ML20206A730
| ML20206A730 | |
| Person / Time | |
|---|---|
| Issue date: | 11/13/1986 |
| From: | Smykowski S NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Gnugnoli G NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-40 NUDOCS 8704080150 | |
| Download: ML20206A730 (6) | |
Text
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_ WM FILE-NOTE TO'GNG - BURRELL SMP p@
.g@ O NOTE FOR: Giorgio N. Gnugnoli
.WMLU FROM: Steve Smykowski WMLU SUBJECTi. -REVIEW 0F THE BURRELL, PA. VICINITY PROPERTY SITE SURVEILLANCE AND MAINTENANCE PLAN _(S&M PLAN)
Enclosed is a copy of the geotechnical' engineering resiew of the Burrell S&M Plan with suggested recommendations.-:These recomendations consider the most recent' supplemental standards that DOE has proposed in the draft ,
' Radiological Engineering Assessment (REA) dated September 1986. If you have any questions pertaining to the enclosed comments, please contact ~me on x74109.
ORIGI:iAL SIGNED El Steve Sinykowski WMLU WM Record File N D b EC PD W ~
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NAME::SSmykowski : : : : : :
DATE:86/11/13 : : : : : :
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3 DOCUMENTS /GNG/10/30/86 GE0 TECHNICAL ENGINEERING REVIEW The staff continues to view the uncertainites associated with this design to be serious and significant. In light of substandard concerns expressed in the June 25, 1986 and August 8,1986 transmittals to DOE, the staff is providing the following consnents and reconsnendations.
- 1. Section 2.0, Final Site Conditions:
Based on the review of information provided by DOE to date, the NRC staff concluded that monitoring for lateral slope movements would be necessary until the monitoring data indicates a reasonable level of confidence that long-term safety and stability would be ensured. Monitoring details such as types and locations of instruments, required dates of installation, frequency and length of monitoring, etc., need to be established along with corresponding tolerable limits. These details have not been provided in the S&M Plan or any other supporting information. This information is necessary to gauge the integrity of the remedial action construction throughout the S&M phase.
- 2. Section 2.3, Displacement Monuments, Page 3:
The S&M Plan should -identify information relating to monitoring of displacement monuments such as the frequency measurements, the duration of the monitoring period, the action criteria for initiating maintenance and the cover system maintenance and required procedures.
3 DOCUMENTS /GNG/10/30/86 Conditions which can result from significant differential settlements due to the heterogeneous and non-compacted condition of the fill material include:
a) concentrated surface water flows which are greater than those used in the design of the erosion barrier; b) significant quantities of water infiltrating through cracks in the radon barrier resulting in zones of localized saturation in the contaminated fill material. This in turn could result in leaching of contaminants into the ground water, accelerated organic decay, a reduction in shear strength, and additional settlement of the landfill material; and c) an increase in radon gas leaving the cover system.
The staff recommends that the S&M Plan identify the details discussed above which are associated with the proposed displacement monitoring program. Until it can be demonstrated that settlements resulting from placement of the radon barrier and erosion protection layers and from the long-term decay of organic debris have tapered off, monitoring of displacement monuments should be continued.
- 3. Section 2.3, Displacement Monuments, Page 3:
During the July 23, 1986 site visit, the staff recommended to the RAC that DOE should implement an interim monitoring plan which would assure that the integrity of the radon barrier will not be compromised by large differential settlements due to soft zenes in the fill. Placement of the erosion protection
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3 DOCUMENTS /GNG/10/30/86 rock on top 'of the completed pile should be delayed until the interim monitoring program demonstrates that primary compression has been completed and future projected settlements will be tolerable and not compromise the stability of the remedial action construction. Based on recent discussions with the RAC, the staff understands _that placement of'the erosion protection rock on top of the completed pile was planned to begin during the first week of November. The staff has received a sketch showing the locations of the displacement monitoring devices (August 7,1986 telefax from Jim Williams (RAC) to Steve Smykowski-(NRC)), however the staff has not received any data which would indicate that primary compression has been completed. Because timing is a critical factor for both construction completion and for maintaining the fill load prior to final covering, the staff suggests that DOE submit the time-settlement plots before placement of the erosion protection rock on top of the pile. These plots should demonstrate that settlements have tapered off and
~ future projected settlements will be tolerable and not compromise pile stability.
4.- Section 3.1, Phase I Inspection, Page 6:
The S&M Plan indicates that Phase I inspections shall be conducted annually and that the initial inspection shall occur in the spring of 1987. The staff has previously noted that since the existing landfill and contaminated materials-are heterogeneous, considerable uncertainty exists associated with the strength and compression characteristics of the material. Therefore, inspections should be performed more frequently, particularly during the first several years following construction. The staff recommends that observations of displacement
3 DOCUMENTS /GNG/10/30/86 and lateral slope movement monuments be performed monthly for at-least the first 6 months following construction. If the inspections indicate that settlements have tapered off and that the pile settlement has stabilized, then the inspections can be performed at least every 3 months up to the first year following construction and every 6 months thereafter. Upon completion of each inspection, a report of the inspectica should be provided to the NRC for review.
- 5. Proposed East End Final Grading Addendum The NRC staff is not convinced that ponding of water in the depression located at the east end of the site will not occur. If ponding should occur, a localized rise in ground water can be expected. Saturated soil conditions could develop unstable slopes along the embankments of the river and the depression. Ponding of water- could be avoided, if the area from the depression to the river is graded such that water would drain into the river. The staff suggests that DOE consider this alternative, or otherwise provide documentation that would assure that this area of the site will remain stable.
BURRELL S&M/SMYK0
- 6. Section 2.0, Final Site Conditions:
The REA identifies that the compacted cover will reduce site infiltration-and tend to cause a lowering of the ground water table (Page 33). However, the staff recognizes other mechanisms that could cause a rise in the ground water table which, in turn, could affect pile stability. These mechanisms include the following:
a) flood events that could result in the pile becoming inundated. Flood waters would likely saturate the landfill material by infiltrating the cover drain system; b) significant quantities of water from concentrated surface water flows infiltrating through settlement cracks in the radon barrier; c) large differential settlements that could interfere with the effective operation of the drain system; d) clogging of the drain system by sediments which have been easily transported due to the loose nature of the existing landfill material.
Considerable reliance has been placed on the effective operation of the cover and toe drains to assure the stability of the contaminated materials.
Therefore, the staff recomends that instrumentation devices, such as several .
piezometers to measure groundwater levels and magnitudes and distribution of pore pressures, be installed along the face of the embankment to assure the effectiveness of the drain system. The instruments should be read frequently enough to establish fluctuations or seasonal variations in the water table or pressures. . It is suggested that measurements be made concurrently with the displacement and slope movement monuments.
- 7. Additional Radiological Surveying:
Recognizing the additional radioactive contamination recently discovered in the eastern end of the site, the staff recommends that additional limited radiological surveying be perfomed to determine whether more radiological '
material may be located elsewhere on the site. The surveying should be emphasized in the area east of the pile.
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