Kalen and Niall are almost certainly right in their diagnosis. Apparently, these holes have been abandoned for at least 35 years according to one of our members of staff who remembers playing out there as a kid. So, somewhere else on the course is a newer, non Colt hole...or perhaps these hole corridors are part of an abandoned extension scheme? Hopefully someone might know. From Google Earth my guess would be that 9 and 10 have been split in two at some time in the past to form a par 5, Par 3 combo, but maybe someone here knows different.
I'll try to run down and get some photos one evening.