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Category:INTERNAL OR EXTERNAL MEMORANDUM
MONTHYEARML20217D1071999-09-16016 September 1999 Provides Proposed Schedule for Review of Trojan License Termination Plan (Ltp),As Committed in 990903 Memo.Project Manager Should Schedule LTP Meeting Near Trojan Site for Late Nov or Early Dec,Based on Region IV Availability ML20216E4091999-09-0303 September 1999 Informs That Staff Has Performed Acceptance Review of Trojan Nuclear Plant License Termination Plan Submitted by Ltr Dtd 990805.NMSS Determined That Licensee Has Provided Sufficient Info for NRC to Proceed with Detailed Review ML20205R4091999-04-16016 April 1999 Informs That LTP for Trojan Nuclear Plant Did Not Provide Sufficient Info to Perform Detailed Review & Waste Mgt Recommends Returning LTP to Licensee So That LTP Can Be Resubmitted as Complete Application ML20195B6401998-11-10010 November 1998 Notification of 981119 Meeting with Util in Rockville,Md to Discuss Preliminary Plans for Plant Final Site Surveys ML20155G6571998-11-0303 November 1998 Notification of 981119-990331 Meeting with Util in Rockville,Md to Clarify Remaining Technical Issues Associated with Util Application for License to Operate ISFSI at Tpp ML20236S5361998-07-22022 July 1998 Notification of 980812 Meeting W/Portland General Electric in Arlington,Texas to Discuss Status of Decommissioning Activities at Trojan NPP ML20236R6511998-07-15015 July 1998 Notification of 980730 Meeting W/Listed Participants in Kelso,Wa Re Proposed Request from Portland General Electric Co for Approval to Allow one-time Shipment of Plant Decommissioned Reactor Vessel.Meeting Agenda Encl ML20236R6931998-07-15015 July 1998 Notification of 980730 Meeting W/Util to Discuss Request for Addl Info Re Ongoing Review of Portland General Electric Co Request for Approval to Allow one-time Shipment of Trojan Decommissioned Reactor Vessel.Meeting Agenda Encl ML20248L4691998-03-17017 March 1998 Notifies of in-house Research Project Re Digital I&C in NPP & Forwards Technical Training Div (TTD) ML20216E7421998-03-0606 March 1998 Notification of 980318 Meeting W/Portland General Electric in Rockville,Maryland to Discuss Proposed Shallow Land Disposal of Trojan Reactor Vessel ML20199D4951998-01-26026 January 1998 Notification of Licensee Meeting W/Util on 980209 in Arlington,Tx to Discuss Changes to Protected Area for Plant to Facilitate Ongoing Decommissioning of Site ML20199G1121998-01-20020 January 1998 Submits Addl Views on Proposal to Dispose of Trojan Reactor Vessel,Per SECY-97-244 ML20211M5671997-10-0303 October 1997 Forwards Regulatory Documents Comprising Regulatory History of Notice of Proposed Rulemaking Entitled Financial Assurance Requirements for Decommissioning Nuclear Power Reactors, Which Amended 10CFR50,published in Fr on 970910 ML20141G2911997-05-15015 May 1997 Forwards Page A-25 of Rev 5 to PGE-1060, Tnp Permanently Defueled Emergency Plan ML20137W9801997-04-16016 April 1997 Notification of Significant Licensee Meeting W/Util on 970508 in Rockville,Md to Discuss Plans for Decommissioning of Plant ML20137H2231997-03-31031 March 1997 Forwards Info in Support of Pnl Modeling for Fgeis Final Rule on Radiological Criteria for License Termination ML20135B1941997-01-30030 January 1997 Responds to Re Util Position Re Potential for Ash Fall at Trojan Site ML20138J2731997-01-21021 January 1997 Submits Comments on 970113-16 QA Insp of Sierra Nuclear Corp in Scott Valley,Ca ML20134B6001997-01-13013 January 1997 Provides Meeting Minutes from NRC Insp 97-201 Exit Meeting Re Insp of Trojan'S QA Program for Isfsi,From 970107-09 ML20133N2821997-01-0808 January 1997 Requests Comments on Poge Position Re Potential for Ashfall at Trojan Site ML20135B8581996-12-0303 December 1996 Requests Guidance on Use of 10CFR71.41(c) Per Licensee Request for Authorization to Transport Reactor Vessel as Type B Package ML20134D7161996-10-24024 October 1996 Requests That Encl Internet Mail Received from PM Blanch,Dtd Through 960930,be Placed in Pdr.No Distribution Outside of PDR Necessary ML20237F1891996-01-22022 January 1996 Notification of 960131 Meeting W/Util in Rockville,Md to Discuss Planned Removal of Plant Pressure Vessel ML20211M6231994-11-30030 November 1994 Provides Info to Commission on Status of Rulemaking Activities Re Power Reactor Decommissioning Cost Issues,Per 930714 SRM ML20057B6071993-09-16016 September 1993 Notification of 930928 Meeting W/Util in Rockville,Md to Discuss Status of Decommission Activities & Physical Security ML20057A6651993-08-27027 August 1993 Forwards Notice of Consideration of Issuance of Amend to License NPF-1 & Proposed NSHC Determination & Opportunity for Hearing ML20056E5331993-08-16016 August 1993 Notification of 930901 Mtg W/Util & State of or in Rainier, or to Discuss Proposed Studies of Plant Sys at Plant ML20056E4451993-08-0606 August 1993 Notifies of 930812 Meeting W/Util in Rockville,Md for Presentation on Plant Decommissioned TS ML20056E4571993-08-0505 August 1993 Forwards Technical Review Rept Re, Tardy Licensee Actions Initiated Because of Delayed Replacement of Batteries in Uninterruptible Power Supplies at Plant ML20128G0061993-02-0101 February 1993 Notifies of Cancelled 930210 Meeting W/Technical Analysis Corp to Discuss Shutdown Plans & Decommissioning Strategies for Plant ML20127L9741993-01-22022 January 1993 Notification of 930204 Meeting W/Util in Rockville,Md to Discuss Shutdown Plans & Decommissioning Strategies for Plant ML20127J7691993-01-15015 January 1993 Discusses Interim Plugging Criteria for Util & Provides Discription of Core Damage Frequency Derivation & Present RES Plans for Addl Work on Steam Generator Tube NDE That RES Intends to Do This Year ML20127E7821993-01-11011 January 1993 Notification of Significant Licensee Meeting W/Util on 930120 to Discuss Shutdown Plans & Decommissioning Strategies for Facility ML20127F4461993-01-0707 January 1993 Revised Notification of Significant Meeting W/Util on 930202 to Discuss One Violation of 10CFR50.7(f) Identified During OI Investigation of Security Department at Plant ML20127A5381993-01-0707 January 1993 Discusses QC Concerns W/Mine Safety Appliances Co Full Face Negative Pressure Respirators (Ultra View & Ultra Twin) W/Potential 10CFR21 Implications ML20127A5701993-01-0505 January 1993 Provides Position on Interim Plugging Criteria for Plant ML20126G9861992-12-22022 December 1992 Notification of Significant Licensee Meeting W/Util on 930113 to Discuss One Violation of 10CFR50.7(f) Identified During OI Investigation of Security Dept at Plant ML20126E6501992-12-18018 December 1992 Notification of or Energy Facility Siting Council Special Meeting & Hearing on 930105 & 06 in Portland,Or to Discuss Tnp SG Tube Cracking Issue,Interim SG Tube Plugging Criteria & Issues from Current Forced Outage.Agenda Encl ML20126F4271992-12-18018 December 1992 Notification of 921230 Meeting W/Util in Rockville,Md to to Discuss Steam Generator Insp Program & Results as Consequence of primary-to-secondary Steam Generator Leak Event on 921109 ML20126F4821992-12-18018 December 1992 Notification of Cancellation of 921230 Meeting W/Util in Rockville,Md to Discuss SG Insp Program & Results as Consequence of 921109 primary-to-secondary SG Tube Leak Event & Recent Issues Raised Re Interim Plugging Criteria ML20126E7641992-12-16016 December 1992 Notification of 921223 Meeting W/Util in Rockville,Md to Discuss Steam Generator Insp Program & Results as Consequence of 921109 primary-to-secondary Steam Generator Tube Leak Event ML20126F4651992-12-16016 December 1992 Cancelled Notification of 921223 Meeting W/Util in Rockville,Md to Discuss SG Insp Program & Results as Consequence of 921109,primary-to-secondary SG Tube Leak Event ML20125C7641992-12-0909 December 1992 Discusses Technical Aspects of Rationale Used to Support Steam Generator Tube Interim Plugging Criteria for Plant & Independent Conclusions on Viability of Independent Plugging Criteria for One Fuel Cycle ML20126F4711992-12-0707 December 1992 Forwards Draft Rept of RES Position on Steam Generator Tube Integrity ML20126E5221992-11-30030 November 1992 Informs Staff Revised Prioritization Will Be Forwarded for Further Comments in Response to 921124 Memo Re GI 163, Multiple Steam Geneator Tube Leakage ML20125A6311992-11-25025 November 1992 Notification of 921201 Meeting W/Util to Discuss Assessment of Recent SG Tube Leak ML20128C3491992-06-16016 June 1992 Discusses Proposal of New Generic Issue, Multiple SG Tube Leakage, as Resolution to DPO Received Addressing Operation of SGs W/Microscopic Tube Wall Cracks.Dpo Encl ML20128C3141992-03-27027 March 1992 Submits Analysis, Safety Issue Re Continuous Operation W/ Degraded SG Tubes, Indicating Core Melt Probability Frequency of 10 -4/Ry W/Containment Bypass NUREG-5055, Notification of 901017 Meeting W/Util in Rockville,Md,To Discuss Proposed Mods to Control Bldg Per NUREG-50551990-10-10010 October 1990 Notification of 901017 Meeting W/Util in Rockville,Md,To Discuss Proposed Mods to Control Bldg Per NUREG-5055 ML20059C1331990-08-21021 August 1990 Notification of Enforcement Conference 90-143 W/Util on 900830 to Discuss Violation Noted During Special Security Insp 1999-09-03
[Table view] Category:MEMORANDUMS-CORRESPONDENCE
MONTHYEARML20217D1071999-09-16016 September 1999 Provides Proposed Schedule for Review of Trojan License Termination Plan (Ltp),As Committed in 990903 Memo.Project Manager Should Schedule LTP Meeting Near Trojan Site for Late Nov or Early Dec,Based on Region IV Availability ML20216E4091999-09-0303 September 1999 Informs That Staff Has Performed Acceptance Review of Trojan Nuclear Plant License Termination Plan Submitted by Ltr Dtd 990805.NMSS Determined That Licensee Has Provided Sufficient Info for NRC to Proceed with Detailed Review ML20205R4091999-04-16016 April 1999 Informs That LTP for Trojan Nuclear Plant Did Not Provide Sufficient Info to Perform Detailed Review & Waste Mgt Recommends Returning LTP to Licensee So That LTP Can Be Resubmitted as Complete Application ML20195B6401998-11-10010 November 1998 Notification of 981119 Meeting with Util in Rockville,Md to Discuss Preliminary Plans for Plant Final Site Surveys ML20155G6571998-11-0303 November 1998 Notification of 981119-990331 Meeting with Util in Rockville,Md to Clarify Remaining Technical Issues Associated with Util Application for License to Operate ISFSI at Tpp ML20236S5361998-07-22022 July 1998 Notification of 980812 Meeting W/Portland General Electric in Arlington,Texas to Discuss Status of Decommissioning Activities at Trojan NPP ML20236R6511998-07-15015 July 1998 Notification of 980730 Meeting W/Listed Participants in Kelso,Wa Re Proposed Request from Portland General Electric Co for Approval to Allow one-time Shipment of Plant Decommissioned Reactor Vessel.Meeting Agenda Encl ML20236R6931998-07-15015 July 1998 Notification of 980730 Meeting W/Util to Discuss Request for Addl Info Re Ongoing Review of Portland General Electric Co Request for Approval to Allow one-time Shipment of Trojan Decommissioned Reactor Vessel.Meeting Agenda Encl ML20248L4691998-03-17017 March 1998 Notifies of in-house Research Project Re Digital I&C in NPP & Forwards Technical Training Div (TTD) ML20216E7421998-03-0606 March 1998 Notification of 980318 Meeting W/Portland General Electric in Rockville,Maryland to Discuss Proposed Shallow Land Disposal of Trojan Reactor Vessel ML20199D4951998-01-26026 January 1998 Notification of Licensee Meeting W/Util on 980209 in Arlington,Tx to Discuss Changes to Protected Area for Plant to Facilitate Ongoing Decommissioning of Site ML20199G1561998-01-22022 January 1998 Staff Requirements Memo Re SECY-97-244, Waste Classification of Plant Reactor Vessel ML20199G1121998-01-20020 January 1998 Submits Addl Views on Proposal to Dispose of Trojan Reactor Vessel,Per SECY-97-244 ML20211M5671997-10-0303 October 1997 Forwards Regulatory Documents Comprising Regulatory History of Notice of Proposed Rulemaking Entitled Financial Assurance Requirements for Decommissioning Nuclear Power Reactors, Which Amended 10CFR50,published in Fr on 970910 ML20216F2611997-08-26026 August 1997 Staff Requirements Memo Re SECY-97-164, Shipment of Decommissioned Reactor Vessel,Containing Irradiated Internals,From Trojan Nuclear Plant to Hanford Nuclear Reservation,Richland,Wa ML20141G2911997-05-15015 May 1997 Forwards Page A-25 of Rev 5 to PGE-1060, Tnp Permanently Defueled Emergency Plan ML20137W9801997-04-16016 April 1997 Notification of Significant Licensee Meeting W/Util on 970508 in Rockville,Md to Discuss Plans for Decommissioning of Plant ML20137H2231997-03-31031 March 1997 Forwards Info in Support of Pnl Modeling for Fgeis Final Rule on Radiological Criteria for License Termination ML20135B1941997-01-30030 January 1997 Responds to Re Util Position Re Potential for Ash Fall at Trojan Site ML20138J2731997-01-21021 January 1997 Submits Comments on 970113-16 QA Insp of Sierra Nuclear Corp in Scott Valley,Ca ML20134B6001997-01-13013 January 1997 Provides Meeting Minutes from NRC Insp 97-201 Exit Meeting Re Insp of Trojan'S QA Program for Isfsi,From 970107-09 ML20133N2821997-01-0808 January 1997 Requests Comments on Poge Position Re Potential for Ashfall at Trojan Site ML20135B8581996-12-0303 December 1996 Requests Guidance on Use of 10CFR71.41(c) Per Licensee Request for Authorization to Transport Reactor Vessel as Type B Package ML20134D7161996-10-24024 October 1996 Requests That Encl Internet Mail Received from PM Blanch,Dtd Through 960930,be Placed in Pdr.No Distribution Outside of PDR Necessary ML20237F1891996-01-22022 January 1996 Notification of 960131 Meeting W/Util in Rockville,Md to Discuss Planned Removal of Plant Pressure Vessel ML20211M6231994-11-30030 November 1994 Provides Info to Commission on Status of Rulemaking Activities Re Power Reactor Decommissioning Cost Issues,Per 930714 SRM ML20057B6071993-09-16016 September 1993 Notification of 930928 Meeting W/Util in Rockville,Md to Discuss Status of Decommission Activities & Physical Security ML20057A6651993-08-27027 August 1993 Forwards Notice of Consideration of Issuance of Amend to License NPF-1 & Proposed NSHC Determination & Opportunity for Hearing ML20056E5331993-08-16016 August 1993 Notification of 930901 Mtg W/Util & State of or in Rainier, or to Discuss Proposed Studies of Plant Sys at Plant ML20056E4451993-08-0606 August 1993 Notifies of 930812 Meeting W/Util in Rockville,Md for Presentation on Plant Decommissioned TS ML20056E4571993-08-0505 August 1993 Forwards Technical Review Rept Re, Tardy Licensee Actions Initiated Because of Delayed Replacement of Batteries in Uninterruptible Power Supplies at Plant ML20128G0061993-02-0101 February 1993 Notifies of Cancelled 930210 Meeting W/Technical Analysis Corp to Discuss Shutdown Plans & Decommissioning Strategies for Plant ML20127L9741993-01-22022 January 1993 Notification of 930204 Meeting W/Util in Rockville,Md to Discuss Shutdown Plans & Decommissioning Strategies for Plant ML20127J7691993-01-15015 January 1993 Discusses Interim Plugging Criteria for Util & Provides Discription of Core Damage Frequency Derivation & Present RES Plans for Addl Work on Steam Generator Tube NDE That RES Intends to Do This Year ML20127E7821993-01-11011 January 1993 Notification of Significant Licensee Meeting W/Util on 930120 to Discuss Shutdown Plans & Decommissioning Strategies for Facility ML20127A5381993-01-0707 January 1993 Discusses QC Concerns W/Mine Safety Appliances Co Full Face Negative Pressure Respirators (Ultra View & Ultra Twin) W/Potential 10CFR21 Implications ML20127F4461993-01-0707 January 1993 Revised Notification of Significant Meeting W/Util on 930202 to Discuss One Violation of 10CFR50.7(f) Identified During OI Investigation of Security Department at Plant ML20127A5701993-01-0505 January 1993 Provides Position on Interim Plugging Criteria for Plant ML20126G9861992-12-22022 December 1992 Notification of Significant Licensee Meeting W/Util on 930113 to Discuss One Violation of 10CFR50.7(f) Identified During OI Investigation of Security Dept at Plant ML20126E6501992-12-18018 December 1992 Notification of or Energy Facility Siting Council Special Meeting & Hearing on 930105 & 06 in Portland,Or to Discuss Tnp SG Tube Cracking Issue,Interim SG Tube Plugging Criteria & Issues from Current Forced Outage.Agenda Encl ML20126F4271992-12-18018 December 1992 Notification of 921230 Meeting W/Util in Rockville,Md to to Discuss Steam Generator Insp Program & Results as Consequence of primary-to-secondary Steam Generator Leak Event on 921109 ML20126F4821992-12-18018 December 1992 Notification of Cancellation of 921230 Meeting W/Util in Rockville,Md to Discuss SG Insp Program & Results as Consequence of 921109 primary-to-secondary SG Tube Leak Event & Recent Issues Raised Re Interim Plugging Criteria ML20126E7641992-12-16016 December 1992 Notification of 921223 Meeting W/Util in Rockville,Md to Discuss Steam Generator Insp Program & Results as Consequence of 921109 primary-to-secondary Steam Generator Tube Leak Event ML20126F4651992-12-16016 December 1992 Cancelled Notification of 921223 Meeting W/Util in Rockville,Md to Discuss SG Insp Program & Results as Consequence of 921109,primary-to-secondary SG Tube Leak Event ML20125C7641992-12-0909 December 1992 Discusses Technical Aspects of Rationale Used to Support Steam Generator Tube Interim Plugging Criteria for Plant & Independent Conclusions on Viability of Independent Plugging Criteria for One Fuel Cycle ML20126F4711992-12-0707 December 1992 Forwards Draft Rept of RES Position on Steam Generator Tube Integrity ML20126E5221992-11-30030 November 1992 Informs Staff Revised Prioritization Will Be Forwarded for Further Comments in Response to 921124 Memo Re GI 163, Multiple Steam Geneator Tube Leakage ML20125A6311992-11-25025 November 1992 Notification of 921201 Meeting W/Util to Discuss Assessment of Recent SG Tube Leak ML20128C3491992-06-16016 June 1992 Discusses Proposal of New Generic Issue, Multiple SG Tube Leakage, as Resolution to DPO Received Addressing Operation of SGs W/Microscopic Tube Wall Cracks.Dpo Encl ML20128C3141992-03-27027 March 1992 Submits Analysis, Safety Issue Re Continuous Operation W/ Degraded SG Tubes, Indicating Core Melt Probability Frequency of 10 -4/Ry W/Containment Bypass 1999-09-03
[Table view] |
Text
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. . 4 i L ; , ; .g h r[ Ar<x.'4 na sf'a h~ k (-/$ csy / l Docket No. 50-344
, . .. MEMORANDUM FOR: Gus G. Lainas, Assistant Director l
for Operating Reactors, DL FROM: William V. Johnston, Assistant Direcuer ,
Materials, Chemical & Environmental Technology, DE
SUBJECT:
SPIRIT LAKE / TROJAN PLANT FLOODING -SER On March 6, 1985, we provided you SER input addressing the effects of a breakout of Spirit Lake on the Trojan Plant. The conclusions in our SER were based on an unpublished USGS report and did not mention an independent study that had been performed by the applicant. The project manager, Charles Trammell, requested that we revise our SER to include the licensee's evaluation. In response to that request, attached is our revised SER input.
This input replaces our March 6,1985 input entirely. A copy of this revised
- input was provided to C. Trammell on March 13, 1985.
William V. Johnston, Assistant Director.
Materials, Chemical & Environmental Technology .
Division of Engineering .
Attachment:
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HYDROLOGIC ENGINEERING SAFETY EVALUATION REPORT j CONCERNING A POSTULATED BREAK 0UT OF SPIRIT LA){E l AND ITS IMPACTS ON THE TROJAN PLANT 3
- 1. Purpose of Report l On May 18, 1980, Mount St. Helens erupted and caused a massive n'udflow l flood that deposited a large amount of sediment and debris in the 4l Columbia River near the mouth of the Cowlitz River. The Trojan Nuclear I Plant which is located on the west bank of the Columbia River about 4.5 miles upstream of the mouth of the Cowlitz River (See Figure 1) was not directly affected by the sediment deposited in the Columbia River,
^
l althcugh large deposits' w'ere measured near the intake structure. In
, addition to the mudflow flood, the eruption also resulted in an avalanche of rock, mud and ice that swept down the slopes of Mount St. Helens into Spirit Lake and the Upper Toutle River Valley. As the debris avalanche slid into Spirit Lake, it displaced the lake level upward by more than -
200 feet. Th'e avalanche also deposited an estimated 3.9 billion cubic yards (bey) of sediment in the upper 17 miles of the North Fork Toutle _.
River Valley and blocked the outlet channel of Spirit Lake with~ debris
[ ranging in depth to 500 feet. This debris-blockage, which is a massive ard unstable deposit, caused a dramatic increase in the volume of water stored in Spirit Lake. Because of the unstable nature of the debris
, blockage, there was a concern that Spirit Lake could breach the blockage c and cause a mudflow flood that could possibly affect the safe operation of the Trojan Plant. This report addresses the potential effects of such a mudflow flood at the Trojan Plant.
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, , 2. Introduction i
Mudflows associated with the May 1980 eruption moved down the Toutle j
River and carried more than 50 million cubic yards (mcy) of material 1
into the Cowlitz River and its overbank areas. An additional 45 mcy y .
were deposited in the Columbia River, mostly in.a nine mile reach of the river extending from about 5 miles downstream of the mouth of the Ol Cowlitz River to 4 miles upstream.
q In the fall of 1981, a task force organized by the U.S. National Forest Service determined that the effective crest of the debris blocking the a
i Spirit Lake outlet would deteriorate from elevation of 3490 ft to 3475 ft i
during the winter of 1982 _83 because of subsidence and erosion.
It was estiEa~ted that Spirit Lake would fill to elevation 3475 ft (314,000 acre-feet) sometime in March 1983 assuming that no action was taken to reduce the level and volume of the lake and that the annual inflow was average. Were this to happen, there would be a very high potential for )
failure of the blockage and catastrophic flooding downstream. To reduce the potential for failure, the Corps of Engineers, as an interim measure, f
constructed a pumping facility at Spirit Lake and pumping began en -.
November 5, 1982 (see Figure 2). The goal of the pumping operation was to stabilize the lake level at an elevation of about 3,462 ft, which corre-
- sponds to a lake volume of about 275,000 acre-feet. However, greater-than-normal rainfall, failure or disruption of the pumping system and/or
- addition of debris into Spirit Lake from a subsequent eruption could cause i the lake level to rise excessively. In an extreme case the debris
, blockage could fail. Because of the potential public safety hazard associated with a breakout of Spirit Lake, the Corps of Engineers has developed a plan to permanently lower the level of Spirit Lake. This plan consists of drilling a tunnel from Spirit Lake to South Coldwater '
Creek (See Figure 2). This will allow Spirit Lake to drain so that the lake level can be maintained at an elevation low enough to remove the I
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t I
T threat of a Spirit Lake debris dam failure and consequent mudflow flood.
[ Construction of the tunnel was initiated in July 1984. 'It is expected
[. that the tunnel will be completed by April 1985. ,
- 3. Analysis I
In a report titled " Analysis of Flood Level at Trojan Plant Associated with Hypothetical Failure of Spirit Lake Blockage," by Simons, Li and Associates, Inc.; the licensee addressed the potential impact of a Spirit Lake breakout on the Trojan Plant. The depth of flooding in the Columbia River would be dependent Jni the coincident discharge in the river at the time the breakout flood peak arrived at the mouth of the Cowlitz River.
Thus the licensee determined water surfage elevations corresponding to vari 5'u~
s coincident discharges in the Columbia River. Resu.lts of their
~
study were as follows:
SIMMONS AND LI REPORT Resultant Water Surface Elevations in _
the Columbia River at the Trojan Plant due to a postulated breakout of Spirit Lake Coincident Columbia Riv.er Discharge in cfs 125,000 400,000 800,000 Colurbia River Water Surface Elevations in feet at the 31 35 39 Trojan Plant This table shows that a postulated breakout of Spirit Lake occurring coincident '.
with an 800,000 cfs flood flow in the Columbia River would not affect the safe operation of the Trojan Plant because the plant grade elevation, at 45 feet, is 6 feet higher than the flood level would be.
A potential breakout of Spirit Lake was also of concern to the U.S. Federal Emergency Management Agency (FEMA) because flooding from a breakout could .
have a severe impact on public safety and on the regional econcay. To enable -
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. , .. it to plan for such an event, FEMA requested the USGS to study the impacts of a Spirit Lake breakout on the entire lower Columbia River. The USGS has comp 10 tad its study and its report is now (February 1985) b,eing reviewed by i the USGS Federal Headquarters in Reston, Virginia. The study addresses the
- impacts of a postulated breakout of Spirit Lake on the Columbia River from j Bonneville Dam to the mouth. The Trojan Plant is located within this stretch l of the river. -
7 The USGS, using a sediment transport computer model, concluded that following a postulated breakout of Spirit Lake, a large sediment j blockage would form in the Columbia River at the confluence of the Cowlitz, with subsequent irnpoundment of water upstream of the blockage.
^
This blockage would result in a slowly rising water level at the Trojan Planf khich would continue for 16 day's after the blockage', formed.
As stated above, the depth of flooding in the Columbia River would be dependent on the coincident discharge in the rf ver at the time the breakout flood peak arrived at the mouth of the Cowlitz River. The USGS q
also determined surface water elevations corresponding to various coinci-dent discharges in the Columbia River. Results of their study were as m.
follows:
USGS REPORT Resultant Water Surface Elevations in the Columbia River at the Trojan Plant due to a postulated breakout of Spirit Lake Coincident Columbia River Discharge in cfs 233,000 410,000 610,000 750,000 820,000 f Recurrence Interval in years (average) (2 year) (10 year) (50 year) (100 year)\
Columbia River Water Surface 32 38 41 43 44 i Elevation in feet at the ~ ' '
T Trojan Plant The results of the USGS study are similar to the licensee's study in that a
^
a postulated breakout of Spirit Lake occurring coincident with a flood in the -
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ren
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.. .. Columbia River as severe as a 100 year event would not affect the safe operation of the Trojan Plant because the plant grade elevation is higher at 45 ft than the flood level would be.. ,
- 4. Summary and Conclusion By pumping water out of Spirit Lake the Corps of Engineers has been successful in maintaining the Lake level at an elevation that has minimized the chances for a breakout and the potential threat to the Trojan Plant. The staff however, remained concerned because it was uncertain about whether or not a lake breakout and the ensuing flood could affect the safe operation of the plant. The licensee and the USGS studies, however, provide ~'
information that indicates that even if Spirit
~
Lake did break out, the resuitant flood level in the Colubbia River at the Trojan Plant would not rise as high as plant grade even if the breakout occurred coincident with a 100 year'ficed discharge in the Columbia River.
The tunnel being constructed between Spirit Lake and South Coldwater
, i Creek (See Figure 2) will provide a permanent outlet for Spirit Lake.
This tunnel will permanently lower the level of Spirit Lake and remove _ _ .
the threat of a breakout and the potential for high water in'th'e Columbia River at the Trojan Plant.
The staff concludes that a breakout of Spirit Lake will not affect the safe operation of the Trojan Plant. Furthermore, once the Spirit Lake outlet tunnel is completed, there will be no safety concern regarding a breakout as far as the Trojan Plant is concerned.
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/ Extent of debris Deposited by the liay 1980 Eruption FIGURE 1 --
y GENERAL AREA MAP - TROJAN / SPIRIT LAKE / MOUNT ST. HELENS e
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LOCATION OF SPIRIT LAKE OUTLET s
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