United States
Environmental Protection
Agency
Municipal Environmental Research »
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-063 Sept. 1983
SEPA Project Summary
Evaluation of Alternative
Wastewater Collection and
Treatment Methods for Three
Small Kansas Communities
Kenneth C. Wiswall, Alice L Lenthe, and Robert P. G. Bowker
Alternative wastewater management
systems were evaluated for the three
small communities of Corning, Furley,
and Havana, Kansas. All three com-
munities are rural, agriculturally-or-
iented settlements with populations of
less than 200. Numerous failures of
onsite systems have been reported. Soil
conditions are such that individual
wastewater systems such as septic
tank/soil absorption alternatives are
not feasible on a widespread basis. The
wastewater collection alternatives
considered included conventional grav-
ity sewers, small diameter gravity
sewers (conveying septic tank effluent),
and pressure and vacuum sewers; the
treatment alternatives included package
plants, spray irrigation, and continuously
discharging lagoons.
For Corning and Havana, wastewater
collection by pressure sewers using
individual and clustered septic tank
effluent pumps and treatment via
continuously discharging lagoons were
found to be the most cost-effective
wastewater management solutions.
Although the pressure sewer collection
alternative was also found to be most
cost effective for Furley at the projected
future population, the cost effectiveness
of pressure versus gravity sewers was
found to be sensitive to projected
growth. It was thus recommended that
population projections for Furley be
reassessed, which may affect choice of
alternatives. Overall, wastewater col-
lection via small diameter pressure
conveyance of septic tank effluent was
found to be the least costly collection
alternative for the three small com-
munities investigated. Compared with
various pressure sewer configurations
as well as with small diameter gravity
sewers, conventional gravity sewers
had the highest total present worth
cost.
This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory. Cincinnati, OH,
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The Clean Water Act of 1977 (PL 95-
217) requires that alternatives to conven-
tional wastewater treatment be consid-
ered—alternatives that potentially may
reduce capital and operation/main-
tenance costs or reduce energy con-
sumption. For communities with popula-
tions of less than 3500, both alternative
collection and treatment systems may
qualify for increased Federal grant
assistance of up to 85% of the eligible
project costs. Before 1977, the plans for
many facilities did not adequately evalu-
ate alternative wastewater technologies,
many of which are particularly applicable
to small communities.
Methodology
The original facility plans for the three
communities, prepared in 1977, were
analyzed in detail. Site visits were made
to the communities to review the validity
of cost assumptions used in the plans and
to document existing conditions at each
location.
-------
Present and projected populations for
the Kansas communities are shown in
Table 1.
Soil conditions in the area, as con-
firmed by district geologists, local sani-
tarians, and observations during field
visits, are described as "slowly permeable
and unsuitable for septic tank systems."
Soils in the area are predominately silty
clay underlain by clays with moderate-to-
high shrink/swell potential. Bedrock and
groundwater are deep and do not present
a problem with sewer construction or
maintenance of adequate separation
distance between subsurface disposal
systems and bedrock or groundwater.
Soil permeability, however, precludes
virtually all onsite treatment/disposal
alternatives throughout most of the
planning areas. Near each community,
land is available that could be used for
siting treatment facilities (e.g., package
plants or lagoons) or land application
systems.
Because of unsuitable soil conditions
throughout most of the planning areas,
further analysis focused on alternative
collection and treatment systems. Treat-
ment alternatives evaluated for each
community included package plants,
lagoons with spray irrigation of effluent,
and conventional discharging lagoons.
For Corning, collection systems analyzed
were:
(1) Septic Tank Effluent Pump (STEP)
pressure sewers; (2) small diameter
gravity sewers conveying septic tank
effluent; and (3) conventional gravity
sewers. For Furley: (1) STEP pressure
sewers (one STEP unit per user); (2)
clustered STEP pressure sewers (more
than one user per STEP unit); and (3)
conventional gravity sewers. For Havana:
(1) clustered STEP pressure sewers; (2)
partial sewering (approximately one half
the planning area) with STEP pressure
sewers, with the remainder of the homes
served by upgraded onsite systems; and
(3) conventional gravity sewers.
A present worth cost analysis was
performed for the various alternatives for
each community based on future popula-
tions. Assumptions used for the analysis
are listed below:
• Planning period = 20 years
• Interest rate = 7%
• Service life = 20 years for STEP unit
components
• Salvage value = value at end of
planning period
• User costs = calculation based on an
EPA grant:
85% of eligible costs for alterna-
tive collection and treatment
systems, and 75% for conven-
tional collection and treatment
systems
Unit cost assumptions for collection
alternatives were critical for performing
an accurate cost-effective analysis. The
unit cost assumptions used in the
evaluations are summarized (Table 2).
Results
Treatment alternatives were first
evaluated to determine which system(s)
provided reasonable service at the least
cost and with low operation and main-
tenance requirements consistent with
the financial and technical capabilities of
the communities. Table 3 represents a
preliminary cost-effective analysis of the
package plant, spray irrigation, and
continuously discharging lagoon alter-
natives. Lagoons were selected based on
low capital cost and the lack of need for
substantial operation and maintenance
requirements, such as highly skilled
operators, maintenance of mechanical
and electrical equipment, and energy
utilization. In addition, the State of Kansas
considers lagoons to be acceptable, low-
cost alternatives that are particularly
applicable to small communities. Thus,
continuously discharging lagoons were
selected as the most viable treatment
Table 1. Population Data
alternatives for all three Kansas com-
munities. It should be noted thatthe costs
presented in Table 3 are based on
treatment of raw sewage. During the final
cost-effective analysis, these costs were
revised to reflect changes in organic
loading that would result from pretreat-
ment by septic tanks for the STEP
pressure sewer and small diameter
gravity "effluent" sewers.
Various alternative collection systems
including small diameter gravity, grinder
pump and STEP pressure, vacuum, and
conventional gravity sewers were first
subjected to preliminary screening.
Further detailed analyses were limited to
the small diameter, STEP pressure, and
conventional gravity sewer alternatives.
In addition, consideration was given to
the "clustered" STEP collection system,
whereby each pumping unit serves two
or more homes.
The results of the overall cost-effective
analysis are presented in Table 4. For
Corning, the most cost-effective alter-
native was collection via STEP pressure
sewers and treatment using a continu-
ously discharging lagoon. For Furley, a
"clustered" STEP pressure collection and
lagoon treatment system had the lowest
present worth cost. For Havana, partial
sewering via a STEP pressure sewer with
lagoon treatment and upgrading of the
Community
Corning
Furley 1
Furley II*
Havana
No. Units
105
40
40
75
Present
Population
152
97
97
184
Future
No. Units
124
55
165
87
(20 yr)
Population
208
140
500
220
*An additional future population projection was considered to illustrate the impact of potential
growth.
Table 2. Summary of Unit Cost Assumptions for Wastewater Collection Alternatives
Item
4-in. gravity sewer
8-in. gravity sewer
4-in. gravity service connection
1-1 /4-in. PVC pressure sewer
1-1/2-in. PVC pressure sewer
2-in. PVC pressure sewer
2-1 /2-in. PVC pressure sewer
3-in. PVC pressure sewer
4-in. PVC pressure sewer
Conventional septic tank/soil
absorption system (installed)
STEP system (installed, with septic
tank)
STEP pump
Grinder pump
Pump station
Total Installed
Unit Cost ($)
$15.00/ft \
20.00 /ft \
5.00/ft ]
3.00/ft \
3.75 /ft I
4.00/ft \
4.25/ft [
4.7 5 /ft 1
5. 50 /ft. '
3,000.
1,300.
400.
1.750.
—
O&M
<$/yr)
$500/mile
100 /mile
15
45*
75
800
*For each system, not including tank pumping.
-------
remainder of onsite systems had a
slightly lower present worth cost than the
completely sewered STEP pressure
option. However, because of the pre-
dominance of adverse soil conditions in
the area, the totally sewered alternative
was recommended.
Table 5 summarizes the estimated user
charges for each community. The re-
commended alternatives had associated
user costs ranging from $145 to $276 per
household per year. With the exception of
Corning, user charges are considered
within acceptable ranges (as percent of
median income) based on EPA recom-
mendations outlined in Program Require-
ments Memorandum 79-8. Other funding
sources (HUD), which will reduce the
local share of capital costs and thus user
charges, have been secured for Corning.
Conclusions
Alternatives to conventional gravity
collection may be more cost-effective for
small communities or low-density fringe
areas surrounding larger municipalities.
Many factors affect the relative costs of
collection systems, including housing
densities, topography, and soil character-
istics. Pressure sewers often have
Table 5. Summary of Estimated User Costs for Wastewater Collection and Treatment*
Alternative
Median Household
Income, $/yr
User Cost,
$/yr
%of
Median Income
Corning $4,509
STEP pressure sewer
Small diameter gravity sewer
Conventional gravity sewer
Furley 77,700
STEP pressure sewer
"Clustered" STEP sewer
Conventional gravity sewer
Havana 74.335
STEP pressure sewer
Partial STEP with onsite
systems
Conventional gravity sewer
$145
195
295
325
276
337
155
140
270
3.2%
4.3
6.5
1.9
1.7
2.0
1.1
1.0
1.9
* Treatment via continuously discharging lagoons.
economic advantages for low-density
areas, hilly topography, and restrictive
soil profiles. The last two conditions may
substantially increase the costs of gravity
sewer installation because of the require-
ment for deep cuts and/or lift stations
(hilly topography) and the need to provide
shoring and trench dewatering (high
groundwater) and/or blasting (thin soils
over bedrock). Because of their inherent
characteristics, pressure sewers can
generally be installed at a uniform depth
below ground following the natural
topography.
Table 3. Summary
Treatment
Corning
Package plant
Spray irrigation
Discharging lagoon
Furley
Package plant
Spray irrigation
Discharging lagoon
Havana
Package plant
Spray irrigation
Discharging lagoon
of Costs of Treatment Alternatives (1979 $)
Capital Cost, $ O&M Costs. $/yr
$30,000
98,600
53,749
27,000
98,175
71.845
33,000
72.700
39,997
$6.800
5,000
1.500
4.760
3,000
2,000
7.480
3,000
1.500
Total Present
Worth, $
$102.039
151,570
69,640
77,427
129,957
93,033
1 12,243
104.482
55,888
In some cases, feasibility of pressure
sewers should not be based sotely on a
cost-effective analysis. Two other im-
portant factors are the ability to the
community to ensure proper day-to-day
operation and maintenance of the system
and the impact of prolonged power
outages. The latter factor was considered
to be a valid consideration for these study
areas owing to experiences with extended
power outages.
The full report was submitted in
fulfillment of Contract No. 68-03-2775
by Roy F. Weston, Inc., under the
sponsorship of the U.S. Environmental
Protection Agency.
Table 4. Summary of Cost-Effective Analysis (1979 $)
(Includes cost of treatment by discharging lagoon)
Construction, $
Alternative find, land & salvage)
Operation and Maintenance
Annual, S/yr
Present Worth, $
Total Present
Worth. $
Corning
STEP pressure sewer
Small diameter gravity sewer
Conventional gravity sewer
Furley
STEP pressure sewer
"Clustered" STEP sewer
Conventional gravity sewer
Havana
STEP pressure sewer
Partial STEP with onsite
system upgrading
Conventional gravity sewer
$271,978
455,533
505,339
163.550
144,310
226.000
192,785
206.820
315,387
$7.625
6,870
5,010
4,935
4,125
2,190
6.185
4,770
3,405
$80,780
72,780
53,075
52,280
43,700
23.200
65.520
50.535
36,070
$353,000
528,000
558,000
216.000
188,000
249.000
258.000
257.000
351,000
-------
Kenneth C. Wiswall and Alice L, Lenthe are with Roy F. Weston, Inc., West
Chester, PA 19380; and Robert P. G. Bowker is with the U.S. Environmental
Protection Agency, Cincinnati, OH 45268.
Robert P. G. Bowker is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of Alternative Wastewater Collection
and Treatment Methods for Three Small Kansas Communities," (Order No. PB
83-247 197; Cost: $10.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
*US GOVERNMENT PRINTING OFFICE 1983-659-017/7190
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
RETURN POSTAGE GUARANTEED
Third-Class
Bulk Rate
MERLOObii"
81
1L
------- |