CPESC cheat sheet

USLE/RUSLE: A = R × K × LS × C × P, where R is rainfall erosivity, K soil erodibility, LS slope length-steepness, C cover-management, and P support practice.

Detachment, transport, and deposition are the three erosion phases; control works by reducing raindrop impact, slowing runoff, increasing infiltration, or covering soil.

Raindrop impact is the dominant detachment mechanism on bare construction soil; mulch or blankets intercept impact and reduce soil loss.

The LS factor is nonlinear: doubling slope length increases LS by roughly 1.4 to 1.5 times, while doubling steepness increases LS much more.

A bare-soil C factor is about 1.0; dense vegetation or anchored mulch can reduce C below 0.01, lowering predicted soil loss by two orders of magnitude.

Erosion begins when applied bed shear τ = γRS exceeds the soil or lining critical shear stress; vegetation and riprap raise critical shear.

Sheet flow needs surface cover or flow-spreading devices; concentrated flow needs channel linings, check dams, turf reinforcement mats, or riprap.

Temporary stabilization should be initiated promptly after disturbance and completed within permit deadlines; exposed inactive areas are highest risk.

Track walking, roughing, and contouring reduce runoff velocity and increase infiltration, but do not replace cover on steep or long slopes.

Silt fence is a perimeter sediment barrier for sheet flow; it is not a filter for concentrated flow in ditches or channels.

Install silt fence on the contour with a keyed, compacted trench and posts on the downhill side so water ponds and deposits sediment before release.

Sediment basins remove particles by gravity settling; efficiency rises with basin surface area, residence time, and a skimmer or slow dewatering outlet.

Check dams reduce velocity and grade in swales; space them so the crest of a downstream dam is near the toe elevation of the upstream dam.

Storm drain inlet protection must prevent sediment entry without causing unacceptable flooding; inspect and clean before sediment reaches the inlet throat.

Anionic polyacrylamide (PAM) flocculates suspended clay; it requires site-specific dosing and often gypsum where soils are sodic or high in sodium.

Turbidity is an optical measure and TSS is a gravimetric mass concentration; the two are related but not directly convertible without site calibration.

Vegetated filter strips rely on sheet flow, infiltration, and deposition; channelized flow or concentrated discharge bypasses their treatment capacity.

Sediment traps are small temporary basins for limited drainage areas; larger disturbed areas require sediment basins designed with adequate storage.

Rational method: Q = C i A; C is runoff coefficient, i is rainfall intensity for the time of concentration, and A is drainage area; it is limited to small catchments.

Kirpich time of concentration (English units): Tc = 0.0078 L^0.77 S^-0.385, with L in feet, S in ft/ft, and Tc in minutes.

Manning equation (English): V = (1.486/n) R^(2/3) S^(1/2), and Q = V A; R is hydraulic radius and S is energy slope.

Continuity: Q = V A; for a given discharge, narrowing a channel increases velocity and usually increases erosive shear.

Froude number Fr = V / sqrt(gD); Fr < 1 is subcritical, Fr = 1 critical, and Fr > 1 supercritical flow.

A hydraulic jump converts supercritical flow to subcritical flow and dissipates energy; it is often forced below culvert outlets and drop structures.

Average boundary shear stress τ = γ R S; compare it with permissible shear stress to select stable channel linings.

NRCS curve number runoff depth (inches): Q = (P − 0.2S)^2 / (P + 0.8S) for P > 0.2S, where S = 1000/CN − 10.

Design storms are selected by permit or local criteria using intensity-duration-frequency data; peak flow and runoff volume may require different storm durations.

USDA particle-size classes: clay < 0.002 mm, silt 0.002–0.05 mm, and sand 0.05–2.0 mm; texture is read from the soil texture triangle.

Cation exchange capacity (CEC) is highest in clay and organic matter; it increases retention of cations and some contaminants.

The soil erodibility factor K is generally highest for silt loam and fine sandy loam and lower for well-aggregated or very sandy soils.

Sodic soils have high sodium adsorption ratio or exchangeable sodium percentage; clay disperses, surface sealing occurs, and infiltration drops.

Gypsum (calcium sulfate) can improve sodic soil structure by supplying calcium that replaces sodium on exchange sites.

Bulk density is dry soil mass divided by total volume; compaction raises bulk density and lowers porosity, infiltration, and root growth.

Hydrologic soil groups range from A (high infiltration, low runoff) to D (low infiltration, high runoff); group D includes clays and shallow restrictive layers.

Stokes' law shows that larger and denser particles settle faster; clay-sized particles need flocculation or long residence time to settle.

Organic matter improves aggregation, infiltration, and water-holding capacity and lowers erodibility when maintained at adequate levels.

Clean Water Act Section 402 establishes the NPDES stormwater permit program; Section 404 regulates dredged or fill material in waters of the United States.

Section 401 water quality certification is required for federal permits that may discharge into waters of the United States; the state or tribe issues it.

Construction general permits typically cover disturbances of one acre or more, or smaller sites part of a common plan of development that totals one acre or more.

Permit coverage commonly requires a Notice of Intent before discharge and a Notice of Termination after final stabilization.

A SWPPP must identify pollutant sources, describe BMPs, and include inspection, maintenance, recordkeeping, and training requirements.

Municipal separate storm sewer system (MS4) permits require construction-site runoff controls as one minimum control measure.

Total maximum daily loads (TMDLs) can set wasteload allocations that impose additional numeric or practice-based limits on construction stormwater.

Local grading, erosion, and sediment control permits may be stricter than federal requirements; the project must satisfy all applicable authorities.

Endangered species and historic preservation reviews can add conditions or prohibitions to a stormwater permit.

A SWPPP is site-specific: it describes the site, construction activities, pollutant sources, selected BMPs, inspection schedule, and responsible parties.

Use a pollution-prevention hierarchy: eliminate exposure first, then control runoff, then trap sediment, and finally treat remaining discharge.

Concrete washout, fuel storage, sanitary facilities, and material stockpiles are common pollutant sources that need dedicated controls in the SWPPP.

The SWPPP must be updated when site conditions, construction sequencing, or BMPs change enough to affect pollutant discharges.

Inspection records should identify BMPs checked, observed deficiencies, corrective actions, and the date and time of completion.

Corrective actions should be initiated promptly and completed within the permit deadline; infeasible deadlines must be documented with a schedule.

Final stabilization means uniform perennial vegetation or equivalent permanent cover, not merely temporary mulch, unless the permit allows otherwise.

Post-construction controls may include detention, infiltration, filtration, or treatment practices to manage runoff after construction.

Keep the SWPPP and inspection records available on site or at a designated location as required by the permit.

Silt fence fabric should be buried in a keyed trench, attached securely to posts, and inspected for undercutting, tears, and sediment buildup.

Erosion control blankets are anchored in a terminal trench, overlapped according to manufacturer direction, and stapled to maintain soil contact.

Check dams should be keyed into channel banks, with a lower center to pass low flows and prevent bank erosion.

Sediment basins should be cleaned when accumulated sediment reaches the cleanout mark or roughly half the design storage volume.

Inspect discharge points, channels, slopes, and perimeter controls after every significant rain and at permit-specified routine intervals.

Document inspection findings with date, time, weather, location, photographs, and the name of the qualified inspector.

Replace or repair damaged BMPs before the next rain event when feasible; temporary repairs must be followed by permanent repairs.

Track walking and roughing can reduce runoff velocity, but they are not substitutes for mulch, blankets, or vegetation on erodible slopes.

Concrete washout liners should be inspected for leaks and removed before the basin overfills or before stormwater can contact the concrete.

Professionals must practice only within their competence and disclose limitations when a task exceeds their training or experience.

Monitoring and inspection records must be factual, legible, contemporaneous, and retained according to permit and contractual requirements.

Never backdate, alter, or fabricate field data; correct errors with a dated, signed note that preserves the original entry.

Disclose conflicts of interest and avoid accepting work that could impair independent professional judgment.

Photographic documentation is more defensible when it includes date, time, location, scale, and a clear subject description.

Sample handling should use clean containers, proper labels, preservation, chain-of-custody forms, and calibrated equipment.

Report observed noncompliance to the responsible party and, where required, to the permitting authority; do not conceal it.

CPESC certification is a professional credential; maintaining it requires adherence to ethical standards and continuing education.

Client confidentiality must be respected, but it does not justify withholding legally required environmental information.