Irrigation Boulder county colorado Construction of first ditch,1859. Hall.History .Colo. v.3 p.294 Report,nature & production of soil;methods ofj irrgation,1871.Hall.Hist.Colo;v.1 p.547 Mountain streams distribute vegetable mold over fields.Hall.Hist.Colo. v.1 p.548 Chicago-Colo.colony s plans,for irrigation, 1872. Hall.Hist.Colo. v.3 p.341 Highland hake ditch constructed near Longmont, 1872. Hall.Hist.Colo. v.3 p.301