Attachment 3 1 00 02B Corrosivity Report NGWSP Turnout Bldgs 0002

G26

86-68540
2.2.4.21

VIA ELECTRONIC MAIL ONLY

MEMORANDUM

To:

Sara Putnam, P.E., Civil Engineer
Plant Structures (86-68120)
Technical Service Center, Denver, CO

From:

Daryl Little, Ph.D., Supervisory Civil Engineer
Materials and Corrosion Laboratory Group (MCL) (86-68540) Technical Service Center, Denver, CO

Subject:

Soil Corrosivity Testing – San Juan Lateral – Turnout Buildings, Corrosivity Report, Upper Colorado Basin Region, Navajo-Gallup Water Supply Project, New Mexico. Referral Number: 8540-2026-19

INTRODUCTION

Corrosivity testing was performed on 13 soil samples collected from Test Pits near the turnout building locations. Samples were tested at Weld Laboratories, Inc in Greeley, Colorado for resistivity, pH, and soluble chloride and sulfate concentrations.

CONCLUSIONS

Resistivity values fall in the “very severe” range for 6 samples and “severe” range for 6 samples. pH values fall in the “neutral” range for all 13 samples. Chloride concentrations fall in the “low” range for 10 samples. Sulfate concentrations fall in the “low” range for 9 samples, but 3 samples fall into the severe range.
12 of the 13 samples indicate a highly corrosive environment; it is recommended that buried ferrous materials be specified with a protective coating and cathodic protection. Soil chemistry can vary with location; additional testing may be needed to make conclusions about the corrosivity of the soil in other project locations. TSC-MCL staff have expertise in corrosion mitigation.
These results indicate need for special considerations on this project pertaining to corrosion of metallic structures and concrete structures. TSC Concrete and Structural Laboratory (CSL) staff have expertise in concrete mix design. This group can provide additional interpretation and support, if needed.

G27

CORROSIVITY TESTING AND RESULTS

The purpose of corrosivity testing is to quantify properties of soil that indicate a high probability for adverse reaction with buried structures, such as corrosion of metals or sulfate attack in concrete. Such properties include the concentrations of water-soluble minerals that may be dissolved and transported to the structure during periods of high precipitation. Reclamation recommends corrosivity testing for any structure, metallic or concrete, which comes in contact with soil. Corrosivity testing consists of measuring soil resistivity, pH, and the concentrations of water-soluble anions, with primary analytes being chloride (Cl-) and sulfate (SO4-2).