Stormwater infiltration facilities help reduce the hydrologic impacts of residential and commercial development. The design of these facilities is particularly challenging because of large uncertainties associated with predictions of both short-term and long-term infiltration rates. This manual describes step-by-step procedures for collecting and analyzing data and information needed to size infiltration ponds. The procedures were developed recognizing that the performance of infiltration facilities depends upon a combination of nearsurface soil characteristics, subsurface geology, groundwater conditions, and pond geometry. The manual focuses on infiltration ponds located in unconsolidated geologic materials.