NCT CIC described a heavy separation event on final to SFO noting the on-going confusion and interpretation of the new B757 separation standards.

Narrative

I was working CIC (Controller in Charge); listening to the Woodside Controller. I had the monitor ACP (audio control panel) set up to max range; on a mosaic feed. The CPC (Certified Professional Controller) had been working a very smooth final for about 20 minutes; rarely slowing aircraft below 180kts while giving SFO more than required spacing. The CPC slowed Air Carrier X to 160kts; I un-overlapped the data blocks and saw the preceding aircraft was a H/B767. I put on a 5 mile 'bat' and saw that Air Carrier X was close to or less than standard separation on the preceding Heavy. I walked over to the PRM scope and measured it at around 4.6 miles. The Controller thought he needed 4 miles. I told the Controller to send the B757 around. Recommendation; the CPC was confused by several memos that have been posted on B757 separation. A memo was put in the R & I last month which explained that if we were unsure of the weight class of B757s we were to treat them as a heavy if they were leading but as a large if they were trailing. Then a memo came out last week which clarified how we were to treat the 75s after April 8; 2010. The Controller thought you treated all B757s as heavies. To add to the confusion in the area each FLM (Flight Line Manager) treats the February memo differently. Nobody will define what makes us sure of the B757s weight class. Some of the FLMs do it one way; the others do it another.