These specs meet USDA and NRCS requirements
- Our bids do NOT include proper site preparation.
- The customer, or a contractor arranged by us or the customer, must provide a “proper site” for a new tank.
The site should be scraped free of grass and organic matter. If material is used to widen the site, then it must be compacted properly before the gravel is put down and spread.
The NRCS/USDA recommendation is a minimum of 4” of crushed rock. EPM recommends 1/4” to 3/8” size crushed blue rock (commonly called “pea gravel”) because it is least harmful to the tank liners. We recommend an additional sand coating for the longevity of the liner. A minimum four inch layer of gravel is spread evenly over the level site. We recommend application of a thin coating of clean sand for the extra safety and smooth finish. The level site should be about 4’ larger than the diameter of the tank. Minimum of 2’ at any point. On Maui, crushed blue rock sand is available and preferential to beach sand at a lower cost.
NRCS/USDA specifications require a 4″-6″ sand “cove” on the inside of the tank between the metal and the foundation to minimize stress on the bottom seam of the liner. As water sits perfectly level, the water tank must start with a truly level foundation to avoid stress on the water tank frame. The site must be “solid” without soft fill or organic matter and it must be within 1” of level over the required area. Recommendations for the amount of gravel and sand needed for the various size tanks are available. We provide referrals for machine work and delivery of sand or gravel.
If the gravel is spread reasonably level, the sand pile is better located on top of the gravel near the center. The base-scraped earth site should be within 2” over the whole diameter of the tank site. The pea gravel should be spread out over the site carefully and should be within 1” (one inch) of the same level in the area where the tank metal will sit. Preferably, the gravel is level over the whole site extending a minimum of 2+’ larger than the tank diameter.
It is possible to create a bowl shaped site lower in the center as long as it’s the same level all around on the perimeter where the tank will sit. The center of the bowl must be 18” or less deep than the edge. While this system increases the capacity of the water tank, it is labor intensive and is not often done.
We recommend having the tank site level and the gravel spread level over the site about 4’ bigger then the actual diameter of the water tank. When the job is finished the gravel is piled back against the tank bottom to prevent rodent invasion. A proper water tank installation requires a level site with about 4″ of 1/4 to 3/8″ “pea” gravel spread on it and an adequate pile of sand very near the water tank site or thw on the gravel. (about 9 yards of pea gravel for a 28’ tank + 3 or 4 yards of sand). Concrete rings or slabs are also good water tank foundations at a much higher cost.