Subject: Tahera Responses
From: "Greg Missal" <[email-masked]>
To: "Joe Murdock" <[email-masked]>
Cc: "Philippe di Pizzo" <[email-masked]>
Date: Wed, 6 Jul 2005 15:27:39 -0400

Hi Joe,

Below are Tahera's responses to your comments and questions.  I have
placed them in following your points from your earlier email.  You will
also note that there are three attachments.  One is for the results of
some waste rock that was tested and the other two are details of input
which went into determining the pump capacity.

I really hope that these responses enable you to proceed with an
approval as we desperately need to get this underway. 

With Regards,

Greg

 

 

INAC Comments

2.    As expressed by INAC there still is no technical back up on how
You have derived at a "conservative" estimate for depth with respect to
freezing and site water levels. Could you please provide the scientific
know-how on how you deem this conservative? Are there records of data
for design lake levels that can be provided to the NWB? Could you please
indicate how you determined what criteria was used in determining a
design lake level.  There is mention within the report that the decision
was partially based on "regional information regarding ice thickness"
Can you please elaborate on where this information was obtained from and
the technical significance? 

TAHERA RESPONSE: THE INFORMATION IS FROM 'TYPICAL' ICE ROAD & LAKE
THICKNESSES NEAR THE LUPIN MINE ON CONTOYTWO LAKE.  ALSO TAHERA HAS
UTILIZED WATER FROM CARAT LAKE FOR MANY YEARS AND AS NEVER FOUND ICE
THICKNESS TO EXCEED 2.0M.  THIS THICKNESS IS ALSO CONSISTENT WITH ICE
DEPTHS OF OTHER LAKES IN THE AREA.  

THE CAUSEWAY INTAKE PIPE IS TO BE SET IN A 'MINIMUM' 4M OF WATER.  THE
PLAN CALLS FOR THE INLET OF THE HORIZONTAL INTAKE PIPE TO BE SET AT 4.5M
BELOW THE WATER SURFACE LEVEL.  THIS WOULD MAKE THE CENTER OF THE INLET
PIPE 4.05M BELOW THE SURFACE.  IN OUR ENGINEERING JUDGEMENT WE BELIEVE
THIS IS A SUFFICIENTLY CONSERVATIVE/APPROPRIATE DEPTH BELOW EXPECTED ICE
LEVELS.  DESIGN LAKE LEVEL IN THIS CASE IS ELEV 467.0M.   WHILE THE USE
OF THE WORD 'CONSERVATIVE' CAN BE SUBJECTIVE TO THE READER, IT IS LIKELY
THAT THIS DEPTH COULD BE BETTER TERMED 'APPROPRIATE'.

3.    No comment had been made regarding the ingestion and accumulation
of sediments within the pipe and the considerations made. 

TAHERA RESPONSE:  WE DO NOT CONSIDER ANY MINOR SEDIMENT BUILDUP THAT MAY
OCCUR WITHIN THE 0.9M DIAMETER HORIZONTAL INTAKE PIPE TO BE OF CONCERN.
WE DO NOT EXPECT ANY SEDIMENTATION IN THE PIPE TO OCCUR.  SHOULD
UNEXPECTED CONDITIONS OCCUR, THERE WOULD BE THE ABILITY TO 'BACKFLUSH'
THE INTAKE LINE TROUGH THE PUMPING OF WATER INTO THE UPRIGHT WELL CASING
AND OUT THE INLET PIPE.

5.    The answer provided is based on the proponents experience on site.
Could Tahera please provide evidence so the answer provided can be
technically assessed?  This can be done through technical evidence
identifying site specifics or on-site data compiled to back up Tahera
statements.

TAHERA RESPONSE: BASED ON THE EXPERIENCE OF THOSE ON SITE WE HAVE NOT
SEEN ICE RAFTING TO BE A PROBLEM.  THERE WAS NO EVIDENCE OF THIS
HAPPENING IN THE CURRENT YEAR IN THE AREA OF CAUSEWAY.  AS OF TODAY THE
ICE IS LARGELY GONE FROM THE AREA.

7.    Please see the comment made in 5. The same applies.

TAHERA RESPONSE: AGAIN WE USED A PRUDENT ENGINEERING ASSUMPTION OF A 2
METER FREEBOARD.

SHOULD EXPERIENCE DICTATE DURING OPERATIONS, WE ARE CAPABLE OF
INSTALLING PROTECTIVE BERMS AROUND THE PUMPHOUSE IF REQUIRED

 

DFO Comments

> 

Pumping Rates.

>Through the answer provided it can safely be assumed that either design
calculations have been carried through or a model developed assessing
the head loss. Could Tahera please provide the necessary details to
adequately evaluate how 50m of head differential was determined? Was the
calculation based on a theoretical Bernoulli Equation with a
Darcy-Weisbach

friction evaluation? If so what assumptions were made in the
calculations (i.e. roughness height, Reynold's Number). Could Tahera
please provide the technical analysis that can back up the statement?
Could Tahera please also detail how they evaluated the actual pumping
rate with respect to pump capacity? Was a calibration performed?

> 

TAHERA RESPONSE: THE CARAT LAKE LEVEL IS 465M; THE RAW WATER TANK IN THE
PROCESS PLANT WOULD BE OPERATING AT A LEVEL OF 535M.  THE HEAD
DIFFERENCE IN ELEVATION ALONE IS 70 M  THE PUMP SIZING AND CAPACITY HAS
BEEN DESIGNED BY A PROFESSIONAL ENGINEER(BY HATCH ENGINEERING) WHO ARE
REGISTERED IN NUNAVUT.  THE PUMP DESIGN CALCULATIONS ARE ATTACHED, WHICH
INDICATES OVERALL HEAD DIFFERENTIAL OF 85M WHEN CONSIDERING ELEVATION
DIFFERENCE AND PIPELINE FRICTION LOSSES.

AVERAGE PUMPING RATE IS BASED ON WATER USE EXPECTED FOR PROCESSING AND
OTHER USES AND IS DERIVED FROM THE METALLURGICAL WATER BALANCE.  THE
WATER USE IS UNDER 50 M3/HOUR.  TOTAL WATER USE IS REGULATED UNDER THE
WATER LICENSE.

CALIBRATION OF THE PUMP WILL TAKE PLACE DURING COMMISSIONING

> 

Section 1.6-1 Construction Waste Rock

> 

Could Tahera please provide further details and refinement outlining
what parameters will be tested and identified and the frequency
performed?

> 

TAHERA RESPONSE: WASTE ROCK WILL BE REGULARY TESTED FOR ROCK
CHARACTERISTICS.  ROCK INTENDED FOR THE CAUSEWAY HAS BEEN TESTED AND
FOUND TO BE NON-ACID GENERATING.  THE PARAMATERS TESTED INCLUDE:
STANDARD ACID-BASE-ACCOUNTING USING THE SOBEC METHOD, PAST PH, TOTAL
SULFUR, AND 47 ELEMENT ICP-MS SCAN.  FOUR SAMPLES WERE ANALYZED, WHICH
INCLUDED ROCK TO BE USED FOR THE CAUSEWAY, AND RESULTS ARE ATTACHED.
SAMPLES WERE SELECTED TO BE REPRESENTATIVE BY SITE ENVIRONMENTAL AND
GEOLOGICAL STAFF.

Section 2.3 - Silt Curtains

> 

Could Tahera please define the term "clean rock" in a quantifiable term
(i.e. method or % fines specification). How will Tahera ensure that
acceptably low caked fines content on the rock for construction are not
present when used in causeway construction?

> 

TAHERA RESPONSE:  CLEAN ROCK IS DEFINED AS RUN-OF-MINE GRANITE AND IS
GENERALLY ABSENT OF ANY SIGNIFICANT QUANTITIES OF OVERBURDEN OR TILL.
THE METHOD EMPLOYED IS FOR THE TAHERA ENGINEERING AND ENVIRONMENTAL
PERSONNEL TO INSPECT THE ROCK TO BE USED FOR THE CAUSEWAY MATERIAL TO
ENSURE THE ABSENCE OF TILL MATERIAL OR THAT ANY TILL MATERIAL HAS BEEN
CLEANED OFF.

> 

The NWB understand that water will be sampled inside and outside the
silt curtain daily. Could Tahera please provide spatial sampling details
and a further refinement of temporal sampling conditions? Also could
Tahera please provide details in the sampling protocol that will be
undertaken to capture these samples?

TAHERA RESPONSE: TURBIDITY INSIDE AND OUTSIDE THE SILT CURTAIN WILL BE
SAMPLED DAILY.  WATER WILL BE COLLECTED IN CLEAN POLYTHENE BOTTLES AND
TESTED WITH A TURBIDITY METER AT THE MINE SITE BY ENVIRONMENTAL
PERSONNEL.  SAMPLES WILL ALSO BE COLLECTED DAILY AND SUBMITTED TO A LAB
FOR TURBIDITY AND TOTAL SUSPENDED SOLIDS DETERMINATIONS.  A LAB HAS NOT
YET BEEN IDENTIFIED; THE CHOICE CRITERIA WILL BE A CERTIFIED LAB THAT
CAN GUARANTEE THE SHORTEST TURN-AROUND TIME FOR RESULTS.  ONCE A
RELIABLE (AS JUDGED BY THE ASSAY LAB) CORRELATION IS ESTABLISHED BETWEEN
TURBIDITY AND TSS, TSS SAMPLING WILL BE REDUCED TO WEEKLY.  SHOULD A
RELIABLE CORRELATION NOT BE FOUND, DAILY TSS SAMPLING WILL CONTINUE.  

WATER WILL BE COLLECTED FROM 25 cm BELOW THE SURFACE IN BOTH AREAS.
SAMPLES WILL BE COLLECTED FROM DIRECTLY INSIDE THE SILT CURTAIN AT 20m
INTERVALS INITIALLY FOR TURBIDITY AND TSS AND OUTSIDE THE SILT CURTAIN
AT 100m AND 200m DISTANCES(BASED ON THE PRECEDENT USED AT DIAVIK FOR A
MUCH LARGER CONSTRUCTION PROJECT).  SAMPLES WILL INITIALLY BE TAKEN AT
20m INTERNVALS (EXCLUDING THE SHORELINE TO A DISTANCE OF 50m WHERE WAVE
ACTION AND NATURAL SUSPENSION OF SEDIMENT WILL CONFOUND RESULTS. 

SHOULD TOTAL SUSPENDED SEDIMENT RESULTS INDICATE A LOWER SAMPLING
INTENSITY BASED ON HOMOGENEITY OF RESULTS, THE SAMPLING DISTANCE WILL BE
CHANGED TO 40m.  HOMOGENEITY WILL BE TAKEN TO MEAN LESS THAN 20%
DIFFERENCE IN ADJACENT SAMPLES.

 

 

 

 

Greg Missal

Vice President, Government and Regulatory Affairs

Tahera Diamond Corporation

121 Richmond Street West

Toronto, Ontario

M5H 2K1

Ph: 416 777-1998

Fax: 416 777-1898

email: [email-masked]