The cache is not at the posted coordinates.
To obtain the needed information, you can either follow the steps below, or complete the Mill Creek Wetlands Adventure Lab (see note for AL users below).
Mill Creek Wetlands is a gorgeous man-made wetlands cutting the middle out of what used to be Chino Corona Road. It acts both as a habitat for wild and endangered species, and a natural water treatment facility for the Cucamonga Creek, and gives us some gorgeous walking trails as well. This is the bonus for the adventure lab, but if you don't do adventure labs, I've borrowed Webfoot's idea from his nearby Historic Euclid Avenue Adventure Lab Bonus GC8MMG7 and created an alternate, AL-esque puzzle, contained entirely within a standard puzzle cache instead!
Each question will provide you with a single word answer. Take these answers and plug them into certitude, all lowercase, no spaces or punctuation.
1. N 33° 56.750 W 117° 37.206 First bolded word in step 1: _________ structure. (9 letters)
2. N 33° 56.686 W 117° 37.239 The second nearby tribe listed at the top of the sign. (7 letters)
3. N 33° 56.563 W 117° 37.279 The color of the willow next to the Least Bell's Vireo. (5 letters)
4. N 33° 56.701 W 117° 37.103 Fifth heavy metal listed that is removed by rush. (4 letters)
If you're coming here from the AL, here's what you'll need:
N 33° 56.ABC' W 117° 37.1DE'
Use the geocaching.com checker for AL users, certitude doesn't let you have multiple correct answers.
You can validate your puzzle solution with certitude.