High tide problems - What are the solutions?

[BigBrother]

We are working on a project that's oceanfront.

Yesterday, the entire area was relatively dry, but there was water about a foot into the hole, so we installed well points.

When going there today during middle of high tide, this was the backyard.
I haven't inspected it myself and I assume there was a hole or something that let this amount of water in as I struggle to believe it's just groundwater.

That said, has anyone here built under these conditions?

I have reached out to my engineer, but waiting on his response and curious how other pool builders have handled this in the past.

EDIT:

Adding info here for context that was discovered later in the day.
It was a king tide, so abnormal tide.
We do work with engineers and all proper permitting and steps are taken including well points.
Some solutions discussed: sheet piles, sea wall, moving pool entirely

 

[kimkats]

now that is a problem for sure!

Was there a storm last night? What is the wall made of that is between the pool and water?

 

[BigBrother]

now that is a problem for sure!

Was there a storm last night? What is the wall made of that is between the pool and water?

Yes, nightmare problem to wake up to...

It's just a double row of silt fence.

I've been to the property 5 times and never seen the water anywhere close to the backyard.

I see nothing out of the normal other than this being directly at dead high tide.
EDIT: it was a king tide

 

[JoyfulNoise]

Is the water salty?

Did you map out all of the utilities before digging?

Water always finds its own level and it flows to and through the path of least resistance. High tide can exert pressure on the coastal ground saturation and force water to move through soils. Unless a source is found like a broken pipe, then it’s very likely water infiltration from the nearby coast line.

You need to re-dig the well points and have submersible pumps running all the time. Even then, water infiltration may not be stopped.

 

[BigBrother]

Is the water salty?

Did you map out all of the utilities before digging?

Water always finds its own level and it flows to and through the path of least resistance. High tide can exert pressure on the coastal ground saturation and force water to move through soils. Unless a source is found like a broken pipe, then it’s very likely water infiltration from the nearby coast line.

You need to resign the well points and have submersible pumps running all the time. Even then, water infiltration may not be stopped.

It's confirmed ocean water, it's very obvious on site as there is water literally everywhere. Less obvious in the picture.

The pumps alone won't be able to keep up with the ocean, We had a pump with well points on during this.

No pipes were hit, 811 called, etc.

My engineer got back to me and mentioned sheet piles like building a bridge, but that the entire thing would also need helical piles.
Not sure if any builders here have dealt with this before.

 

[JoyfulNoise]

Well, if you have to install steel sheet piles, that's going to make the project cost soar. I don't think there's any other way around this problem as you're too close to the ocean.

Perhaps @setsailsoon (Chris) might offer any insights as he has done plenty of commercial construction projects in his life ... and I believe he lived on the ocean for an extended period of time ... he must really like water or something

 

[JamesW]

You probably need a geotechnical engineer to design a proper plan.

You probably need retaining walls as well as some type of piers or piles for support.

You probably need a drainage system that can keep everything dry while the pool is being built and available for times when the pool has to be drained.

 

[bmoreswim]

I'm curious what flood zone designation the property is in. Could be telling.

 

[BigBrother]

You probably need a geotechnical engineer to design a proper plan.

You probably need retaining walls as well as some type of piers or piles for support.

You probably need a drainage system that can keep everything dry while the pool is being built and available for times when the pool has to be drained.

Based on this picture, I would say that the builder is not qualified to be building in this location as it is quite a disaster.

View attachment 618346

Well, if you have to install steel sheet piles, that's going to make the project cost soar. I don't think there's any other way around this problem as you're too close to the ocean.

Perhaps @setsailsoon (Chris) might offer any insights as he has done plenty of commercial construction projects in his life ... and I believe he lived on the ocean for an extended period of time ... he must really like water or something

Yes, sheet piles are an option being discussed plus helical piles to keep it in place.
Apparently yesterday was a "king tide", so that doesn't help.

My personal opinion is that the owner should install some sort of sea wall though as this water went all the way around the entire house even in areas where there was no digging.

 

[BigBrother]

Yes, sheet piles were an option plus helical piles to keep it in place.
Apparently yesterday was a "king tide", so that doesn't help.

I'm curious what flood zone designation the property is in. Could be telling.

Most of the properties here on the island are high risk flood zones.

 

[BigBrother]

You probably need a geotechnical engineer to design a proper plan.

You probably need retaining walls as well as some type of piers or piles for support.

You probably need a drainage system that can keep everything dry while the pool is being built and available for times when the pool has to be drained.

Based on this picture, I would say that the builder is not qualified to be building in this location as it is quite a disaster.

View attachment 618346

Geotechnical engineer had eyes on this project and piles were discussed.
Well points and drainage were installed.
Retaining walls are being built, but you can't do that under water.
No amount of "drainage" is going to hold the ocean back in a king tide.

"Builder isn't qualified as it's a disaster" isn't very helpful nor a solution.

The question was asking if people had specific experience with ultra high tides and construction in these situations.

After more research, the currently only possible solutions are sheet piles or not putting the pool there.

 

[JamesW]

My personal opinion is that the owner should install some sort of sea wall though as this water went all the way around the entire house even in areas where there was no digging.

"Builder isn't qualified as it's a disaster" isn't very helpful nor a solution.

I did not mean to be disrespectful.

I was just pointing out that you as the builder are not qualified to design, engineer or architect a proper solution for this property.

You need a properly qualified engineer to advise on what needs to be done.

In my opinion, is it helpful to acknowledge when you need help.

Maybe you are a great builder for most properties, but this specific property is beyond your ability to deal and there is nothing wrong with acknowledging this.

 

[JamesW]

I would think that the location requires special permits due to the location near water, which almost always requires more permits than a normal build.

There are usually other Federal, State and County Agencies that get involved when anything is built that close to a river, lake, ocean etc.

 

[BigBrother]

I did not mean to be disrespectful.

I was just pointing out that you as the builder are not qualified to design, engineer or architect a proper solution for this property.

You need a properly qualified engineer to advise on what needs to be done.

In my opinion, is it helpful to acknowledge when you need help.

Maybe you are a great builder for most properties, but this specific property is beyond your ability to deal and there is nothing wrong with acknowledging this.

Correct, hence why I said this in the original post: "I have reached out to my engineer, but waiting on his response and curious how other pool builders have handled this in the past."

 

[BigBrother]

I would think that the location requires special permits due to the location near water, which almost always requires more permits than a normal build.

There are usually other Federal, State and County Agencies that get involved when anything is built that close to a river, lake, ocean etc.

The project is fully permitted and passed all inspections and pre-clears and stormwater and OCRM inspections.

You'd think someone somewhere would have said "hey this floods every month"

 

[JamesW]

Retaining walls are being built, but you can't do that under water.

I suspect that you need all retaining walls to be in place before continuing the project.

Are you doing the retaining walls?

Can you describe the walls being installed?

Will they be able to hold back the water?

 

[BigBrother]

I suspect that you need all retaining walls to be in place before continuing the project.

Are you doing the retaining walls?

Can you describe the walls being installed?

Will they be able to hold back the water?

Project is on hold currently and hole will likely be filled in tomorrow morning to prevent further damage.
Nothing can be done quickly and especially during a "king tide".

It's clear that the homeowner underplayed the amount of water during these ultra high tide situations.

Will need to go back to drawing board with engineer with this new information and come up with a new game plan.

It's possible that all of this work can be done after king tide (installing retaining walls, etc.) but will have to be on a tight time schedule.

One solution discussed with engineer, if it stays dry for ~3 weeks, we can dig, form, steel, everything, run helical piles, and a 12" floor with #5 double mat. Pour concrete.
That would hold the pool in place.
My main worry is that the rest of the elevated decking will have ground water rising issues.

The only options that seem available:
1. sheet piles / work between king tides / build retaining wall to extra engineered specs for stability
2. Raise the pool to the 10' deck (still need piles and extra engineering and massively increased costs, but would be closer to house and thus less risk of water issues)
3. Move the pool elsewhere (not really possible on that property)

 

[JamesW]

2024 Predicted King Tides​

Based on NOAA Astronomical Tide Predictions for the Charleston Harbor Tide Station

• April 8 – 10
• May 6 – 8
• August 19 – 20
• September 16 – 22
• October 16 – 21
• November 14 – 18

For details, see DHEC’s Tide Tables page.

King Tides | Charleston, SC - Official Website

King tides occur when the moon is either new or full and is closest to the earth in its monthly orbit. These especially high tides can cause or worsen coastal flooding.

www.charleston-sc.gov

The SC King Tides Initiative - MyCoast

mycoast.org

2024 King Tide Dates for Kiawah Island - Kiawah Island Community Association

Everyone knows about high tides and low tides, but did you know that there are also King Tides to be prepared for as well? The term describes the highest seasonal tides that happen each year. In Charleston, the average high tide is around 5.5ft, whereas a king tide event can have tides reaching...

kica.us

King Tide Takes Out the Pools in South Carolina

Perhaps these pools were built too close to the water?

www.aquamagazine.com

 

[PoolStored]

You are likely going to struggle even predicting these king tides.

Charleston Data for 2024 tide predictions with King Tide Threshold (Orange)...


The predictions are significantly off from reality...ACTUAL tide levels for 2024 and king tide level (orange)...ended up being 105 King Tide days in 2024...so far...:



Micro example, 11/11 it was predicted to be 6' (which is below the King Tide threshold), ACTUAL ended up being 6.8', .8' over prediction and over the king tide threshold.

 

[JamesW]