10.3 Civil Plan Sets, Legends, Phased Sequencing, and Living Site Maps

Navigating a Civil Engineering and Stormwater Plan Set

A professional civil construction and stormwater plan set (covered in the CESSWI General Principles Review Manual, Chapter 11, Sections 11.5–11.6) is organized in a standardized sequence of drawing sheets:

1. Title / Cover Sheet (G-001 or C-001)

The Title Sheet serves as the legal and administrative index for the entire project:

• Project Identification & Vicinity Map: Displays the official project title, street address, latitude/longitude coordinates, and a regional vicinity/location map showing surrounding roads and receiving streams.
• Sheet Index: A numbered directory listing every drawing sheet in the plan set.
• Professional Stamps and Contacts: Names, addresses, and 24-hour phone numbers of the property owner/developer and civil engineering firm, bearing the signed seal/stamp of the licensed Professional Engineer (PE), Landscape Architect (LA), or CPESC.
• General Notes & Benchmark Datum: Mandatory construction notes, underground utility locate callouts (Call 811 before digging), and the vertical elevation reference datum—most commonly NAVD 88 (North American Vertical Datum of 1988) or NGVD 29 (National Geodetic Vertical Datum of 1929)—along with the physical location and elevation of the on-site Temporary Benchmark (TBM).

2. Existing Conditions, Topographic, and Demolition Sheet (C-100)

Depicts the pre-disturbance landscape before construction equipment alters the site:

• Pre-Development Topography: Dashed contour lines showing existing ground elevations and natural overland drainage pathways.
• Protected Environmental Features: Delineated wetland boundaries, perennial/intermittent streams, Ordinary High Water Marks (OHWM), 100-year floodplains, mandatory $50\text{-foot}$ or $100\text{-foot}$ natural buffers, and heritage trees or woodland stands slated for preservation.
• Demolition Scope: Existing buildings, asphalt parking lots, culverts, and underground utilities scheduled to be demolished, capped, or removed.

3. Grading and Drainage Plan (C-200 / C-300)

Illustrates the engineered three-dimensional finished earthwork and permanent storm sewer infrastructure:

• Proposed Finished Contours & Slopes: Solid contour lines, engineered cut/fill embankments (labeled with horizontal-to-vertical ratios such as $3\text{H}:1\text{V}$), and swale centerlines.
• Critical Spot Elevations: Precise decimal elevations (to the nearest $0.01\text{ ft}$) called out at structural grade breaks:
  • FFE (Finished Floor Elevation): Elevation of the completed building slab.
  • TC (Top of Curb): Elevation along the top edge of a concrete curb.
  • FL or G (Flowline / Gutter): Elevation at the bottom of the curb gutter pan or swale channel where water actually flows (typically $0.50\text{ ft}$ or $6\text{ inches}$ lower than TC).
  • RIM (Rim / Grate Elevation): Elevation of the cast-iron manhole cover or catch basin inlet grate at the surface.
  • INV (Invert Elevation): Elevation of the interior bottom floor of a storm drain pipe where it enters (INV IN) or exits (INV OUT) a catch basin, manhole, or culvert headwall.
  • HP and LP (High Point and Low Point): Grade crest divides (HP) and sump collection points (LP) along paved streets and parking lots.

4. Phased Erosion and Sediment Control (ESC) Plan Sheets (C-401–C-403)

Because a construction site's topography and drainage pathways change dramatically from initial timber clearing to final paving, a single static ESC map is inadequate for medium- to large-scale developments. Best engineering practice—and NPDES permit phasing mandates—divide the ESC drawings into three chronological phases:

• Phase 1 — Initial / Pre-Clearing and Grubbing ESC Plan: Depicts the baseline perimeter and run-on controls that must be completely installed BEFORE bulk clearing, grubbing, topsoil stripping, or mass grading begins. Phase 1 includes staking and flagging the Limits of Disturbance (LOD), erecting Tree Protection Fencing (TPF) along the outer drip line of preserved trees, constructing the Stabilized Construction Entrance (SCE) at all site access points, excavating upslope clean-water diversions to route off-site run-on around the work area, trenching downslope perimeter sediment controls (SF = silt fence, CFS = compost filter socks), and excavating initial sediment traps (ST) or sediment basins (SB) at low points.
• Phase 2 — Interim / Mass Grading and Utility Installation ESC Plan: Governs the active earthwork, road cutting, and underground utility trenching stage. As storm drain catch basins and culverts are installed, Inlet Protection (IP) is immediately deployed on every grate and curb opening; Check Dams (CD) are installed in newly cut roadside ditches; temporary pipe slope drains carry concentrated runoff down unstabilized fill embankments; dewatering filter bags treat trench water; soil stockpiles are ring-fenced and covered; designated Concrete Washout (CW) and secondary containment fueling pads are active; and temporary seeding/mulching is applied to any rough-graded slope inactive for $\ge 14\text{ calendar days}$.
• Phase 3 — Final / Fine Grading and Permanent Stabilization ESC Plan: Governs project completion and permit termination. Temporary sediment basins are dredged, re-contoured, and converted into permanent post-construction detention or bioretention facilities (replacing temporary perforated risers or skimmers with permanent outlet control structures); permanent Rolled Erosion Control Products (RECPs) / Turf Reinforcement Mats (TRMs), sod, and perennial seed mixes are installed; and once the site achieves $\ge 70\%$ of native background perennial vegetative density, all temporary BMPs are removed and their footprints stabilized prior to filing the Notice of Termination (NOT).

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5. Standard Detail and Specification Sheets (C-500)

Provide scaled cross-sectional and isometric engineering drawings for every BMP referenced on the plan sheets. A CESSWI consults the Standard Detail Sheet to verify field installation tolerances—such as verifying that a standard silt fence fabric is buried in a minimum $6\text{-inch deep by } 6\text{-inch wide}$ ($6\text{ in} \times 6\text{ in}$) compacted anchor trench with posts spaced no more than $6\text{ feet}$ apart, or confirming the $D_{50}$ median stone diameter and geotextile filter fabric underlayment of a rock outlet apron.

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Map Legends, Scales, and Survey Stationing

Standard Legend Symbols, Line Types, and BMP Acronyms

Every civil plan sheet includes a Legend defining its cartographic line types, hatching patterns, and standard abbreviations. While minor symbol variations exist among engineering firms, universal civil drafting conventions govern contour and boundary lines:

Graphic Bar Scales vs. Engineer's Ratio Scales

Civil site plans use an Engineer's Scale, which divides each inch on the drawing into decimal multiples of $10\text{ feet}$ (1" = 10', 1" = 20', 1" = 30', 1" = 40', 1" = 50', 1" = 60', or 1" = 100'). This may also be written as a dimensionless Representative Fraction (RF)—for example, 1" = 20' equals $1:(20 \times 12) = \mathbf{1:240}$, and 1" = 40' equals $1:(40 \times 12) = \mathbf{1:480}$.

Worked Numeric Example: Scaling a BMP Length from a Plan Sheet

Problem: On a full-size (24" x 36") ESC plan sheet with a verified scale of 1" = 40', a CESSWI uses an engineer's scale ruler and measures a proposed perimeter silt fence installation as $4.5\text{ inches}$ long on the paper. How many linear feet of silt fence must be installed in the field? What if that same line measured $2.25\text{ inches}$ on a $50\%$ reduced half-size print?

Step-by-Step Solution:

1. Full-Size Calculation (1" = 40'): $$\text{Field Length} = 4.5\text{ in} \times 40\text{ ft/in} = \mathbf{180\text{ linear feet}}$$
2. Half-Size Print Verification ($50\%$ reduction $\implies$ effective scale is 1" = 80'): $$\text{Field Length} = 2.25\text{ in} \times 80\text{ ft/in} = \mathbf{180\text{ linear feet}}$$ (Notice that if the inspector mistakenly used the written 1" = 40' text note on the half-size print, they would calculate $2.25 \times 40 = 90\text{ ft}$—under-ordering the required silt fence by $50\%$!)

Survey Stationing (Sta. 0+00) and Left/Right Offsets

On linear construction projects—such as highways, pipelines, utility corridors, levees, and drainage channels—locations are referenced using Survey Stationing along the horizontal project centerline:

• $1\text{ Station} = 100\text{ linear feet}$, written in the format Sta. H+TT, where the digits before the plus sign (+) represent hundreds of feet and the two digits after the plus sign represent tens and ones of feet:
  • Sta. 0+00 = $0\text{ ft}$ (the beginning baseline point of the project)
  • Sta. 1+00 = $100\text{ ft}$ from Sta. 0+00
  • Sta. 12+35 = $1,235\text{ ft}$ from Sta. 0+00
  • Sta. 18+80 = $1,880\text{ ft}$ from Sta. 0+00
• Calculating Linear Distance Between Two Stations: Drop the plus sign to convert each station into total feet from 0+00, then subtract the lower station from the higher station: $$\text{Linear Distance from Sta. } 12+35 \text{ to Sta. } 18+80 = 1,880\text{ ft} - 1,235\text{ ft} = \mathbf{645\text{ linear feet}}$$
• Reading Left (Lt.) and Right (Rt.) Offsets: Any feature located away from the centerline is identified by its station plus a perpendicular ($90^\circ$) horizontal offset distance to the Left (Lt.) or Right (Rt.)—for example, Drop Inlet #4 at Sta. 15+20, 50' Lt. or Concrete Washout at Sta. 22+00, 35' Rt.. By universal surveying convention, Left and Right are ALWAYS determined while standing on the centerline and looking UP-STATION (facing the direction of increasing station numbers, from Sta. 0+00 toward Sta. 30+00).