The PE Civil Water Resources & Environmental exam covers 80 questions across 12 knowledge areas over an 8-hour testing window. Since the April 2024 format change, the PE Civil exam is depth-only — there is no shared breadth section. You answer all 80 questions from WRE content. The only reference material allowed is the NCEES PE Civil Reference Handbook and the Ten States Standards, provided digitally on the exam computer.

PE Civil WRE Exam at a Glance

  • 80 questions in 8 hours (morning + afternoon sessions with lunch break)
  • 12 topic areas — Hydrology and Hydraulics are highest-weight
  • Computer-based with digital access to NCEES references and relevant standards
  • Most successful candidates study 200–400 hours over 3–4 months

What Does Each Topic Area Cover?

Below is a detailed breakdown of each knowledge area. Use the priority rankings to allocate your study time where it will earn the most points.

1. Project Sitework (~9–14 questions) — Priority: HIGH

The largest topic on the exam, covering site development from a water resources perspective.

Key subtopics: Cut/fill volume calculations, site grading for drainage, erosion and sediment control BMPs (silt fence, sediment basins, check dams), stormwater detention and retention basin sizing, construction dewatering, NPDES construction general permit requirements, SWPPP development.

Critical formulas:

  • Average end area method: V = L(A1 + A2) / 2
  • Modified Rational Method for detention: Vs = (Qi − Qo) × t
  • Revised Universal Soil Loss Equation: A = R × K × LS × C × P

2. Hydrology (~8–12 questions) — Priority: HIGH

Hydrology is the science of predicting how much water will arrive where and when. Expect problems requiring you to compute peak flows, develop hydrographs, and perform flood frequency analysis.

Key subtopics: Rational Method (Q = CiA), SCS/NRCS curve number method, time of concentration (Kirpich, TR-55), unit hydrograph development, IDF curve interpretation, Log-Pearson Type III flood frequency analysis, hydrograph routing (Muskingum method), return period/exceedance probability.

Critical formulas:

  • Rational Method: Q = CiA (Q in cfs, i in in/hr, A in acres)
  • SCS runoff: Q = (P − 0.2S)² / (P + 0.8S), where S = 1000/CN − 10
  • Log-Pearson Type III: log Q = mean(log Q) + K × std(log Q)
  • Exceedance probability: p = 1/T (T = return period in years)

3. Hydraulics — Closed Conduit (~7–11 questions) — Priority: HIGH

Everything that flows in a pressurized pipe. Heavily formula-driven and represents reliable scoring opportunities.

Key subtopics: Darcy-Weisbach equation, Hazen-Williams formula, Moody diagram, minor losses (K-method), pipe networks (Hardy Cross), pump system curves, NPSH, water hammer (Joukowski equation).

Critical formulas:

  • Darcy-Weisbach: hf = f(L/D)(V²/2g)
  • Hazen-Williams: V = k C R0.63 S0.54 (k = 1.318 US, 0.849 SI)
  • Pump affinity laws: Q∝N, H∝N², P∝N³
  • NPSHA = Patm/γ + zs − hf,s − Pv/γ
  • Water hammer: ΔP = ρaV

4. Hydraulics — Open Channel (~7–11 questions) — Priority: HIGH

Manning’s equation is the single most important formula on the entire exam. Open channel flow appears throughout WRE practice.

Key subtopics: Manning’s equation (normal depth), specific energy and critical depth, Froude number, hydraulic jump (conjugate depths), gradually varied flow profiles, weir equations, orifice flow, culvert hydraulics (inlet vs. outlet control).

Critical formulas:

  • Manning’s: Q = (1.486/n) A R2/3 S1/2 (US customary)
  • Critical depth (rectangular): yc = (q²/g)1/3
  • Froude number: Fr = V / (gy)1/2
  • Hydraulic jump: y2 = (y1/2)(−1 + (1 + 8Fr1²)1/2)
  • Sharp-crested weir: Q = Cd(2/3)(2g)1/2 L H3/2

5. Wastewater Collection and Treatment (~7–11 questions) — Priority: MEDIUM-HIGH

Tests both collection system hydraulics and treatment process design. The Ten States Standards for wastewater is a critical reference.

Key subtopics: Gravity sewer design (Manning’s for partially full pipes), lift station design, activated sludge process (F:M ratio, SRT, MLSS), BOD removal kinetics, secondary clarifier design, sludge handling, disinfection.

Critical formulas:

  • BOD remaining: Lt = L0 e−kt
  • F:M ratio = Q × S0 / (V × X)
  • SRT = VX / (QwXr + QeXe)
  • Mass loading: lb/day = 8.34 × Q(MGD) × C(mg/L)

6. Drinking Water Distribution and Treatment (~6–9 questions) — Priority: MEDIUM

The full water supply chain from source to tap. The Ten States Standards for water works is essential.

Key subtopics: Distribution system design (pressure requirements, fire flow), storage tank sizing, disinfection CT concept, coagulation/flocculation, sedimentation (Stokes’ law), rapid sand filtration, membrane filtration.

Critical formulas:

  • CT = concentration × contact time
  • Stokes’ settling: vs = g(ρp − ρw)d² / 18μ
  • Filter loading rate = Q / A (gpm/ft²)

7. Analysis and Design (~6–9 questions) — Priority: MEDIUM

An integrative topic combining engineering economics with WRE design.

Key subtopics: Present worth analysis, annual cost comparison, benefit-cost ratio, life-cycle cost analysis, risk assessment, design storm selection, alternatives analysis.

8. Surface Water and Groundwater Quality (~5–8 questions) — Priority: MEDIUM

Water quality science and regulatory framework.

Key subtopics: BOD/COD/TSS, dissolved oxygen modeling (Streeter-Phelps), nutrient cycles, mixing zone analysis, groundwater contaminant transport, Clean Water Act, Safe Drinking Water Act, TMDLs.

Critical formulas:

  • Streeter-Phelps DO sag equation
  • Dilution: Cmix = (Q1C1 + Q2C2) / (Q1 + Q2)

9. Materials (~4–6 questions) — Priority: LOW-MEDIUM

Key subtopics: Ductile iron pipe classes, PVC pipe (SDR, pressure classes), HDPE (DR ratings), reinforced concrete pipe, corrosion protection, joint types, bedding and backfill (ASTM classes).

10. Project Planning (~4–6 questions) — Priority: LOW-MEDIUM

Key subtopics: Water demand projections (per capita, fire flow, peaking factors), population forecasting methods, master planning, NPDES permits, Section 404 permits, NEPA, floodplain management (FEMA, NFIP).

11. Groundwater and Wells (~4–6 questions) — Priority: LOW-MEDIUM

Key subtopics: Darcy’s law, hydraulic conductivity, confined vs. unconfined aquifers, well hydraulics (Theis, Cooper-Jacob), specific capacity, pump test analysis.

Critical formulas:

  • Darcy’s law: Q = −KA(dh/dl)
  • Theis: s = (Q/4πT) W(u)
  • Cooper-Jacob: s = (2.303Q/4πT) log(2.25Tt/r²S)

12. Soil Mechanics (~3–5 questions) — Priority: LOW

Key subtopics: Soil classification (USCS, AASHTO), permeability testing, effective stress, seepage analysis (flow nets), consolidation theory, bearing capacity, slope stability for levees and embankments.

How Should You Structure a 16-Week Study Plan?

This timeline assumes 12–15 hours per week of focused study:

  • Weeks 1–2: Exam orientation. Download NCEES spec and PE Reference Handbook. Take a diagnostic quiz to identify baseline strengths and weaknesses.
  • Weeks 3–5: Hydrology and Open Channel Hydraulics. Master Manning’s equation, Rational Method, SCS method, critical/normal depth, culvert hydraulics.
  • Weeks 6–8: Closed Conduit Hydraulics and Project Sitework. Darcy-Weisbach, Hazen-Williams, pump curves, NPSH, stormwater detention, erosion control.
  • Weeks 9–11: Wastewater and Drinking Water Treatment. Activated sludge, BOD kinetics, clarifier design, CT disinfection, filtration. Study both Ten States Standards documents.
  • Weeks 12–13: Remaining topics: Analysis & Design, Water Quality, Materials, Planning, Groundwater, Soil Mechanics.
  • Weeks 14–15: Full-length practice exams. Take two timed 80-question exams. Review every missed question.
  • Week 16: Final review. Focus on your 3 weakest topics. Refresh handbook navigation. Rest before exam day.

What Other Resources Should You Use?

Continue your PE Civil WRE preparation:

How to Pass the PE Civil WRE Exam • PE Civil WRE Practice Problems • Best FE Exam Prep Books • 🔢 Calculator Guide • ✅ Exam Day Checklist

Frequently Asked Questions

How many questions are on the PE Civil WRE exam?

The PE Civil Water Resources and Environmental exam has 80 questions answered over 8 hours. It is split into morning and afternoon sessions of 40 questions each, with a one-hour lunch break between sessions.

What are the key topics on the PE Civil WRE exam?

The PE Civil WRE exam covers 12 topic areas. High-weight areas include Hydrology, Hydraulics (open channel and closed conduit), Water Treatment, and Wastewater Treatment. Stormwater management, groundwater, and environmental compliance are also significant.

How long should I study for the PE Civil WRE exam?

Plan for 200–400 hours over 3 to 4 months while working full-time. Focus on the high-weight hydrology and hydraulics topics first, then work through water and wastewater treatment, stormwater, and environmental compliance areas.