Micropiles are small diameter piles that can be installed in a variety of soils from non-cohesive, poorly-graded granular soils, to cohesive plastic clays. Also known as minipiles, pin piles, needle piles or root piles, micropiles can offer a viable alternative to conventional piling techniques, particularly in restricted access or low headroom situations. A micropile foundation system may be advantageous in areas where large boulders are sporadic in the subsurface, as the small diameter micropiles may be able to be installed around such boulders. Micropiles are installed using water flush rotary drilling or rotary percussion drilling techniques. Measuring between 6 and 12 inches in diameter, micropiles consistently achieve capacities of 20 to 100 tons, with special installations up to 200 tons. Micropile drilling methods generate minimal disturbance or vibration to adjacent structures, making micropiles an excellent underpinning alternative.