Load combinations, steel and reinforced concrete beams, soils and bearing capacity, stormwater runoff, Manning's equation, surveying, transportation, civil CAD and BIM, and construction administration.

Structural & Civil Design

On paper, reduce this level run from BM-7 (elevation 52.300 m): BS 1.415 on BM-7; FS 0.982 then BS 1.760 on TP-1; FS 2.334 on point P. Compute HI and elevations, and check that sum(BS) - sum(FS) equals the change in elevation (expected P = 52.159 m).

Open a free topographic map of a place you know, using the USGS National Map viewer (https://apps.nationalmap.gov/viewer/) or USGS topoView. Note the contour interval, the vertical datum and the map's coordinate system.

Pick two points on adjacent contours, measure the horizontal distance with the viewer's tool, and compute the slope as a percentage. Then find a valley and sketch which way the contours point.

Convert one bearing to an azimuth and back on paper: N 30° E, S 45° E, S 60° W and N 15° W (expected 30°, 135°, 240°, 345°).

Install QGIS (https://qgis.org). Create a project, set its CRS to the State Plane or UTM zone for your area, and add an OpenStreetMap basemap (XYZ tiles).

Download a small elevation model tile for the same area from the USGS National Map, add it to QGIS, and generate contours (Raster > Extraction > Contour) at a sensible interval.

Measure one parcel-sized area and one distance in QGIS, and write down which CRS units the results are in and how you checked them.

## Why it matters

Every civil project starts with a survey: where the property lines are, what the ground looks like, where existing utilities run, and what elevations the design must tie into. Civil engineers do not usually run the instruments themselves (licensed land surveyors and survey crews do), but they read survey data every day, and many mistakes in drainage and grading come from misreading it. GIS adds the wider picture: soils, floodplains, zoning, aerial imagery and utilities.

## Elevations and differential leveling

Elevations are measured relative to a **vertical datum** (in the US, NAVD 88, with NOAA's National Geodetic Survey planning a modernized datum). A **benchmark (BM)** is a point of known elevation.

**Differential leveling** uses a level and a rod:

```text
height of instrument  HI = elevation of known point + backsight (BS)
new elevation            = HI - foresight (FS)
```

**Worked example.** Start at BM-1, elevation 100.000 m.

| point | BS | HI | FS | elevation |
|---|---|---|---|---|
| BM-1 | 1.250 | 101.250 | | 100.000 |
| TP-1 | 0.875 | 100.020 | 2.105 | 99.145 |
| A | | | 1.540 | 98.480 |

Arithmetic check: `sum(BS) - sum(FS) = 2.125 - 3.645 = -1.520`, and `98.480 - 100.000 = -1.520`. Crews close every level loop back on a benchmark; the **misclosure** must be within the project's allowable tolerance, or the run is repeated.

## Horizontal position

- **Coordinates** are given as northing and easting in a projected system, in the US usually the **State Plane Coordinate System** on NAD 83 (or UTM). Always note the datum, zone and units (US survey foot vs international foot vs metre); a mismatch can move your design by metres.
- **Bearings** describe line directions as an angle from north or south toward east or west, for example `N 45°30'00" E`. **Azimuths** are measured clockwise from north (that bearing is an azimuth of 45°30'). Property descriptions list bearings and distances around a boundary; adding up their latitude and departure components should close back to the start.
- **Total stations** measure angles and distances; **GNSS (GPS) with RTK** corrections gives centimetre-level positions in open sky; drones and laser scanning (lidar) capture dense point clouds for topography.

## Contours and topography

A topographic survey produces spot elevations and **contour lines** joining points of equal elevation, with a stated **contour interval** (for example 0.5 m or 1 ft).

- Closely spaced contours mean steep ground; widely spaced, gentle.
- Contours point **upstream** where they cross a valley or swale (a V shape pointing uphill) and downhill around a ridge.
- **Slope** between two points = difference in elevation / horizontal distance. Example: two contours 2.0 m apart in elevation, 40 m apart on plan, give 2.0 / 40 = 0.05, a 5% slope.

Grading plans show existing contours (dashed) and proposed contours (solid); reading where they differ shows cut and fill.

## GIS for civil work

A **geographic information system** stores map layers with a coordinate reference system (CRS): parcels, aerial imagery, soils (USDA Web Soil Survey), floodplains (FEMA flood maps), elevation models (USGS 3DEP), roads and utilities. Free **QGIS** (https://qgis.org) loads these layers, reprojects them to a common CRS, draws contours from an elevation model and measures distances and areas. GIS is great for planning and screening; construction documents still rely on a field survey sealed by a licensed surveyor.

## Who can do what

**Boundary surveys** and legal descriptions require a licensed **Professional Land Surveyor (PLS/PS)**; licensure is by state, with exams administered by NCEES (https://ncees.org). Civil engineers rely on sealed surveys and must not re-establish property lines themselves. Checked on 2026-10-23.

## Common mistakes

- **Mixing datums or units** (NGVD 29 vs NAVD 88; US survey foot vs international foot).
- **Swapping backsight and foresight**, which flips the sign of a change.
- **Reading contour direction backwards** in a swale.
- **Designing from GIS data** as if it were survey-grade.

## Safety

Field surveying near traffic, on construction sites or in rough terrain needs site-safety training, high-visibility clothing and traffic control. The activity below uses paper, public maps and free software only.

## Recap

- Leveling: `HI = elevation + BS`, `elevation = HI - FS`; always close the loop and check.
- Coordinates need a datum, zone and unit; bearings and azimuths describe directions.
- Contours show shape and slope; GIS layers give context; boundary work belongs to licensed surveyors.

## Try it

Open the **Do** tab to reduce a level run on paper, read slopes from a public topographic map and load layers in QGIS.


Reduce a differential leveling run, read coordinates, bearings and contours on a survey, and load site data into a free GIS.

Surveying and GIS

How does land surveying work?

How To Read A Survey (Like a Civil Engineer)

## Why it matters

Transportation engineers design roads, intersections, transit, bike and walking facilities so people move safely and efficiently. Two ideas sit underneath much of that work: drivers need enough **sight distance** to see a hazard and stop, and facilities are sized from **traffic counts**. Even site-development engineers use both, for driveways, parking lots and turn lanes.

## Design references

In the US, geometric design follows **AASHTO's A Policy on Geometric Design of Highways and Streets** (the "Green Book", 7th edition 2018, with newer editions in progress), plus state DOT manuals. Traffic control devices (signs, signals, markings) follow the FHWA **Manual on Uniform Traffic Control Devices (MUTCD)**, 11th edition (https://mutcd.fhwa.dot.gov). Capacity analysis uses the **Highway Capacity Manual (HCM)** from the Transportation Research Board. Checked on 2026-10-23. Use the editions your agency requires.

## Stopping sight distance

Stopping sight distance (SSD) is the distance a driver needs to perceive a hazard, react, and brake to a stop. It has two parts:

```text
SSD = reaction distance + braking distance
SI: SSD (m) = 0.278 * V * t + 0.039 * V^2 / a
```

`V` is the design speed in km/h, `t` the perception-reaction time, and `a` the deceleration rate. The Green Book's design values use `t = 2.5 s` and `a = 3.4 m/s^2`, chosen to cover most drivers on wet pavement. On grades, braking distance changes: downhill is longer, uphill shorter.

**Worked example.** At 100 km/h:

- Reaction: `0.278 × 100 × 2.5 = 69.5 m`
- Braking: `0.039 × 100^2 / 3.4 = 114.7 m`
- SSD = 184 m (design tables round this to about 185 m).

Doubling the speed roughly quadruples the braking part, which is why speed management is central to road safety.

### Where SSD shows up

- **Crest vertical curves** must be long enough that a driver's eye (about 1.08 m high) can see an object on the road (about 0.60 m high) at SSD.
- **Sag curves** at night are limited by headlight reach.
- **Horizontal curves** need the inside of the curve kept clear of buildings, cut slopes and vegetation.
- **Intersections and driveways** need sight triangles so drivers can see approaching traffic (intersection sight distance, a related but separate check).

Other sight distances include **decision sight distance** (complex locations) and **passing sight distance** on two-lane roads.

## Traffic counts

Traffic volumes are counted with tubes, loops, video or radar, and summarised as:

- **AADT** (annual average daily traffic): total vehicles per year divided by 365. Short counts are adjusted to AADT with seasonal and day-of-week factors.
- **K factor**: the fraction of AADT in the design hour (commonly somewhere around 8 to 12% on many roads; use local data).
- **D factor**: the fraction of design-hour traffic in the peak direction.
- **Design hour volume** in the peak direction: `DDHV = AADT × K × D`.
- **Peak hour factor (PHF)**: how uneven flow is within the peak hour, `PHF = hourly volume / (4 × peak 15-minute volume)`. A PHF of 1.0 means perfectly even flow; lower values mean a sharper peak.

**Worked example.** AADT = 20,000 vehicles/day, K = 0.10, D = 0.55: `DDHV = 20,000 × 0.10 × 0.55 = 1,100 vehicles/hour` in the peak direction. If the peak hour carried 1,200 vehicles with a busiest 15 minutes of 360, `PHF = 1,200 / (4 × 360) = 0.83`.

These volumes feed the HCM's **level of service (LOS)** analysis, graded A (free flow) to F (breakdown), which drives lane counts, signal timing and turn-lane decisions. Vehicle mix matters too: trucks use more capacity and need longer stopping and turning space.

## Beyond cars

Modern practice designs for everyone: complete streets, pedestrian crossings and accessible routes (ADA and the PROWAG accessibility guidelines), bike facilities, transit stops, and safety programs such as the Safe System approach adopted by FHWA. Crash data analysis (the Highway Safety Manual) identifies locations and treatments.

## Common mistakes

- **Using the posted speed** instead of the design speed.
- **Forgetting grade** in braking distance.
- **Treating a single day's count** as AADT without seasonal adjustment.
- **Mixing directional and two-way volumes** in capacity analysis.

## Professional responsibility

Road and traffic designs are reviewed by agencies and sealed by licensed engineers, often with a professional traffic operations engineer (PTOE) involved. Real designs need review and sealing by a licensed professional engineer (PE) under the codes your jurisdiction adopts. Collecting counts on live roads needs traffic-safety training and approved traffic control.

## Recap

- SSD = reaction distance + braking distance; at 100 km/h it is about 185 m with Green Book values.
- Sight distance shapes vertical and horizontal curves and intersection layouts.
- AADT, K, D and PHF turn counts into design hour volumes for capacity and LOS analysis.


Explain stopping sight distance, read traffic counts (AADT, peak hour factor, design hour volume) and see how they shape road design.

Transportation basics

How Are Highways Designed?

Stopping Sight Distance on a road. Definition, concept and evaluation of SSD with examples.

Install LibreCAD (https://librecad.org) or use QGIS. Start a drawing in metres, and create layers named for boundary, setbacks, building, paving, contours-existing, contours-proposed and annotation, each with its own colour or line type.

Draw a 30 m by 40 m lot boundary starting at coordinates (1000, 2000), with the 30 m side along the street. Label each side with its length and a bearing (for example N 90°00' E for the street line).

Offset a 6 m front setback and 3 m side and rear setbacks on the setbacks layer, using a dashed line.

Place a 12 m by 18 m building footprint inside the setbacks, and dimension its distance from the front and one side property line.

Add a 6 m wide drive from the street to a small parking area, and hatch or shade the paving.

Sketch three existing contours across the lot (dashed) falling 0.5 m each toward the street, and two proposed contours (solid) that slope away from the building; label the finished floor elevation.

Add a title block with project name, 'NOT FOR CONSTRUCTION', date, scale, north arrow and your name, then export the sheet to PDF at 1:200.

Optional BIM step: open FreeCAD's BIM workbench (or Bonsai in Blender), model the building footprint as a simple mass, and export it as an IFC file.

## Why it matters

Engineering ideas reach contractors as drawings and models. A civil engineer's calculations become a **plan set**: existing conditions, demolition, site layout, grading, drainage, utilities, erosion control and details. Producing and checking those sheets, in CAD and increasingly in BIM, is a large part of an entry-level civil job, and clean, standard drawings prevent costly field questions.

## From survey to plan set

A typical site-development workflow:

1. **Import the survey**: points, breaklines and the existing surface (a TIN, triangulated irregular network) in the project's coordinate system.
2. **Layout**: property lines, setbacks, building footprint, parking, drives and sidewalks, dimensioned from the boundary or a control line.
3. **Grading**: proposed spot elevations and contours, building floor elevation, slopes for drainage and accessibility.
4. **Drainage and utilities**: inlets, pipes with inverts and slopes, water and sewer connections, in plan and profile.
5. **Details and notes**: standard details, specifications references, general notes.
6. **Sheets**: title blocks, north arrows, scales, legends, sheet index; issued as PDFs for review and sealed by the engineer of record.

**Plan, profile and cross-section** views are the language of civil drawings: plan shows the layout from above, a profile shows elevation along an alignment (a road or pipe), and cross-sections cut across it.

## Software

- **Autodesk Civil 3D** dominates US civil practice (surfaces, alignments, corridors, pipe networks); **Bentley OpenRoads** is common at state DOTs. Both offer free education licences to eligible students and teachers.
- Free and open options for learning: **QGIS** for mapping and GIS data, **LibreCAD** for 2D drafting, **FreeCAD** (with its BIM workbench) and **Bonsai** (formerly BlenderBIM) for IFC-based models.

Learn the concepts (coordinate systems, layers, surfaces, annotation scale), and the tool switch is manageable.

## CAD standards

Firms and agencies require drawing standards so sheets are consistent and data can be exchanged: layer names, line types and weights, text heights, symbols, sheet numbering. The **US National CAD Standard** is a common basis, and state DOTs publish their own CAD manuals. Always ask which standard and template the project uses before drawing anything.

Good habits:

- Draw in **real-world units and coordinates** (model space); scale only on sheets (paper space or layouts).
- Keep each kind of object on its own layer, with existing and proposed clearly distinguished (often dashed vs solid, or screened).
- Use **external references** for the survey and base files rather than copying them in.
- Annotate so a reader can build it: dimensions, elevations, slopes, pipe sizes and inverts.

## BIM

**Building Information Modeling** is model-based design where objects carry data (a pipe knows its diameter, material and inverts; a wall knows its type and fire rating), and drawings are views of the model.

- **IFC** (Industry Foundation Classes), maintained by buildingSMART (https://www.buildingsmart.org), is the open exchange format; recent IFC versions extend it to infrastructure such as roads, rail and bridges. Checked on 2026-10-23.
- **Level of development (LOD)** describes how complete and reliable each element is at a given stage.
- **Clash detection** (for example in Navisworks) finds conflicts, such as a storm pipe through a water main, before construction.
- A **common data environment (CDE)** keeps the current model versions for all disciplines; ISO 19650 describes how to manage that information.
- **Digital twins** connect the as-built model to operations data.

For civil work, BIM often means 3D corridors and utility models coordinated with the building's architectural and MEP models.

## Worked example: a small site plan

A 30 m by 40 m lot has a 6 m front setback and 3 m side setbacks. Draw the boundary from its bearings and distances, offset the setbacks, place a 12 m by 18 m building inside them, add a 6 m wide drive to the street, and label everything. Then add existing contours from the survey and a proposed finished floor elevation 0.15 m above the highest adjacent finished grade, with the ground sloping away from the building.

## Common mistakes

- **Drawing at sheet scale** instead of real units, which breaks coordinates and dimensions.
- **Wrong coordinate system** for the survey import.
- **Exploding objects or blocks**, which strips their data.
- **Unclear existing vs proposed** linework.
- **Missing north arrow, scale or datum** on the sheet.

## Professional responsibility

Construction documents are sealed by the licensed engineer of record, who is responsible for their content regardless of who drafted them. Real designs need review and sealing by a licensed professional engineer (PE) under the codes your jurisdiction adopts.

## Recap

- Plan sets turn survey and design into layout, grading, drainage and utility sheets in plan, profile and section.
- Work in real-world coordinates, follow the project's CAD standard, and use references.
- BIM adds data-rich objects, IFC exchange, clash detection and managed model information.

## Try it

Open the **Do** tab to draft a simple site plan with free tools.


Understand how civil CAD and BIM models become plan sets, and draft a simple site plan with free tools.

Civil CAD and BIM

What is BIM? Understand Building Information Modeling

Site Design in Civil 3D for Beginner

Set up a simple RFI log (spreadsheet or paper) with columns: number, date received, subject, sheets/specs referenced, assigned to, response due, date answered, cost/schedule impact flag, status. Enter RFI 014 with a response due date 7 days after receipt.

Write down what you would check first in the documents: the profile on sheet C-501, the utility plan, the survey and potholing data, and the specification section for storm sewer installation.

Compute the conflict: with the storm pipe invert at 98.20 ft and its outside top about 1.5 ft above the invert (a 15-inch pipe plus wall), the outside top is at 99.70 ft; the water main top is at 98.45 ft. Write the vertical overlap (1.25 ft) and note what separation you would look up in the water utility's or state's standards.

List two possible design fixes (for example, lower the storm pipe and check its downstream slope and cover, or ask the utility about relocating the water main) and who must approve each.

Draft a written response of 5 to 8 sentences that references the sheet and station, states the proposed revision (or that a revised profile will follow), and asks the contractor to submit any cost or time impact through the change process.

Review your draft for anything that tells the contractor how to excavate, shore or sequence the work, and remove it (means and methods are theirs).

Mark the response 'for review by the engineer of record' and note what would need to happen to the record drawings once it is approved.

## Why it matters

A design is not finished when the drawings are sealed. During construction the contractor finds conflicts, asks questions, proposes substitutions and submits shop drawings, and the engineer's answers keep the project safe, on budget and on schedule. **Construction administration (CA)** is where junior engineers learn fastest how designs meet reality, and where poor communication becomes expensive claims.

## The contract documents

The contract between owner and contractor usually includes:

- **Drawings**: the plan set.
- **Specifications**: written requirements for materials, products, execution and testing, organized in the US by the CSI **MasterFormat** numbering system (for example Division 03 Concrete, Division 31 Earthwork, Division 33 Utilities).
- **General and supplementary conditions**: often based on standard forms from AIA (A201), EJCDC or ConsensusDocs, or an agency's standard specifications for public works.

These define who does what, how questions and changes are handled, and response times. The engineer's CA role is whatever the engineer's own contract with the owner says; read it before you answer anything.

## The main CA processes

### Submittals and shop drawings

Before fabricating or installing, the contractor submits product data, shop drawings (for example rebar placement, precast structures, steel connections) and samples. The engineer reviews them for **general conformance with the design intent and the contract documents**. A typical stamp says "No exceptions taken", "Make corrections noted" or "Revise and resubmit". Review does not relieve the contractor of responsibility for dimensions, quantities, and **means and methods** (how they build it, including temporary works and site safety).

### Requests for information (RFIs)

An RFI is a formal written question from the contractor when the documents are unclear, conflicting or incomplete. A good RFI process:

1. **Log it** with a number, date received and required response date.
2. **Understand it**: read the referenced sheets and spec sections, look at photos, and talk to the contractor if needed.
3. **Find the answer in the documents first.** Many RFIs are answered by a detail or spec clause the contractor missed; cite it.
4. If a design decision is needed, **coordinate** with the right discipline and the engineer of record.
5. **Respond in writing**: clear, specific, referencing sheets and details, with a sketch if helpful.
6. **Flag cost or schedule impact.** An RFI response is not a change order. If the answer changes the work, it goes through the contract's change process (a field order, construction change directive or change order approved by the owner).
7. **Close and file** it; update the record drawings.

### Field observation

Engineers visit the site to observe progress and conformance, document what they see in field reports with photos, and raise concerns. They are not usually full-time inspectors and do not supervise the contractor's workers. Special inspections and testing (concrete cylinders, soil compaction, welding) are often required by the building code and done by qualified agencies.

### Changes, pay applications and closeout

Change orders adjust scope, price and time. Pay applications are reviewed against progress. At closeout come the **punch list**, final inspections, as-built (record) drawings, operation and maintenance manuals, and warranty documents.

## Worked example: an RFI

> **RFI 014.** Sheet C-501 shows storm pipe ST-3 crossing the existing 8-inch water main at station 2+40 with invert 98.20 ft. Potholing found the top of the water main at 98.45 ft. The pipe would hit the main. Please advise.

A good response process: confirm the conflict from the survey and potholing data; check whether the storm pipe can be lowered while keeping minimum cover and the downstream slope, or whether the water main needs a deflection (which involves the water utility); coordinate with the engineer of record; respond with a revised profile or a sketch, the required vertical separation from the water utility's or state's standards, and a note that the contractor should submit any cost or time impact through the change process. Do not tell the contractor how to sequence the excavation or support the trench: that is their means and methods and their safety responsibility.

## Common mistakes

- **Answering verbally** on site and not documenting it.
- **Directing means and methods**, which shifts liability and safety responsibility.
- **Approving changes** in an RFI response without owner authorization.
- **Missing contract response times**, which can support delay claims.
- **Not updating** the drawings, so the next RFI repeats the problem.

## Professional responsibility

Design changes during construction must be made or approved by the licensed engineer of record. Real designs and design changes need review and sealing by a licensed professional engineer (PE) under the codes your jurisdiction adopts. Site visits require the owner's and contractor's site-safety orientation and personal protective equipment.

## Recap

- Contract documents (drawings, specifications, conditions) define roles, processes and timing.
- Submittals are reviewed for design intent; RFIs are logged, answered from the documents, coordinated and documented.
- Keep cost and schedule changes in the change process, and stay out of means and methods.

## Try it

Open the **Do** tab to work through an RFI on paper, from log entry to written response.


Follow the engineer's role during construction: contract documents, submittals, RFIs, field observation and change orders, and draft an RFI response.

Construction administration

Construction Administration 101: Understanding the Basics

RFI in Construction Explained: What It Is and How It Works

Survey data and contours, transportation basics, civil CAD and BIM, and how engineers support construction through RFIs and submittals.