Residential Development: 14 Issues Found in Pre-Permit Review
AI plan checking uncovered 14 issues including critical retention pond sizing discrepancies, retaining wall height conflicts, and drainage calculation errors before permit submission.
The Project
A residential development project requiring comprehensive civil engineering design including retention/drainage pond systems, erosion control, retaining walls, and site grading. The project included multiple building types (treehouses, A-frames, cottages) and required strict compliance with drainage design standards. Critical issues included major discrepancies between engineering report calculations and construction drawings, particularly around retention pond sizing (ranging from 700 sf to 9,300 sf across different documents) and storage volumes.
Critical Findings (3)
A1.02a (Site Plan) labels the retaining wall at/near the drainage pond spillway as "12" WIDE X 2' RETAINING WALL." The Drainage Pond detail on A1.02a labels the spillway retaining wall as "12" WIDE X 42" RETAINING WALL." A1.02b (Erosion Control) shows the spillway retaining wall as 42" as well. This creates an inconsistency for the spillway retaining wall height (2' vs 42").
The Engineering Report uses 9,300 sf for the retention pond calculation, which is ten times larger than the '930 SF' listed on the Drainage Pond detail in the drawings. Additionally, the report summary lists the pond area as 700 sf, creating a three-way conflict.
The Watershed Site Plan (A1.02a) labels the pond area as 5,000 SF total, while the Drainage Pond Detail (2/A1.02a) defines the total pond area as 930 SF. This is a discrepancy of roughly 5.4x.
High Priority Findings (6 Total)
The Engineering Report states a retention pond size and provided storage that do not match the pond detail on the Watershed Site Plan. The report lists the pond as "9,300sf" and indicates "(1,800 cf Provided)", while the A1.02a pond detail shows "930 SF TOTAL POND" and includes a storage callout of "2800 CF".
The silt fence detail on sheet A1.02b contains conflicting information. Note 2 states posts should be 'spaced not more than 8 feet on center.' However, the graphic callout on the same detail states 'STEEL FENCE POST MAX. 6' SPACING.' This is a 2-foot discrepancy in maximum allowable spacing.
The unit schedule on the Watershed Site Plan (A1.02a) shows: Treehouses - 6 units sleeping 6 each (36 total), A-Frame - 1 unit sleeping 4 (4 total), and TC (Overseer Cottage) - 2 units sleeping 4(6) each (8 (12) total). The unit schedule on the Erosion Control sheet (A1.02b) shows: Treehouses - 5 units sleeping 5 each (25 total), A-Frame - 2 units sleeping 4 each (8 total), and TC5 (Oversize Cottage) - 1 unit sleeping 6(8) (6 (8) total).
The Engineering Report states the provided pond volume is 1,800 cf. However, the Drainage Pond detail on Sheet A1.02a shows volume callouts of 2800 CF and 1500 CF, which conflict with the report's stated provided volume.
The drainage pond sizing is inconsistent between the drawings and the engineering report. Sheet A1.02a (Detail 2) specifies a '930 SF TOTAL POND', whereas the Engineering Report calculations cite a 'Retention Pond' area of '9,300sf' and its summary list specifies 'Pond: 700sf'. Additionally, the storage volume provided in the report is '1,800 cf', but the drawing detail contains labels for '2800 CF', '1500 CF', and '600 CF'.
There is a conflict between the Engineering Report and the Construction Drawings regarding the pond depth and associated retaining wall height. The Engineering Report (Ref 3) calculates for a 36" (3') pond depth. However, the Watershed Site Plan (A1.02a) and Detail 2 (A1.02a) specifically call for a '12" WIDE X 42"' (3.5') retaining wall at the pond location. Additionally, other areas of the site plan specify 4' tall walls, creating ambiguity if a uniform height was intended or if the 36" calculation is outdated.
Issue Categories
Civil
Retention pond sizing, drainage calculations, erosion control, retaining walls, and civil engineering coordination
Structural
Retaining wall heights, structural coordination, and structural code compliance
Architectural
Unit schedules, building counts, and architectural coordination
Document Coordination
Drawing vs engineering report conflicts, contradictory requirements, and document coordination issues
Value Delivered
"Finding 14 issues—including 3 critical permit blockers—before submission saved us from weeks of delays, permit rejections, and costly field corrections. The retention pond sizing discrepancies (ranging from 700 sf to 9,300 sf across different documents) would have been an instant plan check rejection. The retaining wall height conflicts and drainage volume discrepancies would have caused major construction problems and potential flooding issues."
— Project Team, Residential Development