How difficult/easy are these majors and can you get a job in Sillicon Valley with these majors?
Environmental Engineering is offered at SCU as a focus within the Civil Engineering major and will be your most difficult option due to the math, science, and engineering course requirements, but you will really enjoy all of the professors, labs, and courses.
Environmental Science you will learn similar things as engineering, but your studies will be focused more on ecosystems and the environment instead of how to design infrastructure that is environmentally friendly.
Environmental Studies involves similar courses to science but with a much lighter science and math course load. This is the option for you if math and science are not your thing.
As for jobs you have many options from the water district, waste diversion, non-profits, etc. to choose from. Civil engineering does have their own career fair every fall (open to all students) so be on the lookout for that shortly after school starts because it never is too early to start looking for internship options. Also talk with professors as they often are looking for students to help them with their research. I personally am in civil engineering so I am biased towards the engineering route (Talk with Dr. Doyle if this interests you) but I have many friends who are doing great things with science and studies. Challenge yourself and follow the degree with the courses that interest you the most as it is easier to switch into an easier program than a harder one.
Also compare the degree requirements posted online to see course descriptions and flowcharts.
https://www.scu.edu/cas/ess/academic-programs/major/environmental-science-major/
https://www.scu.edu/cas/ess/academic-programs/major/environmental-studies-major/
Civil engineering:
https://www.scu.edu/media/school-of-engineering/pdfs/civil-engineering/Focus-Guide-2017-2018.pdf
https://www.scu.edu/media/school-of-engineering/pdfs/civil-engineering/Planning-Guide-2017-2018.pdf