Hank on 7/20/2018 7:51:28 PM:
I might suggest that you park at Chesterfield Valley Athletic complex, where you will access the Monarch Levee trail. Ride this a short distance west and cross the Missouri River on the protected bike lane. The bike path will take you to the Katy Trail at approximate mile 51. Then take the Katy west to Dutzow or Marthasville.
For the return trip, take the Katy Trail back to approximate mile 57, where you can pick up the Hamburg Trail. This amounts to a bit of a scenic detour from the Katy. Take the Hamburg to the Busch Greenway trail, Missouri Research Park trail, and then back to the Katy, where you will be very close to the Missouri River crossing at Chesterfield.
Happy trails!