Complex sentence: The trail crews work on major projects that are beyond the scope of a sister program that allows interested volunteers to "adopt" one of 78 maintenance sections along the trail, each averaging about eight miles long.
Split into simpler sentences: The trail crews work on major projects that are beyond the scope of its sister "Adopt-A-Trail" program. That program lets interested volunteers "adopt" one of 78 maintenance sections along the trail, each averaging about eight miles long.