ML20238F731
| ML20238F731 | |
| Person / Time | |
|---|---|
| Issue date: | 06/19/1975 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20238F347 | List:
|
| References | |
| FOIA-87-235 NUDOCS 8709160306 | |
| Download: ML20238F731 (8) | |
Text
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e MAXEY FLATS LOW LEVEL RADIOACTIVE WASTE DISPOSAL FACILITY HYDROLOGIC ENGINEERING
SUMMARY
PROBLEM:
The Nuclear Engineering Company, Inc. has operated a state licensed low level radioactive waste disposal facility at Maxey Flats, Kentucky since the early 1960's. Recent evidence of migration of trace quanti-I ties of radioactive materials has been discovered in the offsite environ-ment around the disposal facility. The seriousness of this situation l l
l has been investigated and recommendations have been made by the licensee, l l the State of Kentucky, and an Environmental Study Design Committee composed of State, NRC, USGS., EPA and ERDA personnel. As a result of recent publicity suggesting a health and safety problem, and charges by a former State employee of inadequate State regulation, Governor Carroll )
of Kentucky has requested NRC's technical assistance in the form of an l l k
independent assessinent of conditions at Maxey Flats. i I ?,ITE DESCRIPTION:
l The site is on a relatively flat hilltop in northeentral Kentucky.
Most preefpitation (annual average of about 47 inches) that falls on the site runs off and into small streams. Precipitation that doesn't run i
off is either evaporated, const,tmed by vegetation or percolates into the
! ground. The fraction that percolates flows 'at a low rate into under-ground zones for eventual drainage to seeps, wells and stream channels.
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{ _s The .maturfcce material is composed of successive layers of different shales and sandstone. The surficial layer is' clay, a weathered shale.
Groundvatar is considered to move through cracks and fissures in the L sLale. '
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l M,1NTONB7-235 PDR
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Radioactive waste is buried in closely spaced trenches about 25 feet deep. Waste containers dumped in trenches are covered with dirt to a level about 3 feet above the original ground surface. Newer trenches have a two foot thick clay layer beneath the ground sarface. The trenches are designed with one to three gravel filled sumps to facilitate removal of groundwater.
The State's License requires that all liquids collected l in closed trenches be removed until a " dry status" is established.
A
" dry status" is defined as a condition when a pump, pumping at a rate of 100 gallons per hour or less will " gas-out" after 50 gallons or l'ss e !
of liquid is removed from a trench.
A weekly determination of " dry i status" is required until such time as no more than 100 gallons per week l
is removed. Monthly pumping is required thereafter. 1 i
At the present time all water which is removed from the trenches is ,
1 being processed through a radioactive waste evaporator. The evaporator has a nominal capacity of 5 gallons per minute and is being operated 24 i 1
hours a day, five days.a week. A temporary liquid waste storage area has been established adjacent to the older section of the burial ground.
Wastes are stored in surp'lus steel tanks having"a total capacity of about 600,000 gallons.
The storage area is surrounded by a berm, or dike, approximately four feet high.
At the present time about 500,000 gallons of liquid waste is stored in this area.
An apparent act of sabotage last winter resulted in the contents of one of these tanks being dumped within the berm area.
Consequently, all rainfall which is collected within the area must now
3-be treated as radioactive liquid waate. All rainfall collected within the area is now being transferred to a newly lined pond. Leakage from the pond and dilution by additional rainfall is minimized by confining l
the contaminated. liquid between two impermeable medbranes. There are two additional onsite ponds: one is used as a non-potable water supply and the other is a surface drainage pond.
RECOMMENDATIONS:
Although the radioactive materials detected in the offsite environs i
apparently present no significant health hazard to the population residing in the area, the necessity for attempting to remove the bulk of the water from vaste trenches and processing it through an evaporator is indicative of the seriousness with which the present situation at Maxey Flats is 1
viewed. It would appear that the problem can best be controlled by further l l
improving surface and groundwater management techniques at the site.
Every reasonable effort should be made to eliminate or minimize the infiltration of surface water to the completed waste trenches.
The Environmental Studies Design Committee meeting in February 1975 identified needs for additional information on subsurface hydrogeology, biological and agricultural pathways, source term definition, modeling of water movement in the surficial soils, and surface runoff definition.
The Committee recommended studies in each of these areas. The largest study, $750,000 of a total of $1,097,000, was for definition of deep hydrogeology. The length of time required for studies was estimated to
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i range up to the five years required for definition of deep hydrogeology. !
The State has requested that NRC contribute to the costs of the studies recommended by the Environmental Study Design Committee. To make a recommendation on NRC funding necessitates a finding of agency benefit. We note that our recommendations with respect to the proposed studies suggested more positive actions in w'ater management, as opposed to only studying the site. We see little or no benefit to NRC for the recommended studies. In particular, identification of the source tenn of buried wastes appears impracticable, and the likelihood of successfully modeling of groundwater transport appears low, because of the heterogeneity )
of subsurface materials. If the purpose of the studies is to determine !
l the acceptability of the site, that question can be answered affirmatively now. If the purpose is to better define conditions at the site, merit exists, but the recommendations do not appear cost effective.
A list of possible means of improving water management at the site by reducing the amount of groundwater available to transport radioactive contaminants is presented below.
- 1. The applicant has performed a considerable amount of work to reduce the infiltration of surface water into c:mpleted trenches in the older se'etion of the disposal facility. The effectiveness of these efforts is not known'at the present time. Neither do ve know the effectiveness of efforts to minimize movement of contaminated water from the trenches downward to the watertable by periodically removing 1 .
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water collected in the sumps. Consequently, we recommend that additional effort be directed toward further reducing curface water seepage into the' trenches. Following are several means of reducing infiltration which should be considered.
- a. The density of the top surface layers of soil should be determined. If it is not compacted, to near optimum levels, engineering methods should be used to obtain maximum compaction.
- b. If the surfical densities are less than optimum, the surface should be covered with a well compacted layer of some essen-tially impervious material, such as clay or soil cement,
- c. The height of vegetative groundcover should be kept to a minimum. Long grass will hold the rainfall and give it a longer period of time to infiltrate, thus increasing the .
amount of groundwater,
- d. Lined channels should be provided between and around the capped trenches to speed the removal of runoff and thereby decrease the time available for rainfall to infiltrate into the soil.
- 2. We endorse the licensee's efforts to minimize the quantities of contaminated water stored on site. Increased effort should be directed toward reducing the size of the contaminated storage area in order to minimize the quantity of rainwater which the licensee is presently required to store in the double lined pond. This source of con-taminated water should be eliminated as soon as practicable.
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- 3. Evaluate the effect of the non-engineered ponds on site on the groundwater table. Unless it can be demonstrated that the ponds do not significantly enhance disolution of radioactive materials
- in the trenches and/or increase the rate of movement of contaminated !
l groundwater, the ponds should be eliminated or lined. .
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- 4. Measures should be taken to increase the ability to remove water i
from future trenches (once they are closed) . Originally the trenches I were to have a gravel drain on the bottom. This practice was later discontinued because the backfill material was apparently clogging the gravel., Clogging could be prevented if an adequate l layer of sand was provided on top of the gravel.
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- 5. Consideration should be given to burying vaste on top of old trenches as a means of improving existing surface drainage, reducing infiltration and extending the life of the burial ground. I l
- 6. Consideration should be given to effectively encapsulating buried i
l waste in an impervious trench side and bottom liner. Such a liner !
could be constructed of bentonite, hydraulic asphalt or other l I
durable impervious material. Because of the manner in which vaste l 1
is disposed of, such a liner would have to be constructed in sections I along a trench.
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- 7. During any future subsurface investigations, such as.the Deep. !
l Ilydro-geological Study proposed by the Environmental Design Committee, an attempt should be made to determine the extent of the pervious zone indicated by the EMCON Borings 2E, 7E, 8E, 10E, 12E.
l The zone should be located, its leakage investigated, and grouted with a suitable slurry material such as clay if it can be deter-mined that the zone contributes significantly to offsite ground-water flow. A similar technique could be used to seal any other leaky zones encountered'as a result of subsurface explorations.
- 8. The need for the proposed mantle study would be reduced or eliminated i by successful reductions in percolation. Subsurface explorations I
should also be used to establish whether groundwater is reaching the site in the near surface strata by flowing from the north and _
northeast.- If it is determined that a significant amount of water is reaching the site in this manner, an interceptor ditch could be constructed across the north end of the site.
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- 9. Improvement in water extraction measurements from old trenches should I
. be undertaken by requiring stipulated licenpe amounts to be by volumetric measurement, rather than by pump rating. Furth'ermore, consideration should be given to pumping trenches more frequently I at a lower rate than presently specified to minimize water accumu-lat vi. , contact with vaste, and contaminated groundwater.
k .n twal ./. / TAR NO.: 160!
s s L u. - u . i
- REQ. BR.:
U.S. ATOMIC ENERGY COMMISSION
' 1 TECHNICAL ASSISTANCE REQUEST CONTROL FORM t
- iEPARED BY: H. R. Denton !
NEMW m 6 /U/E ACTION:
NEW ASSIGNMENT O NEW INFORMATION O CANCELLATION O COMetEriON@
GENER AL DESCRIPTION / TITLE: Maxev Flats. Kentucky - Low Level Corrercial Waste l l
Burial Tacility TYPE OF REQUEST:
l j TECH. ASSIST O TOPICAL REPORT C REG. GUIDE D l STANDARD C OTHER REQUEST FROM: / /
DATE:
REQUEST CONTACT:
ADDRESSED TO DDTR OTHER:
/ i REQUESTING TARGET DATE: / / / '
DATE RECEIVED:
ASSIGNED ASS)STANT DIRECTOR:
l REACTOR SAFETY O enc:NeEatso O CONTAINMENT SAFETY O SITE SAFETY O i RSBC CPSD EiCs0 OSa0 ..SCO MTEsOSEa0 AreO i:iseO eseO en CAR D asa 0 <
ESTIMATED COMPLETION DATE: / /
R ESPOND INDIVIDUALLY:
ADDITIONAL INFORMATION REQUESTED 0 COORDINATED RESPONSE BY:
REMARKS: F.etao to W. Kerr fm J. Kas tner dtd 6/12/75 SYSTEM CONTROL DATA Copies to:
FACILITY NAME(S) DOCKET (S)
- 1. Recuestor H. Larson
- 2. OPS W. Mcdonald (1) _ _ _- _ _ _ _ 050 00 3.-8. Assigned A/D's H. R. Denton (2) _ _ _ _ _ _ _ _- __
050 00 9.10. Deputy Director.TR T. Schroeder ( 3) __ -- _ _ _ _ _ _ _ _ _ _._ _ _ _ _. _ _0507 00 _
J. Kastner (4) __ 050 00 Kerr (5) _ _ _ _ _ _ _ __ __ _ _ _ _ _ _ 0
{W.. . . . ..
l 1 TOPICAL REPORT REVIEW NUMBER:
i ORB ACTIVITY NO.:
,, . . _ . . . . . ORB ISSUE MILESTONE NO.: ,
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