I would suggest turning the totes so that they slide in the short direction for a few reasons.
1. Totes can hold a ton of stuff, enough that they can be too heavy to carry if full in some cases. A fully loaded tote on the 3rd or 2nd row fully extended would be pretty scary so you are going to have to enforce strict weight limits on them to prevent tipping or drawer failure. Weight limits can be hard if they are not able to be removed for a rough estimate of the weight.
2. Because of the weight issue you are going to have to use pretty strong drawer slides along with a good factor of safety in case someone pushes down on an open drawer. With 9 sets of 32in extension drawer slides you are looking at around $500 in just the slides for the totes. If you slide in the short direction you can use less expensive shorter slides and probably skimp on the safety factor a bit because the worst case moment arm is shorter.
3. Total pit space. If they are lined up long ways it makes it about 7.5ft long, perfect for the entire side of a pit. It is also only ~20in deep leaving you a ~6x8ft pit. In the long pull orientation it leaves a ~5x8ft pit with 3ft square dead space next to it that can only really be used for more storage. The worst part about this orientation is when you want to open a drawer. Since the lids require you slide them all the way out you need to slide it ~60 inches into the pit from the back of the cart leaving you only 36 inches left from the opposite wall. A standard 28in square robot with 4 inch thick bumpers on either side is barely going to fit in the area thats left requiring you to move the robot and/or a pit members every single time you want to open a drawer. MOE has drawers that extend out a foot and even that can be tight when the robot is surrounded by people working.
