Thermal Discharge Strategies

Jason Knutson Wastewater Section Chief, WI DNR

Thursday, February 23, 2017

Why is thermal important? • Reproductive Behaviors

– Gametogenesis

– Spawning/Migration

• Reduces DO saturation point

• Cold Shock

• Elevated metabolism and plant growth

Limit Calculation

Ambient Water

Ambient T = 60 F

7Q10 = 200 cfs

Criteria: Sublethal (weekly avg) = 65 F Acute (daily max) = 82 F

Limit Calculation

Ambient Water

Ambient T = 60 F

7Q10 = 200 cfs

Criteria: Sublethal (weekly avg) = 65 F Acute (daily max) = 82 F

Facility

Effluent

Limit: 80 F (weekly avg) 110 (daily max)

𝑊𝑄𝐵𝐸𝐿 =(𝑊𝑄𝐶 −𝑇𝑎)(𝑄𝑠+ 1 −𝑓 𝑄𝑒)

𝑄𝑒 + 𝑇𝑎

Limits Drop?

• If the P99 is below a proposed limit in a given month, limits are not necessary

Options for Flexibility

1. Monthly Low-Flow Receiving Water Data (Qs)

2. Dissipative Cooling (Municipalities only)

3. Request Additional Mixing

a) Photographic Evidence

b) Visual Dye Study

c) Measured Stream Mixing Study

d) Mixing Zone Modeling

4. Real-Time Limits

5. Site-specific Criteria

6. Alternative Effluent Limitations

1. Use Monthly Low-Flow Data

𝑸𝒔 = Receiving Water Flow Rate

Default Qs = 25% of 7Q10

Flexible Option Qs = 25% of Monthly USGS Low Flow Data

Qs = 25% of 7Q10 = 25% of 200 cfs

Facility

January 257

February 200

March 287

April 350

May 300

June 290

2. Dissipative Cooling Study

• Measure dissipation of temperature to: – Ambient Water

– Atmosphere

• Goal: show that the sub-lethal (weekly average) temperature criterion is not exceeded for an unreasonable amount of area beyond the outfall.

• Municipalities only

Facility

2. Dissipative Cooling Study

• Done in month(s) when limits are of concern

• Measure T at cross-sections (above, at, & below discharge)

• Submit 3400-198 Form

• Limit Calculators are Reviewers and P.o.C.

3. Request Additional Mixing (Above 25% 7Q10)

• Where discharge mixes rapidly with receiving water

• Applicable to other pollutants as well

Qs = Stream Flow (25% of 7Q10)

Facility

3. Request Additional Mixing (Above 25% 7Q10)

• Where discharge mixes rapidly with receiving water

• Applicable to other pollutants as well

Qs = Stream Flow (75% of 7Q10)

Facility

Types

A. Visual/Photo Evidence

B. Dye Study

C. In-stream Plume Mapping

D. Modeling

Lactalis - Belmont

3A: Visual/Photographic

• Appropriate when: – Clear, Apparent Mixing

– 50% or less requested

– Diffuser Present

– No Spawning/Nursery Areas*

• Examples – 50% Requested

– Obstructed flow (100%)

– Diffusers

– Dams

*Requirement for all mixing zone determinations >25% of 7Q10

3B: Dye Study

• Biodegradable Dye – e.g. Rhodamine

– Continuous Injection

• DNR should be on-site

• Submit Photos, Video

• Helpful to map transects

• Best in shallow streams

Lactalis - Belmont

3C: In-stream Plume-Mapping

• Conduct at low-flow

• Measure: – Bathymetry (stream profile)

– Flow Rate

– Temperature

– Conductivity

• Transects at: -1, 0, ½, 1, 2, 3, 4, 6, (+) stream widths

T1 T2 T3 T4 T5 T1/2 T6

3D: Modeling

• Best for:

– New discharges

– In-stream study is infeasible

– Plume changes monthly

• Model mixing zone in every month

• 3D model for deeper waters

Pulliam Mixing Zone Study

4. Real-time Limits

• Limits vary hourly based on:

– Effluent Flow

– Stream Flow & Temperature ie:

NR 106.54

5. Site-specific Criteria

• Collect Ambient Temperature Data

– 2 Years, hourly

• Calculate new criteria using tables in NR 102

– Acute

– Sub-Lethal

• Adjust

• 5th Order Polynomial Regression

NR 102.26

y = 0.0089x5 - 0.2538x4 + 2.4226x3 - 9.3116x2 + 18.125x + 37.864 R² = 0.8517

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14

6. Alternative Effluent Limit (AEL)

• Biological demonstration • Granted when:

“effluent temperature limitations calculated… are more stringent than necessary to assure the protection and propagation of a balanced, indigenous community of shellfish, fish and wildlife in and on the body of water into which the discharge is made.”

• Considers additive effect of thermal pollution with: – other pollutants – other discharges

NR 106.70-77

2 Paths to an AEL

1. No Appreciable Harm to BIC (Balanced

Indigenous Community)

-Comparison of:

-Biological data, IBIs

2. Protection and Propagation of BIC

(Despite previous appreciable harm)

a) Identify RIS (Representative Important Species)

b) Examine impacts to RIS 1) Map/Model Plume

2) Compare in-stream temperatures to RIS’s spawning temperatures,

gametogenesis temperatures, etc. (use DNR’s Thermal Development Doc)

c) Propose Limits Protective of BIC

Current Discharge

Site

Actual

Upstream Reference Site

or Historical

Data

Baseline

Approved Thermal AELs

Port Washington WE Energies

Oak Creek Elm Road WE Energies

Point Beach NextEra

WE Energies - Valley

Alliant Edgewater

7. Other Options • Variance (Economic or due to upstream conditions)

– None in state, yet – Process very similar to variances for chlorides – EPA Review

• Relocate Outfall

– Default classification for unlisted waterbodies (not in NR 104) or 102 is warmwater sport fish

– Cannot have potential to impact a wetland – Must meet NR 207 Antidegradation

• Compliance Options

– Cooling Towers, Chillers, Geothermal Cooling, etc.

Questions

Jason Knutson

Jason.Knutson@wisconsin.gov

(608) 267-7894

Calculation of limits

• WQBEL = Water Quality-Based Effluent Limit • WQC = Water Quality Criteria • Ta = Ambient Temperature • Qs = Stream Flow (Usually 25% of 7Q10) • f = Fraction of water withdrawn from river • Qe = Effluent Flow (actual, not design)

𝑊𝑄𝐵𝐸𝐿 =(𝑊𝑄𝐶 −𝑇𝑎)(𝑄𝑠+ 1 −𝑓 𝑄𝑒)

𝑄𝑒 + 𝑇𝑎

(Assimilative capacity [º]) * (Total Stream Flow)

Discharges to Storm Sewers

• For discharges to storm sewers or other storm water conveyance channels:

13.2 ºF / mile (1 ºF / 400 ft)

Credit for Cooling in Storm Sewers