W2015L2-0001 TSS Amendment Public Hearing February 12, 2016 - - PowerPoint PPT Presentation

Document Control #: Template #: DCON-029-1010 R7

W2015L2-0001 TSS Amendment Public Hearing

February 12, 2016

ENVI-520-0216 R0

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Presentation Outline

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• Overview of Amendment Application
• Areas with Alignment
• Areas with Differences
• Summary

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Context

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Amendment Application – October 20, 2015

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• Management of total suspended solids (TSS) is an important aspect of A21 dike

construction as it was for A418 and A154 dikes previously.

• Construction activities and TSS control measures can be managed adaptively in

response to changing site conditions and measured TSS concentrations.

• It is DDMI’s view that for activities like dike construction that are subject to highly

variable conditions with limited control in the short-term, a time averaged TSS limit is more appropriate.

• A 30-day average TSS limit was previously approved by the Mackenzie Valley Land

and Water Board (MVLWB) through the A154 and A418 Construction Environmental Management Plans (CEMP) however no corresponding revisions were made to the associated Water License condition.

Rationale – TSS Limit

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Rationale - Location Reference

• The amendment application includes removing the phrase “and at a 200 metre

distance in any direction from the centerline of the dike footprint “ from Part H Item 31.

• And instead specifying the location of each Station (1645-82 to 1645-84) as

georeferenced locations in the Surveillance Network Program (SNP) (as they are currently).

• Changing where the location reference is made in the License (from the body of the

License to the SNP) would allow changes to be made to a location with approval of the WLWB rather than with an amendment to the license.

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Areas with Alignment

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Most Interveners and DDMI are in aligned on many issues. 1. Moving the references to monitoring locations from the body of the license to the SNP. 2. The need for DDMI to submit a revised CEMP before construction that includes a revised Trigger Action Response Plan (TARP). 3. SNP samples for TSS should be depth-integrated. 4. That the Newcombe and Jensen (1996) models for salmonid are relevant and appropriate for predicting effects levels for various TSS concentrations and durations. 5. That it is appropriate to apply an averaging period to the TSS Water License Limit. 6. That the averaging calculation needs to be specified in the water license.

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Areas with Differences

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Recommendations differ from DDMI application and/or from one intervention to another. 1. Environmental Effects Thresholds 2. Calculation Method and Enforcement

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Environmental Effects Thresholds

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SEV = 7.65 (DFO1, EC2, DDMI): 25 mg/L – 30-day average SEV = 7.17 (assumed YKDFN): 25 mg/L – 15-day average SEV = 7.07 (GNWT): 15 mg/L – 30-day average SEV = 6.63 (GNWT): 25 mg/L – 7-day average SEV = 6.16 (GNWT): 50 mg/L – 1-day average Diavik Environmental Assessment:

1 – DFO also support lower limits. 2 – EC recommendation is conditional upon a different calculation method during initial 30 days.

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Concentration (mg/L) Duration (days) Severity of Effect1 Highest J J+A A DDMI 25 30 7.65 7.65 7.43 7.25 25 110 8.57 8.57 8.22 7.78 DFO 25 30 7.65 7.65 7.43 7.25 25 110 8.57 8.57 8.22 7.78 GNWT 50 1 6.16 5.76 5.88 6.16 25 7 6.63 6.63 6.55 6.56 11 30 7.07 7.07 6.83 6.63 11 110 7.98 7.98 7.62 7.25 EC 25 1 5.63 5.26 5.37 5.63 25 7 6.63 6.63 6.55 6.56 25 30 7.65 7.65 7.43 7.25 25 110 8.57 8.57 8.22 7.78 YKDFN 25 15 7.17 7.17 7.01 6.92 25 110 8.57 8.57 8.22 7.78

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Calculation Method and Enforcement

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• The “dampening” that would occur during the first 30 daya is inherent in the

concentration-duration approach and is ecologically based.

• In this period a fish has a greater tolerance for a TSS event than if it had been

exposed to an extended period of low level TSS.

• Compliance with the 25 mg/L 30-day limit would be determined on each and every

day of construction. The DDMI proposed approach of a 30-day average limit is the same as the “Maximum Average Concentration” defined in W2015L2-0001.

"Maximum Average Concentration" means the moving average of any five (5) consecutive analytical results collected at six (6) day intervals as submitted to the Board in accordance with the sampling and analysis requirements specified in the Surveillance Network Program. (Water License W2015L2-0001)

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Summary

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• Many areas of alignment – objective of environmental protection and achievable.
• Recommendations differ from DDMI application and/or from one intervention to

another.

• The EC and GNWT approaches result in substantially lower SEV for short –term

exposures than they recommend for 30-day exposures. DDMI found no ecological basis for this difference in SEV.

• YKDFN approach of a 15-day versus 30-day averaging period does not appear to

provide substantive effects reduction.

• DDMI does not believe that a 110-day average TSS limit is necessary – however an
• 11 mg/L 110-day limit could be included in addition to 25 mg/L 30-day limit.
• The “maximum average concentration” that is enforced in the current water license

and provides evidence that the approach is enforceable.

• A 30-day average limit of 25 mg/L appears to have been previously approved by the

MVLWB for the A154 and A418 dike construction.

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Revised Amendment Language

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• DDMI agrees with the additional clarification recommended by EC
• DDMI requests that Part H Item 31 be revised to read as follows:

“31. The Licensee shall ensure that all in-lake dredging, dike Construction, or other in-lake activities meet the following criteria: At SNP Station #1645-82 to 1645-84 inclusive, and at a 200 metre distance in any direction from the centerline of the dike footprint the maximum concentration for Total Suspended Solids shall not exceed a 30-day moving average of 25 mg/L over the background concentration at SNP station #1645-55, as calculated from daily in any grab depth-integrated samples. “

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Masi – Thank You

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