August 29, 2008 File: 2003L8-0007

Distribution List

Dear Sir/Madame:

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Attached for your review and comments is the aforementioned Water Disposal Monitoring Plan as required under the water licence submitted to the Mackenzie Valley Land and Water Board by Canadian Zinc Corporation Incorporated under the terms and conditions of Type 'B' Water Licence, Part D, item 15.

Please submit your comments in writing by September 19, 2008 quoting Water Licence MV2003L8-0007.

If you have any questions regarding the above-noted documents, please contact me at (867) 669-0506 or email

Yours sincerely,

Tyree Mullaney Regulatory Officer

Attachment Golder Associates Ltd.

#300, 10525 — 170 Street . Alberta, Canada T5P 4W2 Telephone (780) 483-3499 Fax (780) 483-1574

18 August 2008 08-1373-0012

Jivko Engineering 5610 50 "A" Avenue , NT X1A 1G3

Attention: Mr. Jivko Jivkov. P.Eng. Principal

RE: Deh Cho Bridge Water Disposal and Monitoring Plan

Dear Mr. Jivkov:

INTRODUCTION

The present letter is submitted to fulfil p artial requirements under Part D, Item 15 of Water License MV2003L8-0007 granted by the Mackenzie Valley Land and Water Board (MVLWB) to the Deh Cho Bridge Corporation. The Water Licence stipulates that a Water Disposal and Monitoring Plan (the is to be submitted to the MVLWB for review and approval. The Plan is required to address water quality issues as they pertain to the protection of aquatic life during the pumping of water from pier cofferdams.

Golder Associates Ltd. (Golder) is under contract with the Deh Cho Bridge Corporation to carry out water quality monitoring activities during construction of the Deh Cho Bridge across the near , NT (the Project). As such, Golder is prepared to work with Ruskin Construction Ltd. (Ruskin) to assist with the monitoring of water pumped from cofferdams.

The volume of water in each of the three nearshore cofferdams is estimated to be 1. 700 in3, whereas the two centre cofferdams will have an approximate volume of 2000 m 3 . The three nearshore piers each require 600 m 3 of Tremie concrete (i.e., water volume displaced) to construct the pier footings. The two centre-most piers require 700 of Tremie concrete. It is estimated that it will take 20 hours to place Tremie concrete at each pier. After the concrete for each pier footing has cured (approximately seven days), each cofferdam will be dewatered to facilitate construction of the remaining portions of each pier under dry conditions.

WATER DISPOSAL AND MONITORING

The contractors will pump water from cofferdams during the placement of the Tre e concrete and final dewatering of the cofferdams (Attac hment 1). Pumped washout water may have elevated total suspended sediment (TSS) and pH levels due to the curing of concrete (i.e., concrete and its laitance feature high TSS and BEST

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OFFICES ACROSS NORTH AMERICA, SOUTH AMERICA, EUROPE, ASIA, AUSTRALASIA .livko Jivkov 18 August 2008 Water Disposal and Monitoring Plan -2- 08-1373-0012 high pH). Disturbance of the river bed may also occur resulting in re-suspension of sediments. Ten-inch diameter pumps will be used to pump water directly into a 13 000-L water truck. Water in each truck-load will be tested for pH on-site by Golder's water quality monitor and, if necessary, treated. Following successful treatment and approval from the water quality monitor. the treated water will be discharged directly into the Mackenzie River. Should water treatment for pH fail, the water will be discharged into a temporary retention pond for further treatment. TSS will be monitored in stream and should elevated levels be encountered, construction will modify techniques or rates of construction to conform to TSS guidelines. Concrete laitance material will be transported off-site for disposal.

Elevated pH and TSS are harmful to the environment; federal guidelines have been established to protect freshwater aquatic life (CCME 2001). Golder (2008a and 2008b) outlined water quality monitoring plans to be carried out during the construction of instream structures and side-casting of excavated river bed materials from cofferdams. These plans have been reviewed by regulators (MVLWB and the Department of Fisheries and Oceans Canada [DFO]) and will form a basis for the approach for the present Water Disposal and Monitoring Plan, as provided below.

Coordination (Deb Cho Bridge Corporation, Contractors, and Field Staff)

The importance of effective and timely communication between the Golder field crew members, Ruskin construction supervisors, and the Deb Cho Bridge Corporation (DCBC) is recognized. This will ensure that monitoring is completed in a professional and safe manner, and that the data collected meets the requirements of the client and regulatory agencies.

Golder field crews will attend pre-construction meetings at the crossing site with the DCBC field supervisor, and construction contractor representatives to discuss the day-to-day operations at the site; establishment of a defined meeting schedule and format (e.g., daily tail-gate meetings to discuss progress, problems, and safety concerns).

The water quality monitoring field crew will be equipped with a satellite telephone and site-to- site communications systems (two-way radios, supplied by construction contractor). As such, they will be in close communication with the DCBC staff (office/field), construction contractors, and Golder's home office to expedite daily reporting and discussion of observed data

TSS

A feedback monitoring program will be implemented during de-watering of each cofferdam to ensure compliance with water quality guidelines. Timely feedback on TSS concentrations in the receiving environment (i.e_, within one hour of recording out-of-compliance TSS levels when feasible) will be provided to the construction contractor. This will facilitate immediate modification or tempering of construction (e.g., reduced pumping rates or discharge water into a temporary retention pond). CCME (2001) criteria will be used to establish compliance limits for TSS during the project construction. These limits, which are based on the water quality guidelines for the protection of aquatic freshwater life, are as follows:

Golder Associates Jivko Jivkov 18 August 2008 Water Disposal and Monitoring Plan -3- 08-1373-0012

• Under "Clear Flow" Conditions (background levels 0 to 25 mg/L) — maximum increase in TSS not to exceed 25 mg/L above background for any short-term exposure (e.g., 24-h period). Maximum "average" increase of 5 mg/L over background levels for longer term exposures (e.g., inputs lasting between 24 h and 30 d);

• Under "High Flow" Conditions (background levels exceeding 25 mg/L) maximum allowable increase of 25 mg/L over background levels when background levels are between 25 and 250 mg/L; levels should not increase more than 10% of background levels when background is greater than 250 mg/L;

A sampling location 500 m downstream from each cofferdam will be established to monitor TSS compliance with CCME guidelines. This distance was established as the compliance location during side-casting of excavated river bed materials, as part of the Controlled Placement Plan (Golder 2008a and 2008b). Background data will be collected 100 m upstream of each cofferdam.

Because TSS requires laboratory analysis (i.e., turn-around time of several days), turbidity will be used to provide a surrogate measurement of TSS. Turbidity is readily measured in the field. A turbidity-TSS relationship has been developed for the Project and will be used to calculate TSS values (linear regression equation). This relationship indicated that increases of 10 Nephelometric Turbidity Units (NTU) in the Mackenzie River are equivalent to 25 mg/L TSS. A few TSS samples will be collected during the monitoring program for further refinement of the turbidity-TSS relationship.

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CCME (2001) specifies pH levels between 6.5 and 9.0 units are required to protect freshwater aquatic life. Fresh concrete typically has a pH level of 12, or higher. For reference, water quality monitoring crews have recently recorded Mackenzie River pH levels ranging between 7.8 and 8.4 units. pH of water exposed to concreted is anticipated to increase proportionally with time.

A modified version of the feedback monitoring system described above for TSS will be applied to monitor pH. Relative to TSS, the effects of pH on freshwater organisms are more acute and adverse; therefore, pH will be monitored with each load at the tanker-truck. Should pH levels greater than 9.0 units be encountered, the water quality monitoring crew will immediately inform construction superintendents/foremen. Ruskin will then act accordingly to modify the pH of water inside each tanker-truck load.

Ruskin will have a pH neutralization system on immediate standby. When necessary, water within the tanker truck will be carbonated. Carbon dioxide gas (which in the presence of water will form carbonic acid) will be pumped with air hoses/diffusers into the contained water; rate of injection will be modified according to monitoring results. The goal is to reduce and maintain pH levels below 9.0 units. This system of pH control has been successfully used by Ruskin and associated contractors on previous projects.

Golder Associates Jivko Jivkov 18 August 2008 Water Disposal and Monitoring Plan -4- 08-1373-0012

Should treatment fail (as monitored by Golder field crew member), the water will be discharged into a temporary retention pond situated approximately 250 m southeast of the bridge abutment. Water within this pond will be treated with either the carbonation system described above for the tanker truck, or mild sulfuric acid, or diluted with river water.

All water sampling, sample preservation, and analyses will be conducted in accordance with methods prescribed in the current edition of"Standard Methods for the Examination of Water and Wastewater" (APHA 2006)_ Three water quality samples will be collected for each pier (at the beginning, middle, and end of each cofferdam disposal and dewatering period) and submitted to an analytical laboratory for verification of field measurements and other parameters. Laboratory analyses will include TSS, pH, conductivity, turbidity, and total metals. Samples destined for laboratory analysis will be submitted to ALS Laboratory Group (ALS) in Yellowknife, NT.

A Hydrolab'rM Model DS5 multiprobe water quality meters will be used to monitor turbidity and pH. In addition a portable OaktonTM pH/fond 10 Series combination meter will be available as a back-up. The water quality meters will be maintained and serviced based on the manufacturer's suggested schedule. The meters will be checked daily for accuracy and calibrated according to the manufacturer's recommended schedule. Turbidity readings are accurate to ±1% for levels up to 100 NTIJ, ±3% for levels ranging from 100 to 400 NTU, and -5% for levels ranging from 400 to 3,000 NTU. The Hydrolab provides a pH accuracy of±0.2 units.

Samples collected for laboratory analysis will include one set of duplicate or triplicate samples from one randomly selected time from each cofferdam disposal period. In addition, one field blank or one laboratory trip blank sample will be submitted to the laboratory (one for each pier).

As field and laboratory results are received, they will be reviewed and checked for errors and anomalies. Once all concerns have been addressed (e.g., requesting re-analysis from analytical labs, flagging/qualifying data), the results will be added to the project's Excel-based database. Where possible, tools will be developed to simplify the updating process and to minimize the amount of manual data manipulation. Spot checks and other routine quality control protocols will be used to verify the accuracy of the database once it has been updated. All data will be subject to Golder's internal review process (i.e., examination by water quality specialist and final review by an Associate or Principal).

A draft final letter report summarizing sampling events, required mitigation methods, and results will be prepared byl5 December in each of 2008 and 2009 for review. A final letter report will be prepared within two weeks of receipt of review comments.

CLOSURE

We trust that information contained this letter is sufficient for your present needs. Should you have any questions, or require additional details or further clarification on the contents, please do not hesitate to contact the undersigned at (780) 483-3499.

Golder Associates Jivko Jivkov 18 August 2008 Water Disposal and Monitoring Plan -5- 08-1373-0012

Sincerely,

GOLDER ASSOCIATES LTD.

Mark Dunnigan, M.Sc P.Biol. Jim O'Neil, B.Sc., P.Biol. Aquatic Biologist Principal, Senior Fisheries Biologist

MDIJPOlkj cnel. cc: Tyree Mullaney, MVLWB Terry Whiteman, Ruskin Construction Ltd. Al Zoobkoff, Ruskin Construction Ltd.

LITERATURE CITED

APHA (American Public Health Association). 2006. Standard methods for the examination of water and wastewater. 20a edition. Prepared in association with the American Water Works Association and the Water Environment Federation, Published in Washington DC, USA. Website = accessed 23 July 2008.

Canadian Council of the Ministers of the Environment (CCME). 2001. Canadian Environmental Quality Guidelines. Environment Canada. Hull, .

Golder Associates Ltd. 2008a. Deh Cho Bridge Water Quality Monitoring Work Plans. Letter dated 24 June to Jivko Engineering, Yellowknife, NT. Golder File No. 08-1373-0012- 3000: 10 p. + 1 Attachment.

Golder Associates Ltd. 2008b. Deh Cho Bridge Revised Water Quality Monitoring Work Plans. Letter dated 21 July to Jivko Engineering, Yellowknife, NT. Golder File No. 08-1373- 0012-3000: 10 p. + 1 Attachment.

Golder Associates

Attachment I

Ruskin's Water Management Plan

For Placing Tremie Concrete and De-Watering Cofferdams August 17, 2008

To further expand on our established procedure with our Pier Footing Tremie Pour — Work Procedure #2.7. This plan shall be used for managing water during the placement of the Tremie concrete and final Dewatering of the cofferdams.

1. Tremie concrete placement into cofferdams will require the displaced water to be pumped out into a container, tested for pH levels, treated if required and discharged into the river.

(a) Pump water from the cofferdam during the tremie concrete pour into a 13,000L water truck. The water level in the cofferdam is to be maintained a minimum of 50mm below the river elevation.

(b) Test water that is pumped into the water truck for pH levels. If pH Levels are of an acceptable level as determined by Golder & Assoc. and only after consultation with the Environmental Monitor then water will be discharged directly into the river.

(c) if high pH levels are present the water shall be treated through carbonation. A carbon dioxide diffuser will be installed into the truck water tank.

(d) if pH levels cannot be reduced to acceptable levels then the water will be discharged into a temporary retention pond. The pond will be located on the east side of the project, approximately 250m from the south abutment. The approximate size of the retention pond 15m x 15m x 1.5m.

Ruskin Construction Ltd. - Division Suite 301, 1281 West Georgia Street, Vancouver V6E 337 Tel: (604) 331-1032 Fax: (604) 331-1034 2. After a concrete curing period the cofferdam will be completely dewatered to allow additional structural concrete to be placed in the dry.

(a) pH levels of the water inside the cofferdam shall be tested prior to discharging any water into the river. If the pH levels are higher than acceptable limits as determined by Golder & Assoc., and only with consultation with the Environmental Monitor, treatment of the water will be required.

(b) The water shall be treated by carbonation or other methods acceptable to the Environmental Monitor.

(c) If the pH levels cannot be reduced to acceptable discharge levels then the water shall be discharged into a temporary retention pond located on the east side of the project, approximately 250m from the south abutment.

(d) The laitance materials produced during the Tremie concrete pour shall be disposed of into the sump. No laitance materials shall be disposed of into the river.

Terry Whiteman, Pro.Mgr. Deh Cho Bridge Ruskin Construction, LTD

Ruskin Construction Ltd. Vancouver- Division Suite 301, 1281 West Georgia Street, Vancouver V6E 3J7 Tel: (604) 331-1032 Fax: (604) 331-1034 FILE NUMBER: MV2003L8OOO7

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Remarks

Water Licence Plan Submission and Review, Z Enclosures Deh Cho Bridge Corp. 0 As requested

El For your approval Delivered by Date

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El Courier Hand 0 Delivered

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