Contemporaneous advice from Colorado was to use a well-graded gravel, not exceeding  and including 25–40% fines passing a  sieve, but not more than 5% passing a #10 (2.0-mm) sieve.
Contemporaneous guidance from Colorado advised utilizing a well-graded gravel, comprising no more than 25–40% fines passing through a sieve of that size, but not exceeding 5% passing through a #10 (2.0-mm) sieve.