Section 319
NONPOINT SOURCE PROGRAM SUGGEST STORY
Salmon on the Rocks: Sediment Controls Improve Water Quality
A/ K H I H Stormwater runoff from gravel mining operations within the city of
VatGrDOuy I nprOVGQ Sitka contributed sediment to Granite Creek. Monitoring showed that
the creek was impaired by high turbidity levels, which prompted Alaska's Department of Environmental
Conservation (DEC) to place 1.5 miles of Granite Creek on the 1998 303(d) list of impaired waters.
Efforts to reduce sediment loads have resulted in improved water quality. If improvements continue,
DEC will remove Granite Creek from the 2010 list of impaired waters.
Problem
Stormwater runoff from gravel lease operations,
material stockpiles, and gravel roadways carried
sediment into Granite Creek, resulting in high
turbidity levels in the creek (Figures 1 and 2).
Water quality monitoring indicated that sediment
and turbidity impairment typically occurred dur-
ing high rainfall events, heavy traffic and material
extraction. The high volume of sediment-laden
water exceeded the capacity of settling ponds, and
the ponds could not provide the optimal residence
time required for treatment. Gravel operations and
runoff from gravel mining were the primary sources
of turbidity and total suspended solids (TSS) impair-
ment (estimated at 65 percent of the total sediment
load entering Granite Creek).
Granite Creek and its tributaries (North Fork and
South Fork) are classified as anadromous, support-
ing Dolly Varden trout and coho and pink salmon.
Excess turbidity and sediment affected the creek's
aquatic life use by impairing the growth and propa-
gation of fish and other aquatic wildlife.
Alaska's Halibut Point Recreation Area, at the mouth
of Granite Creek, is heavily used for recreation
between April and early September. Excess sedi-
ment and turbidity created nuisance conditions that
attracted undesirable wildlife and reduced the water
recreation use value.
Alaska DEC worked with the City and Borough of
Sitka (CBS) to complete the Granite Creek Watershed
Recovery Strategy and Total Maximum Daily Load
(TMDL) for turbidity and sediment impairments.
EPA approved it in 2002. The goal of the TMDL was
to reduce the contributing sources of sediment, to
implement the recommended actions contained in
the strategy and to ensure compliance with sediment
and turbidity criteria in Granite Creek.
Figure 1. The South
Fork of Granite Creek
(see series of arrows)
is adjacent the Tisher
gravel lease operation.
Figure 2. Only a
small buffer existed
between Granite
Creek and gravel
operations in Sitka
before the project.
Alaska water quality standards limit allowable tur-
bidity to 5 NTUs above natural conditions to protect
Granite Creek's default designated use for drinking
water. The turbidity criterion for the aquatic life use
category may not exceed 25 NTUs above natural
conditions. Because Alaska water quality standards
include a narrative criterion for TSS rather than a
numeric criterion, the numeric turbidity criterion
served as an appropriate measurement indicator for
the TMDL. Turbidity measurements were converted
to a gravimetric (weight) indicator for purposes of
TMDL sediment load calculations.
Project Highlights
Implementing the Granite Creek Watershed
Recovery Strategy and TMDL involved more than
25 different tasks, including constructing a series
of settling ponds and routinely cleaning those
ponds. Additional BMPs included establishing and
-------
protecting vegetated riparian buffers along tributar-
ies to Granite Creek; placing physical barriers to
limit encroachment on stream banks; constructing
road, culvert and stormwater drainage improve-
ments (Figure 3); grading and maintaining roads;
educating operators; modifying construction
design; and routinely monitoring water quality.
These BMPs have been instrumental in significantly
improving water quality.
Results
Since 2002 implementing BMPs as outlined in the
Recovery Strategy and TMDL has significantly
reduced sediment loads and turbidity and improved
aquatic habitat. Pink salmon populations in the
lower reaches of Granite Creek have increased from
approximately 1,000 individuals reported in 1978 to
more than 6,000 in 2007.
New sediment load calculations, adjusted from the
original TMDL estimations, verify that TSS levels in
the creek have declined. Annual in-stream sediment
loads of 187.06 tons TSS/yr are below the allowable
load capacity of 244.86 tons TSS/year, which were
adjusted according to the 2007 five-year analysis
(Table 1).
While water quality standards are being met the
majority of the time, five years of monitoring data
show periodic exceedances during the rainy months
of September through December. Overall, the
seasonal and annual sediment loading to Granite
Creek is within the TMDL load allocation. Granite
Creek is showing marked improvements and will be
considered for delisting for sediment and turbidity
in 2010 if the trend continues.
Partners and Funding
Alaska's DEC, CBS, Redburn Regulatory and
Environmental Services (project consultant), Alaska
Department of Fish and Game, U.S. Geological
Survey, and gravel lease operators have worked
together to restore Granite Creek. Since 2002 CBS
has received approximately $200,000 in section
319 Clean Water Act grants for Granite Creek TMDL
implementation and has provided matching funds
to the state.
FigureS. Experimental retrofit for culvert discharge
to improve capture of sediment before it enters
Granite Creek.
Table 1. Monthly suspended sediment loading
capacity and monthly existing (in-stream)
suspended sediment loads in Granite Creek in 2007
Month
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sept.
Oct.
Nov.
Dec.
Annual
Total
Average
Monthly Flow
(cfs)
44.5
29.0
19.8
9.9
13.4
15.5
9.1
62.4
79.5
66.7
138.0
88.7
Natural
Background
Load (tons)
1.86
0.56
0.93
1.50
2.17
1.80
1.24
0.93
3.00
4.34
1.20
3.10
22.63
Loading
Capacity
for TSS (tons)
19.26
11.33
8.57
4.15
5.80
6.49
3.97
27.00
33.29
28.86
57.79
38.38
244.86
Existing
Suspended
Sediment (TSS)
Load (tons)
8.79
3.51
1.86
0.47
0.87
1.12
0.41
16.82
25.95
19.15
75.00
33.11
187.06
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-08-001F
May 2008
For additional information contact:
Mark Buggins, Environmental Superintendent
City and Borough of Sitka
907-966-2256 • markb@cityofsitka.com
Laura Eldred, Environmental Program Specialist
Alaska DEC Division of Water
907-376-1855 • laura.eldred@alaska.gov
------- |