Lower Wild Rice
River Turbidity:
TMDL Critique
Brent Mason, Mackenzie
Consoer, Rebekah Perkins
BBE 5543
November 8, 2011
 TMDL
Overview
 Watershed Background
 Water Quality Standards
 Loading Capacity
 Monitoring and Implementation
 Conclusion
Clean Water Act Section 303 (d) requirements:
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Every 2 years states publish a list of “impaired” waters
TMDL report must be developed for all waters on the
impaired waters list
TMDL Requirements:
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Provides a calculation of the maximum amount of a
pollutant that a water body can receive and still meet
water quality standards
Sums the loads of a single pollutant from all point and non
point sources
Wild Rice River watershed:
 Encompasses just over 1 million acres
 Flows Across 5 Minnesota counties
 Lies within three eco-regions
 Impaired for Turbidity from the confluence of the
South Branch of the Wild Rice River to the Red
River
 Impaired section of River is 30.58 miles in length
and is located entirely within Norman County.
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Lower reach of Wild Rice River lies within the
Lake Plain from Glacial Lake Agassiz
Extremely Flat with level deposits of lake
sediment
Lower Wild Rice River is contained by low
banks and has high sinuosity
Soils tend to be clays with low permeability
and low internal drainage
Cropland dominates the land use of the Lower
Wild Rice River
Upland is heavily drained by both ditch and
tile systems
Designated Beneficial Use:
 Water
body is classified as both 2B and 3B water
 Chose class 2 waters: aquatic life and recreation
**Higher standards
Turbidity:
 25
NTU standard for natural water bodies
 Surrogate measurement for Total Suspended
Solids (TSS) and Suspended Sediment
Concentration (SSC)
 Clarity
of water
 Caused by sediment, microorganisms, dissolved material,
and organic matter
 Measurement of amount of
light scattered
 Measured with dimensionless
unit of NTU
 Blocks sunlight that fish and
plants thrive on
 Degrades aesthetic appeal of
water body
Fishschooled.blogspot.com
Lenntech.com
 Turbidity
is dimensionless and cannot be used to
determine sediment loads
 Relationship between Turbidity and SSC needed
to be derived
 Using paired turbidity and SSC data, simple
regression analysis was used to create a
relationship between the two variables
 Using this relationship: 25 NTU = 38 mg/L SSC
o
o
Majority of
samples are at
low flows and
low turbidity
Limited amount
of data
 Major
inconsistencies between turbidity meters
 Turbidity relationship only based on one year of
data and primarily at one location
**Depending on how the make up of the sediment
changes throughout this watershed, this relationship can
vary greatly
 The
majority of the data was taken during low flows
or winter months
-Only 2 sites
-Underrepresented
Low Flow Zone
TMDL =
WLA + LA + MOS + RC
o Four Identified Potential Sources:
1. Municipal Wastewater Treatment Facilities (WWTFs)
2. Construction Activities
3. Industrial Facilities
4. Concentrated Animal Feeding Operations (CAFOs)
Note: No MS4 permit requirements (stormwater)
o All Require NPDES/SDS permit
o Assumed Full Permit Compliance
o Minor contributors to turbidity impairment
1. Municipal Wastewater Treatment
Facilities (WWTFs)
o NPDES/SDS permit = 45 mg/l
TSS
o Assume TSS values
comparable to SSC
o Similar is stream with high
fine material (Gray et al,
2000)
o Lower Wild Rice ~90%
fine material (MacekRowland and Dressler,
2002)
o Seasonal Discharge Windows
o April-June and Sept-Dec
o Assumes coincides with
High Flows
1.5 tons/day for each flow zone,
except low flows
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Loading Capacity for LOW FLOW ZONE very small
Permitted WWTF loads exceed total daily loading at low
flows
**Not possible because it is a component of total loads
Concentration – based on allocation to sources for low
flow zone
Allocation = (flow contribution from a given source) x (45
mg/L TSS, the permit limit)
2. Construction Activities
o WLA=estimated % of disturbed land=
0.17%
o MPCA stormwater permit records
3. Industrial Facilities
o 2 located in watershed
o No accessible acreage data
o Assumed same as Construction Activities
(0.17%)
4. Concentrated Animal Feeding Operations
(CAFOs)
o 2 located in watershed
o WLA=0 discharge, in accordance with
permit
Construction Activities + Industrial Facilities + CAFOs=
.17% + .17% + 0% = 0.32% of TMDL within each Flow Zone
TMDL = WLA +
LA + MOS + RC
o No NPDES/SDS Permit Requirements
o Major Load Contributors, occurs mostly at HIGH FLOWS
o LA = Total Load Capacity-WLA-MOS
o Primary Drivers in Wild Rice River Watershed
o Upland Soil Erosion
o Stream-Bank Erosion
o Relative contributions?
o Natural Processes
magazine.noaa.gov
TMDL = WLA + LA +
MOS + RC
Margin of Safety (allocation uncertainty)
o Four highest flow zones
o Accounted for flow variability within each flow zone
o Median flow-Minimum flow within each zone (standard
calculation)
o Low Flow Zone
o Implicit MOS used (built into TMDL allocations)
o Conservative assumptions
o Discharge periods = High flows
o Discharging below permit limits
TMDL = WLA + LA + MOS +
RC
Reserve Capacity (future loading uncertainty)
o Population Growth
o 4/10 cities decline
o 6/10 cities increase from 1.9% to 7.5%
o WWTFs operating below loading limits, no planned expansion
o RC = 0
Lower Wild Rice River Suspended Sediment Loading Allocations
100%
90%
Total Daily Loading Allocation
80%
70%
60%
50%
40%
30%
20%
10%
0%
High
Moist
Mid
Dry
Flow Zone
WLA (Permitted WWTFs)
WLA (Construction/Industrial Stormwater)
LA
MOS
 Flow
Zone Sample Representation
 NPDES/SDS permit compliance
 Assume TSS values comparable to SSC
 Seasonal Discharge Windows Coincide High Flow
 Land Disturbance % = Loading Allocation %
 Natural Background Insignificant
 RC = 0
Current Monitoring Activities
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Red River Basin Watch
USGS flow monitoring and sediment analysis
MPCA milestone and condition monitoring
Future Monitoring Plans
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Future monitoring is being developed by the Wild
Rice Watershed District with the assistance of its
Flood Damage Reduction Team
Restoration Plan under development:
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Focus of plan: Identify sources of sediment
spatially
Funding for Implementation: Existing
programs (Clean Water Legacy,
Conservation Reserve Program, etc.)
Soil and Water Conservation District:
Encourage the funding of programs that will
reduce non point sources of turbidity
Best Management
Practices (BMPs)
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Filter Strips
Riparian Buffers
Grassed Waterways
Cover Crops
Conservation Tillage
 Requires
collaborative effort by many
individuals and organizations
 Assumes land use practices do not change
significantly
 Restoration costs are estimated to be in the
tens of millions of dollars
 Restoration tools suggested will occupy many
acres of valuable farmland.
 Turbidity
and SSC were monitored
 Numeric standard of 38 mg/L derived
 Load duration curve developed to
evaluate load exceedences
 Monitoring and implementation plans
being developed
 Many assumptions were made but few
assumptions had a significant impact on
overall load calculations