ML20138E035
| ML20138E035 | |
| Person / Time | |
|---|---|
| Issue date: | 08/26/1985 |
| From: | Haisfield M, Johnson T NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Martin D NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-48 NUDOCS 8510240547 | |
| Download: ML20138E035 (3) | |
Text
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MEMORANDUM FOR: Dan E. Martin Low-Level Waste and Uranium WM48 s/f '
Recovery Projects Branch WMLU r/f Division of Waste Management NMSS s/f M Haisfield FROM: Mark Haisfield DE Martin Low-Level Waste and Uranium LB Higginbotham Recovery Projects Branch T Johnson Division of Waste Management RE Browning -
MJ Bell Ted Johnson JO Bunting Geotechnical Branch Division of Waste Management PURPOSE: 1: TO VISIT THE DURANGO SITE AND ALTERNATE SITES AND MEET WITH URF0, TAC, AND COLORADO STATE REPRESENTATIVES REGARDING THE DURANGO DRAP.
- 2. TO OBSERVE THE CSU FLUME EXPERIMENTS.
DISCUSSION:
On August 13, 1985, along with Pete Garcia (URFO), we met with Paul Darr (TAC) to examine in detail the Bodo Canyon alternate site. This site was chosen as the preferred alternative in the PFEIS.
During our visit, we noted the presence of steep and incised gullies which are currently eroded to the outlets of the perimeter ditches proposed in the DRAP.
These natural gullies appeared to be 10 20 feet deep with slopes in excess of 5-10%. In addition, the presence of steep natural ground slopes may require that the proposed perimeter ditches will need to be designed with slopes in excess of 10%. These natural slopes may require the implementation of design measures available inwhich call for the area. Weextensive noted that erosion protectionoptions few alternative which such may(not be readily as flatter slopes) are available due to the limited area available for placement of the tailings.
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We next made a brief examination of the Long Hollow site to acquaint ourselves with the overall layout of the site. We noted in particular the presence of water discharging from a well near the centerline of the proposed pile (if this option were to be chosen - see PFEIS), even though the groundwater levels could be expected to be at minimum levels during this time of the year.
We next examined an area of several proposed rock sources near Trimble Bridge, about 10 miles north of Durango. Based on ar. examination of the rock stockpiled at one quarry operation, there appeared to be readily available rock of adequate size for the top and sides of the pile. However, rock with a diameter of 18 inches or more - needed for the perimeter ditches and gully erosion protection - did not appear to be readily available at this location.
TAC indicated that such rock may need to be quarried. We then examined one potential source of quarried rock, but this source seemed to be sandstone, which may not have adequate durability. TAC indicated that additional investigations will be undertaken by the RAC to locate suitable sources.
On August 14, we met at URF0 to discuss NRC draft comments on the Durango DRAP.
The meeting focused on two primary deficiencies of the current DOE plan. (1)
The liner and cover soils are not of a stable type and are very dispersive. A 4% lime mixture may be needed to provide adequate stability and dispersive characteristics. This, however, presents construction mixing and long-tem suitability problems. (2) The currently proposed design cannot withstand a PMP. NRC staff provided DOE with draft questions regarding the design of the erosion protection; these were discussed in detail. Based on these comments, DOE (TAC) agreed to redesign the erosion protection to provide an acceptable design. Our formal comments to DOE will only address the proposed design in the DRAP.
On August 15, we drove to Colorado State University (CSU) in Ft. Collins, Colorado to observe the fiume studies currently being performed by CSU. Ve first observed the indoor flume, which is 8-feet wide and has a variable slope of 0 5%. This flume is being used to determine the stability and flow transmission capability of small rocks (up to 2" diameter) on flat slopes (0-5%). We principally observed the flow-sensing devices that will be used to gather data on friction relationships for flow through and over a graded rock layer.
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WM48/MH/85/08/20 gg 2 61985 We next observed the outdoor flume, which is 12-feet wide and has a slope of 20%. On this particular day, the 2-inch diameter rock layer was tested to failure under varying flow rates. We observed the entire failure process including how gully formation occurs, how and where damage to the riprap i starts, and the time it takes for gullies to work from the toe up the side slope. Of particular interest was the fact that there appeared to be '
significant flow concentration under flow conditions much less severe than those which the layer is designed for. Based on visual examinations, it appeared that nearly 50% of the flow down the slope tended to concentrate in a 3-foot width across the 12-foot wide flume.
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Mark Haisfield Low-Level Waste and Uranium Recovery Projects Branch Division of Waste Management v
C Ted Johnson Geotechnical Branch Division of Waste Management
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