  Giant Lya nebulae (or Lya "blobs") are likely sites of ongoing massive galaxy
formation, but the rarity of these powerful sources has made it difficult to
form a coherent picture of their properties, ionization mechanisms, and space
density. Systematic narrow-band Lya nebula surveys are ongoing, but the small
redshift range covered and the observational expense limit the comoving volume
that can be probed by even the largest of these surveys and pose a significant
problem when searching for such rare sources. We have developed a systematic
search technique designed to find large Lya nebulae at 2<z<3 within deep
broad-band imaging and have carried out a survey of the 9.4 square degree NOAO
Deep Wide-Field Survey (NDWFS) Bootes field. With a total survey comoving
volume of ~10^8 h^-3_70 Mpc^3, this is the largest volume survey for Lya
nebulae ever undertaken. In this first paper in the series, we present the
details of the survey design and a systematically-selected sample of 79
candidates, which includes one previously discovered Lya nebula.
