Timeline of a Civil Engineering Project

In the same vein as the project cost article I did I thought it might be interesting to cover the typical time of a civil engineering project. As part of a program management team on a rail corridor for the past two years I have been exposed to the entire lifespan of several Public Works projects.

Here is an example of what part of an overview-level schedule might look like:

Here is how the process works, from the eyes of someone in the industry. I use the following general rules to develop the baseline schedules for project's when they are just beginning.

Major Project Phases

Preliminary Engineering
Engineering, Environmental Clearance, Right of Entry
Advertise and Award
Close Out


First the project is in the planning stage. Studies are conducted to determine when and if the project should be built, the results of these studies for several projects are compared to see which ones should be built first to be most cost-effective. Extremely rough estimates of cost are thrown around (eg a road tunnel being $30,000/foot for XXXX amount of feet). Projects can be in planning for any number of years. The client I work for has some projects in planning that may not be built until 2040-2050.

Preliminary Engineering (2%)

When the time comes that the project should be implemented, budget is allocated for it (or maybe just for the projected first few years of it) and a consultant is brought on board to do preliminary engineering. The product of this effort is some sort of Project Study Report that includes definitions of the project, it's outputs (both good and bad), a slightly more engineered estimate (eg a road tunnel would be separated into excavation, grading, support structures, pavement costs) but still pretty general. This study is used by the agency to "define" the project. They use it as a "resume" to apply for funding grants with various lenders (FRA, FTA, local government bodies etc.) A more permanent budget may be set using the costs of the study and using the guidelines in the Budgeting a Public Works Project post.


With the initial study done, a DIFFERENT consultant is brought on board to do the actual design. They start with the preliminary report and get cranking.

Basis of Design (2%)

Their first major goal is to submit a Basis of Design report which will state design facts and physical limitations on the project, such as curve X cannot exceed Y degrees, Z grade, and E superelevation, due to obstructions or whatever and any other limitations and guidelines they have to design within. They also state what codes and regulations they will follow in their design.

Alternatives Analysis (10%)

Following the Basis of Design report the design consultant works towards a 10% design level. This is commonly referred to as the alternatives analysis submittal. At this stage they define the main alternatives to the project and provide the most details possible for each. Once completed, several meetings take place between the designers, owners, and all other stakeholders in the project area (transit authorities, interested groups etc). They determine what option is best. In some cases it is a draw between two alternatives and they continue with the design of both.
Usually starting with the 30% submittal, and following with every subsequent one, a very formal review process involving third-party engineering professionals takes place. The review process typically lasts a month or two following each major submittal.


Around this time is when the environmental requirements of the project begin to be defined. In order to get environmental clearance, quite a bit has to be known about the project and surrounding area. Endangered species reports, project impact footprint, biological opinion reports, and many other activities may take place now. The main environmental document for NEPA (federal) and any State regulations for clearance may also begin to take form. Common NEPA documents are Categorical Exclusion (CE), Environmental Assessment (EA), and Environmental Impact Statement (EIS).

30% Design

The designer has continued on with the design(s) of the project. At this point a definite alternative is chosen, rarely do more than one alternative advance past this point. This is also when environmental activities are in full swing and the Draft NEPA document should be being reviewed or possibly already approved.

60% Design

At this point the Final Environmental Document has hopefully been approved. The Final document will outline any extra environmental requirements the project must include in order to be built so it is nice to get it done at 60%. Also at this point it is fairly well defined what properties the project may impact both permanently and during construction. The Right of Entry process should begin now and the owners of the parcels need to agree to let construction go on near and in their property (they are also paid for this). Eminent Domain may be enforced if the project is valuable enough to the community and the owners are being stubborn.

90% Design

Things are really shaping up on the design. Project costs are close to final and the program managers are probably allocating adequate funds for construction of the project.

100% Design

Design is "complete". Following the last review session the design is "conformed" into the bid-ready state. The design is comprised of the Drawings, General Specifications, and Technical Specifications. These are handed over to the client/owner who (in our case) has a contracts department that will review it and get it ready to bid.

Bid Preparation

It usually takes a month or two from the time the final design is handed in until it is ready to be advertised to the bidders. The "package" that the bidders are given takes this amount of time to prepare, check for errors, and have legal counsel also review (there are a lot of opportunities for lawsuits at this stage so attorneys become involved to review everything).


The project is advertised publicly and the prepared bid package is made available to those interested in bidding for the construction work. Questions are asked by the bidders and the owner provides answers back to the public. Everyone must be able to see all questions and answers or you could be opened up for lawsuits.

Bid Opening

Bids are opened a few months (2-4) after advertising. For us the winner is the "lowest responsive, responsible" bidder, and those terms are heavily defined legally so that they can cut the ties to someone who may not be qualified. The low bidder wins automatically if everything checks out, there were no mistakes in their bid, and they are qualified. If the first bidder gets the boot it goes to the second, and then the third etc.


The construction contract is awarded to the main contractor, a construction management consultant is brought on board, and construction work commences!


The project is finally built! This can last from a few months to several years!

Close Out

After the main construction work is complete the contractor is "relieved from work" (legal wording) is paid and congratulated. There might be a "grand opening" at the project site.
But the work is not done! Several things still need to be done, often completed by the construction management consultant. Outstanding payments need to be processed. All of the construction documentation of exactly what was built are combined into the As-Built documents that are kept by the owner. There may be pending lawsuits from contractors that are resolved at this point. Any required long term "mitigation" or "revegetation" period that was required from the environmental permits is also conducted at this point. With all of these things combined, the close-out period sometimes lasts as long, or longer!, than the construction period. Seriously, some close-out periods are five years for a two-year construction project.

When all is said and done a project that takes one to three years to build, is actually a five year project minimum, with ten not being out of the question. For reference, most of the projects I am involved with are rail and rail-improvment projects like new track, new bridges, new stations etc.

Time of Concentration

The time of concentration (t_c) is the time needed for water to flow from the farthest point in a watershed to the outlet of the watershed. Definition aside (which is taken straight from Wikipedia) there are a lot of formula's that solve for time of concentration. So many that I doubt it's validity in all cases and wonder if it will be on the breadth test :). Without further ado, the formula's:

In all of these examples the following variables are used:
L     Length of flow path
S     Average Slopw
C     Overall rational coefficient (C_{avg})
i      intensity (in/hr)
n     manning's roughness coefficient

Kirpich (general, mostly rural)

 t_c = 0.0078L^{0.77}S^{-0.385}

Kirpich's equation should be used for a lot of areas in general.

FAA Formula (Urban Areas)

 t_c = \dfrac{1.8(1.1-C)\sqrt{L}}{S^{1/3}}

Manning's Kinematic Wave Formula (Paved Areas)

 t_c = \dfrac{0.938}{i^{0.4}} \left( \dfrac{nL_o}{\sqrt{S}} \right)^{0.6}

NCRS Lag Equation (Small urban areas, most cities)

 t_c = \dfrac{1.67 L_o^{0.8} \left(\dfrac{1000}{CN}-9 \right)^{0.7}}{1900S^{0.5}}

Kerby's Equation

 t_c = 0.67 \left( \dfrac{nL_o}{ \sqrt{S} } \right)^{0.467}

I am not a hydrologist, so which of these to use is a shot in the dark. I think part of being a hydrologist is picking your favorite of these methods and modifying it to fit your own needs for your region.

For those of us just tackling this stuff on the breadth test, well, I am definitely taking these formulas into the test with me... will I use them? I hope not, but if I have to  I will pick one of them based on what variables I am given.

Some OSHA Regulations

The Occupational Safety and Health Administration has a few rules you should to be aware of:


Banks over 4 feet must be shored

Trenches deeper than 4 feet and longer than 8 feet must be shored

Shoring slope cannot exceed 1:2 (H:V)

Bell bottom trenches (wider at the bottom) must have bracing on the thin part to prevent cave-in. Workers entering these should wear a life-line.

Ladders must be provided at 25 feet intervals for all trenches deeper than 3 feet.

Construction Site

Toilets must be provided at the site.


< 20  1

>20   1 toilet and 1 urinal for every 40 workers

>200 1 toilet and 1 urinal for every 50 workers

The Prime contractor assumes all obligations. If the work has been subcontracted they may share obligations with the sub-contractor.

Employer must have an emergency action plan for evacuation

First aid supplies are required

Incident rate = number of injuries (annual) /  number of annual hours * 200,000

Employees must be protected form high sound levels

Employees must be protected from extreme light intensities

Proper signs must be placed.

The Critical Fall height is 6 feet. Anything over this height must have guardrails or other protective measures taken. Guardrails must be 42 inches.

Masonry Walls

While construction masonry walls a limited access zone must be set up adjacent to the wall. The size of it needs to be the wall height plus four feet. Only employees constructing the wall can enter it.

Site Layout

Construction sites need to have adequate access to roads around the site to ensure safe transportation of construction equipment and materials. Pedestrian and vehicle access in nearby roads must be maintained and controlled.

The site must be firm, properly drained and dry, and have adequate space to perform the work, operate equipment etc, and be large enough to store needed materials.

Rainfall Intensity Analysis

The intensity (I or i) of a rainfall event is a storm characteristic that measures the rainfall rate. In America this is in inches per hour ( \dfrac{in}{hr} ).

I think the primary reason to determine the intensity is for use in the rational method of determining peak storm flow.

The two main methods I have found to get the intensity are from Intensity-Duration-Frequency (IDF) Curves and from empirical formulas (Steel Equation).

IDF Curve

IDF Curves are curves that have been put together for a specific region using multiple years (decades) of recorded storm data. Here is an example.

To get intensity, you need to know the storm frequency as well as the storm duration. If the storm frequency is not one of the common ones (5, 10, 15, 20, 50 etc) you may have to interpolate on the graph and give your best estimate. The duration also may need to be interpolated.

With the above pictured IDF Curve (which is for some place in ReviewCivilPE land), a 10 year storm that lasts for d minutes would correspond to an intensity, i. Easy!

Steel's Formula

 I = \dfrac{K}{t_c+b}

The steel equation is an empirical equation for for estimating intensity and requires knowing the time of concentration (another process). You also need to determine values of the coefficients c and b (I can't seem to find names for these at the moment).

Both the CERM and AIO provide a map of the United States divided up into geographic regions for use with Steel's formula, and an accompanying table of c and b values.

  1. Find your region
  2. Find your return period (storm frequency)
  3. Get c and b values
  4. Success

With your time of concentration and c and b values, the Steel formula can be solved and your intensity obtained for use in the ration method.

When to Choose IDF or Steel Formula

Ah the golden question, what are the indicators of going with one method or the other? If you are given an IDF curve, and the frequency and duration I think this is a no-brainer, get it from the IDF curve!

If you are given a city or region, but no IDF curve, then you should probably shoot for the Steel Formula, they had better given you enough info to also calculate the time of concentration.