Wastewater Collection and Treatment System
for the Community of Palo Verde, California
May 15, 2015
U.S. Environmental Protection Agency | Region 9
75 Hawthorne Street
San Francisco, CA 94105
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1.0 INTRODUCTION
The United States Environmental Protection Agency (EPA) administers the Border Environment
Infrastructure Fund (BEIF), which provides grant funding for water and wastewater infrastructure
projects located within 62 miles (mi) (100 kilometers [km]) of the international boundary between
the United States (U.S.) and Mexico.
EPA policy for use of BEIF funds requires planning and design and certification of projects by the
joint Border Environment Cooperation Commission (BECC)-North American Development Bank
(NADB) Board as a condition for receiving a BEIF award for construction. The EPA requires that
a proposed project comply with the National Environmental Policy Act (NEPA) before BEIF funds
can be authorized.
In accordance with the U.S. Council of Environmental Quality (CEQ) regulations, 40 CFR Parts
1500-1508, and EPA regulations (40 CFR Part 6) as guidance, this Environmental Assessment (EA)
documents the environmental consequences in the U.S. of the proposed federal action. The purpose
of this document is to comply with NEPA documentation requirements for the proposed federal
action under consideration, which consists of the Environmental Information Document for the Palo
Verde Wastewater Collection and Treatment System, Palo Verde, California. This EA incorporates
by reference the October 2012 Environmental Information Document for Palo Verde Wastewater
Collection and Treatment System Project.
1.1 STUDY LOCATION
The community of Palo Verde is located in the far northeastern corner of Imperial County, with
Riverside County abutting the community to the north (Figure 1-1). Palo Verde is approximately
50 miles north of the US-Mexico international border, 6 miles west of the Colorado River, and 13
miles south of Interstate 10 (1-10). State Highway 78 (Ben Hulse Highway) runs north and south
through the community and is the main highway in Palo Verde (Figure 1-2). The Palo Verde
Lagoon and Outfall Drain are in the Palo Verde Valley, and the community of Palo Verde is
centered on these water features. The valley is bound on the north by the Big Marina Mountains,
on the west by Palo Verde Mesa, and on the south and east by the Colorado River.
1.2 PURPOSE AND NEED
The proposed project would provide increased health, sanitation, and security to residents within
Palo Verde. The proposed wastewater collection and treatment system would use an aerated
facultative pond with percolation/evaporation basins, and would eliminate wastewater overflows
and leaks through the abandonment of existing failed and nonconforming septic systems in the
area. The project would also address issues of non-compliance through the elimination of septic
systems located within 50 to 100 feet of the Palo Verde Lagoon and Outfall Drain, which is
designated as a setback area. The proposed wastewater system would protect groundwater and
the Palo Verde Lagoon, thereby improving water quality and providing potential health benefits
by reducing the elevated levels of E.coli and other fecal coliform bacteria.
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1.3 SCOPE OF ANALYSIS
The scope of this EA includes the evaluation of the impact to the relevant environmental resources
within the defined area of concern in the U.S. As defined in the CEQ regulations (§1508.25), the
scope consists of the range of actions, alternatives, and impacts to be considered in a NEPA-
compliant document.
Figure 1 Location Map
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2
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Figure 1-2 Community Map
LEGEND
| I Sorvieo Area Boundary
PALO VERDE
3
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2.0
PROJECT DESCRIPTION AND ALTERNATIVES
The proposed action would include the installation of a new gravity and pressure wastewater
collection system in the project area that would provide service to 222 parcels (164 parcels are
currently occupied and 58 are vacant) and a project population equivalence of 328 persons.
Additionally, the project would involve the installation of a new wastewater treatment plant
(WWTP) to provide centralized treatment for wastewater generated and collected in Palo Verde.
The WWTP would serve the same area and population as the newly installed wastewater collection
system.
Initially, five alternatives were considered, but three alternatives were eliminated due to cost or
environmental constraints. This EA examines two alternatives: Alternative 1 (the Preferred
Alternative) - installation of a new wastewater collection system and aerated facultative pond
WWTP (WWTP) in the northeast portion of Palo Verde that discharges into
percolation/evaporation basins; and the No Action Alternative - under which the Proposed Action
would not be implemented.
2.1 PROPOSED ACTION
The proposed action, the Preferred Alternative (Alternative 1), consists of the construction of two
components in Palo Verde: a residential wastewater collection system and a WWTP.
Collection System
The collection system would include the installation of 8-inch diameter gravity sewer lines, 4-inch
diameter service laterals, manholes, one pump station and an associated force main to convey
wastewater to the WWTP site. Construction would be completed by open trench technologies.
A pump station and force main would be constructed to convey wastewater across the Palo Verde
Lagoon at Fourth Street. The 4-inch-diameter PVC force main that would span the bridge would
be installed inside an 8inch-diameter steel casing pipe. The annular space between the force main
and casing pipe would be grouted and a leak detection apparatus would be installed inside the
casing pipe to provide notification if a leak does occur in the force main. The force main would
be attached to the bridge deck to cross the Palo Verde Lagoon as the preferred engineering method
due to operational advantages and financial considerations. Under this option, the casing and force
main pipes would be installed on top of the bridge deck, which would increase the weight load on
the bridge by approximately 35 pounds per foot, for a total weight of 4,130 pounds. This option
would require a structural assessment of the bridge in order to determine if it could support the
additional weight added by the casing and force main pipes.
Alternately, if the bridge were determined to not be adequate to support the additional force main
weight, the force main could be placed approximately 30 to 40 feet below ground surface and/or
approximately 10 feet below the lagoon bottom via directional drilling under the lagoon. This
depth is required to provide a safe distance between the top of the force main and the bottom of
the lagoon including the scour depth of the lagoon.
Solar power would be installed on pumps, aerators and other mechanical equipment to the extent
feasible. Pipeline construction would entail trenching, pipe laying, soil stockpiling, covering pipes
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with stockpiled soil, and operation of equipment to construct infrastructure to serve 222 parcels.
Additionally, power lines cross the project area, which would require coordination between
Southern California Edison (SCE), Imperial County, and the Palo Verde Irrigation District (PVID)
prior to pipeline construction including obtaining all necessary permits. The wastewater collection
system would route flows to the proposed WWTP located on the northeast (island) side of Palo
Verde.
Table 2-1. Pipes Required to Provide
Wastewater Collection under Alternative 1 (Pond WWTP and Collection System)
Pipe Type
Pipe Purpose
Pipe Diameter
(inches [in],
centimeters |cm|)
Amount needed for
Construction (feet |ft|,
meters |m|)
Depth of Pipe
PVC SDR-35 pipe
Gravity Sewer Pipe
8 in or 20.32 cm
13,396 ft or 4,083 m
5.0-20.0 ft or
1.5-6.1 m
PVC SDR-35 pipe
Sewer Service Line
4 in or 10.16 cm
17,098 ft or 5,212 m
4.0- 8.0 ft or
1.21-2.43 m
PVC C-900 pipe
Sewer Force Main
4 in or 10.16 cm
510 ft or 155 m
0.0-5.0 ft or
0.0-1.5 m
Under the Preferred Alternative, most wastewater pipelines would be installed within or on the
sides of roads as other underground utilities permit. Excavation trenches for the 4-inch diameter
sewer service lines would range from 4.0 to 8.0 feet (1.21 to 2.43 meters [m]) in depth and 3.0 to
6.0 feet (0.91 to 1.83 m) in width. Trenches for the 8-inch-diameter gravity sewer pipe would
range from 5.0 to 12.0 feet (1.5 to 3.66 m) in depth and 6.0 to 13.0 feet (1.83 to 3.96 m) in width.
The embedment would be a minimum of 1.0 to 3.0 feet (0.30 to 0.91 m) in depth for all wastewater
installations. Asphalt or other paved surfaces would be replaced where cut, as required by Imperial
County Public Works Department. Additionally, implementation of this alternative would entail
the abandonment of existing septic systems and yard restoration. See Table 2-1 for more
information regarding pipes required to provide wastewater collection.
WWTP System
To treat the collected wastewater, a WWTP would be constructed under the Preferred Alternative
and would consist of an aerated facultative pond with percolation/evaporation basins, screens, grit
removal, flow measurement, influent pump station and an ultraviolet (UV) disinfection system.
The WWTP would be designed to accommodate full build out of Palo Verde with an average daily
flow (ADF) of 57,300 gallons per day (gpd) and a peak hourly flow of 225,934 gpd. The pond
would be a four-cell arrangement with two aerated cells. Each cell would be approximately 190
feet long by 50 feet wide and a total depth of 13 feet. Additionally, two percolation basins,
approximately 135 feet long by 100 feet wide by 6 feet deep, would also be needed. Due to the
shallow groundwater depth in the project area, 8,000 cubic yards of fill material and berm
construction would be required to elevate the WWTP facilities, ponds, and percolation/evaporation
ponds. Potable water of adequate quality and capacity would be available and rehabilitation of
existing infrastructure would not be required.
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The aerators used for the WWTP would include a floating type aerator. The pontoon mounted
aerator would include solar panels to help limit dependence on grid power and reduce operation
and maintenance costs. Additional electrical supply and controls would include a crossover
connection should future potential solar photovoltaic (PV) renewable energy power supplies
become available. In addition, the Preferred Alternative would incorporate green building
practices, to the extent feasible, to be developed in coordination with BECC, NADB and EPA.
The WWTP is proposed to be located on Assessor Parcel Number (APN) 006-220-056 in the
northeastern portion of Palo Verde. The parcel is zoned for residential development (R-l) and has
a land use designation for agriculture. In order to comply with the Imperial County General Plan
and zoning ordinances, the proposed project would require legislative amendments including a
General Plan Amendment and a rezone of the subject parcel to Government/Special Public (G-
S). In addition, the project would require either minor subdivision or a Parcel Map Waiver from
Imperial County. Resolution of land use and zoning consistency issues would be required prior to
construction. Draft applications for land use and zoning modification and supporting
documentation have been prepared and can be submitted at such time as the PVCWD is granted
the authority to provide wastewater service. Project implementation would take place over
approximately 12 months.
2.2 NO ACTION ALTERNATIVE
This alternative includes leaving the community of Palo Verde on existing septic systems, although
community outreach on proper use and maintenance of septic systems would be provided. No
wastewater collection system or WWTP would be installed under this option. The community
would continue to use failing septic systems and experience related water quality degradation in
the Palo Verde Lagoon. The community would continue to face a moratorium on making repairs
or improvements to homes due to the nonconforming septic systems and no County permits would
be issued for building or septic system repairs. In the absence of a wastewater collection and
treatment system, individual residences would need above ground septic systems or the land might
be condemned. No commercial property development would be allowed. The population of Palo
Verde would likely decline.
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3.0 AFFECTED ENVIRONMENT
The purpose of this section is to describe the environmental resources that could potentially be
impacted by the project alternatives described in Section 2.0. The descriptions of the affected
environment focus on environmental resources located within the proposed project area and
adjacent areas.
The climate in the region is continental desert, of extreme aridity, and is characterized by hot
summers and moderate winters. The annual average maximum temperature is 88 degrees
Fahrenheit (°F) (31°C) and the average minimum temperature is 55°F (13°C). Annual
precipitation in the area is approximately 4 inches, with the majority of rainfall events occurring
during fall and winter months. Precipitation is generally severely limited, though rainfall can be
highly variable with precipitation from a single heavy storm one year exceeding the entire annual
total during a following drought year. Most natural vegetation in the Palo Verde Valley has been
replaced by agricultural production and limited areas of light mixed development. However, large
areas of undeveloped Sonora Desert surrounding the Palo Verde Valley and the nearby Cibola
National Wildlife Refuge (NWR) provide valuable habitat to a variety of wildlife species.
According to the US Geological Survey, the elevation in the project area is generally between 232
and 233 feet above sea level. The project area drops significantly (10 to 20 feet) at the banks of
the lagoon. The decline across the project area is approximately 0.02 percent.
3.1 LAND USE
The Community of Palo Verde - which has a current population of approximately 171- is located
in the US-Mexico border region, approximately 50 miles north of the international boundary. Land
use in the Palo Verde Valley is characterized as agricultural and residential uses (Figure 3-1). The
population of the Community of Palo Verde has generally declined and has undergone little
development during the past 20 years.
The Community of Palo Verde consists of mostly residential housing and includes two recreational
vehicle (RV) parks. Palo Verde also contains a small commercial center, fire station, post office,
community hall, church, and sheriffs substation. Palo Verde County Water District (PVCWD)
owns and operates an existing water filtration plant and potable water supply system. Households
in the community currently rely on septic systems for their wastewater disposal needs and many
of these systems are failing. Additionally, many of the septic systems are nonconforming and do
not meet the Palo Verde and Imperial County required setback distances of 50 to 100 feet from the
adjacent Palo Verde Lagoon.
There are seven different zoning classifications in Palo Verde: low-density residential (Rl),
medium-density residential (R3), high-density residential (R4), commercial (C2), agricultural
(A2), government/special public (GS) and recreation (SI). Table 3-1 illustrates the Palo Verde
land classifications.
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Figure 3-1 Land Use Density
first street
SECOND STREET
THIRD STREET
FOURTH STREET
CLARK WAY
SECOND
|ST_-^
PALO VERDE
DESERT VIEW STREET
LEGEND
Low-Density Residential
Residential
Medium-Density Residential
High-Density Residential
Neighborhood Commercial
General Commercial
Government/Special Public
Recreational
Medium Agriculture
Source: Imperial County General Plan 1998.
RIVERSIDE-IMPERIAL COUNTY LINE
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Table 3-1. Palo Verde Land Classification Information
Znninii (l;issiric;ilion
Idcnlirior
No. of l.ols
No. \ iiCiinl
l.iind AiVii
(Acivs)
147
Low-Density Residential
R1
158
27
Medium-Density Residential
R3
1
0
3
High-Density Residential
R4
3
1
3
Commercial
C2
34
16
12
Agricultural
A2
7
5
570
Government/Special Public
GS
10
6
2
Recreation
SI
9
3
9
Total
222
58
747
Source: Imperial County 2004
Currently, approximately 30 percent of the lots in Palo Verde are vacant. A tornado struck the
community in 2007 — a rare occurrence — and destroyed numerous homes in the area,
contributing to the current vacancy rate as many homes cannot be rebuilt due to the current septic
design requirements and absent a wastewater collection and treatment facility.
Outside the community, land uses are almost entirely agricultural. Crop production in the area is
primarily melons, cotton, alfalfa, and produce vegetables. Farmland surrounding the community
is generally classified as Prime or Farmland of Statewide Importance.
3.2 GEOLOGY AND SOILS
3.2.1 Geology
The project area is located in the Palo Verde Valley on the northern border of Imperial County,
just south of Riverside County. The Palo Verde Valley is 29 miles long and 15 miles across at its
widest point. The geology of the area is dominated by a north-trending depression known as the
Colorado River Trough. This trough was formed by historical floods of the Colorado River and
by millions of years of regional faulting, down warping, and sediment infilling. Prior to the
construction of Hoover Dam, the floodplain of the Colorado was considerably wider than the
current meandering course of the river. There are several indications that the Colorado River has
changed course in the area, but normally, it has been contained by terraces along its floodplain.
This floodplain is about 9 miles wide in the Palo Verde Valley.
The Palo Verde Valley is bound on the north by the Big Maria Mountains, on the west by Palo
Verde Mesa, and on the south and east by the Colorado River. According to existing U.S.
Geological Survey elevation data, the elevation in the Palo Verde project area is generally between
232 and 233 feet above sea level. The project area drops significantly at the banks of the Palo
Verde lagoon (10- to 20-foot drops). The decline across the project is approximately 0.02 percent.
The nearest active fault is the San Andreas Fault, located near the Salton Sea, approximately 60
miles southwest of the Blythe area. Several faults are also located about 100 miles to the northwest
in the Mojave Desert. In October 1999, two earthquakes of 4.4 and 4.7 magnitude occurred along
a couple of these Mojave Desert faults. Major local tectonic activities associated with earthquakes
in the Palo Verde area, however, are believed to have ended more than one million years ago.
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3.2.2 Soils
The Palo Verde Valley floor is comprised of alluvium. Soils are generally level, moderately to
well-drained sandy loams and loamy sands. Soil associations in the Palo Verde Valley include
Rositas-Gilman, Cibola-Ripley-Indio, and Imperial-Holtville Meloland. Soil types in the vicinity
of the project area are primarily Indio very fine sandy loam. Other soils in Palo Verde include
Holtville silty clay, Gilman silty clay loam, Imperial silty clay, and Holtville silty clay. Soil erosion
is not a serious concern in this area, although limited areas next to river bluffs and canyons are
subject to erosion hazards.
Salinity control is the major soils management concern. Average annual precipitation in the valley
is usually less than 4 inches while evapotranspiration totals about 48 inches per year. More than
1 ton of salt is left in the land with every acre-foot of irrigation water, and the accumulation of salt
in the root zone can cause soils to become too saline for crop growth.
3.3 WATER RESOURCES
3.3.1 Groundwater
The primary source of groundwater recharge is percolation from crop irrigation and irrigation
canals sourced from the Colorado River. Recharge by underflow from tributary areas is small by
comparison and direct recharge from rainfall is very minor. The Palo Verde Valley has very
shallow groundwater depths, and historically was found throughout the valley at a depth of
approximately 5 feet. Water works projects occurring primarily in the 1960s, including the
dredging of the Palo Verde Lagoon, provided a drain mechanism for groundwater and lowered
groundwater levels to approximately 10 feet, where they exist currently. The height of water in
the Palo Verde Lagoon generally is equal to or slightly lower than groundwater levels in the
surrounding area. Groundwater is generally unconfined in the Palo Verde region; however, some
confined zones exist in the more than 7,000 feet of alluvial sediments that form the aquifers in
area.
The Palo Verde County Water District (PVCWD) is responsible for supplying water to residents
of the Community of Palo Verde for domestic purposes. The PVCWD operates two deep-water
wells (the North and South wells), which extract groundwater from the basin. These wells extract
approximately 45,000 gallons per day (gpd) of fairly good quality water, which is then treated and
distributed to the Community. The water is stored in two 120,000-gallon tanks located 2 miles
south of Palo Verde, elevated to 20-feet above ground level, which provide water via gravity flow
to the Community. Water pressure is suitable for all general purposes, including fire flow at all
hydrants.
3.3.2 Surface Water
The Community of Palo Verde is localized around the Palo Verde Lagoon, a slow-flowing fresh
water channel. The Colorado River, located approximately 6 miles east and 2.5 miles southeast of
the Community of Palo Verde, is the main source of surface water in the region and much of
Southern California.
Water is diverted from the Colorado River at the Palo Verde Diversion Dam, located
approximately 25 miles north of the Community of Palo Verde, and flows through a 150-mile
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system of open drains/canals that include the Palo Verde Lagoon. Water from these drains is
discharged into the Palo Verde Outfall Drain, which flows south to the Cibola National Wildlife
Refuge (NWR), where it rejoins the Colorado River. The Palo Verde Irrigation District (PVID) is
responsible for maintaining this system of drains/canals, which supplies water to approximately
9,000 acres of agricultural land in Palo Verde Valley. Currently, the PVID has an unlimited
allocation for water as long as it is used to benefit agriculture.
The community of Palo Verde is drained by the Palo Verde Lagoon. Informal drainages channel
water towards the Lagoon; however, limited paved surfaces and scant rainfall reduce the need for
formal stormwater drainage channels.
3.3.3 Wetlands
The US Army Corps of Engineers (USACE) and EPA define wetlands as "those areas that are
inundated or saturated by surface or groundwater at a frequency and duration sufficient to support,
and that under normal circumstances do support, a prevalence of vegetation typically adapted for
life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar
areas" (33 CFR 328.3 [b] 1984). Wetland hydrology is determined by the frequency and duration
of inundation and soil saturation; permanent or periodic water inundation and soil saturation are
considered significant forces in wetland establishment and proliferation. Jurisdictional wetlands
are those subject to regulatory authority under Section 404 of the Clean Water Act (CWA). EO
11990, Protection of Wetlands, requires analysis of potential impacts to wetlands related to
proposed federal actions.
In Imperial County, wetlands are extremely limited due to the desert climate and lack of natural
surface water resources. Due to their limited area and diminishing acreages, the occurrence of
sensitive plants, and the ability to support a diversity of wildlife species, desert riparian and
freshwater marsh habitats are considered sensitive in Imperial County.
According to National Wetland Inventory maps for the area, riverine, freshwater forested/shrub
and freshwater emergent wetlands occur along the Colorado River. No designated wetlands have
been mapped within the project area associated with the Palo Verde Lagoon; however, wetland
vegetation exists along undeveloped portions of the Lagoon.
3.3.4 Floodplains
Floodplains are belts of low, level ground present on one or both sides of a stream channel that are
subject to either periodic or infrequent inundation by floodwater. For the purposes of this EA,
100- and 500-year floodplains that have been mapped by the Federal Emergency Management
Agency (FEMA) as occurring along the Palo Verde Lagoon within the project area were examined.
Inundation dangers associated with floodplains have prompted legislation that largely limits
development in these areas. For example, EO 11988, Floodplains Management, requires actions
to minimize flood risks and impacts. Under this order, development alternatives must be
considered, and building requirements must be in accordance with specific federal, state, and local
floodplain regulations.
Flooding is a hazard within Palo Verde and surrounding areas. Flooding hazards are greatest on
either side of the Palo Verde Lagoon and in the southern portion of the community. The area
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adjacent to the Palo Verde Lagoon and farmlands to the south of the community are considered to
be a natural floodplain; this area is mapped as Zone A on FEMA Flood Insurance Rate Map (FIRM)
panels' 06025C-0300C (FEMA 2008). Zone A represents areas subject to inundation by the 1-
percent-annual-chance flood event generally determined using approximate methodologies
(because detailed hydraulic analyses have not been performed, no Base Flood Elevations or flood
depths are known). Most of the potential flood areas around the Palo Verde Lagoon are developed
with single-family homes. Additionally, the PVID canals and laterals are open channels; however,
flow levels are controlled and hazards from significant flooding from these sources are minimal.
3.3.5 Water Quality
Irrigation water from the Palo Verde Irrigation District (PVID) sustains agriculture in the area, and
large parcels of valley land are used to grow crops such as melons, cotton, alfalfa, and various
vegetables. The Palo Verde Lagoon was historically used for contact water recreation such as
boating, swimming, and water-skiing. However, swimming and other recreational activities are
now prohibited in the lagoon given the high level of contamination.
The State Water Resources Control Board's (SWRCB's) 303(d) list of impaired water bodies
identifies Palo Verde Outfall Drain as "water quality limited" because bacteria concentrations
violate water quality objectives that protect the following beneficial uses: contact and noncontact
water recreation (REC I and REC II); warm freshwater habitat; wildlife habitat; and preservation
of rare, threatened, or endangered species. E.coli and other fecal coliform bacteria are associated
with human and animal fecal waste, and indicate the likelihood of the presence of infectious
pathogens. The main sources of pathogens as indicated by E.coli and other fecal coliform bacteria
in the Palo Verde Agricultural Drain are natural background sources and failed and nonconforming
septic systems. Natural sources of pathogens appear to play a significant role, but their actual
contribution, and contributions from other non-point sources of pollution in general have not been
fully characterized. Studies indicate the probable main sources of pathogens are waterfowl (96.9
percent), mammals (2.3 percent), septic systems (0.4 percent) and songbirds (0.4 percent).
3.4 BIOLOGICAL RESOURCES
Most of the natural vegetation in the Palo Verde Valley has been replaced by cropland and low
levels of urban and rural development. Native vegetation and sensitive biological resources exist
along the Colorado River, the Palo Verde Lagoon, and the Palo Verde Agricultural Drain that
support riparian vegetation; however, the Palo Verde Lagoon and the Palo Verde Agricultural
Drain have been degraded by nutrients and heavy metals from sewage; nutrients, silt, selenium,
and pesticides from agricultural drainage; and invasive nonnative species. Agricultural activities
and other human disturbance have encouraged the spread of opportunistic plant species. Weedy
vegetation tends to dominate ruderal areas, such as roadsides, borders of cultivated fields, and
canal riparian/levee areas, and includes plant species such as cheeseweed, shepherds purse, white
horse-nettle, saltbush, saltcedar, Russian thistle, and Bermuda grass. Riparian habitats are
dominated by non-native species such as saltcedar, common reed, and cattail).
The project area consists of medium-density residential bordered by cultivated/ruderal areas in all
directions. An approximately 30-acre area of disturbed shrub habitat occurs along the eastern
border of the community; however, this is bordered to the north, east, and south by agricultural
development.
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The Palo Verde Valley and surrounding region host a variety of wildlife species. Due to the
cultivated/ruderal nature within the valley, common species are those that have adapted to high
levels of human disturbance and water quality degradation; however, due to the low population
densities and large areas of undeveloped Sonoran Desert surrounding the Palo Verde Valley, other
wildlife sightings are not uncommon. Freshwater fish are found in rivers and canals, and are
dominated by introduced species including the threadfin shad, mosquito fish, red shiner, California
killifish, largemouth bass, and white and channel catfish).
Imperial County is located in one of the most important flyway corridors in the western hemisphere
for migrant waterfowl, shorebirds, and songbirds. Generally, the greatest numbers and diversity
of birds are found during the spring and fall months. Approximately 378 species of birds have
been identified in Imperial County. The Cibola NWR, located approximately 7 miles south of the
community of Palo Verde and downstream from the Palo Verde Lagoon, provides habitat to over
288 species of birds. The Cibola NWR also provides habitat to various reptiles, fish, and large
mammal species such as desert mule deer, bobcat and coyotes. Additionally, a variety of resident
and migrant bat species are found in the area, particularly near agricultural canals and other
waterways.
Due to its proximity to the Palo Verde Lagoon riparian and open water habitat and forage
opportunities provided by the Lagoon and agricultural properties, the area could provide habitat to
a variety of bird species, including the burrowing owl; however, no burrowing owls have been
observed in this area. One mile west of Palo Verde, cultivated land ends and gives-way to the Palo
Verde Mountains Wilderness Area. Due to the proximity of the project area to the Palo Verde
Mountains Wilderness Area and the Cibola NWR, it is likely that a variety of species utilize
habitats and forage opportunities provided by the Palo Verde Lagoon, irrigation channels, and
agricultural fields within and adjacent to the community of Palo Verde.
Endangered or Threatened Species
Several plant and animal species have been found in the Palo Verde Valley, Imperial County, and
throughout California that are federal- or state-listed as threatened, endangered, candidate for
protection, or species of concern. All animal species listed under the ESA or by the CDFG that
occur in Imperial County are presented in Table 3-2. Table 3-3 includes the threatened,
endangered, and rare plant species occurring in Imperial County.
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Table 3-2. Special Status Animal Species Occurring in Imperial County
( (iiniiKiii Niiinc
Scientific Niimo
Sliilo Sliilus
l-VriiTiil Siiiilis
Amphibians
Colorado river toad
Bufo alvarius
Species of Concern
None
Couch's spadefoot
Scaphiopus couchii
Species of Concern
None
Lowland leopard frog
Rana yavapaiensis
Species of Concern
None
Birds
White-faced ibis
Plegadis chihi
Species of Concern
None
Cooper's hawk
Accipiter cooperii
Species of Concern
None
Ferruginous hawk
Buteo regalis
Species of Concern
None
Merlin
Falco columbarius
Species of Concern
None
Prairie falcon
Falco mexicanus
Species of Concern
None
California black rail
Laterallus jamaicensis coturniculus
Threatened
None
Yuma clapper rail
Rallus longirostis yumanensis
Threatened
Endangered
Mountain plover
Charadrius montanus
Species of Concern
None
Gull-billed tern
Sterna nilotica
Species of Concern
None
Black skimmer
Rynchops niger
Species of Concern
None
Western yellow-billed cuckoo
Coccyzus americanus occidentalis
Endangered
Candidate
Elf owl
Micrathene whitneyi
Endangered
None
Burrowing owl
Athene cunicularia
Species of Concern
None
Short-eared owl
Asio flammeus
Species of Concern
None
Gila woodpecker
Melanerpes uropygialis
Endangered
None
Gilded flicker
Colaptes chrysoides
Endangered
None
Vermilion flycatcher
Pyrocephalus rubinus
Species of Concern
None
Brown-crested flycatcher
Myiarchus tyrannulus
Species of Concern
None
Crissal thrasher
Toxostoma crissale
Species of Concern
None
Le Conte's thrasher
Toxostoma lecontei
Species of Concern
None
Arizona Bell's vireo
Vireo bellii arizonae
Endangered
None
Least Bell's vireo
Vireo bellii pusillus
Endangered
Endangered
Sonoran yellow warbler
Dendroica petechia sonorana
Species of Concern
None
Yellow warbler
Dendroica petechia brewsteri
Species of Concern
None
Yellow-breasted chat
Icteria virens
Species of Concern
None
Summer tanager
Piranga rubra
Species of Concern
None
Gray-headed junco
Junco hyemalis caniceps
Species of Concern
None
Fish
Colorado squawfish
Ptychocheilus lucius
Endangered
Endangered
Razorback sucker
Xyrauchen texanus
Endangered
Endangered
Desert pupfish
Cyprinodon macularius
Endangered
Endangered
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Mammals
California leaf-nosed bat
Macrotus californicus
Species of Concern
None
Arizona myotis
Myotis occultus
Species of Concern
None
Townsend's big-eared bat
Cotynorhinus townsendii
Species of Concern
None
Pallid bat
Antrozous pallidus
Species of Concern
None
Western mastiff bat
Eumops perotis californicus
Species of Concern
None
Big free-tailed bat
Nyctinomops macrotis
Species of Concern
None
Pallid San Diego pocket mouse
Chaetodipus fallax pallidus
Species of Concern
None
Southern grasshopper mouse
Onychomys torridus ramona
Species of Concern
None
Yuma hispid cotton rat
Sigmodon hispidus eremicus
Species of Concern
None
Colorado River cotton rat
Sigmodon arizonae plenus
Species of Concern
None
American badger
Taxidea taxus
Species of Concern
None
Yuma mountain lion
Puma concolor browni
Species of Concern
None
Peninsular bighorn sheep
Ovis canadensis nelsoni dps
Threatened
Endangered
Reptiles
Desert tortoise
Gopherus agassizii
Threatened
Threatened
Barefoot banded gecko
Coleonyx switaki
Threatened
None
Flat-tailed horned lizard
Phyrnosoma mcallii
None
Proposed Threatened
Source: CDFG 2009; 2010c.
Table 3-3. Threatened, Endangered, and Rare Plant Species Occurring in Imperial County
(111111111111 Name
Sui-milk Name
Slate Status
leileral Slalus
San I )iego button-celery
liryngiiim arisliilalmn var. parisliii
I Endangered
I Endangered
Peirson's pincushion
Chaenactic carphoclinia var. peirsonii
None
None
Algodones Dunes sunflower
Helianthus niveus ssp. tephrodes
Endangered
None
Mexican hulsea
Hulsea mexicana
None
None
Brown turbans
Malperia tenuis
None
None
Giant spanish-needle
Palafoxia arida var. gigantean
None
None
Mecca-aster
Xylorhiza cognata
None
None
Orcutt's woody-aster
Xylorhiza orcuttii
None
None
Elephant tree
Bursera microphylla
None
None
Munz's cholla
Opuntia munzii
None
None
Bitter rubberweed
Hymenoxys odorata
None
None
Wiggins's cholla
Opuntia wigginsii
None
None
Saguaro
Carnegiea gigantea
None
None
Crown-of-thorns
Koeberlinia spinosa ssp. tenuispina
None
None
Glandular ditaxis
Ditaxis claryana
None
None
Abrams's spurge
Chamaesyce abramsiana
None
None
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Flat-seeded spurge
Chamaesyce platysperma
None
None
Wiggin's croton
Croton wigginsii
Rare
None
Harwood's milk-vetch
Astragalus insularis var. harwoodii
None
None
Peirson's milk-vetch
Astragalus magdalenae var. peirsonii
Endangered
Threatened
Fairy duster
Calliandra eriophylla
None
None
Pygmy lotus
Lotus haydonii
None
None
Mountain Springs bush lupine
Lupinus excubitus var. medius
None
None
Coves's cassia
Senna covesii
None
None
Mud nama
Nama stenocarpum
None
None
Sand food
Pholisma sonorae
None
None
Rock nettle
Eucnide rupestris
None
None
Hairy stickleaf
Mentzelia hirsutissima
None
None
Creamy blazing star
Mentzelia tridentata
None
None
Curly herissantia
Herissantia crispa
None
None
Chaparral sand-verbena
Abronia villosa var. aurita
None
None
Slender woolly-heads
Nemacaulis denudata var. gracilis
None
None
Slender-leaved ipomopsis
Ipomopsis tenuifolia
None
None
Baja California ipomopsis
Ipomopsis effusa
None
None
Las Animas colubrina
Colubrina californica
None
None
Crucifixion thorn
Castela emoryi
None
None
Parish's desert-thorn
Lycium parishii
None
None
Desert spike-moss
Selaginella eremophila
None
None
Notes- Plants rare, threatened, or endangered in California and elsewhere. Plants rare, threatened, or endangered in
California but more common elsewhere Plants about which more information are needed by CNPS.Source: CDFG 2010b.
3.5 CULTURAL RESOURCES
The proposed project is subject to the provisions of Section 106 of the National Historic
Preservation Act (NHPA) of 1966 and its implementing regulations found in 36 CFR 800. A
Cultural Resource Survey was conducted in order to determine impacts of the proposed project on
cultural resources. The cultural resource inventory included a record search for the proposed
project's Area of Potential Effect (APE) through the South Coastal Information Center (SCIC)
within the California Historic Resource Information System (CHRIS). The APE includes the area
identified for the proposed project which includes 11-acres of undeveloped land proposed for the
WWTP and the 222 parcels that will be connecting to the proposed wastewater collection system.
Fifty-nine historic buildings built prior to 1964 were identified within the APE. However, these
buildings were not eligible for listing in the NRHP.
A field investigation was also conducted which included both a pedestrian archaeological survey
and historic building inventory of the APE. No archaeological resources were discovered during
the fieldwork conducted in May 28 and 29, 2013.
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3.6 AIR QUALITY
The community of Palo Verde is located within the Salton Sea Air Basin, which covers all of
Imperial County and parts of western Riverside County. In Imperial County, the Salton Sea Air
Basin is under the jurisdiction of the Imperial County Air Pollution Control District (APCD).
Although the Imperial County APCD has jurisdiction over the air basin, it does not have
jurisdiction over all activities contributing to the health of the air basin (e.g., activities outside the
US). Industrial and mobile sources of emissions in the Palo Verde Valley are few, thus limiting
exceedances of federal and state air quality standards. Due to the low average population density
in the Palo Verde area, air pollution from vehicular activity is relatively low. Particulate matter
(PM) is a major air pollutant that is generated by wind blowing dry soils, particularly during the
late fall, and during dust storms of winter and early spring. Agricultural burning and cultivation
practices contribute most of the airborne dust in the Palo Verde area. Some agricultural practices
that generate dust are regulated, including leaving cultivated fields vacant and open to blowing
winds, burning of crop residues to clear fields for new cultivation, and crop dusting for fertilization
and pest control. Additionally, with the exception of State Highway 78, Sunset Way, and portions
of Fourth Street, Clark Way, and Desert View Street, roads in Palo Verde are not paved. However,
due to low traffic volumes these unpaved roads do not generate substantial amounts of dust and
thus are not likely to contribute substantially to local air quality degradation.
The Imperial County APCD has adopted rules specifying pollutant emission levels and ambient
air quality standards and operates and maintains air quality monitoring stations in Brawley,
Calexico, El Centro, Niland, and Westmoreland. Imperial County is designated as a federal non-
attainment area for PMio, PM2.5 and 8-hour O3, and a State Ambient Air Quality Standards non-
attainment area for 8-hour O3 and PM10, and is unlisted for PM2.5.
3.7 NOISE AND ODOR
The noise environment in the community of Palo Verde is generally low due to the low population
density and is characteristic of a low-density rural environment. Local vehicular traffic is the
primary generator of noise in the project area. Regional traffic noise is associated with State
Highway 78, which runs east-west across Imperial County from Blythe to Oceanside.
The community of Palo Verde consists of residential housing, a small commercial center, a fire
station, post office, community hall, church, sheriffs substation, gas station, and a water filtration
plant. There are no major odor sources in the project area.
Noise is generally described as unwanted sound, which can be based either on objective effects
such as hearing loss or damage to structures or subjective judgments such as community
annoyance. Sound usually represented on logarithmic scale with a unit called the decibel (dB).
Sound on a decibel scale is referred to as sound level. The threshold of human hearing is
approximately 3 dB, and the threshold of discomfort or pain is around 120 dB.
Noise levels occurring at night generally produce a greater annoyance than do the same levels
occurring during the day. It is generally agreed that people perceive intrusive noise at night as
being 10 dBA.
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3.8
ENERGY AND NATURAL RESOURCES
Electricity is provided to the community of Palo Verde and the project area by Southern California
Edison (SCE). Current electrical infrastructure in the Community maintains capacity to allow for
full build out of the community.
There is no natural gas delivery to Palo Verde. A number of residents have propane tanks supplied
by AmeriGas, Ferrellgas, or Suburban Propane, all located in Parker, Arizona.
3.9 TRANSPORTATION
Regional access to the community of Palo Verde includes State Highway 78, which runs east-west,
across Imperial County from Blythe to Oceanside. In addition, Interstate 10 (I-10), located 10
miles north of Palo Verde, is a major east-west route extending from Los Angeles to Phoenix,
Arizona.
There are two primarily north-south streets in Palo Verde: Main Street (State Highway 78) in the
western portion of the community, and Sunset Way on the eastern side of the Palo Verde Lagoon.
Cross streets are numbered (First through Ninth), and are generally aligned east-west. The
majority of streets in the community are unpaved. There are no curbs, gutters, or sidewalks in the
Community. Fourth Street, also called Palo Verde Drive, provides the only access across the Palo
Verde Lagoon to the residential area along Sunset Way. The eastern portion of Fourth Street,
including the bridge, is paved and in generally good condition. The bridge was constructed in
1950 and is approximately 118 feet long and 35 feet wide. The inventory rating of the bridge is
35,935 pounds (lb) (16.3 metric tons) and an operating rating of 50,044 lbs (22.7 metric tons). A
2008 Bridge Inspection Report indicated that the bridge is aging and experiencing cracking, and
recommended the replacement of several deck planks and backfilling the northeast wing wall.
CalTrans has no current plans to improve or repair the bridge.
3.10 WASTE MANAGEMENT
The Environmental Health and Consumer Protection Services section of the Imperial County
Public Health Department serves as the designated solid waste Local Enforcement Agency
implementing federal and state laws and regulations for safe and proper handling of solid waste.
Collected waste is then disposed of at the Palo Verde Landfill located on Bureau of Land
Management (BLM) property in Imperial County. Burning of refuse is permitted in the
Community, but is rarely practiced. The existing rate of disposal from Palo Verde is estimated at
a half ton per day. The landfill is a Class III landfill and is located approximately 3 miles southeast
of the community.
Imperial County Environmental Health and Consumer Protection Services participates on the
Imperial County Hazardous Emergency Assistance Team providing health and safety expertise in
the containment and cleanup of accidental hazardous waste spills. There are no hazardous waste
contamination sites in need of cleanup or response listed within or near the community of Palo
Verde.
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3.11 SOCIOECONOMICS
The Palo Verde Valley has a higher percentage of poverty than many regions in California. In
Imperial County, the estimated 2008 median household income was $41,757. About 9 percent of
households earned less than $10,000 per year, and approximately 22 percent of households earned
between $10,000 and $25,000 per year.
The 2010 population of Palo Verde was 171, a reduction of approximately 27.5 percent from 2000
levels. This reduction in population was in part due to the loss of housing units in the 2007 tornado,
which could not be rebuilt. According to the Southern California Association of Government
(SCAG), the population of Palo Verde is projected to increase to approximately 371 by 2020 and
to approximately 411 by 2035. Population estimates and percentage increase over 2000 population
levels are summarized in Table 3-4 below.
Table 3-4 Population Trends in Palo Verde, California
2000
2010
2020
2035
Total Population
236
171
371
411
Percent Increase from 2000
--
-27.5%
57.2%
74.2%
3.12 ENVIRONMENTAL JUSTICE
In 1994, EO 12898, Federal Actions to Address Environmental Justice in Minority and Low
Income Populations, was issued to focus attention of federal agencies on human health and
environmental conditions in minority and low-income communities and to ensure that
disproportionately high and adverse human health or environmental effects on these communities
are identified and addressed. Because children may suffer disproportionately from environmental
health risks and safety risks, EO 13045, Protection of Children from Environmental Health and
Safety Risks, was introduced in 1997 to prioritize the identification and assessment of
environmental health risks and safety risks that may affect children and to ensure that federal
agencies' policies, programs, activities, and standards address environmental health risks and
safety risks to children.
For the purposes of this EA, Environmental Justice and the Protection of Children were examined
for Imperial County and the Community of Palo Verde.
Based on 2010 Census data, 27.5 percent of the total population in Palo Verde is classified of a
minority background, a majority of whom are Hispanic (19.3 percent of the community's total
population). By comparison, minority populations respectively comprise 80.4, 77.1, and 44.7
percent of the total populations of Imperial County, the State of California, and the nation.
In addition, the percentage of the population in the Palo Verde below the poverty level was 55.9
percent in 2008. This is substantially higher than Imperial County (22.9 percent), the State of
California (13.3 percent) and the nation (13.2 percent).
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Finally, according to 2010 Census, the percentage of the population in the Community of Palo
Verde under age 18 was 14.6 percent. This is less than Imperial County (29.3 percent), the State
of California (21.9 percent) and the nation (21.2 percent).
3.13 SUSTAIN ABILITY AND GREENING
In accordance with EO 13423 - Strengthening Federal Environmental, Energy, and Transportation
Management, Palo Verde would incorporate practices in an environmentally, economically, and
fiscally sound, integrated, continuously improving, efficient, and sustainable manner in support of
their mission.
3.14 PUBLIC HEALTH AND SAFETY
Public Health
Households in the community rely on septic systems for their wastewater disposal needs and many
of these systems are failing. Additionally, many of the septic systems are nonconforming and do
not meet the Palo Verde and Imperial County required setback distances of 50 to 100 feet from the
adjacent Palo Verde Lagoon. Sewage systems are regulated by the Imperial County Public Health
Department's Liquid Waste Program.
Public health concerns usually focus on fecal-associated pathogens; however, warm waters also
harbor other free-living organisms that may cause serious illness in humans. Pathogens pose a
health hazard for humans. Symptoms of water-borne pathogens include gastroenteritis,
dehydration, headache, vomiting, and fever. Pathogens such as E.coli, enterococci, and fecal
coliform have been identified in the Palo Verde Agricultural Drain and the Palo Verde Lagoon.
These pathogens pose a health hazard to humans. They are at levels that violate quantitative water
quality objectives established by the Colorado River Basin Regional Water Quality Control Board
(RWQCB). These violations indicate that Palo Verde Lagoon and Agricultural Drain beneficial
uses are impaired. The probable main source of pathogens to Palo Verde Agricultural Drain is
waterfowl (96.9 percent). Other sources include mammals (2.3 percent), septic systems (0.4
percent), and songbirds (0.4 percent).
Occurrence rates for selected gastrointestinal diseases and Hepatitis A in Imperial County for 2009
are greater than rates for the State of California as a whole. All of these diseases can be contracted
through contact with contaminated water; therefore, it is possible that water quality in Imperial
County, including the community of Palo Verde, could affect the number of cases of these diseases
observed in the project area.
Public Safety
Hazardous materials may include any solid, liquid, contained gaseous, or semisolid material, or
any combination of materials that pose a substantial present or potential hazard to human health
or the environment. Typical hazardous materials include combustible fuels, radioactive materials,
and biohazardous material (i.e., biological material capable of causing disease in humans), and
pesticides and herbicides.
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The use of pesticides in agricultural operations is a large source of hazardous materials usage since
the community and project area is surrounded by agricultural operations. The community does
not have direct authority over the use of pesticides. The Imperial County Agricultural
Commissioner and staff enforce state laws and regulations pertaining to pesticide use at the local
level. Incidences of severe mosquito infestation are fairly common due to ideal breeding grounds
in the Palo Verde Lagoon. Abatement crews from the Imperial County Public Health Department,
Environmental Health & Consumer Protection Services Vector Control Program treat larvae with
larvecides and with adults with adulticide fogging.
4.0 ENVIRONMENTAL CONSEQUENCES
4.1 LAND USE
The proposed project site for the WWTP, Assessor Parcel Number (APN) 006-220-056, is
zoned Residential (R-l) and has a land use designation of Medium Agriculture. In order to
comply with the Imperial County General Plan and zoning ordinance, the proposed project
would require a rezone of the subject parcel to Government/Special Public (G-S).
Additionally, a minor subdivision or a Parcel Map Waiver from Imperial County would be
required to create a separate legal parcel for the WWTP site. Resolution of land use and
zoning consistency issues would be required prior to construction, and upon resolution,
impacts would be less than significant.
The Preferred Alternative would also require acquisition of land and/or rights-of-
way. Portions of each wastewater collection system include pipe installation in State
Highway 78, which would require coordination with the California Department of
Transportation (Caltrans). Installation of the WWTP would require land acquisition, as the
community of Palo Verde owns limited land for siting of the plant. Land for the WWTP site
has been donated and the title is held in the PVCWD's name.
Prior to construction, coordination with the Palo Verde Irrigation District (PVID) would
occur, including obtaining encroachment permit(s) for all water, sewer, stormwater, and any
other underground utilities that would encroach upon existing and proposed PVID right-of-
ways. Southern California Edison (SCE) has overhead transmission lines and both overhead
and underground distribution lines in the project area. Coordination with SCE would occur
prior to construction to avoid disturbance and to minimize power disruption to these
facilities.
Implementation of the Preferred Alternative would allow for the redevelopment of properties
that were destroyed in the 2007 tornado. These properties previously utilized septic systems
that were within the 50- to 100-foot buffer area adjacent to the Palo Verde Lagoon, and
therefore were prohibited from reconstruction. The proposed project would therefore be
beneficial by improving the quality of land use by permitting in-fill development of existing
parcels of record, and potentially reducing vacant properties within Palo Verde.
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Under implementation of the No Action Alternative, a wastewater collection and treatment
system would not be constructed in the proposed project area. Therefore, there would be no
land use changes. Conditions would remain unchanged.
4.2 SOILS AND GEOLOGY
Soils
Under the Preferred Alternative the proposed WWTP would be constructed on currently
undeveloped land in the northeast portion of Palo Verde. The WWTP would have a total
footprint of approximately 11 acres, which would involve construction of an access road
from Sunset Way, ground clearing, soil importation, and earth movement.
Soils in the proj ect area are not considered to be expansive and are suitable for the installation
of utility pipelines. During the course of project development, soils would be exposed or
non-compacted and the potential for wind- and/or water-driven soil erosion would arise. In
order to minimize such potential impacts, BMPs such as watering exposed soils and covering
stockpiled soils would be implemented during construction.
Substantial fill activities would occur during construction of the pond WWTP, particularly
during construction of the four aerated treatment cells which would be 190 feet long by 50
feet wide by 13 feet deep, resulting in a total of 494,000 cubic feet of water capacity. In
addition, due to shallow groundwater depths, the percolation ponds would be built-up above
existing ground level and contained behind earthen dikes. However, since soil disturbance
would be occurring mostly on non-prime soils, erosion would be lessened through BMPs,
and provisions to prevent soil erosion would be incorporated into the SWPPP to be
implemented prior to construction, impacts to soils under this alternative would be less than
significant.
Geology
No known active faults are located in the Palo Verde area and major tectonic activities
associated with earthquakes are believed to have ended more than 1 million years ago.
Consequently, the potential for seismic activity and ground rupture is low. Further, the
proposed facilities would be constructed in accordance with the California State Building
Code (Title 24 of the California Administrative Code), which contains specifications to
minimize adverse effects due to ground shaking from earthquakes and liquefaction. With
the implementation of building and construction standards, impacts to the proposed facilities
resulting from geologic hazards are expected to be less than significant. Since construction
would be occurring in previously disturbed or developed areas, excavation trenches would
not substantially affect soils, geology, or seismicity, potential impacts under the Preferred
Alternative would be less than significant.
Under implementation of the No Action Alternative, no wastewater collection or treatment
system would be constructed in the proposed project area, and no new improvements would
be affected by ground-disturbing activities; therefore, geological and soil conditions would
remain the same.
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4.3 WATER RESOURCES
Groundwater
Under implementation of the Preferred Alternative a wastewater collection and treatment system
would replace the use of septic systems in Palo Verde. Under the Preferred Alternative, failing
septic systems in Palo Verde would be properly abandoned, which would potentially improve
groundwater quality. Leaking septic systems can damage water quality, and proper removal would
ensure that no future contamination from septic system sources would occur.
Groundwater within the Palo Verde Valley, including the project site, occurs at approximately 10
feet below ground service (bgs). Construction of the proposed wastewater collection and treatment
system would occur at or below existing groundwater levels. Excavation trenches for the 4-inch-
diameter sewer service lines would range from 4.0 to 8.0 feet in depth and trenches for the 8-inch-
diameter gravity sewer pipe would range from 5.0 to 12.0 feet in depth. Therefore, dewatering to
remove groundwater from subsurface construction areas would be necessary during the installation
of the wastewater collection and pump components. Dewatering would involve the short-term,
localized removal of groundwater around a subsurface construction area. Dewatering during
construction would not result in any short-term or long-term impacts to groundwater resources.
Implementation of the Preferred Alternative would involve the construction of a WWTP, which
would use percolation/evaporation basins for treated wastewater discharge. To provide sufficient
capacity, the two percolation/evaporation basins would each be approximately 135 feet long by
100 feet wide by 6 feet deep. A minimum of 4.0 feet from the bottom of the percolation/
evaporation basins to groundwater is required to ensure proper function of the ponds. Due to the
shallow depth to groundwater, the percolation/evaporation basins would be elevated with
appropriate fill material to ensure that the minimum of 4.0 feet is maintained between the
percolation/evaporation ponds and groundwater levels. Additionally, an under drain beneath the
percolation/evaporation basins would be installed to prevent groundwater from coming to the
surface. Once constructed, the WWTP would provide groundwater recharge through the
associated percolation basins.
Due to the shallow depth of groundwater, recharge from the percolation/evaporation basins would
occur quickly. A limited increase in impermeable surface area would occur as a result of the
WWTP structure; however due to the minor contribution of rainfall and the relatively undeveloped
nature of the project area, such increase would not affect groundwater recharge rates. Since land
effluent discharges would occur under the Preferred Alternative, which would potentially affect
groundwater, the Palo Verde County Water District (PVCWD) would be required to file a Report
of Waste Discharge with the State Water Resources Control Board (SWRCB) to obtain waste
discharge requirements (WDRs) Form 200. The Preferred Alternative would not substantially
alter groundwater recharge and impacts would therefore be less than significant.
Under implementation of the No Action Alternative, conditions would remain the same, and
potentially adverse impacts to groundwater quality would continue.
Surface Water
Short-term impacts to surface water could result from run-off related to construction of the
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proposed wastewater collection and treatment system. Ground-disturbing activities associated
with the Preferred Alternative would involve new construction of a wastewater collection and
treatment system. Site preparation activities (e.g., grading, trenching) and construction would
result in temporary exposure and compaction of soils, affecting surface water drainage flow
patterns and percolation rates. Increases in surface water runoff could result in increased sediment
loading to the Palo Verde Lagoon and other canals/drainage ways during periods of precipitation.
Precipitation events in the Palo Verde region are minor and infrequent and would not be expected
to result in substantial runoff; however, a Storm Water Pollution Prevention Plan (SWPPP) would
be developed for the proposed project.
Implementation of BMPs, including adherence to the SWPPP, would limit the effects of any
construction adjacent to and/or beneath the Palo Verde Lagoon. For any construction occurring
within the Palo Verde Lagoon, a CWA Section 404 Permit application would be submitted to and
obtained from the US Army Corps of Engineers (USACE) prior to commencement of any
construction activities within jurisdictional waters. With implementation of measures determined
by and in compliance with USACE requirements, impacts to surface water resources would be
reduced to less than significant. In addition, during construction phases, application of BMPs
including development and implementation of a SWPPP, silt fencing, and suspension of
construction activities during rainy periods would mitigate the effects of increased surface water
runoff and sedimentation.
The long-term implication of the Preferred Alternative is the replacement of septic systems in Palo
Verde. Sewage leaks caused by inadequate infrastructure through the development of appropriate
wastewater collection infrastructure would be eliminated, thereby reducing the potential for
untreated or poorly treated wastewater to enter the environment (e.g., surface water).
Implementation of the Preferred Alternative would involve the discharge of treated wastewater
into percolation/evaporation basins (land effluent discharge), where treated wastewater would
enter the groundwater or evaporate. For land effluent discharges, PVCWD would be required to
file a Report of Waste Discharge with the Colorado River RWQCB to obtain waste discharge
requirements (WDRs). Implementation of the Preferred Alternative would not result in long-term
impacts to surface water resources.
Under implementation of the No Action Alternative, new infrastructure for the collection and
treatment of wastewater would not be constructed. Therefore, under implementation of the No
Action Alternative, conditions would remain unchanged, and poor surface water quality conditions
would continue.
Wetlands
No designated wetlands are located within the proposed project area, and no direct impacts to
wetlands would occur; however, indirect impacts could occur from siltation to wetlands located
along the Palo Verde Outfall Drain. Ground-disturbing activities associated with construction of
the Preferred Alternative, particularly trenching and/or excavation, may temporarily result in
increased sedimentation into the Palo Verde Lagoon and the Palo Verde Agricultural Drain;
however, application of BMPs including development and implementation of a SWPPP, silt
fencing, and suspension of construction activities during rainy periods would mitigate the effects
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of increased sedimentation. Thus, no short-term or long-term changes to wetlands are anticipated
as a result of the Preferred Alternative.
Under the No Action Alternative, a wastewater collection and treatment system would not be
constructed. No impacts to wetlands would occur from implementation of the No Action
Alternative.
Floodplains
Under the Preferred Alternative construction would comprise installation of wastewater collection
lines, with collected wastewater conveyed to a proposed new WWTP. The wastewater collection
system would be constructed largely within the Federal Emergency Management Agency (FEMA)
100-year floodplain, which occurs along the banks of the Palo Verde Lagoon for the length of the
Community, as well as areas of southern Palo Verde. Pipeline segments would be buried at depth
and would not be affected by potential flood events. Watertight manhole covers would be used
for all manholes occurring within the 100 year floodplain and wherever the manhole tops may be
flooded by street runoff or high water. The pump station would be waterproofed with sealing
lids/hatches to prevent water from flowing into the pump station. Pumps would be located
approximately 10 to 20 feet bgs at the bottom of the 'wet well' enclosed in a manhole. Therefore
no impacts to flooding would occur related to the wastewater collection system.
The WWTP site for the Preferred Alternative would be located outside the FEMA 100-year flood
boundary, so no direct impacts to structures would occur during a flood event; however, a rise in
groundwater conditions could temporarily affect the function of the percolation/evaporation
basins. To offset the rise in groundwater, the WWTP under the Preferred Alternative would
include installation of an under drain beneath the percolation/evaporation basins to prevent
groundwater from coming to the surface. Impacts would be temporary and less than significant.
Under the No Action Alternative, a wastewater collection and treatment system would not be
constructed. Therefore, there would be no activities that result in either direct or indirect impacts
to floodplains.
4.4 BIOLOGICAL RESOURCES
Under the Preferred Alternative the WWTP would consist of an approximately 11-acre footprint
and would require the construction of an access road. The WWTP would be sited within an
approximately 30-acre site directly east of the community of Palo Verde that contains disturbed
vegetation consisting of interspersed shrub communities, of which approximately 10 acres are
heavily disturbed by a network of informal trails.
Construction activities associated with the collection system and WWTP would be temporary and
would occur primarily along existing roadways and previously disturbed areas, including
agricultural fields. Trenching to install pipelines would occur along previously disturbed areas
within Palo Verde. The impact of most concern regarding wildlife would be indirect noise and
dust related to construction on agricultural land and residential areas. However, this impact would
be temporary, and would no longer be an issue once implementation of the wastewater collection
and treatment system is accomplished. Therefore, species that use agricultural land or residential
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areas have a low potential for being impacted by the project. In addition, implementation of the
SWPPP, and its associated BMPs, would limit the effects of construction adjacent to and/or
beneath the Palo Verde Lagoon during the construction of the bridge crossing. Overall, impacts
to biological resources would be less than significant.
If the No Action Alternative were selected, no improvements to the wastewater collection or
treatment system would be constructed in the proposed project area; therefore, there would be no
activities that result in ground-disturbance and either direct or indirect impacts to habitat or
vegetation, terrestrial, and aquatic wildlife. Conditions would remain unchanged.
Threatened and Endangered Species
EPA is required through this NEPA document to address project impacts to Federally-listed
threatened and endangered species. EPA prepared a biological evaluation of the potential impacts
of the project on aquatic resources found within the vicinity of the Palo Verde Lagoon including
the Razorback sucker, Xyrauchen texanus. The biological evaluation found that the Preferred
Alternative would have "No Effect" on listed fish species, as there will be no direct or indirect
impacts to aquatic environments (namely, the Palo Verde Lagoon). The construction and
operations and maintenance (O&M) phases will occur entirely outside of the lagoon, and as such,
completely avoid aquatic species altogether.
As part of the Preferred Alternative, a pipeline would be constructed on the deck of the Fourth
Street Bridge and over the Palo Verde Lagoon in order to connect the mainland side of the
community to the WWTP on the island side. If not feasible, a secondary option, would involve
directional drilling and placement of the force main pipeline under the lagoon at a depth of 30-40
feet below ground surface and/or approximately 10 feet below the lagoon bottom, which provides
a safe distance from the top of the force main to the bottom of the lagoon, including below the
scour depth of the lagoon.
Regardless of the method chosen, construction crews will not enter the lagoon to conduct work at
any time. All construction activities will be performed from the bridge deck itself, from the island
and mainland sides of the lagoon, or at least 10 feet below the lagoon bottom should the directional
drill method be implemented. Measures will be undertaken to ensure best management practices
will be adhered to. At the forefront of this will be the implementation of a SWPPP that lays out
specific measures to protect all water bodies within and adjacent to the project footprint. A key
component in protecting the lagoon, and any sensitive fish potentially occupying it, is creating a
physical barrier between the construction activities and the water body in order to prevent sediment
or material discharge. As part of the SWPPP, erosion control devices such as silt fences, straw
wattles, filter fabric, and plywood reinforced with t-posts may all be utilized to contain spoils
generated by construction activities occurring on both the island and mainland sides of the
community. When properly installed and maintained with regularity, these temporary devices will
prevent sediment from entering the lagoon. To prevent discharge of any construction debris while
performing work on the bridge deck, a temporary catchment device is recommended for
installation on the underside of the bridge. The work occurring on the bridge deck is not anticipated
to generate a substantial amount of construction debris, therefore the catchment can be as simple
as a tarp or similar device, which can be easily maintained and removed following the completion
of the project.
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EPA will include the following conservation measure to reduce impacts to the fish and aquatic
species potentially present in the Palo Verde Lagoon:
CM #1: Storm Water Pollution Prevention Program (SWPPP) - A SWPPP will be prepared and
implemented which will include site-specific Best Management Practices (BMP) to contain any
potential spoils generated during construction. The SWPPP will be the guiding framework to
ensure environmental compliance with no effects to listedfish species or any other aquatic species.
In addition, the southwestern willow flycatcher (SWFL) is a state and federally endangered
subspecies of willow flycatcher (Empidonax traillii; WIFL) that was identified as having habitat
within the two-mile radius of the proposed project site. The Preferred Alternative would include
the removal of tamarisk scrub and other vegetation considered to be vital to the SWFL successful
migration. On May 23, 2013, a site inspection was conducted and 10 individual SWFL were
observed within the tamarisk scrub where the WWTP is proposed, plus an additional three
individuals along the Palo Verde Lagoon itself. In addition to occupying areas within the WWTP
footprint, some individuals were observed occasionally foraging for insects over the adjacent
alfalfa fields.
It was determined that approximately six acres of critical habitat would need to be removed for the
Preferred Alternative's proposed WWTP and main line route. The calculation was derived from
the 11-acre WWTP parcel being approximately 50% covered by tamarisk scrub, while the 1-acre
area along the northern 8-inch main line route exhibits approximately 85% tree/shrub cover. Taken
together, this amounts to approximately 53% tree/shrub cover (or six acres), the vast majority of
which is non-native, highly invasive tamarisk. In this condition, the area supports migratory
SWFL. These impacts are considered permanent, as all vegetation would be removed and
prevented from regrowth throughout the operations and maintenance phase of the overall system.
There is no permanent or temporary loss of migratory SWFL habitat anywhere else along the
project footprint.
Due to the loss of six acres of critical habitat for the SWFL, as well as potential impacts to aquatic
species, EPA requested informal Section 7 consultation with the U.S. Fish and Wildlife Service
(Service). EPA determined that the loss of six acres of critical habitat" may affect" SWFL species,
but was "not likely to adversely affect." On December 10, 2014, the Service confirmed EPA's
determination and included the following conservation measures (CM) for protection of the
SWFL:
CM #2:
CM #3:
Habitat Mitisation Management Plan (HMMP) - Preparation of a formal Habitat
Mitigation Management Plan (HMMP) for the SWFL which must receive approval
from the Service. The final design for the proposed project will not be considered
complete until Service approval of the HMMP has been obtained.
Vesetation Management - During the construction phase, all project-related
brushing, clearing and trimming of existing shrub/tree-dominated naturalized
habitats within and immediately adjacent to the proposed project footprint shall
occur outside the two general SWFL migratory periods (May 1 to June 20 and
August 10 to October 10); grading activities must be conducted outside of the
migration period. A qualified biologist experienced with the SWFL shall monitor
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all brushing, clearing, trimming and grading activities. In the event that the
qualified biologist detects SWFL or any subspecies on the site during such
activities, all such activities shall be halted within 500feet of the existing tamarisk
trees or whatever greater distance necessary to reduce noise levels at the edge of
the tamarisk woodland below 60 decibels; the activities will cease within this
distance until the bird is observed to depart the site or cannot be relocated the next
morning.
During the O&M phase, all project-related brushing, trimming, clearing and
grading of existing shrub/tree-dominated naturalized, restored and/or preserved
habitats within and/or adjacent to the project site must be conducted outside the
two SWFL migratory periods. The brushing, trimming, clearing and grading of
shrub/tree-dominated naturalized, restored and /or preserved habitats shall be
monitored by a qualified biologist experienced in identifying SWFL, and
subspecies, in the field, and these activities shall be subject to the terms specified
in all of the other applicable mitigation measures, including those relating to dust
control, noise reduction, night lighting, and general O&Mprocedures. In the event
that the qualified biologist detects SWFL, and subspecies, on the site during such
activities, all such activities will be halted within 500feet of the existing tamarisk
trees or whatever greater distance is necessary to reduce noise levels at the edge
of the tamarisk woodland below 60 decibels. If the bird detected is a SWFL, the
activities will cease within this distance until (a) the bird is observed to depart the
site, or (b) cannot be relocatedwithin an hour of sunrise on the following work day
by any of the following means: visual sighting, passive listening (for its songs/calls)
and a failure to respond to playback of recorded SWFL calls broadcast from a
portable speaker.
All project personnel, equipment, vehicles and materials shall remain within
approved work areas, access routes, lay down areas, construction yards and other
feature workspaces. Existing shrub/tree-dominated naturalized, restored and/or
preserved habitats outside of approved workspaces shall be avoided by
construction and operation and maintenance personnel, vehicles, equipment and
materials throughout all phases of the project. Should additional temporary work
space become required at any time, a variance may be processed, ensuring that no
additional impacts to migratory SWFL are anticipated.
CM #4: Dust Control - The following standard mitigation measures for fugitive dust control
were adoptedfrom the CEQA Air Quality Handbook provided in Appendix B of the
EID (AMEC 2011). In addition to numerous project, wildlife and community
benefits, these measures also serve to reduce impacts on migratory SWFL to less
than significant levels.
All disturbed areas, including bulk material storage which is not being actively
utilized, shall be effectively stabilized, and visible emissions shall be limited to no
greater than 20% opacity for dust emissions by using water, chemical stabilizers,
dust suppressants, tarps or other suitable material such as vegetative ground cover.
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All on site and off site unpaved roads will be effectively stabilized, and visible
emissions shall be limited to no greater than 20% opacity for dust emissions by
paving, chemical stabilizers, dust suppressants and/or watering.
All unpaved traffic areas one (1) acre or more with 75 or more average vehicle
trips per day will be effectively stabilized, and visible emission shall be limited to
no greater than 20% opacity for dust emissions by paving, chemical stabilizers,
dust suppressants and/or watering.
The transport of bulk materials shall be completely covered unless six inches of
freeboard space from the top of the container is maintained with no spillage and
loss of bulk material. In addition, the cargo compartment of all haul trucks is to be
cleaned and/or washed at delivery site after removal of bulk material.
All track-out or carry-out will be cleaned at the end of each workday or
immediately when mud or dirt extends a cumulative distance of 50 linear feet or
more onto a paved road within the community of Palo Verde.
Movement of bulk material handling or transfer shall be stabilized prior to
handling or at points of transfer with application of sufficient water, chemical
stabilizers or by sheltering or enclosing the operation and transfer line.
Vehicle speedfor all construction vehicles shall not exceed 15 mph on any unpaved
surface at the construction site.
CM #5: Noise Reduction Measures - The following standard mitigation measures relating
to noise reduction were adopted from the CEQA Air Quality Handbook provided
in Appendix B of the EID (AMEC 2011). In addition to numerous project, wildlife
and community benefits, these measures also serve to reduce impacts on migratory
SWFL to less than significant levels.
Minimize idling time either by shutting equipment off when not in use or reducing
the time of idling to 5 minutes as a maximum.
Limit, to the extent feasible, the hours of operation of heavy-duty equipment and/or
the amount of equipment in use.
Noise levels generated by equipment, vehicles, personnel, facilities, and all other
project features throughout the construction and operation and maintenance
phases should be kept below 60dBA or existing ambient conditions (if greater than
60dBA) throughout the two general SWFL migratory periods (May 1 to June 20
and August 10 to October 10) over the life of the project.
CM #6: Nisht Lishtins Measures - The following mitigation measures relating to night
lighting serve to reduce impacts on migratory SWFL to less than significant levels.
To reduce impacts on nocturnally roosting SWFL, construction night lighting shall
be reduced to the lowest practicable levels on existing shrub/tree-dominated
naturalized habitats throughout the two general SWFL migratory periods (May 1
to June 20 and August 10 to October 10).
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All exterior lighting associated with long-term facility O&M within the project area
adjacent to existing shrub/tree-dominated naturalized, restored and/or preserved
habitats shall be of the lowest illumination practical for human safety, selectively
placed, shielded, and directed away from stated habitats to the maximum extent
practicable.
General Operations & Maintenance (O&M) Measures - The following mitigation
measures relating to long-term operation and maintenance procedures serve to
reduce impacts on migratory SWFL to less than significant levels.
All vegetation management, dust control, noise reduction and night lighting
mitigation measures shall be followed as applicable to all long-term standard
operation and maintenance procedures of the proposed project. Standard
operation and maintenance procedures shall generally follow those stated in the
Project Evaluation Report (PER) and will generally involve low intensity vehicle,
personnel and equipment demands operating within developed areas on an annual
basis.
If emergency repairs or other unanticipated non-standard repairs become
necessary to maintain the wastewater treatment plant or collection system's
integrity and operational functionality, relevant mitigation measures will be
applied as necessary to remain in compliance.
Qualified Biolosist - The project's qualified biologist shall possess the following
qualifications:
Document training in identifying SWFL and subspecies by either sight or
by calls and songs from those of other riparian bird species;
At least 40 hours of supervised experience successfully detecting and
observing SWFL and subspecies in the field under the supervision of a more
experienced ornithologist. At least 10 hours of the 40 hours of supervised
field experience must have involved the use ofplaybacks ofrecorded willow
flycatcher or subspecies call/songs to elicit vocalizations from SWFL in the
field, and response vocalizations must have been successfully obtained from
wild birds on at least two separate field days; and
Documentation of field training experiences meeting the above criteria, and
current contact information for the trainers, must be submitted to the EPA
and Service.
Reporting Requirements for Construction Monitorins - During
construction, the project's qualified biologist shall record all detections of
SWFL and subspecies to the species level and map the location of the bird
on or near the project site to the most accurate degree feasible. Within 120
days of completion of the construction, the qualified biologist shall submit
a report to the EPA and the Service relating the dates within which ground-
disturbing activities and construction occurred, a brief description of the
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types of construction activities, and a narrative relating the biological
monitoring activities employed during the construction monitoring required
in CM #3, above, including dates of monitoring, methods used, and
especially the species, dates, and location of the SWFL detected during the
monitoring. The report shall include one or more maps depicting the
location of the SWFL and subspecies detected during construction
monitoring.
CM #10 Reporting Requirements for Vegetation Removal durins Operations - The
project's qualified biologist shall record all detections to the species level
of SWFL detected while monitoring vegetation removal or disturbance
activities, and map the location of the bird on or near the project site to the
most accurate degree feasible. The qualified biologist shall submit an
annual report to EPA and the Service relating the dates within which
vegetation removal or disturbance activities occurred, a brief description
of the types of activities which occurred, one or more maps depicting the
location of the activities on the project site, and a narrative relating the
biological monitoring activities employed during the monitoring required
in CM #3, including dates of monitoring, methods used, and especially the
species, dates, and locations of SWFL and/or subspecies detected during
the monitoring. The report shall include one or more maps depicting the
locations of the SWFL species detected during vegetation removal
monitoring. The annual report shall describe any vegetation removal or
disturbance activities and related biological monitoring for each calendar
year (January 1 to December 31) during project operations, and shall be
transmitted to the EPA and the Service by February 28 of the subsequent
calendar year. If no project operations requiring monitoring for potential
impacts to SWFL occurred during the calendar year in question, the Palo
Verde County Water District (District) should sent a notification to that
effect to EPA and the Service by February 28 of the subsequent year. The
notification will take the place of the annual report.
CM #11: Dead and Injured Birds - All project construction and O&M personnel
shall immediately report any observations of dead and injured birds on the
project site to either the qualified biologist (if present) or to the District.
This includes any eagles which appear to be sick.
When an injured bird is found on the project site, the qualified biologist or
the District (as applicable) shall make every effort to transport the injured
bird to a CA Department of Fish and Wildlife (CDFW) rehabilitation center
(www. dfs. ca. sov/w ildlife/WIL/rehab/facilities. html).
Should a bird carcass be found on the project site, the qualified biologist or
the District (as applicable) shall notify the SERVICE (Palm Springs Field
Office, with the Carlsbad Field Office as a fall-back option) and the CDFW
(Blythe office) within 72 hours of discovery of the carcass for further
direction.
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CM #12: Monitoring and Reporting Requirements for the Riparian Woodland
Habitat Restoration - These requirements will be specified in the SWFL
HMMP which will be developed by the EPA subsequent to completion of
the ESA Section 7 consultation.
If the No Action Alternative was selected, the wastewater collection and treatment system would
not be constructed in the proposed project area; therefore, there would be no activities that result
in ground-disturbance and either direct or indirect impacts to habitat or threatened or endangered
species. Conditions would remain unchanged.
4.5 CULTURAL RESOURCES
A cultural resources survey was conducted for the Preferred Alternative's Area of Potential Affect
or APE. No historic properties or archaeological resources were identified as being impacted by
the proposed project. EPA's determination of no affect was confirmed by the California State
Historic Preservation Office in October 2013.
In addition, EPA sent letters to eight Native American governments in January 2013 to determine
whether there were Traditional Cultural Places (TCPs) within the vicinity of the Preferred
Alternative or other issues of concern by the tribes. Communication with the Native American
governments was initiated in accordance with the federal NEPA guidance (42.U.S.C. 4321-43351)
and Section 106 of the National Historic Preservation Act (16 U.S.C. 470, 36 CRFR 800.3). No
TCPs or concerns were identified by the Native American governments.
Under the No Action Alternative, improvements to the wastewater collection and water
distribution system would not be constructed in the proposed project area. Since no construction
and associated ground-disturbing activities would occur, no impacts to cultural resources would
occur and conditions would remain unchanged.
4.6 AIR QUALITY
Imperial County is designated as a federal non-attainment area for particulate matter equal to or
less than 10 microns in diameter (PMio), particulate matter equal to or less than 2.5 microns in
diameter (PM2.5) and 8-hour ozone (O3) (United States Environmental Protection Agency [EPA]
2009a; 2009b). Imperial County is a State Ambient Air Quality Standards non-attainment area for
8-hour O3, PM10, and is unlisted for PM2.5 (California Environmental Protection Agency [CalEPA]
2010).
Short-Term
Short-term pollutant emissions associated with the proposed construction activities would include
fugitive dust emissions during ground disturbance and related site preparation activities, and
combustion emissions from vehicles and heavy-duty equipment. Based upon emission modelling
using the maximum estimated acreage that could be disturbed including sewer line installation, a
projected total of approximately 0.26 tons of dust would be generated during construction.
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Impacts from construction would be minimized through dust control and standard engineering
practices required by Imperial County. Specifically, measures to minimize PMio emissions during
construction include the stabilization of disturbed and material storage areas (watering, dust
suppressants, tarps, etc.), stabilization of on-site and off-site unpaved roads, and a maximum speed
of 15 miles per hour (mph) for all construction vehicles on any unpaved surface at the construction.
The combustion emissions associated with construction-related vehicles and equipment would be
1.38 tons of nitrogen oxides (NOx), 0.71 tons of carbon monoxide (CO), and 0.19 tons of reactive
organic gas (ROG). Since these are short-term emissions and relatively minor, no significant
impacts to regional air quality would occur.
Operational Emissions
Criteria pollutant emissions from the WWTP processes are expected to be negligible. The majority
of criteria pollutants generated would be related to the off-site combustion of natural gas for the
generation of industrial and utility electric power; however, the pump station and WWTP aerator
would include solar panels to help limit dependence on grid power and reduce operation and
maintenance costs. Additional electrical supply and controls would include a crossover connection
for potential future power supply from an anticipated solar park near the water treatment plant in
Palo Verde.
Emissions from off-site utility electric power generation associated with the WWTP, under worst
case conditions where no solar panels are utilized, would likely occur in other air sheds and given
the complexity of the electrical grid system, specific area impacts are difficult to predict. Electrical
generation may include non-polluting sources such as solar, wind, or nuclear power. Operational
emissions were calculated using an emission calculator. Emission factors for California are:
• NOx = 0.000236 pounds per kilowatt-hour (lbs/kWh)
Sulfur dioxide (SO2) = 0.000144 lbs/kWh
The PM10 emission factor was taken from the California Air Resources Board:
• PM10 = 0.000040 lbs/kWh
The CO and ROG emission factors were estimated by taking natural gas combustion emission
factors from EPA AP-42 Table 1.4-1 and 1.4-2 and calculating emissions based on a ratio of the
CO and ROG emission factors to the NOx emission factor.
CO emission factor ratio to NOx is 0.6 based on Low NOx burners, so the estimated
emission factor = 0.00014 lbs/kWh
ROG emission factor ratio to NOx is 0.039 based on Low NOx burners, so the estimated
emission factor = 9.27E-06 lbs/kWh
For calculation purposes, it was assumed the WWTP would not use solar panels and would
consume a maximum of 100,000 kWh/year. It was also assumed that one pump station would
consume a maximum of 7,000 kWh/year with 20 percent of the energy being generated from solar
power.
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Under the Preferred Alternative, long-term emissions would occur related to the one pump station
and the operation of the WWTP. The majority of long-term operational emissions associated with
the Preferred Alternative would relate to the off-site combustion of natural gas for the generation
of industrial and utility electric power, and would occur in unspecified air basins. Estimated
emissions for this alternative would be 20 lbs/year of NOx and 13 lbs/year of SO2, 3.4 lbs/yr of
PM10, 12 lbs/yr of CO, and 0.8 lbs/yr of ROG.
Under the Preferred Alternative, emissions associated with precursor pollutants for O3 (NOx and
ROG) would be well below the significance thresholds under the General Conformity Rule,
therefore a General Conformity analysis is not required. Direct impacts associated with
construction of the Preferred Alternative would be less than significant. Therefore, no long-term
air quality impacts associated with direct operation of wastewater collection and treatment systems
would occur.
Under the No Action Alternative, the proposed wastewater collection and treatment system would not be
constructed in the proposed project area. Therefore, air quality would remain unchanged.
4.7 NOISE AND ODOR
4.7.1 Noise
Short-Term
During construction, implementation of the Preferred Alternative would result in noise levels that
are higher than existing ambient levels. However, construction noise generated during
implementation of the Preferred Alternative would be short-term and temporary and would be
reduced through BMPs - such as the use of equipment sound mufflers and restriction of
construction activity to normal working hours. The project would be required to comply with
Imperial County Noise Element standards, which apply to noise measured at the nearest sensitive
receptor (adjacent residences). County standards would require construction equipment operation
to be limited to the hours of 7 a.m. to 7 p.m. Monday through Friday, and 9 a.m. to 5 p.m. Saturday.
No commercial construction operations are permitted on Sunday or holidays (Imperial County
2008). Therefore, short-term noise impacts would be reduced to less than significant levels.
Long-Term
Long-term operational noise of the WWTP under the Preferred Alternative would generate noise
associated with the operation of WWTP machinery. Noise generated from aeration equipment and
fans are the greatest source of noise associated with pond-type treatment systems. A noise buffer
required for WWTPs range from 250 to 1,000 feet from sensitive receptors (residential properties),
depending on the noise controls included in the WWTP design. Under the Preferred Alternative
the WWTP would be constructed in northeastern Palo Verde, approximately 1,000 feet east of the
northern terminus of Sunset Way and adjacent residences, which would reduce impacts associated
with noise to less than significant. Long-term noise from the proposed pump station would
produce a 'humming' noise for between two to three hours a day. The pump would be located at
the bottom of a wet well, enclosed in a manhole approximately 10 to 20 feet below ground surface
(bgs). Resulting noise generation would therefore be less than significant.
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Once operational, the wastewater collection system (pipelines) would be buried and would not
generate noticeable noise. Noise generated by the WWTP proposed under the Preferred
Alternative would be reduced through the incorporation of noise reducing engineering and design
(i.e., building enclosure) and placement away from residential receptors. Therefore, under
implementation of the Preferred Alternative, no long-term direct or indirect operational noise
would occur and would therefore result in less than significant impacts to noise.
Under the No Action Alternative, no construction activity would occur under this alternative, and
no changes to the existing noise environment would occur. Therefore, no direct or indirect short-
term or long-term noise-generating activity or associated impacts would occur, and conditions
would remain unchanged.
4.7.2 Odor
Long-term implementation of the proposed wastewater collection system would not generate
odors, as odors would be contained within the pipeline system underground; however, short term
odor impacts would potentially occur during the abandonment of existing septic systems. Septic
system abandonment would occur in accordance with Imperial County procedures which include
either removing the septic tank completely or abandoning the tank in place. The abandonment of
existing septic systems would result in a long-term decrease in odors in the project area, through
the elimination of wastewater leaks and overflows.
Under the Preferred Alternative the WWTP would be constructed to the northeast of Palo Verde,
approximately 1,000 feet east of Sunset Way and adjacent residences. Despite this buffer, there is
some potential for odors to occur within Palo Verde under the Preferred Alternative. Winds in
Palo Verde tend to be from the west or southwest, which would generally direct odors away from
residential areas and to the east of the proposed WWTP; however easterly winds do occur and
would occasionally direct odors towards residential areas.
The removal of septic systems would eliminate the overflow or leak of untreated treated
wastewater into the environment, thereby eliminating associated odors. Under the Preferred
Alternative odor would be minimal.
Under the No Action Alternative, the leak and overflow of untreated wastewater from failing septic
systems to the proposed project area would continue to be released into the environment,
contributing to odor. Therefore, current conditions would remain unchanged.
4.8 ENERGY AND NATURAL RESOURCES
Under the Preferred Alternative, energy demand would occur from the one pump station and
operation of the WWTP. The majority of long-term operational energy associated with the
Preferred Alternative would relate to the off-site combustion of natural gas for the generation of
industrial and utility electric power. Energy use in Palo Verde will increase with the
implementation of the Preferred Alternative, however, the Preferred Alternative would not
constitute a substantial increase in existing power use on the electrical grid system. Therefore,
there would be no significant impacts to energy resources. As part of project development,
coordination with Southern California Edison (SCE) would be required to ensure that sufficient
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infrastructure exists to support the proposed proj ect. Increased energy use for pumping wastewater
and operation of the WWTP are the only operational sources of GHG emissions associated with
the project. This would indirectly contribute to GHG emissions through increased power demand
from an offsite utility provider (SCE). The wastewater collection pumps would incorporate
renewable energy sources (approximately 20 percent of energy would be generated from solar
power). Both construction and the operation of the proposed wastewater collection and treatment
system would incrementally contribute to GHG emissions; however, given the limited construction
and energy utilization of the Preferred Alternative, contributions would be considered less than
significant.
Under the No Action Alternative, a wastewater collection and treatment system would not be
constructed in the proposed project area and conditions would remain unchanged.
4.9 TRANSPORTATION
Under the Preferred Alternative construction activities would occur along existing roadways.
During construction, roadway access by residents or users of the proposed project area would be
temporarily restricted. Short-term impacts regarding access would be minimized by the use of
standard engineering and traffic management practices. Once operational, wastewater treatment
infrastructure would not impact vehicular traffic or other transportation methods. Access at the
Fourth Street Bridge would be temporarily impacted during construction of the force main across
the Palo Verde Lagoon. The inventory rating of the bridge is 35,935 pounds (lb) and an operating
rating of 50,044 lbs. Due to the aging nature of the bridge, no construction equipment weighing
greater than a maximum of 35,935 lbs would be able to cross the bridge. In addition, if a structural
assessment concludes that the bridge is capable of supporting the proposed force main, the force
main would be placed on top of the bridge on one of the existing walkways. Therefore, only short-
term impacts to transportation associated with the Preferred Alternative would occur.
Under the No Action Alternative, a wastewater collection and treatment system would not be
constructed in the proposed project area. Conditions would remain unchanged.
4.10 WASTE MANAGEMENT
Upon implementation of the Preferred Alternative, waste conveyed to the wastewater treatment
system would be contained within the system until fully treated. No hazardous chemicals or
hazardous materials would be utilized in the operation of the proposed WWTP or stored at the
facility. The WWTP ponds would need to be drained and waste sludge (bio-solids) removed two
to four times per year. Depending on the WWTP final design, biosolids would need to be removed
from the grit screen either monthly, at worst, but likely quarterly. It is anticipated that bio-solids
would either be land applied or disposed of at an appropriate landfill. Appropriate disposal of bio-
solids would be determined in a Bio-Solids Management Plan, which would be developed as part
of the final WWTP design and would be consistent with local, state, and federal regulations. The
removal of septic systems would eliminate the discharge of untreated or partially treated
wastewater into the environment. Therefore, long-term impacts from the implementation of the
Preferred Alternative would be beneficial by improving the quality of waste management in Palo
Verde.
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Under the No Action Alternative, the wastewater collection and treatment system would not be
constructed in the proposed project area. Conditions would remain unchanged. The leakage of
untreated wastewater into the environment would continue, which would result in continued
adverse impacts to waste management in Palo Verde.
4.11 SOCIOECONOMICS
Implementation of the Preferred Alternative is intended to eliminate sewage leaks caused by
inadequate infrastructure through the development of appropriate wastewater collection and
treatment infrastructure, thereby reducing the potential for untreated wastewater to enter the
environment and improving the water quality of the Palo Verde Lagoon. For project construction,
construction crews would likely be hired from the available pool of workers in Palo Verde, Blythe,
and nearby communities, resulting in an increase in short-term construction employment.
Completion of the wastewater collection system would also allow for the redevelopment of
properties that are abandoned or vacant as a result of the 2007 tornado, and that are currently
undevelopable due to inadequate setback from the Lagoon. Construction activities would provide
temporary employment and economic activity in Palo Verde.
Maintenance and upkeep of the WWTP proposed under the Preferred Alternative would be
conducted by existing Palo Verde Community Water District (PVCWD) staff thus, no significant
long-term employment would be generated. Increased utility costs for Palo Verde residents may
result from implementation of the Preferred Alternative. The increased costs would be based on
numerous factors including the total project construction costs, project financing, potential
governmental assistance, and future billing structure. Due to the higher than average poverty rate
of the project area, increased utility costs have the potential to adversely affect residents and
businesses; however, with potential cost increases unknown, and with the potential to offset some
of these costs through government or other programs, the full impact to socioeconomics is difficult
to quantify. It is anticipated that adverse but less than significant impacts to socioeconomics would
occur.
Under the No Action Alternative, the wastewater collection and treatment systems would not be
constructed in the proposed project area. Socioeconomic conditions would remain unchanged or
may worsen as more homes are vacated and community development remains stalled.
4.12 ENVIRONMENTAL JUSTICE
Implementation of the Preferred Alternative is intended to eliminate sewage leaks caused by
inadequate infrastructure through the development of appropriate wastewater collection and
treatment infrastructure, thereby reducing the potential for untreated wastewater to enter the
environment and improving the water quality of the Palo Verde Lagoon. As a result of project
implementation under any alternative, risks to public health (e.g., water-borne pathogens) resulting
from the leakage of untreated wastewater and interaction with Palo Verde Lagoon water would be
reduced. No significant direct or indirect environmental impacts from either construction- or
operations-related activities are anticipated to affect low-income populations, minority
populations, or children in Palo Verde or the surrounding area. No significant short term or long-
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term impacts are anticipated to occur; therefore, children and minority and low income populations
would not experience direct or indirect disproportionate impacts related to the Preferred
Alternative. A beneficial effect of the construction of a wastewater collection system is that
sewage leaks would no longer occur, resulting in fewer contaminants in local waterways than
under current conditions. Therefore, implementation of the Preferred Alternative would result in
beneficial impacts for children and low-income populations because it would reduce exposure of
the human population to pathogens found in untreated water.
Under the No Action Alternative, the wastewater collection and treatment system would not be
constructed in the proposed project area. Conditions would remain unchanged and public health
concerns related to the exposure to wastewater in the environment would continue in the project
area, resulting in adverse impacts.
4.13 SUSTAIN ABILITY AND GREENING
Energy would be provided to the proposed project primarily from off-site combustion of natural
gas for the generation of industrial and utility electric power; however, the pump station would be
fitted with solar panels and the WWTP aerator would likely also be fitted with solar panels that
would then be able to provide a secondary source of energy to reduce dependence on grid power,
and reduce operation and maintenance costs. Grid power electrical generation may include air
nonpolluting sources such as solar, wind, or nuclear power; however, power in the region is
generally provided by combustion of natural gas. Anticipating potential future availability of
renewable energy, electrical distribution supply and controls would include a cross-over
connection should supply from an anticipated solar park near the water treatment plant in Palo
Verde become available.
For this analysis, operational energy requirements of the WWTP were estimated under worst case
conditions where no solar panels are utilized, and it was assumed the WWTP would consume a
maximum of 100,000 kWh/year. Additionally, the pump station would consume a maximum of
7,000 kWh/year with 20 percent of the energy being generated from solar power.
Under the Preferred Alternative, energy demand would occur from the one pump station and
operation of the WWTP including aerators. The majority of long-term operational energy
associated with the Preferred Alternative would relate to the off-site combustion of natural gas for
the generation of industrial and utility electric power. However, the Preferred Alternative would
not constitute a substantial increase in existing power use; therefore, there would be no significant
impacts to energy resources. As part of project development, coordination with SCE would be
required to ensure that sufficient infrastructure exists to support the proposed project. Increased
energy use for pumping water and operation of the WWTP are the only operational sources of
GHG emissions associated with the project. This would indirectly contribute to GHG emissions
through increased power demand from an offsite utility provider (SCE). The wastewater collection
pumps would incorporate renewable energy sources (approximately 20 percent of energy would
be generated from solar power). Both construction and the operation of the proposed wastewater
collection and treatment system would incrementally contribute to GHG emissions; however,
given the limited construction and energy utilization of the Preferred Alternative, contributions
would be considered less than significant.
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Under the No Action Alternative, a wastewater collection and treatment system would not be
constructed in the proposed project area and conditions would remain unchanged.
4.14 HUMAN HEALTH AND SAFETY
Implementation of the Preferred Alternative is intended to eliminate sewage leaching and leaks
caused by failing septic systems through the development of appropriate wastewater collection
and treatment infrastructure, and thereby reducing the potential for untreated wastewater to enter
the environment. The high levels of pathogens currently found in the Palo Verde Lagoon would
be reduced upon implementation of the Preferred Alternative. As a result, risks to public health
(e.g., water-borne pathogens) resulting from the use or contact with the Palo Verde Lagoon would
be reduced. Further, potential contamination of well water resulting from leaking septic systems
would be eliminated. Therefore, implementation of the Preferred Alternative would result in
beneficial public health and safety impacts because it would reduce exposure of the human
population to pathogens found in inadequately treated wastewater.
Under the No Action Alternative, the wastewater collection and treatment systems would not be
constructed in the proposed project area. Public health and safety conditions would remain
unchanged.
4.15 CUMULATIVE EFFECT
Cumulative impacts on environmental resources result from incremental impacts of the Preferred
Alternative when combined with other past, present and reasonably foreseeable future projects in
an affected area. Cumulative impacts can result from minor but collectively substantial actions
undertaken over a period of time by various agencies (federal, state or local) or persons. In
accordance with NEPA, cumulative impacts resulting from projects that are proposed, under
construction, recently completed or anticipated to be implemented in the near future are discussed
in this section.
No other projects are currently scheduled within Palo Verde; however, a solar power array has
been discussed for development near the potable water plant at the southern margin of Palo
Verde. This project is in the initial planning stage and no application has been submitted to
Imperial County; the project is therefore not likely to be implemented until well after the
construction of the Proposed Action is completed.
Implementation of the Preferred Alternative, if conducted simultaneously with other unforeseen
planning improvements to Palo Verde, would have the potential to cumulatively impact air quality,
water quality, and noise in the immediate area; however, impacts would be short-term and the use
of BMPs would reduce impacts to less than significant levels. Long-term cumulative impacts
associated with Preferred Alternative would be beneficial to water resources, public health and
safety, land use, socioeconomic conditions and environmental justice and protection of children.
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