UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION IX
1OO CALIFORNIA STREET
SAN FRANCISCO. CALIFORNIA 94111
To Whom It May Concern:
In a November 6, 1974 letter to EPA, the Council on
Environmental Quality requested the preparation of a supple-
ment to the Final Environmental Impact Statement (F-EPA-24005-
6A), Wastewater Treatment and Conveyance System, North Lake
Tahoe-Truckee River Basin, (Tahoe-Truckee Sanitation Agency).
This supplement was to discuss various unresolved environmental
issues which remained within recognized technical issues that
were identified in the final impact statement prepared by EPA,
Region•IX.
A period of 30 days, commencing with the publication in
the Federal Register of this supplement's receipt by CEQ,
will be initiated for your review and comment on the enclosed
supplement. Each of the six environmental issues raised by
CEQ precede EPA's response. Also, included as a seventh issue,
is a brief summary of what appeared in the November 1974 Hydro-
geological Investigation of Land Disposal of Reclaimed Waste-
water ^Near Truckee, CA. Any comments made should be directed
to Mr. Paul De Falco, Jr., Regional Administrator, U.S. Environ-
mental Protection Agency, 100 California Street, San Francisco,
CA 94111. In addition, please forward a carbon copy of any
comments on the supplement to the Council on Environmental
Quality, 722 Jackson Place, N.W., Washington, DC 20006, attn:
William Matuszeski.
Sincerely,
C*. fywUW j^&+*~+
Paul De Falco, Jr.
Regional Administrator
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Comment
J. Land Use
a. EPA has stated that the sewer system sizing
project 4.4 noŁ b built to reach that ultimate design require.
clarification by EPA. It i& unclear how the population
data pre&ented, which i& ba&ed on the California V-150
methodology ^or projections, i& con&i&tent with applic-
able growth policies &or the service area. In thi&
regard, the fiinal EIS should present evidence oft contact
and discussion with appropriate local and regional land
use agencies concerning the size and timing OjJ facilities
as they relate to both current population and ultimate
design year population. Any deviations in population
projections (up or down) firom a continuation otf past
growth rates in the service area should be explained.
R-la. The study area represents a portion of the California
Sierra-Nevada Region and includes large portions of Placer and
Nevada Counties as well as a small area of El Dorado County.
A total of about 380 square miles is included, characterized
by a relatively small degree of development. Existing acre-
age and land use category breakdown may be found on pages 49
through 52 in the Amended Project Report. (1) Land uses for
those portions of Placer and Nevada Counties within the
North Lahontan Basin are obtained from surveys conducted by
the California Department of Water Resources, (DWR).
Land use projections for Placer and Nevada Counties,
1970 through 2000, are listed in Table 43, page 254 of the
Environmental Impact Assessment. (2) These same projections,
plus those for El Dorado County, may be found in Table 12-5
of the latest North Lahontan Basin Plan (3) of the State Water
Resources Control Board (SWRCB). The DWR land use projections
have been compared with county land use projections, and no
major conflicts have been found.
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The long-term trend in land use within the project area
is towards more urbanization; however, the general nature of
the area will not change significantly over the next 30 years
since about 83 percent of the study area consists of isolated
wilderness composed of rugged mountains, forests, and plains.
The greatest projected changes in land use will occur primar-
ily in the urban land category. Currently, only minor amounts
of land are used for industrial purposes. Future increases
will be limited to that required for light industrial pur-
poses. No growth is anticipated for heavy industry.
Because over three-fourths of the project area is general
forest and because of the climatic and geographic conditions,
recreational attractions result in a small permanent popula-
tion being swelled in the summer months and in the peak weeks
of the skiing season by a much larger seasonal and recrea-
tional population.
Population projections used in determining eligible
capacity for California projects are based upon State Depart-
ment of Finance (DOF) projections disaggregated to service
areas by the SWRCB in accordance with Section 2133 of the
California Clean Water Grant Program Regulations. (4) While
the DOF does not project population for cities or unincorpo-
rated areas, it does so for counties. The methodology used
to determine the portion of the total project to be supported
by Federal and State grant funds is explained in detail on
page 82 of the Environmental Impact Statement (EIS). (5)
As with all grant assisted projects throughout the State
of California, grant participation in the construction of the
project is determined pursuant to these regulations which
limit grants to interceptor capacity projected 20 years from
the start of construction and treatment facilities to 10 years.
These regulations provide that the 20-year population projec-
tion shall be based on the most current data of the DOF and
DWR. A 1970 baseline population is established and then a
percentage growth rate is applied to the baseline.
Since the 1970 census is an unreliable measure of
population in seasonal resort destination areas, the base
population for the Tahoe-Truckee Sanitation Agency (T-TSA)
project was derived from various sources of information
including house counts, visitation data, building permit
information, etc. The base year 1974, therefore, is related
to an actual on-the-ground situation, both in terms of popu-
lation, population equivalents, and wastewater flows. In
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order to establish an accurate baseline population which
includes seasonal, recreational and day use, the State Board,
Environmental Protection Agency (EPA), and the applicant
reviewed the most recent data provided by the Nevada County
Planning Department, local county water districts, the U.S.
Forest Service, California Department of Parks and Recreation,
and the Tahoe Regional Planning Agency (TRPA).
The projected populations are derived from statistical
demographic trends, and are not related to a future on-the-
ground situation. Consequently, they are not related to
growth policies of local governments, and are not related to
future land use patterns or densities. While grant applicants
are expected and encouraged to compare their projections with
those of the areawide planning organization and/or county
planning agency, it is explicitly stated in the State regu-
lations that, grant assistance is based on the population
projected by the appropriate DOF series. Past trends in
population growth are valuable but are not consistent to
the point that they would be used to forecast future trends,
especially in the Tahoe Area where highly dynamic seasonal
changes are evident.
The local land use planning policies and procedures do
not set forth growth policies per se. Rather, the plans
delineate the spatial dimensions of land use at some future
(unspecified) date. The land use plans do not provide for
rate and time of build-out and, therefore, it is difficult,
if not impossible, to derive a population in 1984 from land
use maps which can be used reliably for sewer sizing. In
addition, the highly dynamic nature of Tahoe-Truckee Area
population and the components of population are related more
to the seasonal recreation pattern rather than any land use
pattern.
Since the sewer system sizing for this project was not
based upon an analysis of wastewater generation from existing
and projected land uses but upon statistical demographic
trends, the latter approach to sewer sizing does not depend
on what existing land uses are, or what future land uses will
be, with or without the sewerage project. The sewerage works
will serve wastewater flows derived from existing land uses
(and, therefore, existing peak seasonal population), and will
serve whatever new wastewaters are derived from any new land
uses up to the capacity limitations imposed by the demographi-
cally based design size.
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There is sufficient reserve capacity in the eligible
treatment plant and interceptor to accommodate the design
year population derived for each local sanitary district:
Flow Comparison MGD
District
August 1973
Summer Peak
Existing Flow
Summer Peak
Grant Eligible
TCPUD/NTPUD
ASCWD
SVCWD
TSD
Truckee
Canyon
AVG
1.52
0.04
0.09
0.32
- 0 -
MAX
2.00
0.05
0.11
0.95
- 0 -
Treatment
(1985)
2.94
0.16
0.32
1.16
0.25
Interceptor
(1994)
3.89
0.22
0.44
1.35
0.33
Total Treatment
Plant Design Capacity
4.83
This analysis shows that grant eligible capacities as
derived by the population projection methodologies specified
by the California Clean Water Grant Program Regulations (4)
provide sufficient reserve capacity in the T-TSA system as
required by Section 204(a)(5) of the Federal Water Pollution
Control Act (FWPCA).
fa. It u)ou.Łd at&o be. appropriate, to e.x.pŁain the. ie.la.tion
OjJ th
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R-lb. The Lake Tahoe Basin was designated by the States of
California and Nevada, as an interstate planning area on
March 11 , 1974. The TRPA was designated as its single repre-
sentative organization. The EPA, on August 5, 1974, approved
the designations, and on December 23, 1974 a grant offer in
the amount of $650,000 was made to TRPA.
The 208 work plan is devoted to the development of an
"Erosion Control and Surface Water Management Plan" for the
Lake Tahoe Basin. All areas outside the Basin are excluded.
The T-TSA service area lying outside TRPA's jurisdiction
(Zone 2 of the EIS) has been made a non-designated area by
the State of California. Therefore, the SWRCB is doing waste
treatment management planning for point and non-point source
control for the T-TSA service area outside of the Tahoe
Basin pursuant to Section 303e of the FWPCA.
The 208 Plan is devoted almost entirely to the non-point
source pollution of Lake Tahoe. Sewerage facilities will be
considered to the extent that future sewerage needs are pro-
vided in the existing export systems. For purposes of the
Tahoe 208 Program, the T-TSA export system, located in the
jurisdiction of TRPA, is assumed to be existing or "in place".
No new construction is anticipated and the program will have
no direct or immediate bearing on the present grant offer to
T-TSA.
The TRPA is required by Section 208 to plan a waste
treatment management program for pollutants eminating from
point sources over a twenty-year period. Therefore, planning
for future facilities within the common TRPA/T-TSA jurisdiction
will be developed through the 208 planning process.
2. Se.ct4.on 114 oj the. FWPCA kmo.ndmo.ntA (P.I. 92-500]
Spe,c.
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?m>ithe
beŁ*.eve EPA ha& not ye,t ade.qu.ate.ly addie,64ed the.
OjJ ŁfU* p>iOje.Q.t on the. e.^e.c.tive. imple.me.ntation o<(
Season 114.
R-2. In Section 114 of the Federal Water Pollution Control
Act Amendments of 1972, Congress expressed a concern for the
"fragile ecology of Lake Tahoe" and directed EPA to prepare
a major study of the Lake Tahoe Basin to accomplish the
following objectives:
1. Conduct a thorough and complete study on the
adequacy of and need for extending Federal over-
sight and control in order to preserve the fragile
ecology of Lake Tahoe.
2. Examine the interrelationships and responsibilities
of the various agencies of the Federal Government
and State and local governments.
3. Consider the effect of various actions (of Federal,
State, and local governments) in terms of their
environmental impact on the Tahoe Basin, treated
as an ecosystem.
4. Establish the necessity of redefinition of legal
and other arrangements between the various govern-
ments .
5. Make specific legislative recommendations to
Congress .
The Lake Tahoe Study (6) is now in its final form and
will be transmitted to Congress in the near future. The
study has undergone an extensive review by State and Federal
agencies and by the Executive Office of the President.
The study examines the environmental and ecological
dynamics of the Lake Tahoe Basin; the myriad activities of
Federal agencies, State agencies, the TRPA, local general
purpose governments, special purpose districts, and pri-
vate parties; and the legal and institutional arrangements
in operation in the Tahoe Basin. The study identifies
problem areas as legal or institutional deficiencies which
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are preventing fully effective management of environmental
and ecological values, and which consequently are impacting
on the "fragile ecology of Lake Tahoe". The study examines
tools and options to remedy the problems; the options range
from Federal policy statements and coordination, to legal
changes in the Tahoe Regional Planning Compact/ to air and
water pollution control programs, to land acquisition.
Finally, the study makes specific recommendations to Congress.
The Lake Tahoe Study does address land use issues and
sewerage issues in the Tahoe Basin. The historical example
of exemplary intergovernmental coordination to implement the
sewer export mandate to protect the quality of Lake Tahoe is
given; moreover, it is directly acknowledged that the sewer-
age export systems constructed with State and Federal funds
were oversized and contributed to the stimulation of urban
development. This knowledge of the sewer/land use relation-
ship prompte'd EPA to rigorously review population forecasts
for the T-TSA Regional System.
The Lake Tahoe Study recognizes that even as development
proceeds in the Tahoe Basin within the confines of the Tahoe
Regional Plan and ordinances and within the available sewerage
capacity, land and water quality impacts will occur as land
and soils are disturbed. Erosion, sedimentation, and the
transport of nutrients into Lake Tahoe are very critical
environmental and ecological problems, and are directly
related to the intensity of land use in the watershed. At
the same time that EPA and the States are pursuing a strategy
to protect water quality through sewage export, an active
program of erosion control and surface water management is
in progress to remedy the impacts of urban development that
has been and is permitted in the watershed. For example,
EPA has awarded a major $650,000 grant to TRPA to carry out
an areawide waste treatment management planning program
pursuant to Section 208, FWPCA. This program will result in
the development and implementation of erosion control and
surface water management plans to correct existing problems
and prevent new occurrences.
EPA believes that our decisions on the sizing and
environmental impact of the T-TSA project and the implemen-
tation of Section 208 in the Tahoe Basin are actions that
are, in fact, consistent with the Lake Tahoe Study's analysis
and recommendations.
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3. E^ect ot that it be
fie.c.OYi&ide.fie.d. land tie.atme.nt &oi at lua^t a poition 0(J
the. &hktu.e.nt (u)hic.h w»oaŁd piovide. ^u.ithe.1 pacification
via natiie.nt aptake. by v eg e.tatio n , and ie.tain OjJ wate.1
to the, n.ive.1 via ande.idiain&] woatd appear, to me.iit
fiuithe.1 anaty&i&.
Cto&e. c.on^ide.iation ofi thi& Land tie.atme.nt atte.ina-
tive. vooaid be. c.on*>it>te.nt u)ith Se,ction 20? o& Title. II Oj}
the. fe.de.iat Wate.1 Poltation Contiot kc.t kme.ndme.nt& o/J
1972. U
R-3a. Although there will be certain total dissolved solids,
chlorides, etc., remaining in the effluent from the regional
treatment plant as suggested by CEQ, it has been shown in
Table 13-3 of the Amended Project Report (1) and the Table
which appears on page 236 of the Environmental Impact State-
ment (5) that, with the high degree of treatment proposed,
the water quality standards established for the Truckee River
will not be violated under the proposed treatment and disposal
conditions. However, as a result of the calculations made in
these studies it was apparent that an extremely high level of
treatment operating at a high level of reliability would be
required in order not to violate the Truckee River standards .
\J FWPCA Amendment ie.qaiie. that "wa&te. tie.atme.nt manage.me.nt
ptanA and piac.tic.e.6 bkatZ. piovide. &oi the. be.&t piac.tic.abte,
voa&te. tie.atme.nt te,c.hnotogy betfote any di&c.haige. into ie.c.e.iving
viatui, inclading ie,c.taiming and ie.cycting 0(J wate.1, and c.on-
&ine.d di&po&at oft pollatant* &o the.y witt not migiate. to caa4e
taate.1 01 othe.1 e.nviionme.ntal pottation . . . and the. ie.c.yc.ting
0)5 pote.ntial & engage potlatantA thioagh the. piodac.tion o
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Land treatment was considered during these studies, but
it was concluded that this method of treatment could not
achieve the necessary results in terms of nutrient removal
and thus could not meet the stringent standards set for the
Truckee River. Although nutrient uptake occurs in a land
treatment system, essentially complete nutrient removal as
dictated by the receiving water standards could not have
been possible.
Additionally, the practice of land treatment by irriga-
tion is impractical in this cold, wet, wintry climate, in
these soils, and in this terrain. A very short growing
season in this sub-Alpine environment results in sparse
growth in the vicinity of the plant site. It is not consid-
ered feasible to rely on nutrient removal by plant uptake
in this location. Another problem exists in the vicinity
of the airport, less than a mile from the proposed site.
Fog generation and consequent airport closure is a common
occurrence due to nearby ponds and surface moisture available
for the fog generation. The peculiar climatic conditions that
cause this fog have prompted the airport district to discourage
additional reservoirs or surface spraying of any kind during
critical periods and in fact the airport board is anxious to
eliminate the lagoons that are part of the present disposal
system of the Truckee Sanitary District.
In addition to the studies which have indicated that
the receiving water quality standards will not be violated
under anticipated advanced waste treatment conditions, it
should be noted that pilot studies and stream simulation
studies were conducted by an engineering consultant (7) and
by the University of California's Sanitary Engineering
Research Laboratory. (8) The consultants operated a pilot
advanced waste treatment plant; the University study team
conducted the stream simulation analyses. The results of
these studies indicated that the pilot plant effluent did
not increase the algal growth potential in the Truckee River
but that lesser levels of treatment had significant detri-
mental effects. Laboratory spiking tests corroborated the
field studies.
The Regional Water Quality Control Board has, in its
Board Order 6-74, (9) required compliance "with the Monitoring
and Reporting Program No. 74-44 and the 'General Provisions
for Monitoring and Reporting1 as specified by the Executive
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Officer." By these provisions the Regional Board will be
able to keep close control of the effluent discharges and to
assure protection of the receiving aquifers as well as the
Truckee River.
fa. Ene.n.gy Con4eivaŁtow A4pec.t6
Land tfie.atme.nt o& e.&&tue.nt, a& dji&c.u.t>*e.d above., would
aŁio appeal to be. a te.&& e.ne.iQy Jinte.n&po&aZ. me.thod. The. e.ne.fi.gy consumption
que,&tia.
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requirement. The carbon dioxide produced from this process
and the burning of the methane gas will be used for the
recarbonation processes following lime treatment. The
stabilized organic solids from this treatment process will
also be returned to agricultural lands if a market can be
found.
The proposed treatment plant processes are described in
considerable detail in a Preliminary Design Report (10)
dated February 1974. This study also included a number of
analyses of energy consumption for various unit processes.
Comparisons were made of energy consumption for the following
processes: Oxygen vs. air for biological treatment; ozone
vs. chlorine for disinfection; chemical vs. electrolytic
processes for the ammonia stripping-recovery process; and
incineration vs. land disposal for both organic and chemical
sludge. These energy considerations and the rationale
leading to selection of the processes providing for the most
optimum energy budget are contained in Chapter II of the
report. On-site sludge incineration and calcining were
eliminated from the proposed plant as a result of these
energy analyses.
4. E^e.c.t on Qu.ant4.ty o& Wa.te.si. Jin Pyramid Lake.
Ex.plic.it information on. the, e.^e.c.t afi the. tie.at-
me.nt me.thod on the. &u.H.vivat OjJ Pyramid Lake. i& a matte.*.
0(J Qfie.at importance, to the. Paiate. Indian Ttiibe.. EPA
Ah.ou.ld clarify why it be.iie.ve.& that (aate.fi volume. M4.it
be ^,u.^ic.ie.ntiy high to &ati&{>y the. Indian*' wate.1
Jie.qu.itie.me.ntA Jin the. Z.OUMLH Ttiu.c.kee R-C.VC.A and in Pyramid
Lake..
R-4. The proposed alternative is deliberately chosen and
designed to retain all effluent within the Truckee River
system indirectly through underground aquifers near the
proposed plant site. There will be no appreciable water
loss to the Truckee system as a result of the water use,
sewage treatment, and disposal conditions. The water con-
sumption and indirect recycle through injection of effluent
into the aquifer only amounts to a few percent of the normal
flow in the Truckee River.
Water quality effects in Pyramid Lake will be insignifi-
cant since effluent quality has.been dictated by the water
quality standards of the Trucked River receiving water near
the plant site. Increases in such parameters as nutrients,
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total dissolved solids, chlorides, etc., which may result
from the plant effluent are negligible in comparison to
current background levels existing at Pyramid Lake. If
there is any significance in the quality differences at
Pyramid Lake as a result of the proposed treatment facility,
it is that the current nutrient emissions from the existing
sewerage agencies will be greatly reduced as a result of the
proposed high degree of treatment.
Chapter V of the Amended Project Report (1) deals
exclusively and specifically with the water environment and
the subject of water quantity in the Truckee River systems.
Estimates of the natural flow of the Truckee River were
presented on page 72 of that report and indicate a mean flow
into Pyramid Lake of 549,000 acre-ft. per year. This is
referred to on page 128 of the EIS (5) where it was stated
that the consumptive loss due to the T-TSA project would be
less than 1800 acre-ft. In view of the insignificance of
this consumption loss and of the bi-State water compact
allocation of water to California from the Tahoe Basin of
23,000 acre-ft., the reduction in flow in the Truckee River
is not in any way critical. The availability of water in
the Tahoe-Truckee Basins may be a significant influence in
the future with regard to decisions on the extent of allow-
able or desirable population growth in the area but this
project, however, is well within the bounds of water avail-
ability to California.
5. The, future, o& the. Eating Tahoe. City Piimaiy TfLe.atme.nt
Plant
It 4.& unc.le.ai fiiom the. intimation pie.& nnte.d whe.the.1
the. Tahoe. City tie.atmc.nt plant which wa-6 upgraded in 7969
i& to be. pha&e,d out. We. unde.i&tand that thi& plant i*
pie.*cntly ove.iloade,d; hou)e.ve.i, lathzi than abandon it, a&
i* &u.gge.&te.d -in the, EIS, it& poA&ible. ute. Ł01 tzcondaiy
tne.atme.nt a& pait oft the. fie.Q4.onal *yAte.m mtght allow a
>ie.du.c.tik.&. M.te.H.nat4.ve.ly, -cjj the. old plant to be.
he.ld i.n me.i\)e. ^on addtt-ional jju-tu'ie tne.atme.nt capacity,
th
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R-5. The Amended Project Report (1) referenced in the EIS (5)
makes it clear that the intent is to abandon the Tahoe City
primary treatment plant. There is physically no room at the
existing site for plant upgrading to secondary treatment so
it will not be maintained in reserve. The U.S. Forest Service
cinder cone is to be returned to its native state when the
permit expires and the land used in this system should be
returned to other beneficial use. Equipment in this plant
is not compatible with the proposed new facility. The facil-
ities in the existing Tahoe City plant are also needed for
treatment up until the time the sewage is diverted to the
new T-TSA facility.
In the Addendum to the Amended Project Report (11)
published in May 1973, three specific plans were presented
that would retain the Tahoe City treatment site. Table 4 on
page 34 of that report clearly demonstrates that even after
full tertiary treatment including nutrient removal effluent
from the cinder cone would violate the present Truckee River
standards at the 100 cfs flow rate. The volume of water is
regulated at the Tahoe Dam by the Federal water-master to
maintain a proper balance in the Truckee River drainage. For
example, if the Truckee River system were operated in accord-
ance with the Bureau of Reclamation Operation Study S-l (see
pages 86-89 of the Amended Project Report (1)), the monthly
average flow in the river at the point of discharge from the
cinder cone would be below 100 cfs in an average of seven
months each year. At that flow, the standards for total dis-
solved solids, chlorides, nitrogen and phosphorus would be
exceeded. Additionally, direct discharge to the surface
waters of the Truckee River from any treatment plant is pro-
hibited in the Federal/State Water Quality Standards.
The Tahoe City Public Utility District is not presently
overloaded although the rate of connections to this system
must be allocated very carefully to keep within the terms
of the U.S. Forest Service special use permit and those of
the Lahontan Board.
The new sewage treatment plant and interceptor are not
oversized for population to be served due to the retention
of the Tahoe City Treatment Plant. The regional system was
sized for the population projected for the entire service
area.
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6. In^iltiation and E^^iltiation
It ha& been Augge-a-ted by at te.at>t one ie.vie.tae.1 that
EPA condition it* giant on a ie.quiie.me.nt tfoi..i -6ugge-6ttnta>c.n4
that exjj/c^^a^on can be de-tec-ted through wate.fi quality
monitoring and enforcement otidtn& a4 needed.
to u.4 moie co4t-e^ect^i;e, and
Section 201 [g] (3) OfJ tne FWPCA Amendment, faon tke.
kdmini&tnaton. to nnquitie. the. apptic.ant pnion to giant
approval, to &hou) that each Aei/oe/i coŁŁect-con &ij&tz.m that
wiLt di&c.han.ge. into the. proposed tie.atme.nt u)on.k& , whe.the.fi.
aid on n-ew, i& not ^abject to exce^-tve infatuation.
Th-e Aize. oft the. &y&te.m buitt might be. abte. to be adju&tzd
dovonwatid i& Auch in^ittiation 0(J wate^t couŁd be /tedaced.
In addition, mainte.nanc.e. oft wate.fi quality wiif. be be.tte.n.
a44a/ted by &uc.h a ie.quiie.me.nt.
R-6. An infiltration/inflow analysis was included in the
February 1974 Preliminary Design Report (10) as Chapter 4.
A cost effective analysis in that report, in accordance with
State and EPA guidelines, indicated that the local agencies
were making progress in controlling infiltration and that such
infiltration-control programs were continuing. The I & I
analysis concluded that infiltration/inflow to the new
regional treatment facility has been shown not to be exces-
sive. However, many segments of the collection systems which
exist in some of the districts have severe infiltration/
inflow problems. The most cost effective solution to accom-
modate these isolated elements of infiltration/inflow entering
the sanitary sewer system is based on rehabilitation. An
example of this is the older portion (1908) of the Truckee
collection system. This portion of the Truckee system is now
being replaced and work is continuing in all districts on
these isolated segments of existing collector lines subject
to infiltration/inflow.
Since raw sewage is being pumped in close proximity to
Lake Tahoe, the real possibility of exfiltration through
leakage or breakage in the lines exists. Raw sewage entering
Lake Tahoe could have a severe impact on water quality if it
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were allowed to occur over a long period of time. The moni-
toring programs in Lake Tahoe, while not as comprehensive as
may ultimately be desirable, are capable of detecting gross
pollution of the near-shore waters.
7. HydfLoge.otog.oŁ.og4.c.
R-7. Hydrogeologic studies (12) have been completed and were
received in the EPA regional office in January 1975 (T-TSA
transmittal letter dated 15 January 1975) . These studies
concluded the following:
1. The 22-acre disposal site will readily accept
design percolation flows.
2. The height of the mounded percolate will not rise
high enough to impede the downward movement of
percolating effluent.
3. The mounded percolate will not reach the existing
invert of the deepest gravel pit within Sanderson's
property.
4. Movement of the percolated effluent, upon reaching
the water table, will be northeasterly where it
will surface in the Truckee River and Martis Creek.
The flow will be away from any existing domestic
supplies to the south drawing water from the same
aquifer system or systems in hydrologic continuity.
Any percolated effluent which did penetrate into
the Truckee Formation, which is unlikely to occur,
would also eventually surface into the Truckee
River or Martis Creek.
5. The total time for the effluent to reach the points
of discharge into the Truckee River or Martis Creek
will vary from 140 to 280 days depending on the
discharge rate and flow path.
6. Since the water quality of the plant effluent will
be extremely good in terms of suspended and organic
matter, no appreciable variations from the model
predictions are expected with prolonged disposal.
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BIBLIOGRAPHY
1. Dewante & Stowell; Cook Associates,
Amended Project Report, Regional Sewerage Project,
Tahoe-Truckee Sanitation Agency, Sacramento,
February 1973.
2. Jones & Stokes Associates, Inc.,
Draft Environmental Impact Assessment, Tahoe-
Truckee Sanitation Agency, Sacramento, February 15,
1973.
3. State Water Resources Control Board; Lahontan Regional
Water Quality Control Board,
Water Quality Control Plan Report, North Lahontan
Basin (6A)."Draft, South Lake Tahoe, February 1975
4. State WaŁer Resources Control Board,
Clean Water Grant Program Regulations, Sacramento,
August 16, 1973.
5. U.S. Environmental Protection Agency; Region IX,
Final Environmental Impact Statement; Wastewater
Treatment and Conveyance System, North Lake Tahoe-
Truckee River Basin (Tahoe-Truckee Sanitation
Agency), San Francisco, September 17, 1974.
6.
The Lake Tahoe Study; .. .as requested by_ the 92nd
Congress in Section 114 oT the FedeFaiWater Pollu-
tion Control Act Amendments of 1972, San Francisco,
May 1974.
7. Environmental Quality Engineering, Inc.,
Demonstration of a Biological-Chemical-Physical
Treatment Process for Assessment of Biological
Effects on the Truckee River.Preliminary Report,
Oakland, December 1972.
8. State Water Resources Control Board,
Assessment of Biological Effects of Treated Waste-
water on the Truckee RiverTFTnar~Report by
H. P. Skarheim, et al., Publication No. 52,
University of California, Sanitary Engineering
Research Laboratory. SERL Report No. 73-2,
Berkeley, June 15, 1973.
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9. California Regional Water Quality Control Board,
Lahontan Region,
Board Order No. 6-74; Waste Discharge Requirements
for Tahoe-Truckee Sanitation Agency..., South Lake
Tahoe, April 25, 1974":
10. Cornell, Rowland, Hayes & Merryfield; Clair A. Hill
& Associates,
Preliminary Design Report; Truckee Interceptor,
water Reclamation Plant, Effluent Disposal System
- Regional Water Reclamation Project, Tahoe-Truckee
Sanitation Agency, Redding, Feburarv 1974.
11. Dewante & Stowell; Cook Associates,
Addendum, Amended Project Report, Regional Sewerage
Project, Tahoe-Truckee Sanitation Agency, Sacramento,
May 1973.
12. Cornell,' Rowland, Hayes & Merryfield; Clair A. Hill
'& Associates,
Hydrogeological Investigation of Land Disposal of
Reclaimed Wastewater Near TrucEee7~California for
Tahoe-Truckee Sanitation Agency, Redding, November 1,
1974.
All of the above references, with the exception of
#7, are available for viewing at the U.S. Environ-
mental Protection Agency, Region IX, 100 California
Street, San Francisco, California.
Number 7 is available for viewing at the State Water
Resources Building, Division of Planning and Research,
Room 1018-25-K, 1416 Ninth Street, Sacramento,
California.
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