NC0024911_approval_19840620

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DIVISION OF ENVIRONWMAL MANAGEMEtff
June 20, 1984
M E M O R A N D U M
TO: Walter Taft
FROM: W. Lee Fleming, Jr.
S[&JECr: Standby Power Requirements for Dunoombe {munty MMSD
Due to the present and future standby power capabilities of the
Buncombe County MSD's wastewater system and the distance before effluent
involvement with A-fI waters, the MSD has met the equivalency of Standby
Power Requirements.
WLF':cs
cc: dandy Dom.

DIVISION OF ENVIRONMENTAL MANAGEMENT
June 13, 1984
M E M O R A N D U M
TO: Forrest Westall
FROM: Randy Dodd
THRU: Randy Williams
R E, V E D
i Ij Pi ' ci 1984
VIATER 01JAJjTY SECTION
OPF: !, Z. ,wr,.,
SUBJECT: Standby Power Requirements for Buncombe County MSD WWTP
The Construction Grants Section has requested that the Operations
Branch provide a decision regarding the necessity of standby power at the
Buncombe County MSD WWTP. Based on a fecal coliform modeling analysis, it
appears that the release of untreated sewage could impact the French Broad
River at the "A -II" classification 33 miles below the outfall under "worst
case" conditions. However, the only potential user of the French Broad in
this reach is the Tbwn of Hot Springs. Hot Springs is currently using a
well system. The French Broad enters Tennessee 4 miles below the A -II
classification boundary.
A major CP&L sub -station is located adjacent to the treatment plant.
This substation is fed from three separate power sources. The MSD is also
in the process of procuring their own power source from the Craggy Dam
Hydroelectric facilities on the French Broad River. During the past three
years, one outage of about 15 minutes duration occurred. Raw wastewater
did bypass during this period. After completion of the hydropower project,
the MSD will essentially have a source of standby power from CP&L. The
201 plan has been updated to include the procurement of power from the
hydropower facility, and contractual arrangements have been made with CP&L.
Analysis and Results
Standard fecal coliform modeling procedures were used to assess the
impact of the discharge of untreated sewage in the event of a power outage.
This analysis was performed for the 40 mgd wastewater treatment plant and
the Weaverville (0.6 mgd) and Carrier Bridge (10 mgd) lift stations.
The analysis was performed under "worst -case" assumptions (7Q10 flow,
low disappearance rates, high waste concentrations) and "liberal" assumptions
(average flow, high disappearance rates, low waste concentrations). A
background concentration of 760/100 ml was assumed. This level is the median
value reported at the USGS gaging station roughly two miles above the discharge.
The 7Q10 and average flows in the French Broad are 419 cfs and 2090 cfs
respectively.

Forrest Westall
June 13, 1984
- page two -
Impact of Treatment Plant
Because of the large design wasteflow (40 mgd) and high concentrations
of fecal coliforms present in untreated domestic waste, the discharge was
predicted to cause instream levels at the outfall to increase 8 times under
liberal assumptions and 200 times under "worst -case" assumptions. Under
liberal assumptions, concentrations should return to background levels before
the water intake at Hot Springs. Under "worst -case" assumptions, concentra-
tions should still be roughly 40 times above background levels. It should
be noted that this would occur if 1)6a discharge of 40 mgd occurred with
waste fecal concentrations of 2 x 10 /100 ml; 2) the river was at or near
7Q10 conditions, and 3) little decay occurred between Asheville and Hot
Springs (i.e., K = .8/day). These results should be considered as very crude
approximations because of the variability observed in input parameters and
the assumptions which had to be made to perform the analysis (e.g., steady-
state conditions).
Impact from Lift Stations
A discharge of raw waste from the 0.6 mgd Weaverville lift station would
raise the instream fecal level by roughly 4 times under "worst -case"
assumptions. Concentrations would reach background levels well before the
A -II reach of the river. Under average flow conditions, little or no elevation
of the instream fecal level is anticipated.
A discharge of raw waste from the 10 mgd Carrier Bridge lift station
would raise the instream fecal level by roughly 50 times under "worst -case"
assumptions. Concentrations would still be roughly 10 times above background
conditions at the A -II classification boundary. Under average flow conditions,
levels would increase by 10 times at the outfall, but would be close to back-
ground levels by the A -II segment.
Conclusion
Under current DEM policy, reliability requirements should be analyzed
for A -II waters at the water intake; and for B waters, at the classification
boundary. With this in mind, a "worst -case" modeling analysis predicts that
a discharge of raw sewage from the Buncombe County MSD WWTP could result in
fecal coliform violations 33 miles downstream of the outfall at the A -II
classification boundary. Nb raw water intake exists in this segment. However,
the probability of this occurring is extremely small. Similarly, the 10 mgd

s
Forrest Westall
June 13, 1984
- page two -
Carrier Bridge lift station could impact this reach in the event of a power
outage under worst -case assumptions. The 0.6 mgd Weaverville lift station
is not expected to impact the river under any feasible operational and
environmental conditions.
It is important to note that the MSD currently has a very reliable
power source, and will, in fact, increase this reliability in the future.
I hope this information is useful in determining if additional reliability
requirements are needed for the Buncombe County MSD system.
RD:cs

DIVISION OF ENVIRONMENTAL MAA7AGEMENT
May 15, 1984
MEMORANDUM
TO: Randall Williams
NCDEM Operations Branch
FROM: Bill _Hoffman i"
NCDEM Cdnstruction Grants Section
Engineering Management Unit
SUBJECT: Buncombe County MSD WWTP
Standby Power Requirements for Wastewater Treatment
EPA Project No. C370391-08
NPDES Permit No. NCO024911
This is to advise of our determination in regard to standby power for
the subject facilities.
Due to the limited monies which the State/EPA have to fund wastewater
facilities, we are required to determine the reasonableness and necessity
of the proposed facilities, including standby power.
Based on our review of the attached information received May 14, 1984
from the Grantee's Consultant Engineer (AE), Harry Hendon and Associates,
we cannot determine additional standby power generation to be necessary
or EPA eligible for this facility. Please review the enclosed information,
and provide us with your decision.
If you have questions, please call Larry Horton at 919/733-6900.
LH:tn
Enclosures
cc: Mr. Roy Davis
Mr. Larry Horton

Harry Hendon and Associates
I N C O R P O R A T E 0
ENGINEERS
\� TELEPHONE [phone]
` ADDRESS REPLY TO P. O. BOX 5176
25 REED STREET • ASHEVILLE, NORTH CAROLINA 28813
HARRY H. HENDON May9, 1984
11904 -1973)
A. B. JOWERS
H. D. HUGER
P. L. BENTLEY
Mr. Larry Horton
NCDEM Construction Grants Section
P. 0. Box 27687
Raleigh, North Carolina 27611-7687
Re: MSD of Buncombe County
EPA Project No. C-370391-08
Standby.Power Requirements
Dear Mr. Horton:
D. W. BERRYHILL
S. G BOYD
H. E. BYAS, JR.
During our meeting in your office on April 27, 1984, you requested
information regarding the reliability of electric power for the MSD
wastewater plant. In this regard, we offer.the following comments
numbered the same as the items are numbered in the draft memorandum of
March 27, 1984, to Randall Williams. Only the applicable items are
addressed.
Item 2. History of Power Outage
Three previous years of.power outage.records are kept at the
plant. During this previous period, one outage of about fifteen
minutes duration occurred. Several "blinks" occurred during this period
but the frequency was not recorded since these "blinks" are of a
momentary duration and do not cause any serious problems or bypassing.
Raw wastewater did bypass during the one fifteen minute outage.
Item 4. Detention Time .in System y"J
y
em detention time in the i
Systs stem at s estimated to be less - -
---than five minutes: Due to grades, wet well size, and structure design
at the wastewater plant,very little volume in the gravity system is
available for storage.
Item 5..Lift Station
Two lift stations (Carrier Bridge @ 10.0 MGD and Weaverville
@ 0.6.MGD) do not have standby power. These stations have a combined
r� fated capacity of 10.6 MGD.
1 � -
MAY 14 1984
CONSTRUCTION GRANTS PROGRAK
ENGINEERING REVIEW UNIT

Mr. Larry Horton
May 9, 1984
Page 2
In full consideration of power requirements, it should be noted
that a major CP&L sub -station is located adjacent to the MSD treatment
plant. This sub -station is fed from three separate power sources and
with the automatic switchgear, a very reliable source of power is provided.
The MSD is also in the process of rebuilding the Craggy Dam Hydro
Electric facilities on the French Broad River. This dam site is also ad-
jacent to the MSD wastewater plant. Proposals for procurement of the
generators and switchgear will be received by MSD on June.8, 1984. Con-
struction of the facilities is scheduled to be completed in about two
years after ordering of the equipment. The firm order for the equipment
will occur on or before December 1, 1984.
This facility will generate a minimum of 2400 KW and will become the
primary power source for the plant. Thus, upon completion and activation
of the hydro facility, the wastewater plant will, in effect, have four
sources of power.
Please advise if you have any questions.
Very .truly yours,
HARRY HE AND ASSOCIATES, INC.
By
n e W. Be'Yryhill, P.
DWB/pc
cc: Bill Mull
Dean Huber