Document: NUREG-0800
Document ID: 217f75d5-3db3-41ce-939d-8f7a5fcf0f68
Document Type: srp
Title: feet 0.76 m (2.5 ft).   The applicant in Section 2.4.12 of the PSAR has described the
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070262.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.5
CFR Part: 
CFR Title: 

Content:
or remedial action after detection of system degradation. III. Situations Identified During Previous Reviews Four general categories of situations have been identified during case reviews, as follows: (a) Estimating and Confirming Permeability Values 2.4.12-17 DRAFT Rev. 3 - April 1996 It is necessary to estimate the amount of water that will be collected so that system components such as strip drains, blanket drains, collector pipes, and pumps are adequately designed and sized. One of the most important and most difficult parameters to evaluate is the permeability of the soil and rock existing at a site. A permeability value could be affected significantly by conditions of concentrated flow along joints in fractured and weathered rocks, or within other aquifers affected by foundation excavation. In addition, geological and foundation conditions that were not detected in site explorations may affect flow conditions and cause the estimated permeability values and flow regimes to be substantially different from those assumed at the CP or early site permit56 preliminary design stage. These conditions are often first detected during construction dewatering. Therefore, we have required a commitment to consider construction excavation and dewatering data in the final design of underdrain systems. (See situation (d) below.) (b) Operational Monitoring Requirements To guard against system malfunctions and to assure ensure sufficient time is available for implementation of remedial measures before groundwater could rise to an unacceptable level, provisions must be made for early detection of system failures and contingency measures for these failures must be well defined prior to plant operation. Since drain systems are usually buried and concealed and there may be no direct way of inspecting them, reliance must be placed on piezometers, observation wells, manholes, and monitoring of collected water to detect problems or malfunctioning of the system. The details of an