I clean it out ever 10K, (the one under the passenger seat of my '13 PIP) while it's on the ramps changing the oil. A bit over 9.5 pounds of crushed lava rock, what my county uses in some place on their non paved roads. I have some scrap EPDM rubber roofing material, and will use some to fabricate a diaper for the thing, to keep road gunk out of there, mud flaps are on order also.
