Site & Civil Symbols Guide
A complete reference for symbols and conventions used on civil engineering and site development drawings — covering utility color codes, underground and overhead markings, drainage structures, survey notation, pavement details, and standard abbreviations.
APWA Uniform Color Code
The American Public Works Association assigns a standardized paint color to each underground utility type. These colors are used for field marking before excavation and appear on civil drawings and utility plans as a universal identification system.
Red — Electric Power
Identifies electric power lines, cables, conduits, and lighting circuits. Red markings indicate energized or potentially energized conductors below grade.
Yellow — Gas, Oil & Steam
Marks natural gas, petroleum, and steam distribution lines. Yellow indicates hazardous materials that require extra caution during excavation.
Orange — Telecommunications
Designates communication lines including telephone, cable television, fiber optic, and alarm or signal wiring running underground.
Blue — Potable Water
Identifies drinking water supply mains, service laterals, and irrigation lines connected to the municipal water system.
Green — Sewer & Storm Drain
Marks sanitary sewer lines, combined sewers, and storm drainage piping. Green utility markings indicate gravity or pressurized waste conveyance systems.
Purple — Reclaimed Water
Identifies non-potable reclaimed or recycled water lines used for irrigation, industrial processes, or cooling systems. Must not be connected to potable supply.
White — Proposed Excavation
Outlines the planned excavation area or route. White markings delineate where digging will occur so utility locators can mark conflicts within the work zone.
Pink — Temporary Survey
Used for temporary survey markings such as property boundaries, construction staking, and layout points that guide earthwork and building placement.
Underground Utilities
Line symbols and letter designations used on site utility plans to identify buried infrastructure. Each utility type has a distinct line pattern and label.
W — Water Line
Domestic water supply main or service lateral. Shown as a solid line with "W" labels at intervals, including pipe size and material designation.
SS — Sanitary Sewer
Gravity or force-main sanitary sewer piping carrying wastewater to the treatment facility. Labelled with pipe size, slope, and invert elevations at structures.
SD — Storm Drain
Storm drainage piping that collects and conveys rainwater runoff. Shown with pipe diameter, slope, material type, and connection points to catch basins and outfalls.
G — Gas Line
Natural gas distribution or service line. Marked with "G" labels and typically shown with a distinct dashed line pattern to distinguish from other buried utilities.
E — Electric Underground
Underground electrical power conduit or direct-buried cable. Includes voltage designation, conduit size, and duct bank configuration where applicable.
T — Telephone / Data
Underground telecommunications conduit carrying telephone, data, or cable television lines. May include duct bank details and pull box locations.
FO — Fiber Optic
Fiber optic cable route shown with a distinct line type and "FO" labels. Includes conduit size, splice vault locations, and hand-hole positions along the run.
Overhead Utilities
Symbols for above-ground utility lines and support structures shown on site plans and civil drawings.
OH — Overhead Electric
Aerial electric power lines carried on poles or towers. Shown on site plans with a dashed line and "OH" labels, including voltage and minimum clearance heights above grade.
OHT — Overhead Telephone
Aerial telephone or communication cables strung between poles. Distinguished from overhead electric by a different line type or label and typically positioned lower on shared poles.
Power Poles
Represented as a circle with a center dot on plan drawings. Poles may carry electric, telephone, or cable lines. Labels indicate pole number, material type (wood, steel, concrete), and height.
Drainage Structures
Symbols for stormwater and sanitary drainage infrastructure shown on grading and utility plans.
Manhole (MH)
Vertical access shaft for underground sewer or storm drain maintenance. Shown as a circle labelled "MH" with an ID number, rim elevation, and invert elevations for each connecting pipe.
Catch Basin (CB)
Surface drainage inlet that collects stormwater from paved areas. Shown as a square labelled "CB" with grate type, rim elevation, and outlet pipe size and invert.
Cleanout (CO)
Capped access fitting at grade that allows cleaning and inspection of underground piping. Required at changes in direction and at maximum spacing intervals per plumbing code.
Inlet / Outlet
Pipe openings at detention ponds, retention basins, or outfall locations. Inlets bring water into a structure; outlets discharge it downstream. Labelled with pipe size and invert elevation.
Drop Inlet
A surface inlet where stormwater drops vertically into a below-grade drainage structure. Used in curbed areas, parking lots, and roadway medians to intercept runoff at low points.
Headwall
Concrete or masonry retaining structure at the end of a culvert or outfall pipe. Prevents erosion and provides structural support at the pipe opening where it daylights to a channel or swale.
Site Features
Symbols representing landscape, utility, and infrastructure elements located above grade on site plans.
Existing Tree
Shown as an irregular circular canopy symbol with trunk mark at center. Labels typically include species, trunk diameter (DBH), and protection status during construction.
Proposed Tree
Similar canopy symbol drawn with a lighter line weight or different pattern to distinguish from existing trees. Labelled with species, caliper size, and spacing requirements.
Tree to Be Removed
Existing tree symbol overlaid with an X or shown with dashed lines and a removal note. Indicates the tree must be cleared before site work begins.
Light Pole
Circle with radiating lines indicating fixture direction. Labels include pole height, fixture type, wattage or lumen output, and mounting configuration.
Sign
Small rectangle or flag symbol at the sign location. Includes references to the sign schedule for dimensions, content, material, and mounting details.
Fire Hydrant
Circle with radiating ticks or small protrusions. Placed on water mains with notation for size, outlet configuration, and required clearance from buildings and roadways.
Transformer Pad
Rectangle with "XFMR" or "PAD MTD XFMR" label indicating a ground-mounted electrical transformer. Shows required clearance zones and connection conduit routing.
Survey & Grading
Symbols and conventions used on topographic surveys and grading plans to communicate elevation data and property boundaries.
Property Corner
Shown as a small circle or triangle at property boundary intersections. Represents a monumented point established by a licensed surveyor defining the legal property limits.
Benchmark (BM)
Fixed reference point with a known elevation, shown as a triangle with the elevation value. All vertical measurements on the project are calculated from this datum point.
Spot Elevation
An X or plus sign with an elevation number at a specific point on the plan. Used at critical locations like building corners, pavement edges, drainage low points, and top-of-wall elevations.
Contour Line
A line connecting points of equal elevation. Closely spaced contours indicate steep slopes; widely spaced contours show flat areas. Labelled with the elevation value at regular intervals.
Existing Contour
Drawn as a thin dashed line representing the current ground surface before any earthwork. Elevation labels appear along the line at intervals to indicate the pre-construction topography.
Proposed Contour
Drawn as a solid line showing the intended finished grade after grading operations. Comparing proposed contours to existing contours reveals areas of cut (excavation) and fill (embankment).
Pavement & Hardscape
Symbols and notation for paved surfaces, curb details, and hardscape elements appearing on civil site plans and detail sheets.
Curb & Gutter
Shown as a thick line along the pavement edge with a parallel gutter line. Detail references specify face height, gutter width, material, and cross-slope for drainage.
Concrete Pavement
Paved area with a stippled or lightly dotted fill pattern. Labels indicate slab thickness, reinforcement, joint spacing, and subbase preparation requirements.
Asphalt Pavement
Shown with a dense dot or speckle pattern distinguishing it from concrete. Notes specify lift thicknesses, aggregate base course depth, and compaction requirements.
Expansion Joint
A thick line or double line across pavement indicating a full-depth joint filled with compressible material. Allows thermal expansion and contraction without cracking adjacent slabs.
Accessible Ramp
Shown at curb transitions with slope arrows, detectable warning surface pattern, and landing dimensions. Must comply with ADA and local accessibility codes for slope, width, and landing size.
Common Civil Abbreviations
Standard abbreviations found on civil engineering drawings, grading plans, and utility plans.
BM
Benchmark — a permanent reference point with a known elevation used as the vertical control datum for the entire project.
EL
Elevation — the height of a point above or below the established project datum, measured in feet or meters.
INV
Invert — the lowest interior point of a pipe or channel at a given cross-section, critical for calculating flow gradient and capacity.
FL
Flow Line — the lowest point of the interior of a pipe, essentially synonymous with invert in most civil engineering contexts.
TC
Top of Curb — the elevation at the top face of a curb, used for calculating curb reveal and roadway cross-section geometry.
TW
Top of Wall — the elevation at the uppermost point of a retaining wall, used for grading coordination and fence or railing layout.
BW
Bottom of Wall — the elevation at the base or footing of a retaining wall, used for structural design and excavation depth calculations.
FF
Finished Floor — the elevation of the completed floor surface at building entry points, coordinating building access with site grading.
ROW
Right of Way — the legal corridor of land reserved for public use, typically along roadways and utility easements. Shown as a line with the ROW width dimension.
PL
Property Line — the legal boundary of the parcel, shown as a long-dash-dot line type on civil drawings with bearing and distance labels.
CL
Center Line — the center axis of a roadway, pipe, or linear feature. Shown as an alternating long-dash-short-dash line and used as the reference for offset dimensions.
STA
Station — a distance measurement along a baseline or centerline, expressed in hundreds of feet (e.g., STA 4+50 = 450 feet from the starting point).
MH
Manhole — abbreviated on civil plans and profile drawings to label sanitary sewer and storm drain access structures with their ID numbers and elevations.
CB
Catch Basin — abbreviated on storm drainage plans to identify surface water collection structures connected to the underground storm system.
RCP
Reinforced Concrete Pipe — a pipe material designation indicating concrete pipe with embedded steel reinforcement, used for storm drains and culverts in larger diameters.
PVC
Polyvinyl Chloride — a lightweight, corrosion-resistant plastic pipe material widely used for sanitary sewer, storm drain, and water service lines in smaller diameters.
Frequently Asked Questions
What do the APWA utility color codes mean?
The American Public Works Association Uniform Color Code assigns a specific paint color to each type of underground utility for field marking before excavation. Red indicates electric lines, yellow marks gas or oil, orange designates telecommunications, blue identifies potable water, green represents sewer and storm drain, purple indicates reclaimed or non-potable water, white marks proposed excavation boundaries, and pink is used for temporary survey markings.
How do I distinguish existing contour lines from proposed contour lines on a civil drawing?
Existing contour lines are typically drawn as thin dashed lines with elevation labels, representing the current topography of the site before construction. Proposed contour lines are drawn as solid lines with elevation labels, showing the intended finished grade after earthwork operations are complete. Both types are labelled with their elevation values to indicate height above the project datum.
What is the difference between a manhole and a catch basin on civil drawings?
A manhole is a vertical access shaft that allows maintenance personnel to enter underground utility lines such as sanitary sewers or storm drains. It is shown as a circle labelled MH with an identification number. A catch basin is a surface drainage inlet — typically a grated or curb-opening structure — that collects stormwater runoff from paved surfaces and channels it into the storm drain system. It is shown as a square labelled CB.
Why is a benchmark important on a construction site?
A benchmark is a permanent reference point with a known, verified elevation. All vertical measurements and grading operations on a construction site are calculated relative to this point. Surveyors use benchmarks to establish elevation control so that foundations, utilities, pavements, and drainage systems are built at the correct heights. Without a reliable benchmark, vertical accuracy across the project cannot be maintained.
Related Resources
Drawing Symbols Guide
170+ symbols across architectural, structural, MEP, fire protection, and civil drawings.
Construction Abbreviations
250+ common abbreviations and acronyms used on construction drawings and documents.
Knowledge Base
Guides, references, symbols, abbreviations, and review checklists for AEC professionals.
Ready to Automate Your Drawing Review?
Book a demo to see how Structured AI identifies utility conflicts, grading errors, and missing site details across your civil drawings automatically.
Try Automated Drawing Review