 Water and Sewer rates for Gadsden, Arizona
|
Year
|
Average Water Monthly
|
Average Wastewater Monthly
|
Combined Water and Wastewater
|
|
2003
|
18.30
|
22.01
|
40.31
|
|
2004
|
18.30
|
25.86
|
44.16
|
|
2005
|
18.30
|
28.45
|
46.75
|
|
2006
|
18.30
|
31.29
|
49.59
|
|
2007
|
18.30
|
34.42
|
52.72
|
|
2008
|
18.30
|
37.86
|
56.16
|
|
2009
|
18.30
|
41.65
|
59.95
|
The wastewater fee will increase gradually over the years
until it reaches a total of $41.65 per month. Once the water rates are factored
in, the water and wastewater fees will be $59.95 in the year 2009. This amount
includes the assessment fee paid to service the $600,000 USDA Rural Development
loan.
The City of San Luis
will manage the project and it has adequate management capacity and staff to
operate and maintain the proposed improvements to the collection system.
5. Community
Participation
Comprehensive
Public Participation Plan: The Yuma County Department
of Development Services and the Gadsden Community Development Group submitted
the project public participation plan in June 20 and approved on June 21,
2002. The County and Group had been
carrying out public outreach for some time and the public participation plan
submitted for approval was incorporated into the existing process.
Steering Committee: The Gadsden Community
Development Group was formed in 1995 as a nonprofit to encourage Gadsden
citizen participation in the development of a Gadsden Community Development
Plan that was considering issues such as land use and public facilities and
services. The Gadsden Community Development Group became the steering committee
for this project since it had been instrumental in circulating information
regarding various community projects and in particular in helping to obtain
public input and support for the sewer project in the town for several years.
The Group was lead by life long resident Louie
Gradias, President; and included Margarita Meraz, as secretary; Blanca Mendoza
and Norma Garcia, of the Gadsden School District; Nena Garcia, Maria Frausto,
Federico Flores, Alfonzo Dominguez, and Flavia Miranda, all of them local
residents of Gadsden; and Robert Frazier, a former school principal.
Steering Committee
The committee had
the support Yuma County staff Nancy Ngai, Community Planner, Yolanda Galindo,
Grants Administrator, and Rachel Stallworth, District Specialist; as well as
the Districts legal counsel and the consulting engineer.
Local Organizations: Throughout the life of the
project the Gadsden Community Development Group and Yuma County staff had
ongoing contact with residents and local organizations and businesses to
disseminate project information and solicit their support. Some of these are
the Gadsden Elementary School; Sams Convenience Store; Ramirez Used
Agricultural Equipment, Kingdom Hall Jehovah Witness; and the postmaster at
their local post office. All showed
support for this project. A Letter of
Support was received from the Gadsden Elementary School.
Public Information: The Preliminary Engineering Report, Environmental Assessment
Report, and the draft Project Certification Document for the project were
available at the Office of Yuma County Development Services. A fast sheet was developed, distributed to
local residents, and available at the public meetings. Public meeting notices that were published
in the Yuma Sun and Bajo el Sol newspapers and also posted at the County
Administration Building. Television
coverage was provided through the Yuma County Government Channel 77. All notices were provided in both English
and Spanish.
Public
Meetings:
Three public meetings were held in 2002.
The first meeting took place on July 10 with over 50 people in
attendance. The second public meeting
was held on July 31 and over 55 people attended. The third public meeting was held on October 22 with about 70
people present. Exit surveys indicate
that of 160 surveys collected at all three meetings, no one opposed the project
or the rate.
|
|
|
|
|
July 10th
2002, Public Meeting
|
|
October 22nd 2002,
Public Meeting
|
6. Sustainable Development
The project
was developed within the context of sustainable development. Sustainable development integrates
environmental, social and economic needs of a community through the protection
of natural resources and its sustainable use.
The
project followed the definition principles of sustainable development:
Principle
1 of the Sustainable Development Criteria indicates that a project must produce
a benefit for human health. The project fulfills this principle as
detailed below.
·
The project will improve the human health conditions in
the area by providing a wastewater collection system and reduce overflows of
raw wastewater attributed to failing septic tanks.
Principle 2 states that a project must be implemented in a
way that provides equitable development both in present and in future. The
project fulfills the principle as discussed below.
·
The project was selected by evaluating and selecting
the most cost-effective alternative.
The wastewater treatment plant in San Luis, Arizona will be used to
treat the flows generated in Gadsden, thus making use of economies of
scale.
·
As mentioned, the proposed collection system will
protect human health in the area of Gadsden.
Principle 3 indicates that a project must have an
integrated component of environmental protection. The project contemplates the
following.
·
The prevention of raw wastewater overflows and
infiltration into the local aquifer.
Principle 4 states that residents must participate in the
development and implementation of the project.
·
A public participation plan was prepared and
implemented as part of the project. A
wastewater improvement district was created to address the environmental
problems associated with failing septic systems.
·
The district has signed a contract with the City of San
Luis, Arizona for the operation and maintenance of the system, as well as
treatment of the collected wastewater in Gadsden.
Institutional and Human Capacity Building
The sewer system will be operated and maintained by the
City of San Luis, Arizona, as required to serve the community of Gadsden.
Conformance with Applicable Local and Regional
Conservation and Development Plans
The construction of the system is consistent with the Yuma
County 208 Wastewater Plan.
Natural Resources Conservation
The proposed project reduces the percolation of raw
wastewater from overflows attributed to failing septic tanks into the local
aquifer.
Community Development
Community development receives a positive impact by this project
because once better fundamental services exist; the number of people who will
want to live in this community will increase, and will reduce human health
impacts to the community.