ML20065F276

Proposes to Discontinue Survey Between North Anna Main Dam Ref Monuments & Us Coast & Geological Survey Monuments Performed Once Every 10 Yrs to Verify Locations of Ref Monuments

ML20065F276
Person / Time
Site:	North Anna
Issue date:	04/05/1994
From:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Crisp R FEDERAL ENERGY REGULATORY COMMISSION
References
F93-018, F93-18, NUDOCS 9404110295
Download: ML20065F276 (2)

Text

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m 5 l JAMts P. O'llANLON -

' innsbrook Technical Cente

. Vice President - Nuclear Operations 5000 Dominion Boulentd,

] lb Glen Allen, Virginia 2J060

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806 273 2101 l

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April 5, 1994 3

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Mr. R. W. Crisp Serial No. F93-018 j

LRegional Director.

Federal Energy Regulatory Commission i

3125 Presidential Parkway, Suite 300 f

Atlanta,. Georgia 30340 i

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Dear Mr. Crisp:

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PROJECT NO. 6335-VA j

NORTH ANNA HYDROELECTRIC PROJECT TEN-YEAR SURVEY OF REFERENCE MONUMENTS AT MAIN DAM V

l Currently, the survey between the North Anna main dam's reference monuments and the United States Coast and' Geological (USC&G) Survey monuments is.

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performed once every ten years to verify the locations of the reference monuments.

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We have determined that the survey.between the monuments does not provide j

significant information relative to settlement'or horizontal movement of.the dam.

a We have discussed this with Mr. J. C. Lyon, Jr. of your office.

The bases-for our determination are the stability ~of the main dam's reference monuments and the relative distance between the main dam's monuments and I

those of the USC&G. The main dam's reference monuments are founded in rock and therefore are inherently more stable than the USC&G Survey monuments which are founded in soil. - Additionally, the distance between the main dam's reference monuments and the USC&G Survey monuments'used for horizontal

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measurements (4?r miles) can induce a relatively large degree of error compared to j

. the accuracy of the annual survey (between the main dam's reference monuments i-and the dam's alignment settlement markers) an_d the Indicated movement over the past twenty years. For vertical measurements, the distance between the USC&G monuments and the reference monuments (1!r miles)'also potentially induces a j

relatively large error compared to the results of the annual surveys of the alignment settlement markers.

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Discussions with Mr. J; C. Lyon,.Jr. of your office indicated agreement that the distances between the North Anna main dam's reference monuments and the i

USC&G _ Survey monuments could induce'slgnificant survey errors which might i

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tend to' mask any actual movement of the dam's alignment settlement markers.

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Therefore, we propose to discontinue these surveys. _ Relative movement of the dam will continue to be monitored annually through the' performance of surveys

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between the hydroelectric project's reference monuments and the suivey blocks along the main dam.

^ M o'4110295 940405

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'PDR ADOCK 05ooo338

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l' if 'you have any questions, please contact us.

1 Very truly yours, 0

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J. P. O'Hanlon.

1 cc:

United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Docket Nos.

50-338 and 50-339-Ucense Nos. NPF-4 and NPF-7 United States Nuclear Regulatory Commission

. Region II -

101 Marietta Street, N.W.

- Suite 2900 -

Atlanta, GA 30323 Mr. R. D. McWhorter NRC Senior Resident inspector.

North Anna Power Station i

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