4 ft slope and a total of 17 ft retaining wall

[Rick81]

Hello All, I have a situation that I cant figure out. My backyard has a big slope. I want to build a pool, given I am not a wealthy person, I want to go with fiber glass.
My issue is (Please let me know if the description is not clear enough). My backyard has about 16 ft high retaining wall. i.e. the house behind is about 16 ft down from ground level.
there's 8 ft of Fill with flay, silty, limestone fragments, and damp. Then another layer, about 7 ft, of Clay, dark reddish brown with silt with limestone fragments.

Termination depth is about 16.8 ft down from the patio.

the companies bidding for this project have proposed that they'll have excavate all the way down and build up or they'll have to use piers and beams. both options are being quoted above $200k.

I am a newbie to all this and I dont know what to do next. I hope kind folks on this forum can point me in the right direction.

 

[JamesW]

You probably need a geotechnical engineer to investigate the soil conditions and come up with a plan.

To do it right, it is not going to be cheap.

What is the budget?

 

[JamesW]

there's 8 ft of Fill with flay, silty, limestone fragments, and damp. Then another layer, about 7 ft, of Clay, dark reddish brown with silt with limestone fragments.

Termination depth is about 16.8 ft down from the patio.

Where did you get this information?

the companies bidding for this project have proposed that they'll have excavate all the way down and build up or they'll have to use piers and beams. both options are being quoted above $200k.

At the end of the day, you can only choose from the people willing to show up and do the work.

How many Proposals have you received?

Have you contacted all qualified builders for Proposals?

What soil testing has been done by the builders to verify the Proposed building plans?

Are the builders relying on a professional licensed engineer to certify all plans or to do the plans?

Maybe you can negotiate with them by asking for a detailed breakdown of the costs and then look for opportunities to do parts of the project cheaper if possible.

What is the engineering cost of the build vs. the pool build?

Can you show pictures of the proposed location?

 

[.ben]

A 16-foot-tall retaining wall is a significant structure. Adding an adjacent pool requires careful engineering to ensure the stability of both the new pool and the existing retaining wall.

The choice between excavation and fill vs. pier and beam should be made after careful consultation with a qualified structural engineer and geotechnical engineer. I have limited information, but my initial gut reaction is to lean towards supporting the pool on piers.

I would not assume that fiberglass pool is less expensive than a concrete pool, especially considering the complexities of this project. If the pool is supported on piers, it may be possible that your engineer integrates the concrete piers with the pool concrete structure.

It is your (+Builder & Engineer) responsibility to ensure the stability of the existing retaining wall. I bet your lower neighbor would appreciate a head's up before this project starts with assurance that the project will be done by a qualified builder and with proper permits.

I obviously don't have the full picture, but a proposal of $200K+ does not shock me.

A less expensive option may be to sell your home and purchase another home with an existing pool.

 

[Rick81]

HI All, so geo technical survey was done, I have attached screen shots of that survey.

Aqua pool guys have no concerns, they want to level the pool area. attached pictures. Their quote is about $100k.

I'll also respond to other questions by James and Ben.

My budget is ~130k

 

[JamesW]

Based on the slope, it will definitely require professional engineering.

Maybe you can get the engineering done by a different contractor and then have the pool builder do only the pool part.

Maybe get a general contractor who can then hire the pool builder as a subcontractor.