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Western Dam Engineering 13 event these discussions need to be referred to later (i.e., in the unfortunate case of dispute). In addition to these regular meetings, it may be desirable to define a meeting schedule at the initiation of each new major work item of the project, so that specific requirements of that work item can be presented and discussed. Anticipating Delays in the Delivery of Specified Materials or Products Engineers need to be aware that specified pre- manufactured items, such as gates, valves, operators and other mechanical systems may not be readily available on the desired timeline during construction. To help overcome this problem, standard off-the-shelf items should be used in the design whenever possible, rather than special-production items. In any event, engineers should attempt to identify the availability of required/specified manufactured items early, and allow for long-lead items in the project and submittal schedules. Experience indicates, for example, that the delay between order and delivery of larger gate systems can be several months. Therefore, provisions should be made to require the ordering of these materials early in the construction project to ensure their availability when needed. As an alternate plan, the owner may wish to procure long lead items in advance of the project to be provided to the Contractor. Frequency/Location of Quality Control Testing of Earth Fills Quality Assurance and Quality Control (QA/QC) testing considerations for dam construction could easily fill a separate article and are dependent on the level of complexity of the project, confidence in the contractor, and variability of available materials. QC refers to the primary testing being conducted to validate the quality of the completed work. QA refers to testing performed to validate another party’s test results (i.e. an owner doing spot check test to verify contractor supplied testing). The assignment of responsibility for QC testing was discussed in the second article of this series. The type, frequency and location of testing on an embankment fill should be described under “QA/QC” in the Earthwork section of the specifications, stating who is responsible to perform the testing. This should be described even if the owner/engineer is performing the testing to notify the contractor of the testing plan. This section provides a brief discussion of some key considerations in selecting testing frequency for earthfill materials commonly used in dam construction. Numerous other QA/QC requirements typical of dam construction are not covered. These may include foundation preparation inspections, rebar inspections, concrete testing, grouting, etc. Low Permeability Core Materials Representative tests to verify specified earthfill properties, such as gradation, Atterberg limits, specific gravity, and Proctor density curves, should be performed during borrow area development or in the stockpile area prior to fill placement. Frequency of this testing may depend on the variability of the borrow source materials, but in general should be on the order of one test for every 10% of total required volume, with the exception of Proctor tests. A sufficient number of Proctor density curves should be obtained to represent the range of material available. Periodic one-point Proctor tests should be performed throughout material placement to verify the appropriate representative curve is being used for QC comparison. Frequency of compaction testing for critical earthfills, such as those being placed for low permeability cores, should be at least one per 2 to 5% of the total volume (e.g., if 20,000 cy total are being placed, a test every 500 cy) or at least one per day, per area of placement. Additional testing may be warranted (1) in areas where the degree of compaction is suspected of being inadequate; (2) in areas where small working areas lead to rapid fill placement; and (3) in areas requiring special compaction techniques. Granular Materials Compaction testing of granular materials (e.g., sand filters) is generally not performed during placement and instead QA/QC consists of visual inspection of the method-based compaction procedures (visual confirmation of number of passes of the specified equipment). Gradation testing is the most important for granular materials, and one test should be performed for every 2 to 5% of total placement volume for filter/drain materials and less frequently for shell and bedding materials. Testing should be