| Use: | Monitoring well installation in moderately deep to deep holes where contamination by drilling fluids is not a concern. Technique provides a very flexible and rapid drilling method for a wide range of borehole diameters in consolidated and unconsolidated materials. |
Description:
Direct mud rotary drilling uses a rotating drill pipe with a hard-tooled drill bit attached at the bottom. Fluid is forced down through the drill pipe and then back up the borehole. It is then discharged at the surface through a pipe or ditch into a sedimentation tank, pond, or pit. As the cuttings settle in the pond, the fluid overflows into a suction pit, where a pump recirculates the fluid back through the drill rods. The drilling fluid serves to: (1) cool and lubricate the bit, (2) stabilize the borehole wall, and (3) prevent the inflow of formation fluids, thus minimizing cross contamination of aquifers. Casing is not required during drilling. When unconsolidated materials overlie a bedrock aquifer, mud rotary can be used to drill the bedrock, the hole can be cased, and a less intrusive drilling method (such as air rotary) can be used to complete the well.
Reverse circulation rotary drilling is a variant of the mud rotary method in which drilling fluid flows from the mud pit down the borehole outside the drill rods and passes upward through the bit. Cuttings are carried into the drill rods and discharged back into the mud pit. Equipment is similar to direct mud rotary except that most pieces of equipment are larger.
Analytes:
| 1. Non-Halogenated VOCs | 5. PAHs | 9. Inorganics |
| 2. Non-Halogenated SVOCs | 6. Pesticides/Herbicides | 10. Explosives |
| 3. Halogenated VOCs | 7. Metals | 11. TPHs |
| 4. Halogenated SVOCs | 8. Radionuclides |
Media:
| Soil: | Ground Water: | Surface Water: | Gas/Air: |
| MODERATE | MINIMUM | Not Applicable | MAXIMUM |
Samples can be obtained directly from the circulated fluid by placing a sample collection device, such as a shale shaker, in the discharge flow before the settling pit. For more accurate sampling, the flow of drilling fluid can be interrupted and a split-spoon, thin-wall, or consolidated core sampler inserted down the drilling rod with the sample taken ahead of the bit.
| Maximum Depth: | >1000 feet is the usual limit, but greater depths are possible depending on the borehole diameter, mud pump capacity, and ability to maintain circulation. |
| Production Rate: | Sample is available after a short amount of time. |
| Investigation Derived Waste Volume: | Large volume of waste. |
| Technology Status: | Commercially available and routinely used field technology. |
| Certification/Verification: | Technology has not participated in CalEPA certification and/or CSCT verification program. |
| Relative Cost per Sample: | Mid-range expense. Increases with difficult drilling consolidated and clay layers. An experienced driller is required along with additional equipment. |
Limitations:
ASTM Standards:
| D 5783 - 95 | Guide for Use of Direct Rotary Drilling with Water-Based Drilling Fluid for Geoenvironmental Exploration and Installation of Subsurface Water-Quality Monitoring Devices. |
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