Which Standard Plans series cover drainage?

The 425 series covers structures and inlets; the 430 series covers pipe, culverts, and end treatments.

What is the most common drainage finding?

Schedule-to-plan mismatches — structure inverts, pipe lengths, or types that disagree between the schedule and the drawings.

Plan Review Checklists

Drainage Plan Review Checklist

Short answer

Reviewing drainage plans means checking the inlet and pipe schedules against the plans, that the hydraulic grade line works against the design tailwater, that outfalls are properly detailed and protected, and that the correct Standard Plans indexes are cited.

Drainage is where roadway design meets hydraulics — and where review findings carry the most water, literally. A structure count that does not match the schedule or an outfall with no erosion protection is the kind of miss that floods a road or erodes a slope.

The checklist below follows the water: inlets and pipes, hydraulics, outfalls, then the Standard Plans citations and erosion control.

What a review of drainage plans checks

Drainage structure schedule matches the plans — count, type, inverts, grate types.
Pipe schedule matches plan callouts — size, material, length, slope.
Hydraulic grade line clears the design tailwater and throat of each inlet.
Outfalls detailed with end treatments and erosion protection.
Standard Plans cited correctly — structures to the 425 series, pipe/end treatments to the 430 series.
Cross drains sized and located against the drainage map and basin areas.
Soil box and underdrain details shown where required.
Temporary and permanent erosion control covers all disturbed drainage paths.

Schedules vs plans

The structure schedule is the single most-checked table on drainage sheets — every structure on the plans should appear in it with matching inverts and types, and vice versa. Quantity-by-hand checking here is slow and error-prone, which is why it is the first place cross-referencing tools pay for themselves.

Hydraulics and outfalls

Check that the hydraulic grade line stays below grate elevations against the design tailwater, and that every outfall ends in a detail — an endwall, mitered end section, or rip-rap — with erosion control. Undetailed outfalls and floating tailwater assumptions are the recurring findings.

Standard Plans for drainage

Drainage structures and pipe end treatments live mostly in the 425 and 430 index series — citing the right index imports its Plan Content Requirements, which the library on this site lists per index.