EXECUTIVE PANEL REPORT TO THE ADMINISTRATOR
ON
THE PROPOSED MONTGOMERY COUNTY ADVANCED
WASTEWATER TREATMENT PLANT
ADMINISTRATOR'S EXECUTIVE PANEL
Paul A. Brands
John Rhett
Daniel J. Snyder,III
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
AUGUST 6, 1976
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EXECUTIVE PANEL REPORT TO THE ADMINISTRATOR
ON
. THE PROPOSED MONTGOMERY COUNTY ADVANCED
WASTEWATER TREATMENT PLANT
INTRODUCTION
On March 19, 1976, the State of Maryland transmitted
to EPA a construction grant application for an advanced
wastewater treatment (AWT) facility proposed for construction
by Montgomery County in the vicinity of Dickerson, Maryland.
Though -EPA has been involved with this project during the
last few years, increased public concern about potential
contamination of drinking water supplies, and substantial
changes in both the costs associated with building the plant
and the flow projections upon which it is justified, raise
sufficient concern to warrant a detailed EPA review at this
time. .This is particularly true with respect to the legisla-
tively mandated cost-effectiveness review requirements.
Because of the complex, controversial nature of the
proposed facility, the Administrator recently formed a
special Executive Panel consisting of Paul A. Brands, Deputy
Assistant Administrator for. Planning and Evaluation; John T.
Rhett, Deputy Assistant Administrator for Water Program
Operations; and Daniel J. Snyder III, Regional Administrator,
EPA Region III, to review the proposed project.
The Panel members were instructed to analyze and assess
all major issues relating to the grant application, to
prepare an options paper for the Administrator and to recom-
mend a specific course of action. In response to this
charge, this report contains a summary'of the assessments of
the major issues and a series of optional courses of action.
The Panel members will not recommend a decision on a specific
course of action to the Administrator until after the Panel
has had an opportunity to obtain additional information and
comments at the public meeting scheduled for August 11,
1976.
RECENT HISTORY OF THIS PROJECT
A number of important events have occurred since EPA -
received the grant application in March. On April 7, 1976,
EPA issued a draft National Environmental Policy Act (NEPA)
review of the proposed project subtitled "Tentative, Pre-
liminary Document for Discussion and Comment." Such reviews
are required for all wastewater treatment plants involving
Federal cost-sharing- participation. The review raised
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several concerns about the Dickerson proposal and presented
cost data which indicated that at least one possible alter-
native site/ located in the vicinity of Piscataway in Prince
Georges County, appeared substantially more cost-effective
than the Dickerson proposal.
On May 14, 1976, EPA received a report entitled "Maryland
Response to the Tentative U.S. Environmental Protection
Agency Report on the Dickerson Advanced .Wastewater Treatment
Plant." The Response rejected the cost comparisons in EPA's
draft NEPA review, and presented cost data showing that the
cost of an alternative treatment scheme at Dickerson
(resulting in a lower level of treatment than originally
proposed) would approximately equal the cost of the Piscataway
alternative. In addition, the Response argued that the
Piscataway alternative was socially and politically unaccept-
able to Prince Georges County, and that Dickerson was the
only option which could be implemented soon enough to
provide the treatment capacity desired by the County to end
the sewer moratoriums imposed by the Maryland Department of
Health and Mental Hygiene.
To narrow the areas of controversy and facilitate
an exchange of information with respect to the major issues
involved in the proposed wastewater treatment project, EPA
staff have'held a series of meetings with the staffs of many
of the impacted governmental bodies — the State of Maryland,
Montgomery County, Prince Georges County and the Washington
Suburban Sanitary Commission.
MAJOR ISSUES RELATED -TO THE PROPOSED PLANT
The significant issues raised in the review of the
Dickerson proposal have been examined by the Panel in con-
siderable detail. The following pages summarize these
issues and the Panel's findings.
Population and Sewage Flow Projections
The size and cost of a proposed wastewater treatment
plant is determined to a major extent by the population
projections for the area to be served by the facility.
Since the facility proposed for Dickerson was originally
planned to serve Montgomery County, the Panel began by
reviewing wastewater flows for the Montgomery County
service area.
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This review included examination of the flow projec-
tions submitted by the applicant in support of the grant
application as well as more recent population projections
made by other local and regional planning entities.1]
Through a careful analysis of available population projec-
tions, the Panel developed an independent estimate of sewage
flow requirements»
Estimates for Montgomery County sewage flows are tied
to projections of the construction of dwelling units. Since
last fall, the County Planning Board has published a series
of growth scenarios, two of which have received endorsement
from the County Council (Table I). The first of these is the
"intermediate" forecast which the county feels is an accurate
estimate of growth in population and construction over the
next 10 years. However, for planning purposes the County has
adopted a higher "trend" projection.
TABLE I
MONTGOMERY COUNTY PLANNING BOARD ESTIMATES
OF DWELLING UNIT CONSTRUCTION
•(UNITS PER YEAR)
1975-1980 1980-1985
Intermediate Forecast 4,000 6,000
Trend Forecast 6,400 7,600
The presentation of two forecasts by the county has
posed a significant problem to analysis of flows. Sound
cost-effectiveness analysis argues that the "intermediate"
forecast rather than the "trend" should be used,since the
council appears to believe the former estimate most accurately
represents expected future growth.
In order to insure adequate treatment capacity, the
Panel has based its independent flow analysis on a forecast
of 6,000 new dwelling units per year over the projects
planning period. This compares with the basis of the
applicant's estimate which is an average of 7,000 units per
year.
JJ Montgomery County Planning Board, Washington Metropolitan
Council of Governments, and the National Planning Association,
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The resulting projected sewage flows for Montgomery
County to the year 2000 are shown in Table II. The assump-
tions upon which the projections are based are included in
Appendix A.
TABLE II
ESTIMATES OF MONTGOMERY CODNTY SEWAGE FLOWS
Applicant
EPA
Total Treatment
Sewered Flow Capacity
Year Population Estimate Need*
(million gallons/day)
Total Treatment
Sewered Flow Capacity
Population Estimate Need*
(million gallons/day)
1975 515,700
73.5
515,700
70.0
9.5
22.5
34.9
47.2
59.8
*Total projected flow minus 76.6 mgd allocation at Blue
Plains wastewater treatment plant; these figures do not
include planned capacities of Montgomery County interm
treatment facilities.
1980
1985
1990
1995
2000
587,200
664,746
735,996
807,246
878,496
86.1
99.1
111.5
123.8
136.4
578,563
630,054
688,872
748,804
808,437
78.9
86.8
94.9
102.7
111.7
2
10
18
26
3
2
3
1
35.1
As outlined in the Response, the State and Montgomery
County now, however, are generally justifying the proposed
60 mgd capacity on the basis of Dickerson being a regional
plant which would directly or indirectly service flows from
the District of Columbia and Virginia as well as Montgomery
County. While there is some history suggesting that the
proposed plant at Dickerson would treat regional flows,
discussion of specific offers to provide permanent treatment
capacity to other jurisdictions is relatively new. Because
no formal agreements have been consummated among the
regional jurisdictions as to what capacities they would be
willing to "buy" or "sell,"'it is not possible to assess
adequately the magnitude of potential regional flows that
would be serviced by the proposed Dickerson plant.
The Applicant has recently offered 7 1/2 mgd of permanent
capacity to the District of Columbia. The District has
indicated that it would accept such capacity if there would-
be no adverse water supply impacts and if treatment costs
were not greater than those of other alternatives. ,
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Even more recently, the Applicant has offered 10 mgd of
permanent capacity and 10 mgd of temporary capacity to
Virginia. While Virginia has stated that it would not
"purchase" temporary treatment capacity/ it has indicated
that it would consider approving a permanent allocation of
capacity at Dickerson. Montgomery County, however, has
offered capacity only to Fairfax County, whereas the State
of Virginia appears concerned about obtaining capacity .for
additional jurisdictions.
Assessment of this issue indicates that a plant of
35 mgd capacity could be justified from a flow standpoint on
the basis of projected Montgomery County sewage flows.
However, should firm commitments of capacity utilization
(based upon reasonable flow projections) by Virginia and the
District similar to those that have been offered actually
be consummated, then a plant of 50-60 mgd capacity could be
justified from a flow standpoint.
Cost-Effectiveness
The cost-effectiveness of five basic treatment plant
alternatives were examined by the Panel:
o Dickerson I —'a 60 mgd plant as proposed in the
March 19 grant application. This facility would
provide nitrogen as well as phosphorous removal and
would involve a 23-mile force main delivery system
with five pumping stations. This is the only
alternative for which plans and specifications have
been submitted.
o Dickerson II — a 60 mgd plant reflecting the design
changes suggested by the State in their Response
document. This facility would provide phosphorous
removal and nitrogen oxidation and would involve the
same force main system as proposed under Dickerson I.
o Dickerson II - 35 mgd -- a smaller version of "Dicker-
son II" sized to treat 35 mgd.
o Piscataway Alternative - 60 mgd — a 60 mgd expansion
of Prince Georges County's proposed 30 mgd plant in
the vicinity of the Piscataway plant, including the
additional transmission costs necessary to deliver
Montgomery County flows to the project site. The
plant would provide nitrogen oxidation treatment
similar to the treatment now provided at the Blue
Plains treatment plant.
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o Piscataway Alternative - 35 mgd — a smaller version
of "Piscataway - 60 mgd" sized to treat 35 mgd,
including the additional transmission costs for
Montgomery County flows.
The cost estimates for the Piscataway alternatives
include the costs of constructing and operating the following
related facilities:
o Enlargement of the proposed force main between Blue
Plains and Piscataway.
o Construction of an additional 7 mgd of interim plant
capacity in Montgomery County to serve county flows
temporarily between 1981 and 1984.
o Operation and maintenance of all interim plants (14.5
mgd) for 3 years from 1982 through 1984.
o Construction of relief sewers, pumping stations and
other works to convey Montgomery County flows to the
Potomac Interceptor sewer.
o Augmentation of Potomac Interceptor capacity by
construction of retention facilities when conveyance
capacity is reached.
In addition to the five treatment plant alternatives
examined in this analysis, other alternatives such as varia-
tions in the Darnestown proposal, a re-rating of Blue Plains,
and additional Dickerson modifications were examined. They
were not examined in as much detail, however, either because
.of substantially higher project costs, potential impacts on
drinking water supplies, insufficent data available at this
time, or other similar problems and limitations. This does
not imply that other feasible alternatives do not exist.
The present worth comparisons of the five alternatives
examined in detail are displayed in Table III.1J A more
detailed cost-effectiveness presentation is included in
Appendix B. The present worth calculations are in accordance
with the requirements of Appendix A of the Construction
Grants Regulations. Secondary costs or benefits (e.g.,
potential loss of tax revenue at the county level) are not
included in this comparison — they are discussed as separate
issues.
JJ The present worth calculations involve laying out the
expected annual flow of capital and O&M dollars and then
discounting those dollar flows back to a base year (in
this case 1980). This approach reflects the time-value of
money.
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TABLE III
PRESENT WORTH COMPARISON OF ALTERNATIVES
Capacity Present Worth *
Alternative (mgd) (million dollars)
Capital O&M Total
Dickerson I " 60 $273 $108 $381
Dickerson II 60 247 90 337
Piscataway 60 mgd 60 154 82 236
Dickerson 11-35 mgd 35 175 67 242
Piscataway 35 mgd 35 103 65 168
*1980 present worth in 1975 dollars
Table III indicates that the Dickerson alternatives
are substantially more cos.tly than the comparable capacity
of the Piscataway alternatives. In the case of the 60 mgd
alternatives, the Piscataway plant would cost about $100
million less than Dickerson II — about 30-35 percent less.
Similarly, the difference for the 35 mgd alternatives is $75
million — about 30 percent less costly.
The Maryland Response also presented a present worth
comparison between Dickerson II and "Piscataway - 60 mgd" .
The analysis in the Response concluded that there are
essentially no total cost differences between the two
alternatives.
The principal reasons why there are wide cost differ-
ences between those two alternatives as calculated by the
Panel, while the Response estimates them to be about equally
costly, involve the following four factors:
o Interim capacity. Based on the revised flow require-
ments, less than 7 mgd rather than 14 mgd of additional
interim plant capacity would be required to serve
Montgomery County needs from 1981 to 1984 — thus
reducing the Panel's cost estimates associated with
Piscataway in comparison to the Response's estimates.
o Conveyance capacity. The Panel's estimate includes
lower costs to provide conveyance capacity due to '
augmenting capacity of the Potomac Interceptor
through construction of retention facilities rather
than constructing a relief tunnel as provided in the
Response estimate.
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o Virginia facilities. Considering only Montgomery
County flows, the Panel believes it inappropriate to
include the costs of providing Virginia interim
treatment facilities. If the alternatives are
assessed on a regional basis/ there is inadequate
information to support cost estimates for interim
treatment facilities in Virginia.
o Value of water supply. For reasons discussed later
in this paper, the Panel feels it inappropriate to
include in the cost comparison a value for water
supply augmentation as was done in the Response
comparison.
After careful review of the issues involved in deriving
cost comparisons, the Panel believes that the costs as shown
in Table III more accurately reflect the appropriate costs
which should be included in a cost-effectiveness comparison.
Public Health Considerations
The proposed 60 mgd AWT facility at Dickerson calls
for wastewater effluent discharge 20 miles above the Washington,
D.C. drinking water intakes and 8 miles above the proposed
drinking water intake for Leesburg, Virginia. Because.small
quantities of organic contaminants, trace metals and viruses
could be found in the effluent, concern about possible
public health risks is an important issue..
In the grant application and related documents both
Montgomery County and Maryland have said that the proposed
facility is designed to avoid any undue public health risk.
They point to the breakpoint chlorination and charcoal
filtering processes included in the proposal as insurance
that the effluent would pose no risk to public health.
In making its assessment of the factors relating to
public health, the Panel requested the EPA Office of Water
Supply and the EPA Municipal Environmental Research Laboratory
to evaluate the effects of the proposed discharge on the
quality of downstream drinking water supplies. In- response,
the Office of Water Supply acknowledged that there is a
possibility that contaminants would not be removed so completely
as to eliminate all potential risk to health. In addition,
it indicated that experience with AWT facilities and health
data for the kinds of contaminants known to be in sewage are
not sufficiently extensive or precise to predict accurately
all the health effects which might result.
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To minimize the risks posed by "upsets" in the treat-
ment process within the plant, clear water reservoirs (i.e.,
after-treatment storage lagoons) are incorporated in the
facility design. The Office of Water Supply states that
from its perspective these reservoirs are necessary features
for the plant.
The official responses from the Research Laboratory and
the Office of Water Supply concluded that from a drinking
water health standpoint the risks associated with the high
quality effluent discharge from Dickerson I or Dickerson II
would be minimal. However, these responses also indicated
that, because of the many unknowns associated with the
situation, "the best alternative would be to discharge all
sewage below the water intakes."
After reviewing all available evidence on this issue,
the Panel's assessment is that, though it would be preferable
to discharge below the metropolitan area's water intakes, the
health risks associated with the discharge from the proposed
project do not, by themselves, warrant rejection of the
proposed facility and denial of the grant application.
Cost of Delay
In examining the total costs :— secondary as well as
first-order costs -- associated with the five alternative
treatment plants, it is important to consider whether
potential treatment plant construction delays will result in
loss of tax revenues.
In the State Response the argument is advanced that if
the Dickerson treatment plant is not constructed in the near
future Montgomery County will incur substantial losses in tax
revenue because of a stifling of growth. The Response
includes an estimate that continuance of a sewer moratorium
would reduce revenues by about $120 million.
The Panel's review of the data presented in the State
Response suggests .that the cost of delay has been substan-
tially overstated for two reasons: first, because interim
plants either under construction or planned for construction
are expected to ^eliminate any treatment capacity shortage;
and second; because, in any case, the Response does not
consider the costs associated with providing the services
which must accompany growth (e.g., schools and roads). The
Response focuses solely on -the potential loss of tax revenues
which would be generated by expected growth in Montgomery
County.
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Though there are many assumptions and uncertainties associated
with this type of analysis, a Montgomery County study indicates
that a slightly higher growth rate would place the county in
a more favorable fiscal position. However, other studies of
land development indicate that the type of growth generally
experienced in suburban communities frequently creates more
costs for the local government than it produces in tax
revenues .jj
The assessment indicates that if interim treatment plants
are constructed as planned there will be no loss of.revenue.
In the event they are not constructed on schedule the.potential
net cost of delay would likely be very limited — certainly
. substantially less than the estimated $120 million.
Land Opportunity Cost
The Maryland Response contends that EPA has not
considered that there would be an added land oportunity cost
of $6 million associated with an expansion at Piscataway.2J
While the concept of land opportunity cost is valid, the
Panel's review indicates that the calculations in the
Response do not accurately reflect the situation. The
Response's estimate of the amount of land which must
be secured at Dickerson does not include the 150 acres
currently owned by PEPCO which would also be removed from
the tax base. But most important, the Response does not
include the fact that development of land cannot occur
without county investment in public services. Hence, it is
the Panel's view that when all appropriate factors are
considered, the land opportunity cost differences between
these two alternatives would be minimal.
Water Supply Augmentation Value
As the Washington metropolitan area's demands for water
increase, greater withdrawals will be required from the
Potomac River. Because of projected water supply shortages,
the potential value of recycling water in the river should
be considered.
jj One such report on Fairfax County concluded that the
development associated with an influx of population of
• 23,000 to 24,000 would have a negative fiscal impact.
This study calculated that for each new house the County
would pay $38 more to provide services than it would
receive in tax revenues.
2j Land opportunity cost can be viewed as the value of the
land if it were used for another purpose. In this case
it was assumed the land would be developed.
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The State Response estimated a water supply augmenta-
tion value of $19 million (later revised to $14 million) for
the 60 mgd facility proposed for Dickerson. This estimate
was derived by calculating the least cost alternative method
of achieving equivalent additional water supplies.
• The Panel's assessment is that the value associated
with water supply augmentation is much smaller than that
estimated in the Response. By including Potomac River flows
not considered in the Response, and by maintaining the
option, to use for water supply purposes flows which the
Response assumed would be by-passed to the estuary, the
Panel believes that water supply deficits would not likely
occur during the planning horizon of the proposed facility.
Based on the above, the Panel concludes that in the context
of the Dickerson issue, the water supply augmentation value
would be small, certainly far less than $14-19 million.
At the same time it should be pointed out that there
are in fact several unquantifiable benefits to water supply
augmentation. Additional flows could provide aesthetic and
fisheries benefits in the short term, and in- the longer term
(beyond the 20 year planning horizon) could help meet the
eventual need for additional water supplies.
'Water Quality
Preliminary findings by both the Applicant and EPA
indicate that the Dickerson facility as proposed in the
grant application would meet applicable water quality
standards. However, modifications to the original proposal
to reduce projected plant costs would result in the dis-
charge of nutrients at levels greater than originally
anticipated. Specifically, in place of the pure oxygen
activated sludge and .breakpoint chlorination for nitrogen
removal in the Dickerson I configuration, the modified
facility would have an air activated sludge nitrification
system. Total nitrogen concentrations expected with this
configuration would be 19 mg/1 as opposed to the 3 mg/1
concentrations in the original proposal. Average phosphorus
concentrations are expected to increase from 0.1 mg/1 for
Dickerson I to 0.2 mg/1 for Dickerson II.
Examination of this change indicates that the increase
in nutrient discharge-from Dickerson would tend to aggravate
a nutrient problem in the upper reaches of the Potomac
Estuary. However, the degree to which the situation
would be impacted is uncertain. The EPA Annapolis field
station has not yet completed its review of these water
quality impacts.
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The Panel's assessment suggests that Dickerson II would
be acceptable from a water quality standpoint, but additional
information is needed prior to reaching a final decision on
this issue.
Land Use Impacts
Considerable apprehension has been expressed concerning
construction of the proposed Dickerson delivery line (force
main) through the "green wedge" section of Montgomery
County. It has been asserted by a number of groups that
such a sewer line would encourage development in the wedge
that would be .in conflict with the County's Wedges and
Corridors General Plan.lJ
The County and State say that this is not a significant
concern in that there are adequate safeguards and procedures
to insure the integrity of the General- Plan, including: .
- New planning requirements and approval procedures.
Rezoning of 104,000 acres in the "green wedge" from •
2-acre to 5-acre minimum tracts.
State and County control through development and
revision" of the Ten Year Water and Sewerage Plan.
- Application of "the adequate public facilities
ordinance" to prevent unwanted development.
In addition, both the State and County feel that
lack of adequate treatment capacity results in distorted
growth patterns which are at least as environmentally
undesirable as possible development in the "wedge" areas.
The Panel's assessment indicates that although there
are safeguards in place and current county officials seem
dedicated to resisting unwarranted developmental pressures,
construction of such a sewer line clearly holds the potential
for future large scale development in conflict with the
County's General Plan. However, the Panel believes that the
decision with respect to the proposed Dickerson plant should
not be based primarily on this concern as it is essentially
a local land use issue.
A plan approved by Montgomery County in 1969 which lays
out the desired major physical developmental plan for the
county.
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ALTERNATIVE COURSES OF ACTION
The specific decision confronting the Agency at this
time is to determine the disposition of the grant application
submitted March 19, 1976 for construction of a 60 mgd '
advanced wastewater treatment plant at Dickerson, Maryland.
A positive decision calls for "continuing the processing of"
the grant application, while a negative decision would
terminate further consideration of the grant application.
.The Panel's assessment of the issues related to this
specific decision suggest the following considerations argue
in favor of proceeding with the grant application process:
Construction of Dickerson I could be initiated in the
immediate future. Other alternatives would require
further delay, hence, inflation might largely offset
any anticipated savings associated with these solutions
The population and flow projections submitted by the
State indicate a need for a 60 mgd facility. Uncer-
tainty with respect to area growth-forecasts may make
these estimates as valid as any others.
The Dickerson site has been selected after a long
review process. Presumably it represents the most
"acceptable alternative to area residents.
Dickerson I has the potential of meeting both
Montgomery County needs and regional requirements.
On the other hand, the considerations listed below
argue that it would not be advisable to proceed further with
the grant application process:
- The.Panel's analysis indicates that Montgomery
County's additional treatment requirements (35 mgd
capacity) do not support a plant of 60 mgd.
- The Panel's cost-effectiveness analysis indicates
that there are at least two substantially more
cost-effective alternatives to the treatment plant
proposed in the grant .application.
The absence of firm agreements among the local
jurisdictions on the treating of regional flows at
Dickerson precludes approval of the proposed treat-
ment plant as a regional facility.
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If the decision is made to terminate further considera-
tion of the March 19th grant application, it may be approp-
riate, because of the complex nature of this issue and in
the interest of time, to provide "guidance" to Montgomery
County, Maryland, the District of Columbia, and Virginia as
to. how they might want to proceed to meet the metropolitan
area sewage treatment needs. Should you "desire to do this,
selection of one of the options presented below could
provide the basis for structuring that "guidance."
Considering only Montgomery County flows, the Panel
estimates a projected unsatisfied treatment capacity need of
35 mgd in the year 2000. Thus, you might want to consider
at least the following thr.ee alternative solutions:
Alternative 1; Dickerson II - 35 MGD
>
This alternative is generally acceptable from
both a water quality and water supply point of
view, but it is less cost-effective than the other
two alternatives. It would supply all of Montgomery
County's additional capacity needs until about the
year 2000. This alternative would probably be
more acceptable politically than Alternative 2.
Alternative 2; Piscataway - 35 MGD
This alternative is more cost-effective than
Alternative 1 ($74 million less costly). It would
also satisfy Montgomery County's sewage treatment
needs until 2000. However, it is likely that there
would be substantially more political opposition to
it than to Alternative 1.
Alternative 3; Intermediate - range solution
Montgomery County is currently carrying out a
program to construct small (1-5 mgd} sewage
treatment plants which could (according to the
Panel's flow projections) provide treatment
capacity until a long range solution is found.
The County either has under construction or has
made commitments to construct 7 1/2 mgd of treatment
capacity and has plans proceed toward construction
of 7 mgd of additional capacity if permanent
treatment is not forthcoming in the near future.
This combined total of 14 1/2 mgd of capacity would
meet Montgomery County's needs until approximately
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1988 and would permit enough time to develop a long
term regional solution to the sewage problem. The
impacts on water quality and drinking water appear
acceptable, but the acceptability from a political
standpoint is unclear.
Though the present lack of firm commitments for the
treatment of regional flows at the proposed Dickerson '
site preclude approving it as a 60 mgd regional plant, you
may want to address the regional issue in your "guidance"
statement. The following information should be considered
with respect to that issue:
o Dickerson II at 60 MGD
This option is estimated to be substantially more
costly than a Piscataway alternative (by about $100
million). More precise cost comparisons cannot be
made until the Virginia counties, which would be part
of a Dickerson agreement are identified and the
flows from both Virginia and the District which
would be conveyed to such a regional treatment
facility are specified.
o Piscataway Expansion of 60 MGD
As an example of a less costly regional solution this
approach would cost about $100 million less than the
Dickerson approach. However, there would likely be
substantial political problems associated with
it.
The Panel members believe there are other longer term
regional alternatives — such as expansion of existing
treatment plants (e.g., the Blue Plains plant) or the con-
struction of facilities at other sites — which probably
warrant further detailed examination.
RECOMMENDATION
The Panel members, at this time, are not recommending a
specific course of action. Following the August llth meeting,
after having had the opportunity to obtain additional informa-
tion and to hear additional points of views, the Panel
members will make their recommendation.
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ASSUMPTIONS v MONTGOMERY COUNTY. FLOW PROJECTIONS
1. Use 1975 Base Population Sewered of 515,700 based on WSSC No. 2
Projections, as submitted by WSSC to EPA in letter of 2/13/76.
2. Assume 40.1 ingd 1975 base domestic flow, and 77.8 gpd per capita
flow in 1975, both from WSSC letter to EPA, 2/13/76.
10
11.
Use 1975 Base Total Flow of 70
12.7 mgd commerical/industrial
infiltration/inflow.
0 mgd, including 40
flow, and 17.2 mgd.
1 domestic flow,
due to
Assume domestic per capita flow remains constant in future years at
77.8 gpcd due to water saving devices, price increases, and County
policy (e.g., WSSC requirement that new housing and other construction
utilize 3.5 gallon flush toilet, compared to previous standard
5 or 6 gallon models).
Assume construction of new dwelling units at 6,000 units/year from
1975 on, based partially on-the Montgomery County Planning Board's
projected intermediate growth rates.
Assume 5% on new residential growth will occur outside sewer service
area (in accordance with General Plan).
Assume household size will gradually decrease, as reported by the
Planning Board:
People/Dwelling Unit
3
2
2
2
2
2
04
92
78
70
64
59
As'sume that 50 gpcd of the 77.8 gpd per capita flow is attributable
to personal use.
Assume that 8,000 new jobs per year from 1975 on, with a 52.3 gpd
per employee flow.
Assume trfat infiltration/inflow in 1975 represented 24.6% of the total
flow and that this will be reduced 1% every five years until 1995
whereafter it will remain constant.
A wet weather flow allowance (7 percent) is not included in the pro-
jections, primarily because the proposed wastewater treatment
-'facilities are designed to accomodate peak flows and infiltration and
inflow resulting from wet weather conditions.
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APPENDIX B
Monetary Cost Comparison- Dickerson &
Piscataway Wastewater Treatment System Alternatives
Intorduction
This appendix compares direct monetary costs of wastewater
treatment options at the proposed Dickerson site in Western •
Montgomery County with costs of comparable options at a site in
Prince Georges County about 20 miles below the Blue Plains waste-
water treatment plant (see map). The analyses are based largely
on EPA review and appropriate adjustments and revisions of infor-
mation and evaluations developed by the State of Maryland and by
CH2M Hill, Inc., Consulting Engineers. These latter evaluations
are presented, respectively, in the Maryland Response of May 1976,
a supplement to the Dickerson Project Development Report-- Con-
sideration of Alternate Treatment Processes --and a number of mem-
oranda and discussions after the documents were submitted*
First, this appendix compares initial capital costs of
design and construction of the Dickerson 60 MGD system, including
the Nitrogen removal plant under the pending Step 3 grant
application, with costs of a 60 MGD Dickerson II system featuring
a Nitrogen oxidation plant, and with costs of a 60 MGD Piscat-
away. plant. 'Then, present worths^of the 60 MGD Dickerson II
wastewater treatment system are compared.with those for-the •
Piscataway system. Finally,:^ this appendix "compares-. 35':MGD
options at the proposed Dickerson and Piscataway sites.
Wastewater Flows
The year 2000 wastewater flow (over existing flow) forecast
for Montgomery County totals about 35 MGD. Thus, the two 35
MGD treatment options would serve only Montgomery County needs.
Currently, Maryland is negotiating with Virginia and with Wash-
ington, D.C. for 10 MGD and. 7.5 MGD allowances in the proposed
wastewater treatment alternatives. Montgomery County could
provide for these allowances through corresponding reduction in
its current 76.6 MGD allocation in Blue Plains and treating
the resultant additional Montgomery County flows at either
Dickerson or Piscateaway, Although the inter-jurisdictional
aggreements required for a Step 3 grant award have not been
reached to date, the 60 MGD alternatives have
nevertheless been assumed to provide for 17.5 MGD of regional
flows plus a Montgomery County allowance greater that the year
2000 need of 35 MGD.
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Wastewater Treatment System Alternatives
The Dickerson alternatives I and II (60 and 35 MGD) each feature a
treatment plant, a 23-mile force main and 5 pumping stations with some
lifts approaching 300 feet. Ihe plant effluent line would discharge
into the Potomac River about 18 miles upstream from the most upstream
water supply intake for D.C. The Dickerson I system includes an advanced.
wastewater treatment plant (the pending Step 3 grant application) pro-
viding for Nitrogen as well as Phosphorous removal.. The plant features:
1. Prdjnary treatment
2. Secondary treatment
3. Lime treatment for Phosphorous removal
4. Recarbonation treatment
5. Filtration
6. Breakpoint Chlorination for Nitrogen Removal
7. Carbon treatment
8. Clearwater Reservoir
9. Hypochlorite Generation
10. Clearwater Reservoir
11. Railyard
12. Sludge processing facilities.
The Dickerson 2 plant option provides for Phosphorous removal and
Nitrogen oxidation.. It departs from the above processes by modifying
the secondary treatment to provide for Nitrogen oxidation, substituting
post chlorination (disinfection) for Breakpoint Chlorination and omitting
the Hypochlorite Generation facilities.
The Piscataway alternatives (60 MGD and 35 MGD) would provide for
Nitrogen oxidation similar to Blue Plains. They comprise: i
1. Expansion of a proposed 30 MGD advanced wastewater treatment
plant to 90 MGD (60 MGD option) and to 65 MGD (35 MGD option).
*
2.. 60 MGD and 35 MGD enlargements of a proposed force main between
Blue Plains and Piscataway.
3. Construction of an additional 7 MGD of interim plant capacity
in Montgomery County to temporarily serve county needs between 1981
(scheduled completion of Dickerson plant and 1984 (estimated completion
of Piscataway plant^.
4. Operation and maintenance of all interim plants (14.5 MGD) for
three years (1982 through 1984).
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5. Construction of certain relief sewers, pumping stations and
appurtenant works, not otherwise needed if the Dickerson plant were
built, to convey Montgomery County flows to the Potomac Interceptor.
6. Augmentation of effective Potomac Interceptor capacity by
construction of diurnal retention storage when present conveyance
capacity is reached.
Comparisons of Initial Capital Costs
Table 1 compares initial capital costs of design and construction
for the 60 M3D Dickerson— I (Step 3 Grant application) with the
Dickerson -I£ alternative. It shows that the treatment plant changes
previously described would reduce capital posts by about $23 million in
1975 dollars. The costs tabulated below are the same as those presented.
by Maryland and Montgomery County documents.
Table 1 - Comparison of Initial (1976-^1 98!)
Capital Costs of Dickerson I and Pick
II Systems (60MQ3)
Items Cost in Millions of March 1975 Dollars
Dickerson .S
1. Plant • 166 143*
2. Force Main 98 ' 98
3. Ttotals 264 241
*Includes added design cost of $3.2 mi, XT Inn
Table 2 summarizes jLnitial capital costs for the exapnsion of the
proposed 30 MGD^pianc ^o^Q MGD and compares EPA and Maryland estimates
for this expansion. The table shows the total capital costs . '. to
be about $92 and 68 million less than those for Dickerson I and II,
respectively.
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Table 2 - Initial (1978^384) Capital Costs of
60 MGD Piscataway System
Items Cost in millions of March 1975 Dollars
EPA Estimate Maryland Estimate
1. Plant Capacity 98 98
. increase (30 to 90MGD)
2. Added design cost 5
«k
3. Piscataway Force Main 27 27
4. Montgomery Co. Relief 29 40
Sewers
5. Montgomery Co. Interim 13. 24
plants (7MGD)
6. Dulles Relief Tunnel - 70
7. Va. Interim AWT & Con- - 27
veyance
Totals 172 286
The Item 1 cost of the 60 MGD increase in plant capacity is the
same as the Maryland estimate, although calculated independently using
a somewhat different approach. Item 2 represents the estimated design
cost for Piscataway above the $3.2 million estimate for design changes
for Dickerson II. The Maryland cost estimate for the Piscataway Force
Main was adopted.
The Maryland estimate for six relief sewers was accepted except for
one change. The proposed Seneca Tunnel was assumed to be replaced with
a force main, thus reducing the overall cost estimate from $40 million
to $29 million in 1975 dollars.
Based on the Montgomery County flows presented in the main report,
less than 7 MGD rather than 14 MGD of additional, interim plant capacity
would be required to serve the county from 1981 (scheduled completion of
the Dickerson plant) to 1984 (estimated completion of the Piscataway
plant. This assumed reduction of interim plant capacity (14 to 7 MGD)
decreased 1975 capital costs from $24 million to $13 million.
. The Maryland estimate included $69.7 million for a Dulles relief
tunnel. This item has been deleted from the initial capital cost estimate
because the expected reduced flows are. not likely to exceed the
capacity of the existing Potomac River (Dulles) interecptor
until beyond 1990 and, when needed, diurnal retention storage
is likely to be a less costly means of augmenting the flow
carrying capability of the interceptor. The present worth
estimates include cost of adding retention storage beyond 1990.
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Table 4 presents present worths of capital and operation and main-
tenance costs for the 60 and 35 MGD variations of the Dickerson II alter-
native. Appropriate scaling factors (e.g. x = 0.8 for treatment plants
and x = 0.5 for force mains in the formula - (C = KQT) were used to
reduce costs from the 60 MGD base to the 35 MGD (Montgomery Co. flows
only) option., The slope of cost curves of treatment plant flow versus
operation and maintenance costs were used in scaling down the 60 MGD
plant O&M costs to 35 MGD O&M costs. The Maryland present worth estimates
were used for the 60 MGD Dickerson II alternative.
Table 4 - Present Worth Costs
of Dickerson II Alternatives
1980 p.w. (minions of 1975 dollars)
Capital Costs 60MGD 35MGD
Plant 149 100*
Force Main 98 75
Subtotals 247 175
O&M Costs
Plant 69 55
Force Main 21 12
Subtotals 90 67
Totals 337 242
*Includes $3 million of added design costs for plant resizing.
Table 5 lists 1980 present worths of cpaital and operation and
maintenance costs for the 60 and 35 MOD variations of the Piscataway
system alternatives. The 35 MGD estimates were derived in the same
manner as the Dickerson 35 MGD estimates.
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Table 5 - Present Worth Costs
of Piscataway Alternatives
1980 p.w. (millions of 1975 dollars)
Capital Costs 60 MGD35MGD
1. Plant 79 51
Added design cost 5 5
Force Main 20 15
Interim Plants (Maryland) 10 . 10
Potomac Interceptor Retention
Storage (1990-1995) 10-20 . 5-10
Montgomery Co. Relief 20_ 12
Subtotals 154 103
O&M Costs
1. Plant . 52 . 41
Force Main 12 7
Interim plants 16 16
Montgomery Co. Relief _2_ _1
Sewers
Subtotals 82 65
Totals 236 168
Table 6 summarizes and compares the present worths of the Dickerson
alternatives with the Piscataway alternatives.
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Table 6 - Present Worth Comparison
of Dickerson with Piscataway Alternatives
1980 p.w. in millions of March- 1975 dollars
60M3)
Dickerson I
Dickerson II
Piscataway
35MS)
Dickerson II 175 67 242
Piscataway 103 65 168
The above table indicates the Piscataway alternatives to be about
30 percent less costly than the Dickerson II alternatives. Also,
the 60 MGD Piscataway alternative is about 38 percent less costly than
Dickerson I.
Capital
273
247
154
O&M
108
90
82
Total
381
337
236
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DETAIL
EE PLATE
UPPER POTOMAC
INTERCEPTOR
POTOMAC INTERCEPTOR
BLUE PLAINS
TREATMENT PLANT-
(Under Construction To
309 mgd}
GRAVITY SEWER
-> -fORCE MAIN
33115.0) PIPE DIAMETER AND CAPACITY
SEWAGE PUMPING STATION, CAPACITIES:
92 mgd (4) 20.4 mgd
A: Uwtr
PISCATAWAY
•TREATMENT PLANT
(Under Construction To
30 mgd)
©20.0 mgd © 6.0mgd
(5) 2.7mgd @ 0.9mgd ' '.';,
(NOTE:Some Minor Station* Not Shown)
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