USING 21 cm ABSORPTION IN SMALL IMPACT PARAMETER GALAXY-QUASAR PAIRS TO PROBE LOW-REDSHIFT DAMPED AND SUB-DAMPED Lyα SYSTEMSBased on observations with (1) the telescopes of the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc., (2) the SOAR Telescope, a joint project of Conselho Nacional de Pesquisas Cientificas e Tecnoligicas CNPq-Brazil, The University of North Carolina at Chapel Hill, Michigan State University, and the National Optical Astronomy Observatory, and (3) the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.