CSLB Land Development Engineering common mistakes
CSLB Land Development Engineering · Understand the traps and how to avoid them.
Treating a preliminary grading concept as final and carrying cut/fill volumes straight into a bid or cost estimate without recomputing from the balance line.
Candidates learn the mass-haul diagram as a calculation exercise and skip the iteration step where the design grade is adjusted to balance earthwork on site.
What to do instead
Before using any volume, produce a mass-haul diagram, locate the balance point, and confirm the profile grade was set to minimize import/export; state the topsoil stripping and shrinkage/swell assumptions explicitly.
Routing storm drainage to a downstream point without checking whether the receiving system or channel has capacity for the developed peak flow.
Attention goes to sizing the on-site pipe network and inlet spread, and the discharge point is treated as an infinite sink.
What to do instead
Perform a downstream capacity check at every outfall, compare pre- and post-development peak flows at the point of discharge, and document any required detention or flow-control measure.
Using a single uniform runoff coefficient for the whole site instead of area-weighted values for pervious and impervious surfaces, and applying the rational method to a basin far larger than its valid range.
Shortcut formulas and textbook examples use one coefficient, and candidates do not check the method's applicability limits.
What to do instead
Compute area-weighted C values by surface type, and switch to a hydrograph or NRCS-type method when the contributing area or time of concentration exceeds the rational method's practical limits.
Drawing a street profile that meets centerline grade limits while ignoring the crown-to-flowline grade, curb return radii, and the cross-slope transition at intersections.
Candidates check the controlling numeric standard on the centerline and stop, missing the geometric details that govern drainage and vehicle path.
What to do instead
Check both centerline and edge-of-pavement grades, verify curb returns and intersection cross-slopes, and confirm the profile ties to the existing pavement at both ends.
Placing sediment control devices only at the project perimeter and omitting controls at the actual disturbed-area boundary and around inlets.
The plan is organized by property line rather than by drainage area, so small internal catchments drain untreated off site.
What to do instead
Delineate drainage areas on the ESC plan, place perimeter controls along the downgradient limit of disturbance, and protect every inlet with an appropriate device.
Designing a sanitary sewer with flat or negative slopes at the upstream end and relying on a cleanout or lift station to fix it later.
Candidates focus on the downstream trunk and treat the upper reach as a detail, forgetting the minimum self-cleansing velocity requirement.
What to do instead
Check every reach against minimum slope and velocity criteria for the pipe material and diameter, and verify the profile maintains cover and positive slope from the most upstream manhole.
Assuming a permit issued by one agency covers the project, without mapping which approvals come from the city, county, regional board, or state.
Candidates conflate the grading permit with the stormwater permit and the building permit, and do not trace each approval to its issuing authority.
What to do instead
Build a permit matrix listing each approval, its issuing agency, its trigger threshold, and its dependency on other approvals before submitting anything.
Sizing a water main on velocity alone and omitting fire flow and residual pressure checks at the most remote hydrant.
The pipe diameter is selected from a demand table and the hydraulic model is not run to the worst-case node.
What to do instead
Run the distribution model at peak-hour demand plus fire flow, confirm residual pressure at the critical node, and verify the main diameter and valving support that scenario.
Classifying a site as flat or gently sloping from a small-scale topographic map and skipping the field check of drainage patterns and existing swales.
Desktop review feels sufficient and the map contour interval hides local low points and flow paths.
What to do instead
Walk the site or review finer-interval survey data, mark existing drainage divides and swales, and confirm the assumed flow directions before laying out lots or grades.
Treating a geotechnical report as boilerplate and designing footings or pavement sections without using its bearing capacity, expansion potential, or corrosion recommendations.
The report is filed as a submittal attachment rather than read as a design input.
What to do instead
Extract the specific design values from the report into a summary table, apply them to foundation and pavement design, and flag any assumption the report contradicts.