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10/6/2015 9:57:30 AM
WESTERN DAM ENGINEERING NEWSLETTER, VOLUME 3, ISSUE 2, MAY 2015
SAFETY INSPECTIONS, SPILLWAYS, GEOLOGY 101, GOOD FOUNDATIONS
Document Type - Reference Library
Research, Thesis, Technical Publications
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<br /> <br /> <br /> <br />4 <br /> Hand level & rod, binoculars, probe (old ski pole) <br /> 100’ tape, 25’ tape, 6’ folding rule, measuring <br />wheel <br /> Flashlight and/or mirror <br /> Bucket and timer (to measure seepage rate) <br /> Stakes, flagging, poke stick <br /> Aerial photo of inspection area <br /> Rubber boots, snake chaps, sunscreen, insect <br />repellant, Bear Spray, First Aid Kit, sensible <br />clothing for weather <br /> Drinking water, food <br /> Rubber hammer <br /> Outlet inspection camera and sled, a Do-It- <br />Yourself (DIY) camera and sled was included in a <br />previous article titled, You Con-du-it; How to Fix a <br />Leaky Pipe <br /> Confined space entry equipment and paperwork <br /> An experienced yet open and creative mindset <br />Assemble Documentation – Documentation may <br />include a map or drawings of the dam and the <br />inspection form. Below is a list of some other <br />documentation that may be useful: <br /> List of potential failure modes <br /> Previous inspection checklists <br /> Old construction photos <br /> Plots of instrumentation data <br /> List of previous repairs or modifications and <br />repair recommendations <br /> The dam’s electronic project file (if available), <br />loaded on a tablet for reference, if needed <br /> Talk to last year’s inspector about problems or <br />issues and document. <br />General Inspection Guidance <br />The purpose of an inspection is to observe every part <br />of a dam and its appurtenant structures to identify <br />changes between inspections. Performing inspections <br />by the same person, during the same time of year <br />under the same type of reservoir loading has <br />advantages and disadvantages. For example, it is <br />important to inspect a dam when the reservoir is at a <br />similar level as the previous inspection to confirm <br />observed seepage is similar to previous inspections. <br />However, there are also advantages to inspecting the <br />dam during different seasons with different people and <br />during different reservoir levels. A late season <br />inspection often provides the inspector the <br />opportunity to see the upstream face of the dam…a <br />good opportunity to look for sinkholes, as described <br />below. If the dam has piezometers, arrangements <br />should be made to measure the static water level <br />during the inspection (preferably at full pool). The <br />inspector(s) may need to have a bit of flexibility in their <br />schedule(s) to see how the dam responds to varying or <br />similar conditions. <br />Terminology – Make sure to use accurate dam <br />terminology. It’s better to use upstream and <br />downstream, left and right – typically facing <br />downstream, instead of using compass directions. <br />Providing clear definitions for good, fair, and poor <br />condition is also important for future inspectors to <br />understand how the condition was assigned. <br />Use the SIMPLE Rule – For documenting defects, <br />Sketch the location of the defect, Measure the defect <br />(depth, width, length), Photograph the defect, Locate <br />the defect in reference to a known location (use <br />existing stationing or measure from a known feature <br />like the outlet works or spillway). <br />Photo Tips – Consistency: Take photos at the same <br />location and orientation as previous photos. Using a <br />scale in the photos helps document size and/or extent <br />of the feature being documented. Photos can be used <br />for comparison if conditions change. <br />Zigzag vs. Parallel – These are two methods primarily <br />used to inspect a dam: zigzag or parallel (Figure 1). <br />Typically, the zigzag method can be used on small <br />dams by inspectors who are physically fit. The parallel <br />method is useful for steep or rocky slopes. For both <br />methods, it is important to make sure that the <br />inspector stops periodically and turns 360˚ to observe <br />the slopes near and far for anything unusual before <br />continuing on the inspection. <br />Teamwork – If inspecting with two people, develop a <br />system so that one person is taking photos and <br />keeping the photo log and the other person is <br />measuring and documenting observed conditions. The <br />person with the gym membership can be the one to <br />hike up and down the slopes while the other walks <br />along the crest.
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