ML20072B961

Testimony of L Holish Re Consolidated Contentions 39 & 109 on Assumptions Used in Determining Time Radioactive Contaminants Released to Groundwater Would Take to Travel to Nearest Well.Related Correspondence

ML20072B961
Person / Time
Site:	Byron
Issue date:	03/01/1983
From:	Holish L COMMONWEALTH EDISON CO., SARGENT & LUNDY, INC.
To:
References
ISSUANCES-OL, NUDOCS 8303080098
Download: ML20072B961 (15)

Text

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e Date: 3/1/83 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION

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COMMONWEALTH EDISON COMPANY 2 ' ~ )' - Docke Nos. 50-454 OL

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SUMMARY

OF TESTIMONY OF LAWRENCE HOLISH REGARDING CONSOLIDATED CONTENTIONS 39 AND 109 Mr. Holish is an engineer, employed by Sargent &

Lundy, the Byron Station Architect-Engineer. He is Head of w

the Geotechnical Division at Sargent & Lundy, and was in-volved in the geologic and geotechnical work performed with j respect to establishing the Byron foundation design criteria l

and for the Byron. project design assessment. Mr. Holish's testimony addresses the assumptions used in determining the time it would take radioactive contaminants released to the l groundwater to travel to the-nearest well.

Mr. Holish first describes the hydrogeological and -

geological characteristics of the Byron site. He then dis-cusses data, and his analysis of that data, which were derived from field pumping tests on wells located near the Byron site. Mr. Holish concludes that, based upon these data, the transmissivity of the rock. is approximately 700 8303000098 830301 PDR ADOCK 05000454 T PDR ,

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• gallons per day per foot of aquifer. Mr. Holish then con-cludes that because the transmissivity value utilized in performing the design basis event analysis for Byron was 2000 gallons per day per foot of aquifer, the 18 year travel time calculated for the design basis event is most likely conservative. Finally, Mr. Holish presents a general ais-cussion of travel times which would be associated with a core melt scenario at Byron. He concludes that the travel time associated with such an event would be approximately 24 years, which would allow ample time to take action to interdict the flow of contaminated water thereby mitigating tiie consequences of the release of contaminants to the groundwater.

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Date: 3/1/83 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In The Matter of )

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COMMONWEALTH EDISON COMPANY ) Docket Nos. 50-454 OL

) 50-455 OL

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(Byron Nuclear Power Station, )

Units 1 & 2) )

TESTIMONY OF LAWRENCE L. HOLISH Ol: Please state your name.

Al: Lawrence L. Holish.

02: By whom are you employed?

A2: Sargent & Lundy Engineers.

03: In what capacity?

A3: I am Head of the Geotechnical Division.

04: Please describe your educational and pro-fessional background.

e4:

} In 1963 I received a B.S. in civil engineering from Michigan Technological University. Since graduation I have been employed by the West Virginia Road Commission, Charleston, West Virginia, Stone and Webster Engineering Corporation, Boston, Massachusetts, and Sargent & Lundy Engineers for 2, 5, and 10 years, respectively. During these 17 years I have participated, and in most cases, provided administrative control of the investigation, evaluation, and design of foundations for 15 nuclear gener-I L

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. ating stations and 25 fossil fuel stations.

Prior to becoming Head of the Geotechnical Division at Sargent & Lundy, I was a Senior Soil Engineer. In that capacity I was responsible for .he establishment and pre-paration of the technical criteria and procedures developed for the Byron Station foundation grouting program, and subsequent earth work. During the initial design and con-struction of the Byron Station, I provided the interpretation of geologic and geotechnical subsurface exploration data required for foundation design criteria and for subsequent project design assessment.

05: What is the scope of your testimony?

AS: My testimony addresses those aspects of consolidated Contentions 39 and 109 which bear upon the hydrological characteristics of the Byron site and the analyses which were performed regarding movement of ground-water.

06: Please describe the hydrogeological charac-teristics of the Byron Site.

A6: As a preface, it should be noted that a com-plete detailed description of the geologic characteristics of the Byron site is contained in Chapter 2.5 of the Byron FSAR. To aid in the understanding of the following descrip-tion I have attached as Exhibit 1 to this testimony a stratographic column of the Byron site geologic formations.

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. The four most significant hydrogeologic units at the site are the glacial drift, the Galena-Platteville dolo-mites, the sandstone units of the Cambrian-Ordovician Aquifer (the St. Peter, Ironton and Galesville Sandstones), and the Mt. Simon Sandstone.

The site area is covered with a mantle of glacial drift consisting mainly of glacial till covered by a few feet of loess (windblown silt). A study of borehole logs at the site indicates that the thickness of the drift averages 16 feet. Due to the generally low permeability and thinness of the till, it is not possible to develop groundwater wells by drilling into the drift. The drift is recharged by precipitation.

Beneath the thin mantle of drift are dolomites and limestones of the Ordovician-age Galena and Platteville Groups. Borehole logs indicate that the thickness of the Galena-Platteville dolomites at the site range from 100 to 225 feet. The depth to the top of the dolomite equals the thickness of drift. The dolomites are extensively fractured l near the top, with solutionally enlarged openings in places.

l These characteristics are not found at depth where the dolomites become dense.

In the site area, the Galena-Platteville dolomites i

are recharged by precipitation through the overlying glacial drift and discharge into the Rock River and its associated tributaries and into shallow domestic wells.

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. _4-Regionally, the Galena-Platteville dolomites are hydraulically continuous with the lower sandstone units of the Cambrian-Ordovician Aquifer. However, in the vicinity of the Byron site, groundwater in the Galena-Platteville dolomites is perched on the Harmony Hill Shale Member of the Glenwood Formation which has low permeability. The low permeability of the Harmony Hill Shale Member was demonstra-ted by comparing the head relationships measured in observa-tion wells. Specifically, piezometric levels in piezometers installed below the Harmony Hill Shale Member are at least 686 feet MSL, whereas piezometric levels in piezometers installed above the Harmony Hill Shale Member are at least 745 feet MSL.

The Glenwood Formation grades down into the thick sandstones of the St. Peter Sandstone. The Ordovician-age St. Peter Sandstone is permeable and has a relaticely uniform lithology throughout the area. In the regional area, the St. Peter Sandstone is discharged primarily through wells for small municipalities, subdivisions, parks, and small l

industrial concerns.

Lower in the stratigraphic column are the Ironton and Galesville Sandstones comprising a portion of the aquifer which is about 150 feet thick in the regional area. In the site area, the Ironton and Galesville Sandstones are about 105 to 115 feet thick. The sandstones are discharged primarily through wells serving various industries and municipalities.

The Ironton and Galesville Sandstones are considered the

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, best bedrock aquifer in northern Illinois because of their consistent permeability and thickness. Yields on the order of hundreds of gallons per ainute may be obtained from the Ironton and Galesville Sandstones in wells less than 1,000 feet deep.

Below the Ironton and Galesville Sandstones is the Eau Claire Formation, about 405 feet thick. The basal part of the Eau Claire Formation and the underlying Mr.

Simon Sandstone (which is about 1,430 feet thick) form the basal Cambrian-age Mt. Simon Aquifer. Wells which terminate in the Mt. Simon Sandstone have yielded many hundreds of gallons per minute.

07: Please describe the geologic characteristics of the Byron plant site.

317: Within the Galena-Platteville dolomites is the Dunleith Formation which is the upper bedrock unit at the site and provides topographic control and forms the foundation of the power block safety related structures.

l This unit is slightly to moderately weathered as it is the upper bedrock unit. Solution activity has occurred along many of the joints, fractures, and bedding planes, and l reddish-brown clays or yellow silty sands may be found along these planes.

The Dunleith Formation contains zones of thin green shale partings which are predominant in its lower por-l tions.

At the plant location, these shale partings grade in ,

l at approximate elevation 804.

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, During foundation preparation activities for the Byroa Plant, 154 borings, ranging in depth from 5 to 317 feet, were drilled. Rock samples were cored from the bed-rock using 2-3/4 inch diameter double tube core barrels.

Results of the drilling indicate that the Dunleith formation is fractured, jointed, and thin bedded, but there are no large openings along joints and bedding planes. The variation in the quality of bedrock at the plant location results from vertical variations in lithology and the proximity of the boring to principal joints which traverse the site.

Four joint patterns are present in the site area:

(1) a northwest trending pattern paralleling the regional structural trend; (2) a northeast pattern essentially per-pendicular to the regional structure; (3) a north-sou*h pathway transverse to the structure; and (4) an east-west pattern which is also transverse to the structure.

i Based on analysis of areal photography data the joint patterns have a normal spacing of approximately 200 to 500 feet. Examination of bedrock exposures indicates that these four patterns are detect'ble below the surface, and that the spacing decreases with depth. Near surface joint l

patterns mapped in the plant area are reported in Chapter 2.5 of FSAR. Some joints are clean with openings ranging from 1/16 to 1/8 inches. Some joints are clay filled.

Examination of outcrops and cores indicate that fracturing and weathering appears to decrease below the Dunleith-l

. 1 Guttenburg Formational contact. Specifically, rock quality measurement values of rock in the Dunleith are always low whereas in the formations below the Dunleith rock quality measurement values are higher except near areas of joints.

Zones of solution activity, low rock core recovery', and low rock quality measurements have served as channelways for the movement of groundwater, and examination of the rock cores suggest that solution activity has occurred along these channelways.

Because of these bedrock characteristics, it was decided to fill and seal all major solution enlarged joints, bedding plane, and other planar features of the bedrock by i

pressure rock cement grouting. The geologic descriptions indicated that grouting 7f the main plant area down to the Platteville-Ancell contact would significantly retard the downward and horizontal percolation of groundwater, and hence also limit the rate of solution activity. The grouting program is described in FSAR Attachments 2.5A and 2.5B.

Insitu testing of the grouted foundation rock mass verified that the grouting program resulted in making the l rock mass significantly more impermeable than it had been prior to grouting. This would greatly restrict the seepage i of any uccidentally released effluents into the surrounding i groundwater environment.

I Q8: Have you performed any field tests designed to determine the water movement characteristics of the aquifer underlying the Byron site?

, A8: Field pumping tests on wells located on the western edge of the site were conducted in June and July, 1974. These pumping tests were not conducted for the spe-cific purpose of determining the water movement character-istics of the aquifer. Instead, they were conducted to determine.whether there were significant levels of cyanide in the water drawn from these wells. At the time, we were concerned that well water may have been contaminated due to the existence of a land burial waste dump in the area.

However, the data derived from these pumping tests is helo-ful in evaluating the water movement characteristics of the site area.

09: Nhat conclusions do you derive from these pumping test data?

A9: Based on the pumping test results, we are able to determine the approximate rate at which the wells are recharged. Assuming a saturated thickness of 111 feet and 90 feet of the two wells, we calculated that the hy-draulic conductivity of this portion of the aquifer to be 6.3 gpd/ft 2 for one well and 22.2 gpd/ft for the other well. Hydraulic conductivity represents the volume of water which will flow through a unit area during a given period of time assuming a given hydraulic gradient. Based on the geophysical measurements made in site borings and from literature, we determined the effective porosity of this portion of the aquifer to range from 0.05% to 0.10%. The transmissivity characteristic associated with the aquifer, 1

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. based upon these data, would be approximately 700 gallons per duf per foot of aquifer.

010: What was the transmissivity value utilized in performing the design basis event analysis?

A10: The design basis event regarding ground water contamination considers the postulated rupture of a boron recycle holdup tank and subsequent release of radio-activity into the ground water. For the analysis of the ungrouted bedrock we assumed a transmissivity value of 2000.

Oll: How does that value compare to the value derived from the pumping tests described above?

All: The value utilized in performing the accident analysis assumes a higher transmissivity leve1; that is groundwater would travel faster under the assumed transmis-sivity level than it would under the level calculated from the pump testing data.

012: Are you able to draw any conclusions from the fact that a higher transmissivity value was used for the ,

accident analysis than the value which was derived from the pumping tests?

A12: Yes, the groundwater travel times associated with the design basis event (i.e., approximately 18 years to reach the nearest well) are most likely conservative for the Byron site.

013: Are you aware of any other information which supports this conclusion?

A13: Yes. Subsequent to the interpretation of field collected effective porosity data, a comparison was

, made to other sites where similar bedrock conditions have been encountered. The literature reviewed indicates the values of effective porosity measured at the Byron site are similar to those described by E. R. Ekron in his 1974 U.S.

Geologic Survey Open File Report 74-158 entitled, " Geologic and Hydrologic Considerations for Various Concepts of High-Level Radioactive Waste Disposal in Conterminous U.S."

014: Have you considered the hydrogeologic aspects of a postulated core melt event at Byron?

A14: For the purpose of addressing concerns raised by the intervenors, we have performed two alternative quali-tative evaluations of fluid flow, based upon the previously collected hydrogeologic properties, to interpret the ground-water flow in conjunction with the radionuclide release postulated from a reactor core meltdown scenario.

The first evaluation assumed the existence of most of the hydrogeologic parameters used in performing the baron tank analysis. Conservatively, only the hydraulic gradient was varied by assuming that the molten core would reach a depth of 20 feet below the reactor base-mat foundation. No credit for additional impermeability of the rock mass was taken despite the likely creation of ceramic surface due to melting of the shales in the Dunleith foundation bedrock or the initial hydraulic gradient reversal as the molten mass moves below the phreatic surface and flashes the groundwater to steam to be vented to the containment. The lower ef-l fluent egress elevation for the core melt mixing zone 1

amounts to an 81% reduction in the hydraulic gradient.

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The determination of travel time along the postulated path-way of the effluents from the unit one reactor core location to the nearest well is estimated to be approximately 24 years.

The second evaluation considers the approach of D. T. Snow as reported in the American Society of Civil Engineers Journal of Soil Mechanics, Foundation Division Volume 94, 1973. Snow's work indicates that, for a rock of given conductivity, the fracture porosity depends on the joint (fracture) spacing and to some extent on apperature widths and joint (fracture) orientations. He also reported that joint porosity decreases with depth approximately logarithmically although certain weathered zones were ex-cluded from the study. For the Byron site, the principal joint systems spacing and patterns have been identified through air photo interpretation and examination of rock outcrops. In addition, 43 comprehensive detailed geologic maps were constructed of the main plant excavations and are reported in the FSAR. Detailed descriptions were provided of the foundation material type; the location, arrangement, attitude and apperature size of all joints and location of

, fault data. Based upon the (1) measured hydraulic conduc-tivity of the foundation bedrock for both the grouted and ungrouted rock; (2) the closest continuous joint spacing noted during the geologic mapping program and; (3) a corresponding aperture opening, effective porosity was calculated. The effective porosity is 1/2 to as much as 10 times less than porosities determined from insitu water L

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. pressure test and geophysical data collected at and adjoin-ing the station site. The calculated reduction in porosity would reduce the effluent flow rate thereby increasing the radionuclide release travel time.

015: Are you aware of any steps which could be taken to reduce the flow of groundwater in the event of a radioactive release?

A15: Yes. Two possible methods exist. The first method consists of pumping and retrieving contaminated groundwater and storing it for treatment. This can be done by installing multiple groundwater wells at the perimeter of the Station's property that extend down to the Galina-Platteville formation. These wells would be close enough together so that the area the wells influence overlap to create an extensive drawdown of the groundwater and reverse the hydraulic gradient. Groundwater monitoring wells also would be installed down gradient from the spill at varying elevations.

The second method of retarding the flow of con-taminated groundwater would involve constructing an im-permeable barrier in rock. This could be accomplished

through pressure rock cement grouting the entire Galena-i Platteville rock formation down gradient from the spill.

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