It would be a pretty tight schedule to fit all of the CE or MSE and political science required courses, and the breadth requirements for both Letters and Science and Engineering, into 8 semesters, unless you took overload schedules or come in with a lot of advanced credit.
In 8 semester, you will likely take about 32 courses or 120 to 128 units.
Political science requires 12 courses of about 48 units.
Materials science and engineering requires about 104 units.
Civil engineering requires about 95 units.
L&S breadth not fulfilled by the majors requires about 5 courses or 20 units. Engineering breadth, normally about 6 courses or 24 units, will be covered by overlap with L&S breadth and the political science major.
So political science and civil engineering would be about 153 units. It is fairly common to bypass a semester of English, one or two semesters of math, and a semester of chemistry with AP, IB, or A-level credit (or 3 or 4 courses or 12 to 16 units). But even that would mean needing about 137 units if you want to do it in 8 semesters, meaning a lot of 5 course semesters. L&S does let you have a ninth semester if you have two majors, but Engineering requires you to petition for a ninth semester in any case. If you do get a ninth semester, then it may be doable with relatively normal course loads with very careful schedule planning.
Since you are a spring admit, you do want to ask L&S and Engineering if a semester at Extension's Fall Program for Freshmen or community college counts as one of the semesters to the 8 or 9 semester limit. If it does not, then you can effectively almost gain a tenth semester if you choose your Fall Program for Freshmen or community college courses carefully*, further easing your schedule.
Of course, extra semesters will come at extra cost.
*Suggested courses if you attend Fall Program for Freshmen:
+English R1A, or R1B if you have credit for R1A (Engineering requires R1B regardless of AP/IB/A-level credit)
+Math 1A or 1B if you have not already completed freshman calculus (e.g. 5 on AP calculus BC, 5/6/7 on IB Math HL, or 1/2/3 on A-level Math H2/H2/Pure/Further)
+remaining courses in either political science, a history course usable for the political science major
, or which fulfill L&S breadth
in art and literature or biological science (which are not fulfilled by the majors)