PODED-G General Guideline for Drilling and Blasting Coral Reef for Armor Stone at Enewetok Atoll, M,I. 5. Horizontal survey controls are necessary for locating exploratory Paths and positioning exploratory and shot holes to be drilled to measure and map the coral reef crust thickness and hardness. Exploratory paths (lines) can be laid out on about 100 feet centers normal to dry land or reef front. Locate preliminary investigative shot holes on approxi- mately 50 centers. Decrease the distance between shot holes if correla- tion between holes is not apparent. E. INVESTIGATIVE OBSERVATIONS AND MEASUREMENTS. 1, Thickness of reef crust can be determined by exploratory and shot holes by measuring the depth where the hole caves when the bit is removed. Caving normally is where underlying loose sand prevents deepening by a percussion drill due to the increase enecgy needed to blow the hole clean, 2. Hardness of the reef crust will vary with the sound and response of the drill. 3. Timing the rate of drilling and comparing with investigative rock excavation will provide experience in siting a quarry area. Strips painted on drill steel aids in making estimates of drilling rates. Comparing the rates of drilling for bit sizes 2", 3' and 4" can be used to plan drilling and blasting arrays. 4. Uniformity in drilling operations is necessary when comparing results. To minimize variations in percussion drilling the compressor must maintain a constant CFM volume at controlled pressure and the sequence of drilling and blowing should be nearly uniforn. 5. The success of observations and measurements depends on the experience and ability of the drill operator. F, BLASTING DESIGN ~ l. Criteria for blasting design can be found in TM 5-332 ~ Pits and Quarries, EM 1110-2-3800 - Systematic Drilling and Blasting for Surface Excavation. 2. layer. Shot hole arrays will depend on the thickness of the reef crust Vary hole spacing and powder-rcok ratio as necessary to obtain desired results. (The anticipated yield is about 15%). 3. The following general criteria will aid in planning initial test blasting: