The Clients experience on project “AB” illustrates typical issues with selecting racking and doing facility design before characterizing the site and soils bearing capacity. It also demonstrates how AquaSoli leverages our experience and contacts to solve expensive design and deployment issues.
- If the Posts Length exceeds the Pile Driver Machines Capability something has gone wrong in the planning process…
and might result in exploding Machinery Cost. 
A Client came to us with a racking system and asked us to perform geotechnical site assessment, analytical load testing and foundation design for 3 projects.
On the largest site conventional foundation design specified a total pile length of 13.5 feet for the single center post racking system. Our experience indicated that a pile of this length requires special handling which increases installation costs as much as 30%.
Working with the rack manufacturer and re-analyzing the dense load test data we collected, AquaSoli identified two cost saving foundation alternatives.
1. Discussions with the manufacturer applications engineers determined that the specified foundation stickup included adjustability to accommodate site grade variation. Our site experience allowed the manufacturer to agree to reduce the specified stickup, thus shortening the required pile length.
2. Our analytical foundation load testing identified anomalous vertical bearing behaviour for the preferred foundation profile. By rigorously reanalyzing the soils data and foundation behaviour, we provided a suitable design based on an alternative foundation profile with a reduced embedment depth. The alternative profile design reduced pile length enough to allow the lowest cost installation technique.
The net result is that the client will save about 3 times the cost of our services in installation costs alone.
In addition we identified an opportunity to save as much as 10% on the materials costs by reducing the required foundation stickup.
On a second site we are working to solve a similar issue but resulting from weak horizontal bearing capacity. Site work determined that the soils were mechanically disturbed to a depth of 5 feet. The weak soils and single post rack design dictated a total pile length that required installation by a specialized pile driver. Use of the oversized pile driver increased projected installation costs as much as 300%.
We have identified several alternatives to solve the issue. However by selecting the racking before understanding soils conditions the Client adversely impacted both their schedule and project costs and risked a great deal more.
Lesson to learn: If solar specific site evaluation and load testing is completed first, AquaSoli can recommend standard design and racking alternatives that provide routine solutions for individual site issues. Routine solutions support low costs and schedule compliance. (Author of this text: US VP Bob Donaldson)
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