PRC Controller working one of the two Local Control positions described an unsafe situation when straight in approaches were approved by the second Local creating a conflict; reporter suggesting this facility practice was problematic.

Narrative

I was working Local 1 on our most complex Runway 30. Training was going on at the Local 2 feeder position. My downwind traffic had to extend for large volumes of arrivals and also had to climb for terrain. The Local 2 feeder position asked for; and the previous controller had approved; straight-ins at or above 6;500 feet. The CIC alerted me and the Local 2 trainer to the fact that I had Aircraft X turning base to a five mile final at 6;500 and the local 2 feeder was talking to an aircraft approaching a five mile final at 6;500 that would be traffic for my aircraft. The Local 2 controller was able to turn his straight in away from Aircraft X to avoid a potential mid-air. Recommendation; it becomes almost automatic now at our facility to APREQ a blanket approval for straight-in entries at or above 6;500 feet. We have so many people in training; with no experience or knowledge; that this practice adds complexity and reduces safety. Our trainers should teach the Local 2 Controllers to follow the standard operating procedures which require all aircraft to be sequenced to the 45 degree entry. The Trainer at Local 2 should have realized what was transpiring before the CIC alerted us to a problem. The trainer is a part time employee and I don't think he is as proficient as he should be and probably shouldn't be training.