What 'era' will your railroad originate from? Steam era, transition, modern, museum?
IOW, a more contemporary turntable/engine facility might be dressed out differently than as seen in photos from back when those features were in use literally 24/7, constantly repairing, maintaining equipment.
If you want your TT to be of the steam-into-transitional appearance, I'd suggest the surrounding ground would be virtually void of any vegetation, and have several inches thick of cinders...black or dark gray...for ground cover accumulation. In the steam era, those cinders were free. They found their way into everything, everywhere around engine facilities. I suppose as the transitional era...to diesels...occurred, the facilities were a bit 'cleaner'...but hardly squeaky so! So, maybe old cinders ended up being mingled with local soil...browns, muddy colored spots...which might have given way to spotty, weedy vegetation patches. Of course, as these facilities became less used or abandoned, Mother Nature probably took over even moreso. But, I'm sure your investment (looking good!!
) is going to be far from abandonment!!
I'm not a fan of bonding ballast along railroad ROW's for a variety of reasons. But, in the engine facility, I would definitely bond the ground cover, cinders, gravel, dirt,...whatever. Into wet paint (black or dark gray, perhaps) or using the wet water pre-wet followed by thinned white glue or matte medium.
If your facilities will be focused solely in the modern era...e.g., museum displaying restored, freshly painted equipment, lots of visitors, photogs, etc., etc., etc. (The turntable recently hauled from its former location to a newly purposed site, freshly painted, squeaky clean) you might want to use a 'cleaner' ground cover...light gray ballast/gravel...even large areas of poured concrete pavement more foot-friendly, easier to keep clean.
Spend some time searching the web for photos. There'll be a lot of Black/White from long ago eras...the heyday of turntables...so you'll have to use some judgement about the true coloring of ground cover. Kalmbach, and other publishers, have created some special books through the last few yearsthat focus on engine facilities, in which they may reference what you're seeking.
And when you're done with that next step...be sure to show us your results!
FWIW...
KD
