How Measured



11. Leachate hydraulic head on the primary liner

Vibrating wire piezometers and liquid-level measurements in sumps using drop-down resistivity probes

Assess the performance of the leachate collection and removal system

Measurements beyond sumps are rare, although vibrating wire piezometers on the liner have performed well in some cases

12. Volumetric seepage in the LCRS and LDS

Pumped volume or flow meter, depending on the system

Evaluate the effectiveness of LCRS and the primary liner system

Can provide an indirect assessment of cover performance, LCRS efficiency, liner integrity, and development of clogging

13. LCRS continuity

Dye testing and pumping tests

Indicates any clogging in the LCRS

Rarely used in practice

14. Leachate constituent concentrations

Chemical analysis of leachate samples for organic and inorganic constituents

Identify constituents of concern and evaluate the potential for mass flux of contaminants and degradation of the barrier system (e.g., hydraulic conductivity)

May be misleading (with respect to constituents of concern) due to chemical transformation within the liner system and subgrade

15. Geomembrane continuity

Electrical leak detection using conductive geomembranes or wire grids placed below membranes

Establish the location and frequency of defects in geomembranes

Typically used only in CQA, as the measuring techniques are ineffective when soil or waste cover on the geomembrane exceeds a meter or more

16. Settlement (surface and at depth)

Survey markers, settlement forks, extensometers

Determine settlement of cover systems

Total and differential settlements are required to assess cover performance

17. Temperature of soil and geosynthetic barrier components


Estimate the service life of geosynthetics, determine thermal gradients, and conduct heat and moisture transfer analysis

Historically, rarely used in practice, but some recently reported field studies indicate measurement is important

18. Vertical barrier continuity

Geophysical methods, field measurements of hydraulic conductivity of slurry walls and of heads and constituent concentrations inboard and outboard of the wall

Identify defects in vertical barriers

Geophysical methods have potential but are rarely used in practice; hydraulic conductivity measurements are employed primarily for CQA via tests on field-recovered samples

19. Vertical barrier leak detection

Wells, drainage layers installed along the midsection of vertical barriers

Determine the amount of leakage and thus the performance of vertical walls

Results of questionable reliability; rarely used in practice; requires installation of the collection and removal system in the barrier; integrity of half of the thickness of the barrier is assessed

20. Radioisotope concentrations

Total radiation dose

Identify releases and establish concentration gradients

Primarily of concern for low-level radioactive waste

NOTES: CQA = construction quality assurance; EM = electromagnetic; GPR = ground-penetrating radar; LCRS = leachate collection and removal system; LDS = leak detection system; TDR = time domain reflectometry.

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