Budgeting at concept stage

Someone has to put a number in a capital plan before there is a design, a survey, or a permitting position. That number then becomes the number, and everything afterward is measured against it.

The problem is not that a concept estimate is imprecise. Everyone knows it is. The problem is that the imprecision gets forgotten and the figure hardens into a commitment.

What to establish first

Before estimating anything, four facts change the answer by more than any pricing assumption:

1. What is the mechanism? Erosion at the toe, a stability failure, a channel that is degrading, or scour at a structure. They need different treatments at different costs, and armoring a stability failure is money spent on the wrong problem. See how to read a failing bank.

2. What is actually at risk, and how far away? This sets urgency and whether doing nothing, or setback, is viable. On a rural bank with nothing within fifty metres, the honest concept answer may be to monitor.

3. How much of it? Length, height, and depth. Rough measurements are fine; an order of magnitude is not.

4. Can plant reach it? Access is the largest single cost driver and it is knowable from a site visit. See what drives installed cost.

Building the estimate

Get the quantity approximately right. Length times protected height gives area; extent below the water line and at the toe is where quantity is most often underestimated. The protected footprint at a structure is larger than the structure.

Estimate the material. For bagged armor: the units and the local fill. Send the site conditions through the quote form and you get sizing and quantity back within one business day, at no cost, which is a better basis than a rule of thumb.

Estimate the placement. Crew and plant days, at a rate appropriate to the method, adjusted for access and any window constraint.

Add the temporary works honestly. If the method needs dewatering, that is a package in its own right and it belongs in the concept number — see what dewatering really adds. If the method does not, say so, because that is a real difference between options at this stage.

Add the soft costs. Survey, hydraulic analysis, design, permitting, certifications, and any consultation. On a permitting-heavy site these are a substantial fraction, and they are the ones most often omitted from a concept figure entirely.

Add site management. Traffic management, environmental controls, welfare, access construction.

Add contingency appropriate to the stage. At concept, before survey, that is a large number, and it should be shown as a range rather than buried in a single figure.

Present a range, not a point

The single most useful thing you can do.

A range with the assumptions attached survives revision. A point estimate does not, and when the real scope arrives, revising it looks like an overrun rather than what it is — the estimate doing its job.

Record the assumptions

Whatever form the estimate takes, attach:

The extent assumed, and how it was determined
Whether dewatering is assumed
The access assumption
The material source assumption
Whether the mechanism has actually been diagnosed or inferred
What permits are assumed, and whether a general permit is expected to fit
What is excluded

That list is what lets you revise defensibly. “The estimate assumed a general permit and the district required an individual permit” is a documented change of scope. Without the list, it is an overrun.

What most often blows a concept budget

In rough order:

The mechanism was misdiagnosed, and the treatment does not address it
Extent was underestimated, particularly below the waterline and at the toe
Dewatering was not in the number
Access needed construction
Permitting took longer, pushing into the next window and adding a year
Soft costs were omitted
The specified material was not available locally

Six of those seven are knowable before design. A site visit, a rough survey, and a conversation with the Corps district would resolve most of them, and doing that work at concept stage is cheap relative to the error it prevents.

The option that belongs in the comparison

Include do nothing as a costed option, with its consequence and timescale.

Sometimes it is the right answer, particularly where retreat is slow and nothing is close. Where it is not the right answer, having it costed is what makes the case for the work.

Also worth including, where the site allows: relocate what is at risk. On rural and undeveloped reaches, setback can cost less than armor over any long period. See outer bend erosion.

Where to go next

Concept-stage enquiries are welcome and there is no charge for engineering support at this stage. A project at feasibility with no funding is still worth a conversation — send what you have through the quote form.