The objective of these tests is to investigate the hydrological properties important to repository performance:

• Fracture permeability
• Effective porosity
• Characteristics of seepage into drift

The lower lithophysal unit has many fractures that are less than 1 meter in length, and lithophysal cavities ranging in size from 15 to 100 cm. Both the fracture and lithophysal cavity size and spacing vary significantly along the 5-meter drift walls over an 800-meter stretch within the same unit. Therefore tests are conducted in 20-m-long boreholes at regularly spaced locations along the drift irrespective of (and unbiased to) specific features from fractures and lithophysal cavities.

Systematic Approach

A systematic approach is taken in order to gain an understanding of the "average" and the "statistical distribution" of the hydrological characteristics for the spatially heterogeneous unit.

Equipment System

Two criteria govern the design of the equipment system: automation and mobility. Because the field-scale measurements involving liquid flow in unsaturated rocks require continuous testing for periods of weeks to months, the control of test equipment must be fully automated to allow the equipment system to be operated remotely with no human presence at the field site. The second criterion of mobility is achieved by designing all equipment needed for the systematic characterization as a complete unit to fit on flatbed rail carts. This way, the equipment system can be efficiently transported from one test station to another along the tunnel for testing in the regularly spaced low-angle boreholes.

The systematic testing equipment functions to distribute water at a specified rate along three isolated sections of the borehole and to capture any water that makes its way from the borehole through the rock formation as seepage into the drift. The key components of the system are the packer assembly, the water supply hardware, and the seepage capture system. The packer assembly isolates the 20-m long borehole into three 2-m-long unsealed sections into which water can be introduced at a specified rate. Due to the small-angle incline of the borehole, the vertical distance from the three unsealed zones to the drift crown ranges from about 1 to 5 meters. Seepage capture at each zone is by means of a horizontally mounted V-shaped PVC curtain that funnels water into twin collection bottles. The volume of water in each bottle is determined by a differential pressure transducer at the base of the bottle. Each delivery section in the borehole is supplied by its own water supply system consisting also of twin vertical cylindrical bottles to supply and measure the water that is delivered. The test functions (e.g., filling of supply bottle, pumping of water from supply bottle to the borehole, drainage of seepage collection bottle, and recording of data) are controlled by computer that can be operated remotely via network.

Schematic of the water collection system

Liquid Supply System	Data Acquisition System
Seepage Collection	Computer Control of Equipment

For more information, please contact:
Yvonne Tsang
Ph: 510-486-7047