Union will play Valley, and Oamaru will face Albion in the Borton Cup semifinals after the final round-robin matches were completed at the weekend.
Valley, Glenavy, and St Kevin's were locked in a battle for fourth place, making every result crucial.
Waitaki Boys’ secured their first win of the season, upsetting Glenavy at Milner Park.
Jordan Horrell (72) and Harry Mavor (23) helped Waitaki post 167 in 44 overs, while Hamish McCulloch (four for 23) and Rodney van Leewuen (three for 30) led Glenavy's bowling.
McCulloch (43) gave Glenavy a strong start, but he got little support as they slumped to 114 for nine.
Jack Murphy (20 not out) and Sehu Nijam (13) put on 36 for the final wicket to inch Glenavy closer before Billy Wilson dismissed Nijam. Glenavy were all out for 150 in 33 overs.
Wilson (two for 40), Eric Strachan (three for 21), and Archie Haywood (three for 24) did the damage.
At Centennial Park, St Kevin's batted first, reaching 173 for eight in 50 overs.
Nick Kelly (34), Oscar Waldron (24), and Flynn Sanford (27 not out) led the scoring, while Lachlan Brookes (two for 19) and Quinn Wardle (two for 18) bowled well for Oamaru.
Oamaru lost Brookes early but dominated through Hunter Wardle (50) and Nick Johnston (63 not out), who put on a 96-run stand for the second wicket. Oamaru reached 176 for four in 43 overs.
Jacob Fowler (two for 25) was the best bowler for St Kevin’s.
At Weston, Valley faced third-placed Albion.
Jack Price (34) and Toby Growcott (54) set a solid foundation before Hunter Growcott (44) and George Franklin (26) pushed Valley to 218 in 49 overs.
Hayden Creedy (four for 37) and Aneesh Bose (three for 65) were Albion's best bowlers.
Albion collapsed to 25 for six inside 10 overs. Sabareesh Ramesh (46) fought back, but Albion was dismissed for 107 in 30 overs.
Jake Matthews (four for 34) and Reuben Simpson (two for 19) sealed Valley's win.
By Scott Cameron
