CSLB Land Development Engineering cheat sheet

General plan land-use designations set the allowed density and intensity; zoning must be consistent with the general plan.

Floor area ratio (FAR) = gross building floor area / net lot area; density is usually expressed as dwelling units per acre.

Net lot area excludes rights-of-way and often slopes or floodplain; gross area includes them.

Common residential densities: 1-8 du/ac low density, 8-20 medium, 20+ high density (varies by jurisdiction).

Setbacks, height limits, and lot coverage are separate zoning standards applied after the land-use designation.

Slope analysis: sites over 15% average slope typically trigger hillside ordinances and reduced density.

Parkland dedication is often 3-5 acres per 1,000 residents, or an in-lieu fee.

Access, frontage, and emergency-vehicle turnaround requirements constrain lot layout independent of zoning.

Slope (%) = (vertical rise / horizontal run) x 100.

Cut/fill volume between stations: average end area = (A1 + A2)/2 x L.

Prismoidal volume = L/6 x (A1 + 4Am + A2) for more accurate earthwork between varying sections.

Rational method peak flow: Q = CiA, with C runoff coefficient, i intensity (in/hr), A area (acres), Q in cfs.

Time of concentration is the travel time from the hydraulically most distant point to the design point.

Balancing cut and fill on site minimizes haul and import/export costs.

Minimum finished floor elevation is often set at or above the 100-year flood elevation plus freeboard.

Stormwater quality volume and hydromodification requirements often exceed simple peak-flow control.

Standard Proctor (ASTM D698) vs Modified Proctor (ASTM D1557): modified uses greater compactive effort and yields higher maximum dry density.

Relative compaction is field dry density divided by laboratory maximum dry density, expressed as a percentage.

Typical structural fill compaction is 90-95% relative compaction; trench backfill may require higher.

Expansive soils (high plasticity index) require overexcavation, lime treatment, or moisture conditioning.

Bearing capacity is reported by the geotechnical engineer; allowable values commonly range 1,500-4,000 psf for native soils.

Shrinkage and bulking factors convert in-place, loose, and compacted volumes for haul calculations.

Liquefaction risk depends on saturated loose granular soils, high groundwater, and seismic shaking.

Benching and keying into bedrock or competent native soil stabilize fill slopes.

Stopping sight distance = perception-reaction distance + braking distance.

Braking distance = V^2 / (2g(f + G)), with V in consistent units, f friction factor, G grade.

Superelevation counteracts centrifugal force on horizontal curves; e + f = V^2/(gR) in consistent units.

Minimum horizontal curve radius depends on design speed, superelevation, and side friction.

Vertical curves: K value = length of curve / algebraic grade change; K relates to stopping sight distance.

Typical local residential street: 50-60 ft right-of-way, 28-36 ft curb-to-curb, 25 mph design speed.

Cul-de-sac turnarounds commonly require 50-60 ft diameter right-of-way.

Crown and cross-slope (typically 2%) provide pavement drainage; curb-and-gutter conveys flow to inlets.

Hazen-Williams head loss: hf = 4.73 L Q^1.852 / (C^1.852 d^4.87) in US customary units.

C factors: new ductile iron ~130-140, older unlined cast iron ~80-100.

Minimum residential fire flow commonly 500-1,500 gpm depending on building type and separation.

Distribution systems should maintain minimum residual pressure of 20 psi under fire flow conditions.

Normal operating pressure typically 40-80 psi; above 80 psi pressure-reducing valves are used.

Water main minimum size is often 8 inches for residential and larger for commercial or looped systems.

Storage capacity must meet peak demand plus fire flow plus emergency reserve.

Backflow prevention (RPZ or double check) is required at cross-connections and irrigation services.

Manning's equation: Q = (1.486/n) A R^(2/3) S^(1/2) in US customary units.

Typical Manning n for vitrified clay or concrete sewer is 0.013; PVC ~0.010-0.013.

Minimum self-cleaning velocity is 2 ft/s; maximum is 10 ft/s to limit scour and sulfide generation.

Minimum sewer slope for 8-inch pipe is typically 0.40% (1/240).

Design flow is often peaking factor times average dry weather flow plus infiltration/inflow.

Sewer mains are typically designed to flow 50-75% full at peak design flow.

Manholes are required at grade changes, direction changes, and maximum spacing (often 300-400 ft).

Inverted siphons and force mains require special design for velocity and maintenance.

Rational method Q = CiA is valid for small urban catchments, generally under 200 acres.

Runoff coefficient C values: pavement 0.85-0.95, lawns 0.10-0.30, roofs 0.75-0.95.

Rainfall intensity i is selected for the design storm (e.g., 10-year, 25-year, 100-year) and time of concentration.

Manning's equation is used for pipe and channel capacity; full-flow capacity Q = (1.486/n) A R^(2/3) S^(1/2).

Detention storage routes peak outflow below pre-development levels using a stage-storage-discharge relationship.

100-year floodplain elevation is the base flood; freeboard of 1-2 ft is often required above it.

Culvert design considers inlet control, outlet control, and headwater limits.

Energy dissipators are required where high-velocity discharge could erode downstream channels.

The Revised Universal Soil Loss Equation (RUSLE): A = R K LS C P.

Sediment basins are sized to capture runoff from disturbed areas, often based on 2-year storm or specified volume.

Silt fence is placed on contour downslope of disturbance, with stakes and fabric keyed into the ground.

Construction sequencing limits the area and duration of exposed soil.

Stabilization (seeding, mulch, blankets) is required on disturbed areas within a short period after final grading.

Check dams reduce channel velocity and promote sediment deposition in swales and ditches.

Storm drain inlets must be protected with gravel bags, inserts, or filter fabric during construction.

Inspection and maintenance of BMPs is required after each rain event and at defined intervals.

CEQA (California) requires environmental review for discretionary projects; NEPA applies to federal actions.

Clean Water Act Section 404 permits from the USACE are required for discharge of dredged or fill material into waters of the US.

NPDES Construction General Permit requires a Storm Water Pollution Prevention Plan (SWPPP) for sites disturbing 1 acre or more.

Section 401 Water Quality Certification from the state is required for federal 404 permits.

California Fish and Game Code Section 1602 requires notification for streambed alteration.

Local grading permits typically require engineered plans, erosion control plans, and geotechnical reports.

Subdivision Map Act governs tentative and final maps; the Subdivision Map Act and local ordinances control lot creation.

Fire safe regulations and water supply requirements apply to new development in very high fire hazard severity zones.

Floor area ratio (FAR) = gross floor area / net lot area.

Density is usually measured in dwelling units per acre (du/ac).

General plan designations set allowable uses; zoning must be consistent with the general plan.

Parkland dedication is commonly 3-5 acres per 1,000 residents or an in-lieu fee.

Average slope over 15% often triggers hillside ordinances and reduced density.

Setbacks, height, and lot coverage are separate zoning standards from land-use designation.

Slope (%) = (rise / run) x 100.

Average end area volume = (A1 + A2)/2 x L.

Rational method: Q = CiA (Q in cfs, i in in/hr, A in acres).

Time of concentration is the travel time from the most hydraulically distant point to the design point.

Balancing cut and fill minimizes haul and import/export costs.

Minimum finished floor elevation is often set at the 100-year flood elevation plus freeboard.

Standard Proctor (ASTM D698) uses less compactive effort than Modified Proctor (ASTM D1557).

Relative compaction = field dry density / lab maximum dry density x 100%.

Structural fill is commonly specified at 90-95% relative compaction.

Expansive soils with high plasticity index require overexcavation, lime treatment, or moisture conditioning.

Allowable bearing capacity for native soils commonly ranges 1,500-4,000 psf.

Shrinkage and bulking factors convert in-place, loose, and compacted volumes for haul calculations.

Stopping sight distance = perception-reaction distance + braking distance.

Braking distance = V^2 / (2g(f + G)).

Superelevation and side friction jointly resist centrifugal force on horizontal curves.

Vertical curve K value = length of curve / algebraic grade change.

Typical local residential street: 50-60 ft right-of-way, 28-36 ft curb-to-curb.

Cul-de-sac turnarounds commonly require 50-60 ft diameter right-of-way.

Hazen-Williams head loss: hf = 4.73 L Q^1.852 / (C^1.852 d^4.87) in US customary units.

C factors: new ductile iron ~130-140, older unlined cast iron ~80-100.

Minimum residual pressure under fire flow is commonly 20 psi.

Normal operating pressure is typically 40-80 psi.

Water main minimum size is often 8 inches for residential systems.

Backflow prevention (RPZ or double check) is required at cross-connections.

Manning's equation: Q = (1.486/n) A R^(2/3) S^(1/2) in US customary units.

Minimum self-cleaning velocity is 2 ft/s; maximum is 10 ft/s.

Minimum slope for 8-inch sewer is typically 0.40%.

Sewer mains are typically designed to flow 50-75% full at peak design flow.

Manholes are required at grade and direction changes and at maximum spacing.

Design flow includes average dry weather flow, peaking factor, and infiltration/inflow.

Rational method is generally valid for urban catchments under about 200 acres.

Runoff coefficients: pavement 0.85-0.95, lawns 0.10-0.30, roofs 0.75-0.95.

Pipe full-flow capacity: Q = (1.486/n) A R^(2/3) S^(1/2).

Detention storage reduces peak outflow using a stage-storage-discharge relationship.

100-year floodplain is the base flood; freeboard of 1-2 ft is often required above it.

Culvert design considers inlet control, outlet control, and allowable headwater.

RUSLE: A = R K LS C P.

Silt fence is placed on contour downslope of disturbance and keyed into the ground.

Check dams reduce channel velocity and promote sediment deposition.

Storm drain inlets are protected with gravel bags, inserts, or filter fabric during construction.

Disturbed areas require stabilization (seeding, mulch, blankets) within a defined period after final grading.

BMPs must be inspected after each rain event and at defined intervals.

CEQA requires environmental review for discretionary projects in California; NEPA applies to federal actions.

Clean Water Act Section 404 permits from the USACE are required for fill into waters of the US.

NPDES Construction General Permit requires an SWPPP for sites disturbing 1 acre or more.

Section 401 Water Quality Certification from the state is required for federal 404 permits.

California Fish and Game Code Section 1602 requires notification for streambed alteration.

Local grading permits typically require engineered plans, erosion control plans, and geotechnical reports.