ML19221A969

Srp,Revision 1 to Section 2.4.13, Groundwater

ML19221A969
Person / Time
Issue date:	03/31/1979
From:	Office of Nuclear Reactor Regulation
To:
References
NUREG-75-087, NUREG-75-087-02.4.13, NUREG-75-87, NUREG-75-87-2.4.13, SRP-02.04.13, SRP-2.04.13, NUDOCS 7907120085
Download: ML19221A969 (16)

Text

pa" NUREG 75/087

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o f * )g U.S. NUCLEAR REGULATORY COMMISSION P~

STANDARD REVIEW PLAN

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OFFICE OF NUCLEAR REACTOR REGULATION SECTION 2.4.13 GROUNCWATER REVIEW RESPONSIBILITIES Primary - Hydrology-Meteorology Remch (HMB)

Secondary - Ef fluent Treatment Systems Branch (ETSB)

I.

AREAS OF REVIEW Data presented in the applicant's safety analysis report (SAR) on local and regional ground-water reservoirs are reviewed to Establish the ef fects of groundwater ou plant foundations Other ar eas revie-1 under this plan include identification of the aquifers and the type of onsite groundwater use, the sources of recharge, present and future withdrawals, an evaluation of accident ef fects, c.onitoring and protection requirements, and design bases for groundwater levels and hydrodynamic ef fects of groundwater on safety-related structures and components. Flow rates, travel time, gradients, other properties pertaininq to the novement of accidental contamination, and groundwater levels beneath the site are reviewed, as are seasonal and Climatic fluctuations. Or those caused by man, that have the potential for long-term changes in the local groundwater regime.

ETSB will provide accioent scenarios for HE5 staff use in evaluating accidental spills.

II.

ACCEPTANEE CRITERIA 9

for SAR Section 2.4.13.1 : A full, documented description of regional and local groundwater aquifers, sources, and sinks is required. In addition, the type of qroundwater use, wells, pump 6nd storage fu;ilities, and the flow requirennts of the plant must be de-scribed. If qroundwater is to be used as an essential source of water for safety-related equipment, the design basis for protection frun natural and accident pher mena must compare with Regulatory Guide 1.27 guidelines. Basts and sources of data must 2equately described.

For SAR 2.4.13.2:

A de urn tion of present and projected local and renional groundwater use must be prcvided. Existino uses, including amounts, water levels, location, d, awdown, and sourte aqui*ers must be discussed and should be tabulated. Flow directions, gra-dients, velocities, water levels, and ef fects of potent %l future use on these parameters, including any possibility for revcrsing the directior of groundwater flow, must be indi-cated. Any potential groundwater recharga area within the influence of the plant and ef fects of constru;tien, including dewaterinq, must be identified. The influence of existinq and potential future wells with respect to groundwater beneath the site must also t.e discussed. Bases and

• Jrces of data Fust be described and referenced.

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For SAR 5ection 2. 4.13. 3: Radionuclide transport characteristics of the groundwater q

environr:ent with respect to existing ana future users must be described for both operating and accic'ent conditions Estimates and bases for coefficients of dispersion, adsorption, groundwater velocities, travel tines,1radients, perreabilities, porosities, and ground-water or pietometric levels between the site and existing or future surface and ground-water users must be described and be consistent with site characteristics Potential pathwy s of contamination to groundwater users must also be identi fied. Sources of data must be described and referenced.

One-or two-dinensional nathematical nodels are accept-able to analyze the flow field and convective dispersion of contaminants in surf ace waters, providinq that the models have be7n verified by fiald data and that conservative site-specific hydrologic paraneters are used.

Furthermore, conservatism must be the guido in telecting the aroper model to represent a specific physical situation. Radioactive decay and sediment adsorption may be considered, if applicable, providinq that the aJsorptioa f actors are conservative and site-specific.

For SAR Section 2.4.13.4:

The need for and extent of procedures and measures to prt tect present and projected groundwater users, including monitoring proqran>, must be discussed.

l These item, are site-specific and will vary with each application.

for SAR Sectior 2.4.13.5:

The design bases (and develnent thereof) for groundwater-induced loadings on subsurface portions of safety-relmed structures systems, and corpo-nents must be described. If a permanent dewatering system is erployed to lower design basis groundmater levels, the bases for the design of the systen and determination of the design basis for groundwater levels c.ust be provided. Informatinn must be provided r egard-inq (a) all structures, cceponents, and features of the systen, (b) the reliability of the syst: as related to available perf ennance data for similar syster s used at other locations, (c) the various soil parameters (,uch as pen cability, porosity, and specific yield) used in design of the system, (d) the bases for determination of groundwater flow rates an'1 areas of influence to be espected. (c) the bases for deternination of time available to nitigate toe consequences of system f ailure where system f ailure could cause design bases to be esteeded. (f) the effects of malfunctions or failures (such as a single failure of a critical active component or f ailure of circulating water system piping) on systen capacity and subsequent groundwater levels, and (g) a description of the proposed groundwater level monitnring program and outlet flow conitoring prograr Specific criteria relatinq to the design of permnent dewatering systems are presented in the attach"d Branch Technical Positionj HMB/G5B 1 " Safety-Rela ted Pernanent Dewa tering Sys tems" In addition, if wells are proposed I for safety-related purposes, the hydrodynamic design bases (and development thereof) for protection against seismically-induced pressure waves must t'e described and be c >nsistent with site charicteristics III. REVILW PROC [Dl!Rf 5 Section 2.4.13 of the applicant's SAR is reviewed to identify any missinq data, i n f orni t i on,

or analyses necessary for the staff's evaluation. Applicant responses to the requested information will be tvaluated using the methods outlined below; and staff positions will be developed based on the results of the analysis. Resolution, if possible, of potential groundwater problems or c f dif ferences between applicant's and sta f f's design nases, will

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J. d l tJ Rev. I 2.4.13-2

l be coordinated through the LPM, and the SER will be written accordingly. The review sequence is shown in f igure 2.4.13.

Local and regional groundwater conditions are reviewed b/ comparing the applicant's descrip-tion with reports by the U. 5. Geological Survey (USGS), other agencies, and professional organizations. Other NRC organizational elew nts with related review responsibilities l

will be notified of any applicable groundwater data and analyses If unsite groundwiter u.e and f acilities are safet/-related, the criteria of Regulatory Guide 1.2/ are applied.

The staf f will cumpare the applicant's description of present and projected local and reginnal groundwater use, existing users, including achient use, water levels, location, and drawdown wi th information and data f rom ref erences Drawdown ef fects of projected f u tur. groundwater use, including the possibility for re ersing the groandwater flow, w 11 be evaluated and way be checked by independent calculations. Construction effects, includ-inq dcwatering, on potential recharge areas may also be evaluated.

The staf f will make independent calculations of the transport ceabilities and potential contamination pathways of the groundanter environment under accid % tal conditions with respect to cristing and future users Special attention stluld be diretted to proposed facilities with permanent dowatering systems to assure that pathways create _d by those systems have been identified. The staff will, in cu sultation with the Effluent Treatment Systems Branch (ETSB), choose the accident scenarios leading to the mcst adverse contamina-tion of the groundwater or to surface water via the groundwater pathways. Analysis of the 6%

cuntamination will com nce with the simplest mudels, such as ' hose presented in Peferences 22 and 23, using demonst atably conservative assumptions and coefficients Dilutions and travel times (or il ternat ively, concentrations directly) resul ting f r nm the preliminary analyses will then be checked by ETSB to determine acceptability. If the indicated concentrations of radionuclides, identified by ETSB, are less thun 10 CFR part 20, part B, no further computational efforts will be wirranted. Further analyses using progressively more realistic and less conservative modeling techniques, such as those of Fef erences 9 and 26, will t,e undertaken if the preliminary results arr not acc"ptable.

The needs and plans for procedures, measures, and monitorir-g proqrams will be reviewed based upon site-specific qroundwater featurec. Design bases for groundwater-induced load-ings on subsurface portions of safety-related structure + are reviewed. Independent tal-culations are perforud to determiw the adequacy of the design criteria and the capability to reflect any potential future changes which can be induced by variations in precipita-tion, construction of future wells and reservoirs, accidents, pipe failures, or other natural events.

f'or dewatering systems, calculations are performed to determine phreatic surfaces, rorwal flow rates, flow rates into the system as a result of pipe breaks (cir-culating and service water system pipes), groundwater rebound tire assuming total failure of the systen, and system capacity.

The above reviews are perforr"ed only when applicable to the site or site region. Sone

') p ij1 iter"s of review nay be done on a generic basis.

2.4.13-3 Rev. I

IV.

EVALUATION FINDINGS Jr construction permit (CP) reviews, the findinqs will sumarize the applicant's and staff's estirates of groundwater levels associated with safety-related structures, and where applicable, groundwater flow directions, gradients, velocities, effects of potential future use on these parameters, applicability and reliability of dewaterinq systems, and the ef fects of an accidental release of radioactive liquid ef fluent on existing and 'uture users. If the desian bases estimates are comparable, staff concurrenco m tne applicant's estinates will be stated. If the staf f predicts substantially more conservative ground-water conditions and the proposed plant nay be adversely affected, a statement of the sta f f bases will be r ade, if groundwater conditions do not constitute design bases, the findings will so indicate.

For operatinq license (OL) reviews of plants that have had detailed qroundwater reviews at the CP staqe, the CP conclusions will be referenced. In addition, a review of qroundwater history since the CP review will be indicated and note of any changes in qroundwater conditions or usaqe will be made, for pernanent dewatering systers, any additional infor-mation reqarding soil proper *ies and groundwater conditions cathered during construction will be evaluated to determine the applicability of the assumed CP design basis If no CP groundwater review was undertaken, of the s'. ope indicated above, this fact will be noted in the CL findings in addition to the results of the current review.

i A samle CP statement follows:

" Groundwater is available at the site in low to noderate yields from the followinq four n uifers listed by increasinq depth below the surface: (1) tFe unconfined watertable aquifer consisting of the A and B formations, (2) the confined C-Upper D aquifer, (3) the confined upper D aquifer, and (4) the confined riddle D aquifer.

Groundwater in the A-B town aquifer generally moves toward the local streams, whereas, in the deeper confined aquifers, groundwater generally moves toward centers of pump-inq.

At tne present, saltwater intrusi0n into the aquifers at the site is not evident as a result of brackish water mov' from the E Bay, the F Canci, or G Bay.

"The applicant plans to use groundwater during plant operation at a continuous rate of 140 gpm, of which 100 apm will be used for d s ineralized water requirerents, and 40 qan will be service water for drinking, washing, and filling the fire protection storay tanks The source of this supply will probably be the A D aquifer, for which the applicant has conducted pumping tests at two locations The applicant has indi-cated he may utilize another deeper aquifer for this supply, an i has aqreed to supply additional pumping test data to the staff for evaluation if another aquifer is chosen.

This is acceptable to the staff.

" Precipitation is the source for groundwater recharp to the A-B aquifer. The rccharge area for this aquifer lies to the southwest of the plant site and extends beyond the City of M.

No major recharge areas for the lower confined aquifers are believed to exist in the vicinity of the site.

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Rev. 1 2.4.13-4

"A water-table design level of 65 feet MSL (15 feet below plant grade) v.as selected by the applicant to determine hydrostatic loadings on safety-relatea structures. T ',e staff concurs that this level is conservative sir:e the highest measured water taDie elevation at the plant site following an extremely rainy season was 63.4 feet MSL.

"The staf f postulated an instantaneous rupture of the baron recycle tank veith no con-tainment by plant structures as b9ing the design basis event for contamination of groundwater and surface water. The travel time to the nearest groundwater user was conservatively estimated to be a minimum of 29 years with a dilution of at least 6000. The resultant concentrations were found to be less than 10 CFR Part 20 B.'

V.

REFERENCES In addition to the following, references on methods and techniques of analysis, published data by Federal and State agencies, such as USGS water supply papers, wil.1 be used as available.

1.

J. D. Bredehoef t and G. F. Pir. der, " Digital Analysis rf Areal Flow in Multiaquifer Groundwater Systems : A Quasi Thr"e-Dimensional Model," Water Resources Research, Vol. 6, No. 3, pp. 883-888 (1970).

2

" Finite Element Solution of Steady State Potential flow Problems,' HEC 723-G2-L2440.

Corps of Engineers (1970).

3.

T. A. Prickett and C. G. Lonnquist, " Selected Digital Computer Techniques for Ground-water Resource Evaluation," Bulletin 55 Illinois State Mter Survey, Urbana, Illinuis (1970).

4 D. B. Cearlock and A. L. Reisenauer, "Sitewide Groundwater flow Studies for Brookhaven National Laboratory, Upton, Long Island, New York," Battelle Pacific Northwest Labor-atories, Richland, Washington (1971).

5.

K. L. Kipp, D. B. Cearlock, A. L. Reisenauer, and C. A. Bryan, " Variable Thickness Transient Groundwater flow Model--Theory and Numerical Implementation," BNWL-1703, Battelle Pacific Northwest Laboratories, Richland, Washington (1972'.

6.

D. R. Friedrichs, "Information Storage and Retrieval System for Well Hydrograph P3ta--

User's Manal," BY.JL-1705, 3attelle Pacific Northwest Laboratories, Richland, Washington (1972).

7.

K. L. Kipp and D. B.

Cearlock, "The Trant nissivity Iterative Calculation Routine -

Theory and Numerical Implementation," BNWL-1706, Battelle Pacific Northwest Labora-tories, Richland, Washington (1972).

8.

S. W. Ahlstrom, R. J. Serne, R. C. Routson, and O. B. Cearlock, " Methods for Estimat-ing Transport Model Parameters for Peqional Groundwater Systems," BNWL-1717, Battelle

,p-Pacific Northwest Laboratories, Richland, Washington (1972).

) q, 7]

jj) 2.4.13-5 Rev. I

9.

R. C. Routson and R. J. Serne, "One-Dimensional f% del of the Movement of Trace Radio-active Solutes Through Soil Columns f he PERCOL Model," BNWL-1718, Battelle Pacific Northwest Latoratories, Pichland, Washington (1972).

10.

R. C. Routson and R. J. Serne, "Experimen+.al Support Studies for the PERCO'_ and Transport Models," BNWL-1719, Battelle Pacific Northwest Laboratories, Richland, Washington (1972).

11.

K. L. Kipp, D. B. Cearlock, and A. E. Reisenauer, " Mathematical Modeling cf a Large, Transient, Unconfined Aquifer with a Heterogeneous Perneability Distribution," Paper presented at the 54th Annual Meeting of the American Geophysical Union, Washington, D.

C., April 1973.

12.

L. L. Schreiber, A. E. Reiv nauer, K. L. Kipp, and R. T. Jaske, "Articipated Effects of an Unlined Brackish-Water Canal on a Confined Multiple-Aquifer 5ystes," BNWL-1800, Battelle Pacific Northwest Laboratories, Richland, Washington (1973).

13.

Regulatory Guide 1.27 " Ultimate Heat Sink. '

14 W. H. Li and F. H. Lai, " Experiments on Lateral Dispersion in Porous Media," Jour.

Hydraulics Division, Proc. Am. Soc. Civil Enqinees s, Vol. 92, No. HY6 (1966).

15.

W. H. Li and G. T. Yeh, " Dispersion of Miscible liquids in a Soil, Water Resources Research, Vol. 4, pp. 369-377 (1968).

16.

D. R. F. Harleman, P, F. Mehlhorn, and R. R. Rumer, "Dispersio '-Permeability Correla-tion in Porous Media," Jour. Hydraulics Division, Proc. Am. Soc. Civil Engineers, Vol. 89, No. HY2, pp. 67-85 (1963).

17.

L. E. Addison, D. R. Freidrichs, and K. L Kipp, "The Transmissivity Iterative Programs on the LDP-9 "omputer-- A Nan-Machine Ieteractive Systm," CNWl.-1707, Battelle Pacific Northwest Labvatories, Richland, Washinqton (1972).

IP,

"'u< wentals of Transport Phenomena in Porous Media," International Association for Hyc.c? > Research, Elsevier Publishing Company, New York (1972).

19.

D. K. It 'id, " Groundwater Hydroloqy," John Wiley & Sons, Inc., New York (1959).

20.

J. Bear, "Dyramics of Fluids in Porous Media " American Elsevier Publishing Company, l

l N u York (1972).

-1 NRC Hydrologic Engineering Section, " Dispersion Work book" (in prepara t ior.).

22.

R. Codell and D, Schreiber, "NRC Models for Evaluating the Transport of Rariinnuclides in Groundwater," Proceedings of S r posium on Management of low-Level Radioactive Wastes, May 1977, Georgia Institute of Technoloqy, Atlanta, Georgia (in preparation).

Rev. 1 2.4.13-6 J)

23.

F. A. Appel and v. D. Bredehoeft, " Status of Groundwater Modeling in the U.S.

Geological Surves,' USGS Circular 737 (1976).

24.

feerican Nuclear Society, "5tandards for Evaluating Radionuclide Transport in Ground-water, Draft 2."

25.

J. O. Dugruid and M. Reeves, " Material Transport Through Porous Media: A Finite Element Galerkin Model," ORNL-4928, Oak Ridge National Laboratory, Environmental Science Division, Publication 733, March 1976.

26.

R. L. Taylor and C. C. Brown, " Darcy's Flow Solutions with a Free Surface," Journal of the Hydraulics Jivision, ASCE, Vol. 93, No. HY2, pp. 25-33, March 1967 27.

S. P. Nciman and P. A. Witherspoon, " Finite flerent Method of Ana'yzing Steady 5eepage with a Free Surface," Water Resources Research, Vol. 6, No. 3, pp. 889-897, June 1970.

28.

S. P. Neuman and P. A. Witherspoon, " Analysis of Nonsteady Flow with a f ree Surface Using the Finite Element Method," Water Resources Research, Vol. 7, No. 3, pp. 661-623, June 1971 29.

G. F. Pinder and E. O. Frind. " Application of Galerkin's Procedure to "muifer Analysis," Water Resources Research, Vol. 8, No. 1, pp. 103-120, February 1972.

30.

J. Rubin and R. V. James, " Dispersion-Af fected Transport of Reacting Solutes in Saturated Porous Media: Galerkin Method Applied to Equilibrium-Controlled Exchange in Unidirectional Steady Water Flow," V'ter Resources Pesearch, Vol. 9, Na. 5, pp. 1337-1356, Oc tober 1973.

31.

L. O. Frind and G. F. Pinder, "Galerkin Solution of the Inverse Problem for Aquifer l

Transmissivity,' Water Resources Research, Vol. 9, No. 5, pp. 1397-1410, October 1973.

I 1

32.

G. F. Pinder, ' A Galerkin-f inite Element Simulation of Groundwater Contanination on Long Island, New York," Water Resources Research, Vol. 9, No. 6, pp. 1657-1669, December 1973.

33.

M. Reeves and J. O. Duguid, " Water Movecent Through Saturated-Unsaturattd Porous Media: A Finite Element-Galerkin Model," ORNL-4127, Oak Ridge National Laboratcry, Oak Ridge, Tennessee, February 1975.

1 i

34.

Branch Technical Position HMB/GSB 1, " Safety-Related F entanent Dewatering Systems",

attached to this section.

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BRANCH TECHNICAL PgSITIONS HMB/GSB 1 SAFETY-RELATED PERMANENT DEWATERING SYSTEMS 1.

Suma ry This position has been fomulated to minimize review problens r.nmon to pemanent de.iater-ing systems that are depended upon to serve safety-related purposes by describinq accept-able geotechnit i and hydrologic engineering design bases and criteria. A safety-related designaticn for pennanent dewatering systems is provided since they protect other safety-related structures, systems and components f rom the ef fects of natural and man caused events such as groundwater. In addition, the level of documenution of data and studies which are considered necessary to support safety-related functions is detined. This position applies to both active (e.g., uses pumps) and passive (e.g., uses grav ty drains) dewatering systems. This position does not reflect structural, mechanica: and electrical criteria.

II.

Back round 3

The staf f has reviewed a number of pemanent dewatering system <, including McGuire 1 & 2, Cherokee 1 & 2, Perkins 1 & 2, Perry 1 & 2, WFPSS 3 & 5, Deuglas Point 1 & 2, and Catawba 1

& 2.

Perry, beginning in 1975, was the first plant reviewed with such systems and was reviewed very late in the CP process. Only WPPSS 3 & 5 and Deuglas Point use a passive systm (no pumps).

Penaanent dewatering systems lower groundwater levels to redtce subsurface water loads on plant structures. In addition, they can increase plant op trational dependabili ty and reduce costs. These effects are accomplished by providing added means of keeping seepage water out of lower building levels during the later stages of plant life when normal water-proofing provisions r:ay have deteriorated, and reducing radwiste system operatirg costs by minimizing the amount of drait water that must be treated. l enefits are, therefore, of two types, tangible (dollars) nd intangible (" insurance"). We understand the construction costs of underdrains can vary widely Jepending on the design. Construction costs of between

$125K to $1000K per unit have been suggested. The costs of coping with significant amounts of groundwater inleakage in safety-related building areas, uhich underdrains are expected to minize, is estimated to be in the rjnge of $100K to $200K per year per reactor, lhe construction costs of alternatives to underdrains for structur01 purposes alone (exclusive of inleakage treatment) is estimated to range upward from $300K per unit and is highly dependent on site conditions. Struttural alternatives to termanent underdrains include additional concrete and Steel in the lower portions of buildings, and the use of anchor systems to resist floatation.

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Dewatering systems are generally composed of three compon?nts; the collector system, the drain system, and the discharge systm. Water is first collected in collettor drains 2.4.13-9 Rev. I

adjatent to buildings or excavations. Interceptor drains or piping are then used to convey this water to a final discharge system. The discharge system can be either gravity flow or a pumping system. Most underdrain structures, systems and components are buried along-side and under structures, althcugh some systems employ punping systems within larger structures (such as reactor or auxiliary buildings) to discharge collected water. Finally, permanent dewatering systens are not a required feature at any plant, but may be proposed as a cost effective feature.

Many permanent dewatering systems at ncnnuclear facilities, such as dars and large build-ings, have functioned over the years. However, the likelihood of a portion of such a system tecoming ineffective and, therefore, not Ferforming its intended function ma) be considerably greater than the probacility of occurrence of a nuclear power plant ce basis event such as a Probable Maximum Hurricane, Probable Maximum Flood, or Safe Shutdown Earthcuake. Losses of f unction in the past have generally been attributable to piping of fines, inadequate capacity, or clogging. We have concluded that safety analyses of such systens should consider reliability and failures of features of the system itself, 3s well as potentially adverse ef fects of failures of nearby nonsafety-related features Such systems need not be designed for design earthquakes if they are not intended to nerforn as underdrains fully during or irrediately following a severe earthquake, or if the systen can be expected to perform an underdrain function in a degraded condition. Certain portions of such systems, however, may be required to regularly perform other safety functinns (e.g., poreus concrete base mats) and should be designed for severe earthquakes. Failure of a dewatering system could canse groundwater levels to rise above design levels, resulting in overloading concrete walls and mats not designed to wi.nstand the resulting hydrostatic pressures. In addition to causing potential st uctural and equipment damage, groundwater could enter safety-related buildings and flood components necessary for plant safety.

The basis for staff concerns over the use of such systens is whether they can be expected to perform their function, and prevent structural failures and interior flooding of safety-related structures. The degree of concern is directly related to the corresponding degree to which the safety of the structures and systems rely on the integrity of the dewatering system, particularly with a Hewatering system in a degraded situation. For example, i f structures can accorrodate hydrostatic, loads that would result with a total failure of a dewatering system, our concerns have been primarily limited to the capability of such systems tc perforn their functions under relatively infrequent earthquake situations i

If, however, such systems rust renain functional (e.g., keep water levels down), whether i

in a degraded situation or not to prevent structural failuras and internal flooding under I

I potentially frequent conditions, we have been very concerned with system reliability.

t i

Many applicar,ts have indicated that their plants can withstand, or have been designed against, full hydrostatic loadings that would occur in the absence of the underdrain systems, but net if an earthquu e were to occur.

If the plant can withstad full hydrostatic loading, assuming degradation of the underdrain systen, rany of the staff's concerns nay be eliminated fron further consideration because of the time available for reredial action after detection of systen degradation.

2.4.13-10

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Ill. Situations identified Durinciprevicus Reviews.

Four general categories of situations have been identified durinq case reviews as follows:

(a) Estima ting and Confirminr) Pcrmeability Values It is necessary to es timate the amouat of water that will be collected 50 th2t systen components such as strip drains, blanket drains, collector pipes, and pumps are ade-quately designed ed sized. One of the most important and most dif ficult parameters to evaluate is the penneability of the soil and rock existing at a site. A per-meability value could be af f ected significantly by conditinns of concentrated ficw along joints in fractured and weathered rocks, or within other aquifers af fected by foundation extavation.

In addition, geological and foundation conditions that were not detected in site emplorations may affect flow conditions and cause the est mated permeability values and flow regimes to be substantially dif ferent f rom those assumed at the CP preliminary design stage.

These conditions are of ten first detected during construction dewatering. Therefore, we have required a connitrent to consider con-struction excavation and dewatering data in the final design of underdrain systems.

(See situation (d) t elow. )

(b) Operational Monitoring Ocquirements To guard against system malfunctions and to assure sufficient time is available for implementation of remedial measures before groundwater could rise to an unacceptable level, provisions must be made for earlv detection of system failures, and contingency measures for these failures must be well defined prior to plant operation. Since drain systens are usually buried and concealed and there may be no direct way of inspecting then, reliance nust be placed on piezoneters, observation wells, manholes, and monitoring of collected water to detect problems or malfunctioning of the sy, ten.

The details of an operational monitoring progrr are necessary prior to construction of the undc~drcie. tu assure that e3ch if the following will be p avided: (a) an early detection alarm system during normal operatinq conditions; (b) regu kriv scheduled inspection and nonitoring; and (c) competent evaluation J obserations curing both construction and operation. In addition, the bases for accep M ble contingency reas.res suitable for coping vith various possible hazardo Fust be established at the C" stage.

(c) Pip _e B rea k s A dewatering system might be everloaded by such conditions as 1"

or breaks in either the circulating or service water systems. A 1mk V break may t e n

a very small percentaqe of the total flow of the cooling i, b# large enough to exceed the hydraulic capacity of drains, pipes an.

n the dewatering system. For example, a complete failure of circulating W er fstem piping has been required in the design of the dewatering sy tems re,iewed to date.

This requirement was made to assure that such abnormal occurrences do not adverseiy af fect the integ-rity of safety-related s tructures, 9 tens, and corponents.

9 (d) S_equence of Review f F ^4 r

3

,u Underdrain systems are usually one of the first itens constructed and, h fe. back-filling and construction of subsurface facilities, are the-no longer visible for 2.4.13-11 Rev. I

regular inspection. In most cases, these systems are initially designed based on rather limited information f rom preconstruction field activities, and are tailored specifically for the site and facilities. By necessity then, final review and approval by the staf f of the design must rely in some part on information gathered during construction. Therefore, the review and approval Can be accomplished in two ways:

(1) design details of the permanent underdrain system, the operational monitoring program and plans for constrxtion dewatering can be submitted in the PSAR, with only con-firmation of the details requircd prior to actual construction; or (2) concentual designs of the permanent Aderdrain systen and the operational monitoring progran and Cetails of Construction dewatering can be submitted in the PSAR with the more complete review and approval based on construction dewatering requiring review and ay rt al prior to actual construction. Review and approval of unique designs at post-CP matters is based upon 10 CFR Part 50, Subsections 35(b) and 55(e)(1)(iii). To prevent extending the review schedule, the first procedure would be the most desirable, but the staff recognizes that the detail required may not always be avail-able at the time the PSAR is submitted.

I IV.

Proposed Staff Position We have reviewed and opproved the design of a limited numter of permanent dewatering systems. Howevcr, because of the importance of these systems to plant safety, we have always required that they be designed and used in a conservative manner. The following is a list of requilei design provisions which are consistent with requirements in recent CP reviews:

(a) if the dewatering system is relied upon for any safety-related function, the system cust meet the appropriate criteria of Appendix A and Appendix B to 10 CFR Part 50.

In adJition, cuidance for structural, mechanical ar:d electrical design criteria is provided in related sections of the Standard Review Plan for Category I structur es, system and cor"ponents. However, all portions of the system need not be designed to ar. corr:odate all design basis events, such as earthquakes and tornados, provided that such events cannot either influenct. Lne system, or that the consequences of failure from such events is not important to safety; nevertheless, a clear demonstration of the effectiveness of a backup system and the timeliness of its implementation n.usi.

be provided; (b) the potential for localized pressures developing in areas which are not in contact with the drainage system, or in areas where pipes enter or exit the structural walls or mat foundations, must be considered.

(c) uncertainty in detecting operational problems and providing a suitable monitoring system must be considered; (d) the potential for piping fines and clogging of filter and drainage layers nust be considered; G

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(e) assurance must be provided that the system as proposed can be expected to reliably perform its function during the lifetime of the plant; and (f) where the system is safety-related, is not totally redundant or is not designed for all design basis events, provide the bases for a technical specification to assure that in the event of system failure, necessary remedial action can be implemented before design basis conditions are exceeded.

V.

SAR's (Std. Format & Content Information, Sections 2.4 & 2.b) for each of the plants with permanent dewatering systems should include the following information:

(a) Provide a description of the proposed dewatering system, including drawings showing the proposed locations of affected structures, components and features of the system.

Provide information related to the geotechnical and hydrologic design of all system components such as interceptors, drainage blankets, and pervious fills with descrip-tions of material source, gradation limits, material properties, special construc-tion features, and placement and quality control measures. bote structural, mechanical and electrical information needs described elsewhere.) Where the dewater-ing system is important to safety, provide a discussion of its expected functional rel i a bil i ty.

The discussion of the bases for reliability should include comparisons of proposed systems and components with the performance of existing and comparable systems and components for applications under site conditions similar to those proposed.

Where such information is unavailable or unfavorable, or the application (design and/or site) is unique, the unusual feature of the design should be supported by additional tests and analyses to demonstrate the conservative nature of the design.

In such cases the staff will meet with the applicant, on request, to establish the bases for such additional tests and analysas.

(b) Provide estimates, and their bases, for soil and rock permeabilities, total porosity, effective porosity (specific yield), storage coefficient and other related parameters used in the design of the dewatering system. In general, these site parameters should be determined utilizing field and, if necessary, laboratory tests of materials representative of the entire area of influence of the expected drawdown of the system.

Unless it can be substantiated that aquifer materials are essentially homogerieous, or that obviously conservative estimates have been used as design bases, prcvide pre-construction pumping tests and other in-situ tests performed to estimate the pertinent hydrologic parameters of the aquifer. Monitoring of pumping rates and flow patterns during dewatering for the construction excavation is also necessary tc verify assumed design bases relating tu such factors as permeability and aquifer continuity. In addition, the final design of the system should be based on construction dewatering data and related observations to assure that the values estimated from site exploration data are conservative. Lastly, the final design of the dewatering system and its hydrologic and geotechnical ope.ational monitoring program should be confirmed by construction excavation and dewatering information.

146 001 2.4.13-13 Rev. 1

If such information fails to support the conservatism of design information previously reviewed by the staff, the changed information should be reviewed under 10 CFR Part 50, Subsections 35(b) and 55(e)(1)(ii. ).

(c) Provide analyses and their bases for estimates of groundwater flow rates in the various parts of the permanent dewatering system, the area of influence of drawdown, and the shapes of phreatic surfaces to be expected during operation of the syster. The extent of influence of the draudown may be especially important if a natural or man-made water body af fects, or is affected by, the dewatering systems.

(d)

Pro..ue analyses, including their bases, to establish conservative estimates of the I

time available to mitigate the con, quences of system cegradation* that could cause j

groundwater levels to exceed design bases. Decument the measures that will be taken to either repair the system, or provice an alternate dewatering system that would become operational before the design basis groundwater level is exceeded.

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I (e) Provide both the design basis and normal operation groundwater levels for safety-related structures, systems and components. The design basis groundwater level is defined as the maximum groundwater level used in the design analjsis for dynamic or i

static loading conditions (whichever is being considered), and may be in excess of the elevation for wnicn the underdrain system is designed for norm 31 operation. This l

level should consider abnormal and rare events (such as an occurrence of the Safe Shutdown Earthquake (SSE), a failure of a circulating water system pipe, or a single railure within the system), which can cause f ailure or overloading of the permanent dewatering systes (f) A single failure of a critical active feature or ccmponent must be postulated during any design basis event. Unless it can be documented that the potential consequences of the failure will not result in Regulatory Guides 1.26 and 1.29 dose guidelines being exceeded, either (1) document by pertinent analyses that groundwater level recovery times are sufficient to allow other forms of dewatering to be implecented before the design basis groundwater level is exceeded, discuss the neasures to be implerented and equipment needed, and identify the amcunt of tipe required to acconplish each measure, or (2) design for all system components for all severe natural phenomena and events. For example, if the design basis groundwater level can be exceeded only as a result of a si l e nonseismically induced failure of any l

component or feature of the systcia, the staff may allow the design basis level of the dewatering system to be exceeded for a short period of time (say 2 or 3 days), provided that (1) effective alternate dewatering means can be irplemented within this time period, or that (2) it can be shown that Regulatory Guides 1.26 and 1.29 guidelines will not be exceeded by groundwater induced impairnents of safety-related structures, systems, er components.

• See (f) for considerations of differing system types.

146 002 Rev. 1 2.4.13-14

(g) Where appropriate, docu:nent the bases which assure the ability of the systen to with-stand variou3 natural and accidental phenorena such as earthquakes, tornadoes, surges, floods, and a single f ailure of a cor ponent feature of the 'ystem (such as a failure of any cooling water pipes penetrating, or in close proximity to, the outside walls of safety-related buildings where the groundwater level is controlled by the system) f An analysis of the consequences of pipe ruptures on the proposed underdrain syste:

"ust be provided, and should include considerations of postulated breaks in the l

Circulating systen pipes at, in, or nea r the dewa tering syster, t<uilding either irde-pendently of, or as a result of the SSE. Unless it can be doca; rented that the poten-tial consequences will not be serious enough to affect the safety of the plant to the f

extent that Regulatory Guides 1.26 and 1.29 guidelines could be exceeded, provide analyses to docu:'ent that (1) water releasrd from the pipt; break cannot physically i

I enter the dewatering system, or (2) if water enters the dewaterinq >yster, the syster w;11 not be overloaded by the increased flow such that the design basis groundwater level is subsequent h exceeded, i

(h) Stite the maximum groundwater level the plant structures can tolerate under various signific3nt loading conditions in the absence of the underdrain syster (i)

>rovide a description of the proposed groundwater level conitoring programs f or dewatering during plant construction and for permanent dewat aring during plant opera-

}

tien. Monitoring ;nforration re v ested includes (1) the general arrangemnt in plan and profile with approximate ele ntico of piezoreters and observation wells to be installed, (2) intended zone (s) of placerent, (3) ty; a(s) of oiezoreter (closed or open system),(4) streens and filter gradation descriptions, (5) crawings showing typical t

installations showing limits of filtur and seals, (6) observation schedules (initial and ti:re intervals f or sJbsequent readin]s), (7) plans for evaluation e recorded eata.

and (8) plans for dlarn devices to assure sufficient tir-e f or initiation of Corrective action. Provide a co:ritrent to Case the fin 3l design of the operational ronitoring program on data gathered during the construction ronitoring program (if construction experience shews the assucPd operational program bases to be nor ccnser /ative or impractical). Changes to the operational progra~ are to be documented in the FSAR.

l (k) Provide information regarding the atlet flew nonitoring program. The infornation required includes (1) the general location and type of flow reasure m nt device (s),

and (2) the observation plan and alarn precedure to identify unanticipated high or i

low flow in the system and the condition of *.he ef fluent.

i f

(1) For Ob reviews, but only if not previously roiewed by the staf f, provide (1) sub -

stantiation of assumed design bases using information gathered dur.ng de<.atering f or construction excavation, and (2) all other details of the dewatering systen design i

that implement design bases established during the CP review.

(m) For OL reviews, provide a Technical Specification for periods when the dewatering system raay te exposed to sources of water not considered in the design. An example of such a situation would be the excavation of surface seal raterial for repair of 2.4.13-15 Rev. 1 146 003

piping such that the underdrain would be exposed to direct surface runoff. In addi-tion, where the permanent dewatering systen is safety related, is not corpletely redundant, or is not designed for all design basis events, provide the bases for a technical specification with action levels, the remedial work required and the esti-nated time that it will take to accornplish the work, the sources, types of equipment and mar ower required and the availability of the above under potentially adve-se conc

[See Section V(f)].

O 146 004 Rev. 1 2.4.13-16