Border Environment Cooperation Commission
Wastewater
treatment facility replacement and sewer collection system improvements for the
town of Patagonia, AZ.
December
13, 1999
Financial Feasibility and Project Management
1. Type of Project. The project consists
of the rehabilitation and expansion of the sanitary sewer system and the
improvements to the sewage treatment system.
2. Location of Project. The Town of
Patagonia is a small community located in Santa Cruz County, Arizona, about 80
miles south of Tucson and 20 miles northeast from Nogales, Arizona. According
to the Arizona Department of Economic Security, Patagonia has a population of
968 people, and is expected to increase to 1033 by the year 2020.
3. Description of Project and Tasks. The
project consists of improvements to the wastewater treatment plant, which
include replacement of the existing treatment unit with a new treatment process
encompassing secondary and advanced treatments. In addition, a preliminary
treatment and an enhanced effluent disinfecting process will be added.
Rehabilitation of deteriorated sewer sections of the existing sewage collection
system is also part of this project. This project will address the needs of the
Town of Patagonia for the next 20 years.
The new process will allow the plant to
meet its Aquifer Protection Plan and NPDES Permits requirements. The proposed
treatment is intended to achieve the required reduction of polluting substances
in the discharged effluent to within allowable limits as setforth by the
permits. The target concentration for the effluent relative to BOD and TSS is
30 mg/l. The design average daily flow of the plant is 0.11 MGD (Expected peak
hourly flow of 0.44 MGD). During intense rainstorm events, wastewater flow
rates at the plant increased beyond the plant capacity due to excess water
volumes introduced into the collection system by infiltration and inflow. The
resulting flow rates during these events allowed the discharge of solids and
pollutants with the effluent. In addition, the excessive volumes of incoming
wastewater bypassed treatment and were diverted into the existing lagoons.
These lagoons were part of the former treatment system. Since the lagoons are
not lined, there is a concern that the bypassed wastewater in the lagoons could
percolate to the bottom of the lagoons and pollute the aquifer.
4. Compliance with International Treaties
and Agreements. The project does not affect any international treaties between
the United States and Mexico.
II. Human Health and the
Environment
Human Health/Environmental Needs. Based on
data available from the Arizona Department of Economic Security (DES), the
current population of the Town of Patagonia is 968. In the past 20 years, the
Town of Patagonia has experienced little or no growth due in part to the lack
of proper infrastructure services. The low rate of growth and periodic
decreases in growth have made communities such as the Town of Patagonia face
difficult challenges in maintaining the quality of life for its residents.
Based on the trends of the area's growth, the DES has projected the town's
population to be 1033 in the year 2020. The proposed treatment improvements
will provide wastewater treatment for the projected growth, which otherwise
could not be provided by the existing facilities. Overall, seasonal rainfall,
relatively shallow groundwater levels, and ephemeral stream flows characterize
the hydrology of the project study area. Sonoita Creek, a tributary of the
Santa Cruz River Basin, generally flows through the Town of Patagonia from
southeast to northwest and mostly borders the town on the north. Several
tributaries, which collect surface water from the surrounding mountains,
converge with the creek within the town limits.
The new wastewater treatment plant will be
able to achieve total nitrogen removal as required by the APP and the NPDES
allowable limits.
Environmental Assessment. The project
incorporates improvements that will not affect undisturbed areas, since the
proposed wastewater treatment plant will be constructed in the tract of land
that has been occupied by the existing treatment unit for the past 30 years.
Additionally, the sewer system improvements contemplate only rehabilitation of
the existing sanitary sewage collection lines. The effluent will continue to
being discharged into the Sonoita Creek. However, the quality of the effluent
will be of higher quality and will comply with the APP and NPDES permit
requirements. The EPA ordered the preparation of the Environmental Information
Document. The US-EPA Region 9 reviewing the document and prepared an
environmental assessment (EA) that was issued on November 3, 1999, followed by
a Finding of No Significant Impact (FoNSI), dated November 22, 1999. The EA is
currently under a public comment period of 30 days. It is necessary to have the
FoNSI to enable the EPA to approve the financial scheme relative to the Border
Environment Infrastructure Fund (BEIF) that is being proposed by the North
American Development Bank (NADB).
1. Appropriate Technology. As part of the
wastewater treatment facilities plan for the Town of Patagonia, completed in
May 1999, and prepared under the supervision of the BECC, six wastewater
treatment alternatives were evaluated. The alternatives were developed and
evaluated using a 20-year planning horizon. Additionally, there are sewer
sections that will be rehabilitated based on inspections conducted during the
preparation of the facilities plan.
Wastewater Treatment In accordance with
chemical analysis conducted on the effluent from January 1994 to December 1997,
it was determined that the WWTP effluent was not meeting its NPDES effluent
requirements for the following parameters:
a) BOD5
b) Suspended solids
c) Total phosphates
d) Coliform
e) Total residual chlorine
Thus, EPA issued a Finding of Violation
and an Order of Compliance on February 3, 1998. The NPDES permit for
Patagonia's WWTP stipulates BOD and TSS concentrations of 30 mg/l for both
parameters (monthly average). The effluent from the above period ranged from 39
mg/l to 153 mg/l (monthly average) for BOD, and from 35 mg/l to 132 mg/l
(monthly average) for TSS. The alternative evaluation process considered an
inflow with a BOD of 200 mg/l. For the WWTP the following alternatives were
evaluated.
· Sequence Batch Reactor (SBR)
· Phase Isolation Ditch (PID)
· Oxidation Ditch, Single Channel
· Countercurrent Extended Aeration
· Retrofitting Existing Modular Unit
· Constructed Wetlands
The alternative selected was the Oxidation
Ditch, Single Channel, due to its ability to achieve consistently high levels
of BOD removal and TSS removal with minimum operation, high levels of
nitrification and denitrification with proper operation, easy O&M, ability
to handle variations of flow, and long sludge retention time. The plant will
have an average daily flow capacity of 0.11 MGD, and a maximum daily flow capacity
of 0.14 MGD.
Sewer System
The sewer system of Patagonia was
constructed in 1965 under the town's "Sewer Improvements District
One" project. The sewage collection system consists of 19,000 feet of 6,
8, and 10-inch gravity sanitary sewer pipes. The proposed improvements include
the rehabilitation and replacement of about 5,800 linear feet of
asbestos-cement sewer, with open trench replacement or in-situ repair.
O&M Plan As part of the facility
improvements, the town's operation and maintenance manual will be updated and
expanded to include the new additions and to include the required management
procedures for operating the facilities. The manufacturers will train the plant
operators during the start up phase and after the completion of the
construction and installation activities.
2. Compliance with applicable design norms
and regulations. Arizona Department of Environmental Quality (ADEQ), Rural
Development, and EPA have validated the requirements for construction of the
sewer system and the wastewater treatment facilities. The effluent from the
proposed WWTP will meet the National Pollutant Discharge Elimination System
(NPDES) and Aquifer Protection Plan (APP) permit requirements.
IV. Financial Feasibility
and Project Management
1. Financial Feasibility
The NADB has conducted a preliminary
analysis of the project information presented by the project proponent and
consultant, to determine the project's financial feasibility. Based on this
analysis, the amounts for loan and grant components were determined, as well as
the impact the project would have on the user rates. The results of the
analysis were presented in a public meeting held on October 13, 1999.
The table below summarizes the project
construction costs, as identified by the project the components in May 1999.
Estimated Cost
Wastewater Treatment Plant: $763,000.00
Sewer System Improvements: $495,000.00
Engineering/Administrative: $300,000.00
TOTAL: $1,558,000.00
Based on the analysis developed by the
project consultant, the NADB determined the amount of grant funds and loan
components. It will be necessary to follow the procedure requirements by each
one of the agencies participating in the development of this project.
Financial Structure Recommended by the
NADB
USDA-Rural $481,382.00 Grant
NADB-BEIF $776,585.00 Grant
WIFA $300,033.00 Credit
TOTAL $1,558,000.00
2. Rate model: The rate model has been
developed by NADB's project consultant, and was used to determine the impact
the project would have on the user rates. The rate model developed by the
consultant has been reviewed by the NADB. The proposed sewer rate structure
suggest that the current sewer base service fee of $20.50 be increased $0.90 annually
through the year 2008 to reach $27.70/month, and modified thereon be adjusted
for inflation or other costs increases (e.g., O&M).
3. Project Management The project will be
managed by staff of the Town of Patagonia that has operated the public utility
section for several years. The Town of Patagonia is the agency that will adopt
the rate adjustments. The town will continue to operate in a self-sufficient
manner, supporting itself through charges imposed on the users.
Comprehensive
Public Participation Plan. The
Patagonia steering committee submitted a Public Participation Plan (Plan) in
early September 1999. The Plan includes the development of a steering
committee, meeting with local stakeholder organizations, conducting public
outreach to inform residents of the project, hold two public meetings and
submitting a final report documenting public support for the project.
Steering Committee: A steering committee was formed in
the early phases of the project in early 1998. Committee members are John
Spitler, chairman, Randy Heiss, Gilbert Quiroga, Robert Woods, Susan
Wethington, Robin Baxter and Dick Volz.
The town representative is Keith Weidemann and the technical advisor is
Daniel Kale. Committee representatives attended city council meetings on the
project and disseminated information to the community. In addition, they provided input into the selection of the
wastewater alternative, and
conveyed the concerns and interests of the community in the development of the
facilities planning phase. The committee also developed the Plan and the
Outreach & Information strategies.
Local Organizations: Local organizations contacted to
present the project and solicit their support were 4H Club, Patagonia Community Association, Patagonia Community Foundation,
Arizona
Center for Law in the Public Interest, Veterans of
Foreign Wars, Rotary Club, Nature Conservancy. Letters of support for
the project were received from the Patagonia Community Association, Patagonia
Regional Community Foundation, Arizona Center for Law in the Public Interest
and the Nature Conservancy.
Public Information: Project information has been made
available to the public 30 days prior to the first required public meeting at
the Patagonia Town Hall and public library during business hours, and the
Marshalls office after work hours. The Weekly Bulletin of Sonoita published an
article the 6th of October on the project, which included statements
from the steering committee chairman, and ran another article on the project on
October 20th. Further outreach activities included providing through
the mail a project fact sheet and cover letter from the steering committee to
the public prior to the last public meeting.
Public Meetings: An initial public meeting was held on
January 21, 1998 to introduce the project to the city council and the public.
Two more public meetings were scheduled on October 8 and October 13, 1999 per
BECC requirements.
At the first public meeting approximately
15 people were in attendance. The
steering committee chairman, Town Mayor and several Town Council members were
present. The engineering consultant was there to make presentation of project. After the presentation, during the question
and comment period, the public asked about sludge requirements meeting B grade
level, and the fact that there is not much sludge volume or about 5 yards per
month. The engineer consultant added that project will add a new digestive
system that will reduce sludge. Disinfection was another issue and the pros and
cons of ultra violet disinfection vs. chlorination were discussed. The engineer
mentioned that it ultra violet disinfection is not feasible due to the lack of
a laboratory in town that would give information about discharge infection in
the creek and violation of pollution regulations. Chlorination, it was added,
was more reliable as it gives real time results, is very good and its cost is
equal to ultra violet disinfection. The
issue of flood cycles of whether the technology of the plant considered the
flood flow cycle was confirmed by assuring the community that whatever is to be
built will meet the 100-year flood cycle. The consultant added that the
existing plant does not meet 100-year flood cycle to the question of the potential
of the treatment plant flooding away in a flood. The steering committee chairman added that the project hopes to
make the plant according to the 100-flood cycle but cant know if it will be
safe from flooding. At the end of the
meeting Mayor Chipmann announced the date of the next public meetings to be on
October 13 and 27.
At
the second public meeting that was held on October 13, the financial rate
structure was presented. The NADB consultant for CH2Mhilll stated that the rate
study was based on a $315,000 loan that represents about 25% of the total cost
of the improvements to the wastewater system.
The total cost of the project is estimated to be $1.2 million. The NADB and USDA-RD would provide about 76%
of grant funding while the Water Infrastructure Finance Authority would provide
24% in loans to cover the total cost of the project. NADB would provide transitional funds to cover a $0.90 rate
increase on residential sewer rates for over 6 years. There was discussion on the commercial rates and the
acknowledgement that the rates were low and needed to increase.
The Town Council held a
meeting on October 27, five days before the bond election to authorize the
debt, for further discussion on the project, the debt component and rate
increase and to request public support for the project. On November 2 the bond election was held and
approved by 134 to 12.
1. Definition and Principles. The project
complies with BECC's 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.
With the implementation of this project,
all the environmental parameters (and respective limits and standards) will
have been met and the improved treated effluent will continue replenishing the
Sonoita Creek, maintaining the existing local ecosystem. The principles of
sustainable development are satisfied, which include:
Human beings are the central point of all
concerns for sustainable development; they are entitled to a healthy and
productive life in harmony with nature. This Principal fulfilled by the
project's objective, which is to solve human health problems by improving the
quality of the treated effluent, and decreasing pollution of the environment
and health risks to the population, through sewerage improvements and treatment
of wastewater.
2. Institutional and Human Capacity
Building. The investment of almost $1.6 million dollars in improvements to the
wastewater infrastructure for the Town of Patagonia will have a deep impact on
both the local government and economy, as well as to the community residents.
The improved capacity for wastewater treatment will allow the city to receive
new business, because the city will have the capacity to absorb the increase
that will result from the wastewater treatment demand.
The new wastewater treatment plant will
enable the Town to allocate resources for strengthening their institutional
capacity, by eliminating the potential burden relative to fines imposed for
violating their NPDES and APP permits.
3. Conformance with Applicable
Local/Regional Conservation and Development Plans. ADEQ has validated the
project to improve the sewerage and sanitation system for the Town of
Patagonia. It is consistent with the regional guidelines of the State of Arizona
(Bulletin 11), to plan for providing services of sewerage and sanitation. The
construction of the wastewater treatment plant will comply with EPA
regulations.
4. Natural Resource Conservation. The
construction of the new WWTP and the sewer system improvements will reduce the
load of contaminants that are discharged into the Sonoita Creek and will reduce
the potential aquifer contamination. Furthermore, the improved effluent will
promote proper development of some native and indigenous species, which are currently
listed as endangered species (e.g., Gila Top minnow and willow flycatcher).
Community Development
The construction of approximately $1.6
million dollars in infrastructure will be the foundation for the future growth
of the community. Without an adequate infrastructure, the city could not
accommodate the development of new businesses or the current population growth,
and would be subject to legal action from the U.S. Federal government for
violating NPDES requirements. The positive impacts related to the project are
short as well as long term.