ML20238F773
| ML20238F773 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 08/28/1998 |
| From: | Gabe Taylor SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Padovan L NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RC-98-159, NUDOCS 9809040303 | |
| Download: ML20238F773 (4) | |
Text
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South Caronna Electric & Gas Company Gary J. Taylor
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VirgM C. Summer Nuclear Station Vice Pr;eident.
P.O. Box 88
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. Nuclear Operations aermin.vse. sc 2so8s -
(803) 345-4344 (803) 345-5200 5
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August 28,1998 -
RC-98-0159 Document Control Desk.
U. S. Nuclear Regulatory Commission Washington, DC 20555
' Attention:
Mr. L. M. Padovan Gentlemen:
Subject:
VIRGIL C. SUMMER NUCLEAR STATION DOCKET NO. 50/395 OPERATING LICENSE NO. NPF-12 SERVICE WATER POND DAM SAFETY INSPECTION RESULTS This letter provides a response to the Federal Electric Regulatory Commission (FERC)
Final Operation inspection Report for the Service Water Pond (SWP) Dam at the Virgil C.' Summer Nuclear Station as inspected by the Nuclear Regulatory Commission and FERC on February 27,1997.' The inspection report was received in a letter from your office dated February 27,1998.
The FERC report contained a list of improvements in which a written response was
- required. South Carolina Electric & Gas Company (SCE&G) has reviewed the list of l0 improvements. - The following is the response to the list of improvements:
Remove small brush and trees in the embankment and abutment.
A follow-up walkdown of the SWP Dams was conducted on June 9,1998. All small brush and trees which were located either on or within approximately fifty (50) feet j of the dams, embankments and discharge canal have been removed and/or chemically treated.
.. Test and evaluate accessible embankment dam piezometers.
- There are three (3) accessible piezometers located along the crest of the North Dam above the operating surface water level. These piezometers were monitored until the phreatic levels of the piezometer locations stabilized at approximately water level on both sides of the dam. These piezometers have not been monitored or
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tested since 1982 and their current functional condition is unknown, i
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Document Control Desk MSP 980004 RC-98-0159 Page 2 of 4 i
l SCE&G plans to test and evaluate the functiona1 capability of these piezometers l
during the annual SWP dam walkdown scheduled for the Fall of 1999.
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Inspect tho' dams and west embankment annually. Document conditions and L
, maintain records of the inspections. A checklist and brief narrative is suggested.
~ SCE&G plans to conduct and document an annual walkdown of the SWP dams beginning in 1999. These inspections will be scheduled through the Preventive Maintenance Task Sheet Program for the fall of each year. The RG 1.127 inspection and documentation will continue on the current five (5) year cycle with the next inspection scheduled for 2000, i
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Regrade the abutment of the east dam to direct surface drainage away from the toe of the dam.
The natural abutment located between the East Dam and South Dam has required
. continual maintenance over the years due to the highly erosive characteristics and the lack of nutritional capability to support vegetation growth. The area has been regraded several times, however, the natural flow path for drainage is adjacent to y
the exterior toe of the East Dam. This flow path has existed for approximately 20 years without any detrimental effects observed on the riprap protection for the East L
Dam.
SCE&G has performed additional grading in this area during June 1998 to redirect the flow away from the toe of the East Dam.
.. Regrade the area along the fence east of the SWP pumphouse to allow surface runoff to drain from the toe of the [ west] embankment.
There is an area in the southeast corner of the plant site (between the security
' fences) that does allow ponding of rain water. This does not appear to be'a u
significant problem at this time. SCE&G will continue to' monitor the area during the annualinspection of the SWP dams. If the ponding of rain water does become a significant problem, SCE&G will take the necessary actions at that time, e' Conduct lead-line surveys on the discharge channel side of the south dam and east dam and the discharge channel to ensure'that no erosion has occurred within the dans or channel bottom which might affect dam stability.'
E 1 SCE&G does not believe that this recommendation is warranted based on the following:
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The South Dam is survey monitored along its crest for elevation and alignment every 5 years in accordance with RG 1.127. The results have been very consistent for the past 20 years, showing no signs of potential dam instability. Additionally, due
' the irregularity of riprap surfaces, large tolerances must be assumed for the underwater measurements, therefore, lead-line surveys can only potentially find gross deformations which should also be exhibited by instability or failure problems above the water surface level and thus be identified by the annual walkdowns and survey monitoring.
The East Dam is'a very low profile structure ( as compared to the other dams) which was constructed as a saddle dam along a pre-existing ridge line. The possibility of slope failures of this dam is considered too remote to warrant the need and expense of a lead-line survey, The Discharge Canal (channel) is a non-safety related structure which serves only to return water into Monticello Reservoir. The bottom of the canal was partially excavated several years ago to alleviate a thermal stratification condition which caused several fish kills in the discharge area. The bottom of the canal is now non-uniform due to the method of excavation used, therefore, a lead-line survey would not provide any meaningful results, nor is it considered necessary due to the lack of safety significance of the structure.
Conduct a lead-line survey along the alignment of the SWP pumphouse discharge pipe. This CMP is highly corroded and the survey is to ensure leakage has not eroded embankment materials. Repair or replace the CMP as necessary.
l The approximately 12" diameter Corrugated Metal Pipe (CMP) serves as a non-safety related drain pipe for the SWP pumphouse screen wash pumps. The
~ CMP does leak water onto the surface of the SWP and riprap protection of the West Embankment when the screen wash pumps are operated. However, the rip rap serves to disperse the impact of the this water flow onto the embankment in the same manner as it normally protects for rainfall, yard drainage or surface wave action. This relatively small water leakage source is considered to have an insignificant affect on the integrity of the West Embankment.
The West Embankment is lead-line surveyed in accordance with Operating License Condition 2.C.5.b every 5 years. These surveys are conducted adjacent to each side of the SWP pumphouse and have shown no signs of embankment movement or instability to date. Additionally, the semi-annual survey monitoring of the pumphouse and intake structure has provided very consistent results for the past 20 years showing no signs of significant settlement of the structures or instability of the West Embankment.
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Should you have any questions, please call at your convenience.
Very I yours, -
m Ir SBR /GJT/sr l
c:
J. L. Sk' lds o
W. F. Conway -
R.R.Mahan R. J. White L.A.Reyes L. M. Padovan
_NRC Resident inspector J. B. Knotts,-Jr.
B. C. Williams R. B. Whorton.
RTS (MSP 980004)
File (810.32).
DMS' (RC-98-0159)
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NUCLEAR EXCELLENCE-A SUMMER TRADITION!
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