HomeMy WebLinkAbout2012 ICR TMDL Status Rpt_final
South Tahoe Public Utility District
Indian Creek Reservoir
TMDL Progress Report
for 2012
Final
Ivo Bergsohn, P.G., C.Hg., South Tahoe Public Utility District
2/27/2013
1
1 Introduction
In April 2012, the Lahontan Regional Water Quality Control Board (LRWQCB) developed guidance (draft
Indian Creek Reservoir Total Maximum Daily Load (TMDL) Tracking Plan) to be used by the South Tahoe
Public Utility District (District) for the presentation and analysis of water quality data collected from
Indian Creek Reservoir, Alpine County, CA (LRWQCB, 2012). These data are to be reported annually to
evaluate Total Maximum Daily Load (TMDL) implementation progress and adaptively manage
expectations for meeting TMDL targets at Indian Creek Reservoir (ICR). The following has been prepared
to satisfy this annual TMDL reporting requirement for the 2012 calendar year.
2 Background
ICR is a 3,160 acre-foot capacity fresh water reservoir located approximately 26 miles southeast of South
Lake Tahoe, within Section 4, T 10 N, R 20 in the northeast portion of Alpine County, California (Figure
1). ICR was constructed in 1967 for the temporary storage of treated wastewater. Since 1989, all make-
up water to ICR is provided by fresh water diversions from Indian Creek and the West Fork of the Carson
River.
2
ICR is Section 303(d) listed for eutrophication. Since the 1970s, it has shown symptoms of
eutrophication including impairment of aquatic life and recreational uses and violation of narrative and
numerical water quality objectives. Phosphorus has been identified as the primary nutrient contributing
to eutrophication. The greatest source of phosphorus loading is believed to be from internal sources
(sediment load).
In July 2002, to evaluate water quality improvement, the LRWQCB established numeric targets for five
(5) indicator parameters: Total Phosphorus (TP); Dissolved Oxygen (DO); Secchi Depth (SD); Chlorophyll
a (Chl-a); and Carlson Trophic State Index (TSI). Interim and long-term numeric targets from the ICR
TMDL are summarized in Table 1.
Indicator Interim Target
(Attained by 2013)
Final Target
(Attained by 2024)
≤≤
–
–
–DO % Saturation ≥ 80%;
≥
≥
≤
≤
Table 1. Water quality indicator parameters and numeric targets
3 HOS Operation
In 2004, the Kennedy Jenks Consultants identified hypolimnetic oxygenation as a preferred alternative
to remove beneficial use impairment by reversing eutrophication in ICR (KJC, 2004). In 2005, Alex Horne
Associates researched the methods of hypolimnetic oxygenation employed in lakes and reservoirs and
recommended a submerged down-flow contact oxygenation system (SDCO or Speece Cone) as the best
device for use at ICR (A. Horne Associates, 2005). In December 2006, the District was awarded a Clean
Water Act Section 319 (h) Nonpoint Source Implementation Grant (Agreement No. 06-244-556-0) for
3
the purpose of reducing internal loading of phosphorus to ICR and to optimize reservoir management
for protection and enhancement of aquatic life and recreational uses. In 2007, Brown & Caldwell
consultants developed an engineering pre-design for the ICR Hypolimnetic Oxygenation System (HOS)
(Brown & Caldwell, 2007). In 2008, the District acquired a BLM Right-of-Way Grant to permit the
construction, operation, maintenance and termination of the ICR HOS and completed the engineering
plans and specifications required for construction.
The ICR HOS consists of an:
In-reservoir oxygen delivery system (Speece Cone);
On-site oxygen generation system; and
Underground and submerged utilities connecting the oxygen generator to the Speece Cone.
In June 2008, work for the on-site oxygen generation system started with construction of the equipment
building. In December 2008, the Speece Cone was installed in the deepest portion of ICR (water depth =
approximately 32 feet) and connected to the oxygen generator. The Speece Cone is a 10’ x 5’ diameter,
3/16” mild steel cone fitted with a 2’ x 5’ diameter skirt and bottom plate mounted on a 12’ x 6’ steel
equipment skid. The equipment skid is fitted with a 7.5 hp submersible pump and motor capable of
circulating approximately 2.1 cubic feet per second (cfs) of water through the Speece Cone. The oxygen
generation system connected to the Speece Cone includes a 25 hp rotary-screw compressor and
pressure swing adsorption oxygen generator housed in an on-shore equipment building. The oxygen
generator is an Air Sep AS-450 capable of producing up to 880 pounds per day (lbs/day) of oxygen, as a
95% purity gas. Utility connections between the Speece Cone and oxygen generator system consists of a
1-inch HDPE oxygen delivery line and Type G power cable housed in an 8-inch HDPE protective conduit.
The HOS is operated during the late spring and summer to deliver oxygen to ICR for water quality and
aquatic habitat improvement. Run time (in hours), average generation rate (in pounds per day) and
total amount of oxygen produced (in pounds) for each year of operation is provided below in Table 2. In
2012, the HOS delivered a total of 83,692 pounds of oxygen to ICR. The HOS operated for 2,926 hours,
generating oxygen at an average rate of 442 lbs/day.
YEAR OPERATING PERIOD RUN TIME AVERAGE O2
GENERATION RATE
TOTAL O2
PRODUCED
Start Date End Date (hrs.)(lbs/day) (lbs.)
2011 4/06/2011 10/31/2011 3,856 109,300
2012 4/05/2012 10/12/2012 2,926 83,692
Table 2. ICR hypolimnetic oxygenation system (HOS) operation periods.
During operation, District personnel monitor the oxygen generation system on a daily basis. Operating
parameters include run time, air pressures, air dryer temperature; oxygen pressures; oxygen flow, pump
amps and building temperature. In September 2011, the District inspected the system to evaluate
performance and determined that the oxygen generation system is being limited by elevated building
temperature and limited air receiver tank volume.
4
The equipment building housing the oxygen generator includes electrical equipment and an air
compressor that generate large quantities of heat. The equipment building is ventilated using a 6,750
scfm direct-drive wall exhaust fan. The exhaust fan draws ambient air into the building through an air
vent and exhausts the air through a discharge vent to remove heat from the equipment room. During
hot weather, average high time temperatures at ICR can easily exceed 85 degrees Fahrenheit. In order
to prevent overheating of the air dryer, the District has not run the system during daytime hours. In
August 2012, the District installed new ductwork to better exhaust the discharge from the air
compressor and reduce the heat load in the building. It is hoped that reducing the heat load will enable
the oxygen generator to run without restricting operating hours.
The Air Sep AS-450 uses pressure-swing adsorption technology to produce pure oxygen for delivery to
ICR. The oxygen generator consists of two adsorber vessels filled with an inert ceramic material
(molecular sieve) that adsorbs nitrogen from air under pressure, separating the compressed air into
oxygen. As compressed air passes through one of the adsorbers, the molecular sieve adsorbs the
nitrogen. This allows the remaining oxygen to pass through and exit the adsorber as a product gas which
is delivered under pressure to the oxygen receiver tank where it is stored prior to discharge to ICR.
Before the adsorber becomes saturated with nitrogen; the inlet air flow switches to the second
adsorber. The first adsorber is then regenerated by desorbing the nitrogen through depressurization
(vented to atmosphere) and purging it with oxygen. The complete cycle is then repeated. During the fall
of 2012, the District ordered a new 240-gallon air receiver tank to triple the existing air receiver volume.
The increased air volume should increase the flow volume and air pressure through the Air Sep AS-450,
resulting in increased oxygen production. The new air receiver tank was installed by the District in
January 2013.
Estimated costs for construction, operation and monitoring of the ICR HOS are provided below in Table
3. Total costs for the engineering and construction of the ICR HOS is estimated at $837,300. During
2012, approximately $23,000 was expended by the District for the continued operation and
maintenance of the system and accompanying water quality monitoring.
YEAR
CO
N
T
R
A
C
T
O
R
CO
N
S
U
L
T
I
N
G
EQ
U
I
P
M
E
N
T
&
MA
T
E
R
I
A
L
S
DI
S
T
R
I
C
T
L
A
B
O
R
&
M
O
N
I
T
O
R
I
N
G
OT
H
E
R
PE
R
M
I
T
S
PO
WE
R
SU
P
P
L
I
E
S
TO
T
A
L
2007 $91,880 $39,615 $4,511 $1,850 $137,856
2008 $232,559 $30,355 $60,700 $211,231 $21,003 $45 $1,322 $557,215
2009 $91,733 $24,609 $16,234 $41,616 $266 $10,507 $276 $185,241
2010 $11,431 $15,846 $27,277
2011 $12,237 $17,745 $29,982
2012 $8,490 $14,800 $23,290
TOTALS $324,292 $146,844 $76,934 $324,620 $25,780 $1,850 $58,943 $1,598 $960,861
Table 3. ICR HOS annual construction, operation and monitoring costs.
5
4 Current Data - 2012
The ICR TMDL Tracking Plan (LRWQCB, 2012) requires the reporting of water quality monitoring data
from reservoir stations: ICR-1, ICR-3 and ICR-5 (see Figure 2). ICR-1 is located nearest the Speece Cone,
at the north end and within the deepest portion of the reservoir. ICR-3 is located near the center of the
reservoir and within moderate water depths. ICR-5 is located near the south end of the reservoir within
relatively shallow water depths. Reservoir water quality samples and vertical profiles of field measured
temperature and dissolved oxygen are collected from each station on a monthly basis (weather
permitting). The analytical results for the 2012 raw water samples are provided in Appendix A. The
indicator parameter results are summarized in Table 4. A plot showing the dissolved oxygen monitoring
results is provided as Figure 4.
6
INDICATOR UNITS Interim
Target
(2013)
SITES LRWQCB TMDL
REPORTING
REQUIREMENT
CO
U
N
T
ME
A
N
MI
N
I
M
U
M
MA
X
I
M
U
M
Total
Phosphorus
(TP)
mg/L Annual
Mean
≤ 0.04
ICR-1,
ICR-3,
ICR-5
Annual mean of samples
collected from all depths
from all sites over the
reporting period.
62 0.04 0.021 0.07
Dissolved
Oxygen
(DO)
mg/L 1-day
mean
min.
≥ 4.0
ICR-1,
ICR-3,
ICR-5
Mean of samples
collected from all depths
at each site measured
monthly over the
reporting period.
See Figure 4.
Secchi Depth
(SD)
meters Summer
Mean
≥ 2
ICR-1,
ICR-3,
ICR-5
Mean for all readings
collected over the
reporting period.
8 3.66 2.45 5.11
Chlorophyll-a
(Chl-a)
mg/m3 Summer
Mean
≤ 10
ICR-1,
ICR-3,
ICR-5
Mean for all samples
collected over the
reporting period.
16 2.63 1.00 9.30
Trophic State
Index - Secchi
Disk
[TSI(SD)]
TSI TSI ≤ 45
units
ICR-1,
ICR-3,
ICR-5
Mean of all TSI (SD)
calculated from SD
readings (in meters)
collected from all sites
over the reporting
period.
8 42 37 47
Trophic State
Index -
Chlorophyll-a
[TSI(Chl-a)]
TSI TSI ≤ 45
units
ICR-1,
ICR-3,
ICR-5
Mean of all TSI (Chl-a)
calculated from Chl-a
concentrations (in ug/l)
collected from all sites
over the reporting
period.
16 37 31 52
Trophic State
Index - Total
Phosphorus
[TSI (TP)]
TSI TSI ≤ 45
units
ICR-1,
ICR-3,
ICR-5
Mean of all TSI (TP)
calculated from TP
concentrations (in ug/l)
collected from all sites
over the reporting
period.
16 53 48 65
Table 4. ICR TMDL 2012 Summary of Results.
7
5 TMDL Targets
The ICR TMDL Tracking Plan requires evaluation of the collected indicator parameter data to ascertain
progress toward achieving ICR numeric targets. The following graphs are provided for evaluation.
5.1 Total Phosphorus (TP)
The District collects water quality samples from each site at ICR, one day each month as weather
permits. The interim target for TP is less than or equal to 0.04 milligrams per liter (mg/L), as the mean
annual concentration in the water column. In order to evaluate TP levels in the reservoir, all available
data for sites ICR-1, ICR-3 and ICR-5 were combined and analyzed as an annual mean (see Figure 3).
Review of Figure 3 shows that annual mean TP levels have been at the target level of 0.04 mg/L since
2010.
Figure 3. Total phosphorus levels at ICR, plotted as an annual mean, in milligrams per liter (mg/L).
0.02
0.03
0.04
0.05
0.06
0.07
0.08
2007 2008 2009 2010 2011 2012
AN
N
U
A
L
M
E
A
N
(
m
g
/
L
)
INDIAN CREEK RESERVOIR
TOTAL PHOSPHORUS
≤
8
5.2 Dissolved Oxygen (DO)
The District collects DO readings one day each month, as weather permits, from each site at ICR. The
interim target value requires a single day minimum of greater than or equal to 4.0 mg/L, as the mean
concentration in the water column, at each monitoring site. In order to evaluate DO levels in the
reservoir, the data were analyzed by averaging DO readings collected through the water column at each
site (ICR-1, ICR-3 and ICR-5) and plotted as a daily mean for each month of the year (see Figure 4).
Review of Figure 4 shows that daily mean DO levels at ICR were greater than 4.0 mg/L at each site for
each monitoring day during 2012.
Figure 4. Daily mean dissolved oxygen levels measured at ICR, in milligrams per liter (mg/L).
In order to evaluate ICR TMDL implementation progress, historical daily mean DO levels measured at
ICR-1, ICR-3 and ICR-5 were plotted from 2007 through 2012 (see Figure 5). Review of Figure 5 shows
that daily mean DO concentrations were less than 4.0 mg/L at ICR-1 during August 2007, August 2008
and August 2011. Daily mean DO concentrations were greater than 4.0 mg/L at all sites during 2009,
2010 and 2012.
0.00
2.00
4.00
6.00
8.00
10.00
12.00
Di
s
s
o
l
v
e
d
O
x
y
g
e
n
(
i
n
m
g
/
L
)
INDIAN CREEK RESERVOIR
ICR-1 ICR-3 ICR-5
≥
9
Figure 5. Daily mean dissolved oxygen levels measured at ICR from 2007 through 2012, in milligrams per
liter (mg/L).
5.3 Secchi Depth (SD)
The District collects SD readings one day each month, as weather permits, from each site at ICR. The
interim target value requires a summer mean value of greater than or equal to 2.0 meters water depth
for the entire reservoir. In order to evaluate SD levels at ICR, the data were analyzed by averaging the
SD readings measured during the summer (June, July and August) at ICR-1, ICR-3 and ICR-5 and plotted
as a summer mean for each year (see Figure 6). Review of Figure 6 shows that, since 2009, summer
mean SD levels have been increasing and have been greater than 2.0 meters since 2010.
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
Me
a
n
D
i
s
s
o
l
v
e
d
O
x
y
g
e
n
(
m
g
/
L
)
INDIAN CREEK RESERVOIR
ICR-1 ICR-3 ICR-5
≥
10
Figure 6. Summer mean secchi depth readings measured at ICR during June, July and August 2007
through 2012, in meters.
5.4 Chlorophyll a (Chl-a)
The District analyzes water quality samples collected one day each month, as weather permits, through
the entire water column for Chl-a at each site. The TMDL target value requires a summer mean value of
less than or equal to 10 milligrams per cubic meter (mg/m3), equivalent to micrograms per liter, for the
entire reservoir. In order to evaluate Chl-a levels at ICR, the data were evaluated by averaging the Chl-a
values measured during the summer (June, July and August)at ICR-1, ICR-3 and ICR-5 and plotted as a
summer mean for each year (see Figure 7). Prior to statistical evaluation, an imputed value of one-half
the method detection level (MDL) was substituted for Chl-a values below the MDL. Review of Figure 7
shows that, since 2008, Chl-a levels have been decreasing and were less than 10 mg/m3 for the first time
in 2012.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
2007 2008 2009 2010 2011 2012
SE
C
C
H
I
D
E
P
T
H
(
m
e
t
e
r
s
)
-
SU
M
M
E
R
M
E
A
N
INDIAN CREEK RESERVOIR
SECCHI DEPTH
TMDL Target (≥ 2.0 meters)
11
Figure 7. Summer mean chlorophyll-a concentrations measured at ICR during June, July and August 2007
through 2012, in milligrams per cubic meter (mg/m3).
5.5 Trophic State Index
The ICR TMDL Tracking Plan requires that the summer (June, July and August) TP, SD and Chl-a values be
used to calculate a trophic state index (TSI) for each parameter using standard EPA calculations. The
TMDL target value requires a TSI of less than or equal to 45 units for the entire reservoir. In order to
evaluate TSI, a TSI for each parameter value [TSI(TP), TSI(SD) and TSI(Chl-a)] was calculated. The TSI for
all values were then used to produce an average reservoir TSI for each parameter (see Figure 8). Review
of Figure 8 shows that, since 2009, average reservoir TSI (TP) and TSI (SD) have been decreasing. TSI (SD)
and TSI (Chl-a) were less than 45 units for the first time in 2012.
0
5
10
15
20
25
2007 2008 2009 2010 2011 2012
CH
L
O
R
O
P
H
Y
L
L
-
a
(
m
g
/
m
3
)
-
SU
M
M
E
R
M
E
A
N
INDIAN CREEK RESERVOIR
CHLOROPHYLL - a
≤3
12
Figure 8. Carlson trophic state index (TSI) values for sechhi depth, chlorophyll-a and total phosphorus,
during June, July and August 2007 through 2012, in TSI units.
6 Summary & Conclusions
Evaluation of the 2012 ICR water quality data shows that:
1. Total Phosphorus (TP): the annual mean of samples collected at ICR-1, ICR-3 and ICR-5 is 0.04
mg/L, at TMDL interim target levels.
2. Dissolved Oxygen (DO); the daily mean of samples collected at ICR-1, ICR-3 and ICR-5 are greater
than 4.0 mg/L, in compliance with TMDL interim target levels.
3. Secchi Depth (SD): the summer mean for all measurements collected at ICR-1, ICR-3 and ICR-5 is
3.66 meters, in compliance with TMDL numeric targets.
4. Chlorophyll-a (Chl-a): the summer mean for all samples collected at sites ICR-1, ICR-3 and ICR-5
is 2.63 mg/m3, in compliance with TMDL numeric targets.
5. Trophic State Index (TSI): Using the TP, SD and Chl-a values collected during June, July and
August, the average reservoir TSI are as follows: TSI (TP) = 53; TSI (SD) = 42; and TSI (Chl-a) = 37.
The TSI (SD) and TSI (Chl-a) are in compliance with TMDL numeric targets.
30
35
40
45
50
55
60
65
70
2007 2008 2009 2010 2011 2012
TR
O
P
H
I
C
S
T
A
T
E
I
N
D
E
X
INDIAN CREEK RESERVOIR
TSI (SD)TSI (Chl-a)TSI (TP)
≤
13
7 References
Alex Horne Associates, 2005. Water Quality Improvements in Indian Creek, Alpine County California:
Pre-Design for Hypolimnetic Oxygenation, June 25,2005, revised August 22, 2005.
Brown and Caldwell, 2007. Technical Memorandum No. 1: South Tahoe PUD ICR Oxygenation Pre-Design
Tech Memo, September 11, 2007.
Kennedy Jenks Consultants, 2004. Indian Creek Reservoir TMDL Implementation Plan, December 9, 2004
Lahontan Regional Water Quality Control Board, 2012. Draft Indian Creek Reservoir Total Maximum
Daily Load (TMDL) Tracking Plan, April 27, 2012.
14
APPENDIX A
ANALYTICAL RESULTS
2012 ICR WATER QUALITY DATA