In my experience, for large projects, there’s a construction plan developed, which includes recommendations for silt fences, settling ponds etc, by the contractor and approved by clients CE

For a small project like yous the contractor just manages storm water as needed.

Interesting. The project CD's I'm looking at has a sheet titled "Construction Implementation Plan" which includes the locations of silt fences which were installed. Yet, the project spec also includes a broad requirement that the GC "Prevent surface water from flooding project site".

The building flooded during a thunderstorm and the owner is only going after the contractor.

silt fences and settling ponds do not prevent flooding. a floodwater management plan would be a good start, however some limits must be set such as the height of berms, capacity of channels and pipes, amount of rain, etc. the owner can negotiate any level of flood protection with the contractor that he wants, but should be done before proceeding, not after. broad requirements may not hold up in court. in my experience, this is always the responsibility of the contractor and perhaps some level of review by the design engineer.

When it comes to stormwater management requirements, much depends on the jurisdiction.

In mine (which with regard to stormwater management is one of the most stringent areas in the US) SWMPs are designed and stamped by professional engineers without exception, for ANY project which involves disturbing dirt. Even if that project is as simple as replacing some existing landscaping which already has permanent stormwater runoff control measures in place, we are still required to engage an engineer to evaluate any possible change in the flows hitting the existing measures, and determining if additional temporary controls are needed.

I've worked in other jurisdictions were the general consensus was 'if you put silt fence in you are fine'.

But really, none of this is really pertinent to what you're asking. 'Stormwater' and 'Floodwater' are not the same thing. Stormwater controls in general don't prevent stormwater from flowing; they prevent that flowing water from moving sediment from a site to places where sediment should not be (off the site).

If, by grading the site a certain way, the contractor created a new path for runoff to overtop the foundation of the building, it would seem the contractor is on the hook. If the site experienced a 500 year rain event which would've cause the existing site to flood the building with runoff, and no flood water management was in place per the contractor's contract with the owner, then the contractor is likely going to be able to avoid liability.

Excellent thoughts. Yes, in this jurisdiction, there appears to be a lot of emphasis on sediment control only.

In my case, it seems highly misleading for a civil engineer to provide a Construction Implementation Plan which shows where to place hay bales, sandbags, and silt fences but then turn around when water comes into the building and say it was a "best effort" and blame the contractor.

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there appears to be a lot of emphasis on sediment control but virtually no mention of how to prevent flooding

This is not just your jurisdiction - this is stormwater control in every jurisdiction. Stormwater management is about controlling sediment, so that you avoid contaminating water flows, surface waters, streams, and rivers - it has absolutely nothing to do with preventing damage to a structure from floodwater. Completely separate objectives, which need to be addressed with separate systems and planning.

In my experience, during construction, the GC (I generally just use Contractor) is responsible for site water management... if his site floods, he's responsible for properly getting rid of the water he doesn't want.

During construction, it's not normally a jurisdictional issue unless he tries to dump it where he shouldn't.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

This flood scenario will really be project as well as site specific. If the site is located within a designated flood plain, you can't expect the Contractor to be responsible.

Stormwater plans generally don't address flooding.

We had a project a few years ago where it rained heavily after the Contractor pulled off the topsoil exposing a clay subsoil. The Contractor received a change order for the extra cost of removing swelling clay.

What is the wording of the construction contract?

sorry... I was thinking of run-off water or precipitation issues, not flood plain ones.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

But CVG, I dont think a floodwater management plan (or whatever you want to call it) will be developed for a 1 story commercial building? Maybe I am wrong but thats what ive come to see. Yes 10 acres is a moderately sized site but 90% of the land is being untouched. As such, the contractor would be responsible to keep their work space dry.

Bimr - but thats just bad luck for the contractor, no? Isnt it their responsibility to maintain a dry work space, such as only expose a certain area that you can seal/protect in the next day or two. If they want to expose everything they take the risk themselves.

A force majeure could be considered an exception...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

All great points. This is not in a floodplain, it is simply an issue of having a construction site on a slope and the building was at the base of the slope.

Since there is absolutely nothing in writing stating what rainfall intensity the site would need to be designed for during construction, at what point does the issue transition to force majeure?

Like I mentioned, there were separate civil plans for "Sitework Implementation" and "Erosion and Sediment Control". The implementation plan showed locations of sandbags, hay bales, and silt fencing at the base of the hill, and which failed. It would seem to me that an implementation plan like this would be considered the stormwater management plan. It just seems unreasonable to expect a contractor to run an analysis on a sloped site to determine the level of temporary protection he'd need to install.

If it makes any difference, I dont see how the final grading plans would prevent water from coming into the building.

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it is simply an issue of having a construction site on a slope and the building was at the base of the slope.

They way you're describing this scenario makes it sound, to me, like the building would have flooded during this rain event even if the contractor had not yet touched the site. If that's true, and the contractor was not notified that surface water flow is an existing issue and they needed to mitigate it, then in my opinion there's no chance the contractor is going to absorb responsibility at the end of the day.

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implementation plan showed locations of sandbags, hay bales, and silt fencing at the base of the hill, and which failed

Failed how? Are you saying the silt fence was washed away or damaged by flowing water?

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It just seems unreasonable to expect a contractor to run an analysis on a sloped site to determine the level of temporary protection he'd need to install.

I would agree, that would probably be unreasonable - unless it was stipulated in the contract that surface water flow was a problem and that the contractor needed to control said surface water flow.

Without defining 'reasonable' that's where it comes into play...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

The contractor is responsible for site surface water control during construction. The civil engineer, at the time of design, does not know the contractor's sequencing, staging, nor schedule. He doesn't know when the construction will start and how long it will actually take. For these reasons, it would be impractical for the engineer to anticipate these variables and provide a design for a temporary condition.

The contractor has control over means and methods of construction. He can decide to handle the water or slop around in it during construction which will cost him time and money.

Controlling surface water and controlling flood water are vastly different. Contractors are not qualified or equipped to evaluate flood potential and design systems to control potential floodwater. When I am asked to do this, I hire the correct engineer to do it.

OP has yet to provide enough detail to really know what happened here.

That's why I mentioned a force majeure... and then it depends on how others react to it.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Ron,
Normally I would agree with you that it's the GC's responsibility, but when it's a funky site and the CE seems to admit that it's a funky site by providing a construction implementation plan showing surface water controls to protect the existing portion of the building (just outside the bounds of excavation areas), dont you think that starts shifting the responsibility over to the CE? It certainly risks misleading the GC into thinking that if he places those controls he's good.

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CE seems to admit that it's a funky site by providing a construction implementation plan showing surface water controls to protect the existing portion of the building (just outside the bounds of excavation areas), dont you think that starts shifting the responsibility over to the CE?

The 'construction implementation plan' as you described in your second post- a drawing which shows the location of silt fence and maybe bales/wattles etc, is NOT a surface water control plan. Silt fence/bales/wattles DO NOT control surface water. They control sediment only. 'Stormwater', in the construction lexicon, does not mean 'controlling all water that may enter a site and preventing it from inundating excavations, flooding existing structures, or going places where it is generally not wanted'. 'Stormwater' means controlling sediment and pollution/contamination to the degree required by the AHJ. That's it.

That would make more sense to me if there wasn't a separate Sediment and Erosion Control Plan on this project.

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That would make more sense to me if there wasn't a separate Sediment and Erosion Control Plan on this project.

By definition, silt fence/hay bales/wattles do not control water. They are all fully water permeable, by design.

I can't explain why the civil engineer apparently put the SWMP in two places, but silt fence is not a floodwater control measure; anyone who saw that drawing and thought it would stop flooding is either inexperienced or inept.

It seems to me that the project owner's site engineer would need to have a designed plan to handle the situation long term after the building is finished. Therefore, that plan should be implemented as much as possible at the start of construction. This would be different than a sedimentation & erosion control plan. As others have said, erosion and sedimentation is not flooding.

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But CVG, I don't think a floodwater management plan (or whatever you want to call it) will be developed for a 1 story commercial building? Maybe I am wrong but that's what I've come to see. Yes 10 acres is a moderately sized site but 90% of the land is being untouched. As such, the contractor would be responsible to keep their work space dry.

Contractor will not develop any plan unless it is required by the contract. so if the owner or designer is concerned about protecting the building from flooding (either during construction, or permanently after construction), than put a requirement in the contract drawings and specs to do that. temporary controls are generally designed by the contractors engineer, permanent controls should be designed by the owners engineer.