Reso13 PC 13-09 2859 Initial Study Mitigated Negative Declaration Kensington

Browse Search

Proposed Senior Assisted Living Facility PSI Project No. 575-308-2 August 3, 2011 Page 16 5.8 Corrosivitv Testing was performed to evaluate the corrosivity of the on-site native soils and the potential for attack on concrete and subsurface utility pipes, specifically cast iron and ductile iron. The testing included pH, sulfate, chloride and electrical resistivity. The results of the chemical analysis are as follows: Boring Sample Depth pH Resistivity Water Soluble Water Soluble Number feet ohm-cm Sulfates ppm Chlorides ppm B-6 0-5 6.5 1,200 173 3.09 Concrete mix design should follow the minimum requirements of the CBC. Laboratory testing of a selected soil sample indicates the on-site soils have a /ow degree of corrosivity with respect to concrete. For preliminary design purposes, it is our opinion that the use of Type II cement is suitable for concrete in contact with on-site soils. Final concrete mix design should be evaluated after sulfate tests have been performed on the actual as-graded subgrade material. Corrosivity testing was also performed to determine whether the on-site soils have the potential to attack subsurface utility pipes. Based on the resistivity and chloride test results, the soils are characterized as having a severe degree of corrosivity to cast iron or ductile iron piping (NACE, 1984). PSI does not practice in the field of corrosion engineering. We suggest that a qualified corrosion engineer be consulted to determine if special corrosion protection is warranted. Testing for corrosivity of any fill soils should be conducted after site grading. 5.9 Construction Monitorinq It is recommended that PSI be retained to examine and identify soil exposures created during project construction in order to document that soil conditions are as anticipated. We further recommend that any structural fills be continuously observed and tested by our representative in order to evaluate the thoroughness and uniformity of their compaction. If possible, samples of fill materials should be submitted to our laboratory for evaluation prior to placement of fills on site. Costs for the recommended observations during construction are beyond the scope of this current consultation.