Water tank Spacing 1

[BRIS]

We are developing a site with 3 number 20 million gallon welded steel water storage tanks. Each tank has a diameter of 90 m (295 ft). The site is very tight - I am looking for some guidance on the minimum spacing between tanks and boundary walls. Concerns include access for construction and future maintenance and possible adverse wind loading.


Brian

 

[yogibear1]

I would think among other criteria, the foremost is to have a recommendation from your geotechnical engineer based upon several soil borings per each proposed tank footprint. Do not scrimp on the number of soil borings per tank. The site can have unforeseen differences which may be crucial in the design. You would give the geo-tech the proposed tank size, sidewall heights (I calculated around 39 ft for your tanks), max water level (scupper or spillover pipe setting), closed tank or open, etc. in order to determine weights and then the foundation loadings. They generally develop a foundation recommendation consistent with the site soils. Where tanks have to sit close together they will factor that into the recommendations for the foundation and any potential underground enhancements.
Other considerations:
This height may (may not) trigger a zoning condition or restriction in your community too.

Would you have to have containment walls in case of catasdtrophic failure; where would the water go?

How about stormwater runoff (if covered tanks) due to new impervious area?

Maintenance, you would want at least room for service vehicles to get in and out without backing - so perhaps a circular drive.

Will you have lights?

Will there be any otehr underground utilities w/in the subject area, etc.
And theer may be other considerations as you get specific to your site.

 

[BRIS]

The geolgy of this site comprises a thin soil layer (6 to 10 ft)over rock - we can excvate the whole area and backfill with compacted crushed rock to provide a uniform foundation.

The site is in the Middle East - rainfall runoff, height restrictions etc are not a concern. Temperature variation may be -

Brian

 

[boo1]

Consider access for site mainaince and repairs too.

 

[RCEJD]

Dear Bris:

My firm has dealt with this issue in California many times both from a geotechnical and civil standpoint. Since your site description eliminates many of the concerns ... maintance and construction access are crucial (as you know and has been discussed). In my mind though, the priority is if the tanks were to burst as a result of a catastrophic event, what are the impacts on "downstream" or adjacent properties. The size of one tank warrants concern, but if several are located in close proximity, specific attention should be paid. This is a tough question in most instances, but should be addressed.

Good luck.

 

[cvg]

If you are going to excavate 6 - 10 feet of overlying soil, you could construct the tanks partially below grade.

added benefits include no need to haul in crushed rock, lower height above ground, water stays cooler, release of water from a "burst" tank is less. Potentially less impact from seismic events.

disadvantage - outlet pipes are deeper, harder to inspect the below ground part.

You may want to construct the part below ground with concrete instead of steel.

 

[BRIS]

CVG --

Concrete tanks would be the optimum solution - they would be less eexpensive, could be designed to suit the irregular shaped site and could be partly buried but the client is 100% opposed to concrete. (bad experiences in the Arabian Gulf from chloride attack etc). A steel tank has to be at ground level.