▁Agricult ural ▁activities ▁that ▁cause ▁non - point ▁source ▁poll ution ▁include : ▁ ▁Po or ly ▁managed ▁animal ▁feed ing ▁operations ▁ ▁Over gra zing ▁ ▁Over working ▁the ▁land ▁( for ▁example , ▁p low ing ▁too ▁often ) ▁ ▁Po or ly ▁managed ▁and ▁in effect ive ▁application ▁of ▁p estic ides , ▁ir rig ation ▁water , ▁and ▁fert il izer . ▁ ▁B acter ia ▁and ▁nit r ates : ▁These ▁cont amin ants ▁are ▁found ▁in ▁human ▁and ▁animal ▁was tes . ▁Se ptic ▁t anks ▁or ▁large ▁numbers ▁of ▁farm ▁animals ▁can ▁also ▁cause ▁b acter ial ▁and ▁nit rate ▁poll ution . ▁Both ▁sept ic ▁systems ▁and ▁animal ▁man ures ▁must ▁be ▁carefully ▁managed ▁to ▁prevent ▁private ▁well ▁cont am ination . ▁ ▁Con cent r ated ▁animal ▁feed ing ▁operations ▁( C AF Os ): ▁The ▁number ▁of ▁C AF Os , ▁often ▁called ▁" factory ▁far ms ," ▁is ▁growing . ▁On ▁these ▁far ms ▁thousands ▁of ▁animals ▁are ▁raised ▁in ▁a ▁small ▁space . ▁The ▁large ▁amounts ▁of ▁animal ▁was tes / man ures ▁from ▁these ▁far ms ▁can ▁threaten ▁water ▁supplies . ▁Str ict ▁and ▁careful ▁man ure ▁management ▁is ▁needed ▁to ▁prevent ▁path ogen ▁and ▁nut ri ent ▁problems ▁in ▁private ▁well s . ▁Sal ts ▁from ▁high ▁levels ▁of ▁man ures ▁can ▁also ▁poll ute ▁ground ▁water . ▁ ▁He avy ▁met als : ▁Activ ities ▁such ▁as ▁min ing ▁and ▁construction ▁can ▁release ▁large ▁amounts ▁of ▁heavy ▁met