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Re: minimum fc for Residential slab on grade

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Around here (Marin Co.) no building dept. requires 3000psi. My G/N say provide 3000psi & the design is based on 2500psi. The EOR observes the completed steel placement but no test cylinders are needed.
C. Utzman, P.E.

Stanley E Scholl wrote:
Just specify 2500 psi for all concrete except grade beams, which most jurisdictions require 3000psi min. and thus a deputy inspector, who can also be used to inspect any epoxy you may have designed.
On Wed, 9 Jul 2003 14:28:10 -0700 "Dennis Wish" <dennis.wish(--nospam--at)> writes:
I designed a single story residence (spec home but large) using a slab on grade which is typical in this area. Historically, we placed f'c=2,000 psi concrete for everything but where proprietary frames such as Hardy Frames are used. The typical soil in the area is silty sand with a bearing pressure of 1,500 psf and with increases allowed for depth and width.
I received a plan check correction based on the 1998 CBC and 1997  UBC. He quoted section 1921.2.4 which requires high strength concrete but has an exception that allows for concrete not less than 2,500 psi. This is generally required when inspection of the concrete is called for and not for simple slab on grades. The city has, during the 1997 UBC cycle allowed for f'c=2,000 psi concrete, but the contract plan check company requires 2,000 psi concrete so as not to force deputy inspection.
Are there any comments as how I should address the plan check correction since deputy inspection can be expensive and there are no problems with subsidence or expansive soils in the area.
Am I wrong on this one????? If so, it comes as a surprise.