Lower Wild Rice River Turbidity:TMDL Critique

Brent Mason, Mackenzie Consoer, Rebekah Perkins

BBE 5543November 8, 2011

Outline

TMDL OverviewWatershed BackgroundWater Quality StandardsLoading CapacityMonitoring and ImplementationConclusion

TMDL Overview

Clean Water Act Section 303 (d) requirements: 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: 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

Watershed Background

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.

Wild Rice River Watershed Location

Wild Rice River Watershed

Wild Rice River Watershed Characteristics

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

Wild Rice River Land Use Chart

Wild Rice River Watershed Land Use

Water Quality Standards

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)

Turbidity Overview

Clarity of water Caused by sediment, micro-

organisms, 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 Lenntech.com

Fishschooled.blogspot.com

Numeric Water Quality Target

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

Turbidity vs. SSC Relationship

o Majority of samples are at low flows and low turbidity

o Limited amount of data

Major Assumptions

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

Loading Capacity: Duration Curve Approach

Loading Capacity: Duration Curve Approach -Only 2 sites

-Underrepresented Low Flow Zone

Point Sources: Wasteload Allocation

TMDL = WLA + LA + MOS + RC

o Four Identified Potential Sources:1. Municipal Wastewater Treatment Facilities (WWTFs)2. Construction Activities3. Industrial Facilities4. 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

Point Sources: Wasteload Allocation

1. Municipal Wastewater Treatment Facilities (WWTFs)o NPDES/SDS permit = 45

mg/l TSSo Assume TSS values

comparable to SSCo Similar is stream with

high fine material (Gray et al, 2000)

o Lower Wild Rice ~90% fine material (Macek-Rowland and Dressler, 2002)

o Seasonal Discharge Windowso April-June and Sept-Dec o Assumes coincides with

High Flows

1.5 tons/day for each flow zone, except low flows

Low Flow Allocation Exception

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)

Point Sources: Wasteload Allocation2. Construction Activities

o WLA=estimated % of disturbed land= 0.17%

o MPCA stormwater permit records

3. Industrial Facilitieso 2 located in watershedo No accessible acreage datao Assumed same as Construction

Activities (0.17%)

4. Concentrated Animal Feeding Operations (CAFOs)o 2 located in watershedo WLA=0 discharge, in accordance with

permit

Construction Activities + Industrial Facilities + CAFOs=

.17% + .17% + 0% = 0.32% of TMDL within each Flow Zone

Non Point Sources: Load Allocation

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 Watershedo Upland Soil Erosiono Stream-Bank Erosion

o Relative contributions?

o Natural Processes

TMDL = WLA + LA + MOS + RC

magazine.noaa.gov

Margin of Safety

Margin of Safety (allocation uncertainty)o Four highest flow zones

o Accounted for flow variability within each flow zoneo 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

Reserve Capacity (future loading uncertainty)o Population Growth

o 4/10 cities declineo 6/10 cities increase from 1.9% to 7.5%

o WWTFs operating below loading limits, no planned expansion

o RC = 0

TMDL = WLA + LA + MOS +

RC

Loading Allocations

High Moist Mid Dry0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Lower Wild Rice River Suspended Sediment Loading Allocations

WLA (Permitted WWTFs) WLA (Construction/Industrial Stormwater)LA MOS

Flow Zone

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aily L

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g A

llocati

on

Major Assumptions/Critiques

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

Wild Rice River Monitoring Plan

Current Monitoring Activities Red River Basin Watch USGS flow monitoring and sediment analysis MPCA milestone and condition monitoring

Future Monitoring Plans Future monitoring is being developed by the

Wild Rice Watershed District with the assistance of its Flood Damage Reduction Team

Implementation Strategy

Restoration Plan under development: 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

Tools to Achieve Reductions Best Management Practices (BMPs) Filter Strips Riparian Buffers Grassed Waterways Cover Crops Conservation Tillage

Critique of Reduction Plan

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.

Conclusion

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

Questions?