19 October 2004

Mr. Que Hales
OnBalance
3136 E. Pennsylvania Street
Tucson, AZ 85714

Re: Document Review for Pool Discoloration Project
WJE No. 2004.4477.P

Dear Mr. Hales:

Microscopical analyses of a specimen of pool plaster were conducted by me at Construction Technology Laboratories, Inc. (CTL) in 2003, before I joined Wiss Janney Elstner Associates, Inc. The analysis was performed on behalf of OnBalance and was to investigate possible explanations for the nonuniform appearance of the surface of the plaster. Along with the plaster specimen, you had also submitted to CTL a compilation of reports by Dr. Boyd Clark of R J Lee Group for investigations that he had conducted on similar specimens of pool plaster from different locations.

Results of the analysis conducted at CTL are consistent with, and generally comparable to, the analyses performed by Dr. Clark, whose work predominantly consisted of scanning electron microscopical analyses. In the CTL study, petrographic microscopy was supplemented with scanning electron microscopy, and also included chemical analysis for chloride content. The CTL report presented a chemical mechanism for the development of the non-uniform appearance of the plaster surface. Although this mechanism was based on observations and data from the CTL laboratory study, it is essentially compatible with the data obtained by Dr. Clark.

You may contact me directly with any further questions. We would be pleased to assist you with any further analyses.

Very truly yours,

WISS, JANNEY, ELSTNER ASSOCIATES, INC.

Laura J. Powers
Consultant

2004.4477.P/OnBalanceLetter