CES Cheat Sheet 2026

The 30 highest-yield CES facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Under the Clean Water Act Section 404 program, compensatory mitigation can be achieved through which mechanism? → Buying credits from an approved wetland mitigation bank
2. Why is source reduction important in waste management? → It reduces the volume and toxicity of waste produced
3. Which U.S. EPA guidance document provides the primary framework for conducting ecological risk assessments? → EPA/630/R-95/002F (Guidelines for ERA)
4. A stream classified as 'ephemeral' is characterized by which flow regime? → Flow only during and shortly after precipitation events
5. Under the Clean Air Act Section 112, facilities emitting hazardous air pollutants (HAPs) above major source thresholds must apply which standard? → Maximum Achievable Control Technology (MACT)
6. Which hydrological term describes the maximum rate at which soil can absorb water under given conditions? → Infiltration capacity
7. Which air pollutant is formed when nitrogen oxides and volatile organic compounds react in sunlight, contributing to urban smog? → Tropospheric ozone
8. Which agency enforces federal environmental laws in the U.S.? → Environmental Protection Agency
9. What does a surrogate spike recovery outside the acceptable window (e.g., 70–130%) indicate in an environmental sample? → Matrix interference or extraction/analytical error may have affected results
10. Which of the following is NOT a component of the Convention on Biological Diversity (CBD) three main objectives? → Prevention of invasive alien species introductions
11. A PAMS (Photochemical Assessment Monitoring Station) is specifically required to measure: → Ozone precursors including VOCs and NOx
12. A bioassessment using the Index of Biotic Integrity (IBI) compares sampled communities to: → Reference communities from least-disturbed sites in the same region
13. The Emergency Planning and Community Right-to-Know Act (EPCRA) Section 313 requires facilities to report releases of toxic chemicals through which mechanism? → Toxic Release Inventory (TRI) reporting to EPA
14. What does the term 'non-dispersive infrared (NDIR)' refer to in air quality monitoring? → A technique using infrared absorption to measure CO or CO2 concentrations
15. Hydrodynamic dispersion in a groundwater contaminant plume consists of: → Mechanical dispersion caused by velocity variations and molecular diffusion
16. What is the primary treatment goal of a constructed wetland used for wastewater polishing? → Reduction of pathogens and nutrients via biological and physical processes
17. In a municipal wastewater treatment plant, what is the function of the 'return activated sludge' (RAS) stream? → To recycle settled biomass from the secondary clarifier back to the aeration tank
18. Which statistical distribution is most commonly used to fit species sensitivity distributions (SSDs) for deriving water quality criteria? → Log-normal or log-logistic distribution
19. Which law governs hazardous waste management in the U.S.? → Resource Conservation and Recovery Act (RCRA)
20. What is eutrophication and what causes it? → Excessive nutrient enrichment of water bodies causing algal blooms and oxygen depletion
21. In a Risk-Based Corrective Action (RBCA) framework for contaminated sites, what is the primary basis for setting cleanup goals? → Acceptable risk to human health and the environment
22. Which term describes the restoration of ecosystem services and functions on severely degraded lands, such as abandoned mine sites? → Ecological restoration
23. Which biological process is responsible for converting trichloroethylene (TCE) to vinyl chloride under anaerobic conditions? → Reductive dechlorination
24. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) excludes which of the following from the definition of 'hazardous substance'? → Petroleum and crude oil (in their unrefined state)
25. Which provision of the Clean Air Act governs the accidental release prevention program for facilities handling extremely hazardous substances? → Section 112(r) Risk Management Program
26. Which soil property most strongly influences the retardation factor of organic contaminants migrating through the unsaturated zone? → Fraction of organic carbon (foc) and the contaminant's Koc value
27. Which statistical method is useful for interpreting environmental data? → Regression analysis
28. What is the role of GIS in environmental data analysis? → It performs spatial analysis and mapping
29. What is a biological indicator (bioindicator) species? → An organism whose presence, abundance, or condition reflects environmental quality
30. Which document must accompany a hazardous waste shipment from generator to treatment/disposal facility? → Uniform Hazardous Waste Manifest