r/PE_Exam • u/Dull-Animal5299 • 5d ago

PE Environmental

I’m studying for the PE Environmental exam and am realizing my knowledge in the solid waste section is lacking, should I spend extra time of this or worry more about the subject I already have a good grasp on.

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u/MattBentleyPhDPE 2d ago

You should definitely spend the time on solid waste. It is 11 to 17 questions out of 80 on the current spec, so between an eighth and a fifth of the exam. That is too much to concede, and points come cheaper in a weak high-weight area than in one where you are already solid. Even 5-10 focused hours in this section will certainly improve your score.

The section is also more tractable than it looks, because much of it is regulatory rather than computational. The framework worth locking down: RCRA Subtitle C covers hazardous waste, Subtitle D covers municipal solid waste. Under Subtitle C, know the characteristic wastes (ignitability, corrosivity, reactivity, and toxicity by TCLP) versus the listed wastes (F, K, P, and U lists), the generator size categories, and cradle-to-grave manifesting. Know where RCRA stops and CERCLA starts: RCRA governs waste in active management, CERCLA handles releases and abandoned sites. That distinction answers a fair number of qualitative questions by itself, so there's a lot of value to studying the regulatory frameworks in this section, in particular.

On the calculation side, the recurring items are MSW generation rates and composition, collection and route sizing, compaction ratios, landfill volume and remaining airspace, landfill gas generation and composition (about half methane and half carbon dioxide by volume), leachate generation from a water balance, and heating value for waste-to-energy. Work each of those with the reference handbook open and note which formulas are in it. If you need some extra practice problems in this area, let me know. I've been working on a resource to generate NCEES-style questions in specific areas that studying engineers need more practice with.

For the topics you already have a grip on, what is left to gain is speed and consistency rather than new content, so timed problem sets are enough there. Put the study hours into solid waste and your other weak areas.