140R4026B0002_-_Attachment_3_1_00_00_02B_Corrosivity_Report_NGWSP_Turnout_Bldgs_20261009_0002.pdf
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This is a soil corrosivity testing report from the United States Department of the Interior, Bureau of Reclamation, dated September 13, 2025, for the Navajo-Gallup Water Supply Project in New Mexico.
The report documents corrosivity testing performed on 13 soil samples collected from test pits near turnout building locations along the San Juan Lateral. Testing was conducted by Weld Laboratories, Inc. in Greeley, Colorado using AASHTO standards for resistivity (T288-12), pH (T289-91), chlorides (T291-94), and sulfates (T290-95). Key findings indicate that resistivity values fall in the "very severe" range for 6 samples and "severe" range for 6 samples, with 1 sample in the "moderate" range. All 13 samples measured pH in the "neutral" range (6-9). Chloride concentrations were "low" for 10 samples and "moderate" for 3 samples. Sulfate concentrations were "low" for 9 samples, "moderate" for 1 sample, and "severe" for 3 samples. The report concludes that 12 of 13 samples indicate a highly corrosive environment requiring special design considerations. Recommendations include specifying buried ferrous materials with protective coatings and cathodic protection, and coordinating with TSC Materials and Corrosion Laboratory (MCL) staff for corrosion mitigation and TSC Concrete and Structural Laboratory (CSL) staff for concrete mix design. The report notes that soil chemistry varies by location and additional testing may be needed for other project locations.
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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.
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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).
Samples were tested at third-party laboratory, Weld Laboratories, Inc. The standards used by this laboratory for corrosivity testing are:
o Resistivity – AASHTO T288-12 o pH – AASHTO T289-91 o Chlorides – AASHTO T291-94 o Sulfates – AASHTO T290-95
Resistivity values fall in the “moderate” range for 1 sample, “severe” range for 6 samples, and “very severe” range for 6 samples. The measured values for pH are within the “neutral” range for all samples. Chloride concentrations fall in the “low range” for 10 samples and the “moderate” range for 3 samples:
Chlorides Low Chlorides Moderate
TPTB-25-(1-4, 7, 9-12, and 23)
TPTB-25-(5, 6, and 8)
Sulfate concentrations fall in the “low” range for 9 samples, the “moderate” range for 1 samples, and the “severe” range for 3 sample:
Sulfates Low Sulfates Moderate Sulfates Severe
TPTB-25-(3, 4, 7-12,
and 23)
TPTB-25-6 TPTB-25-(1, 2, and 5)
Test results are included as Appendix A.
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The following table specifies the accompanying test values with their respective range.
Table I. Test Ranges and Values
Range Values
-cm)
Low >10,000 Moderate 5,000-10,000
Severe 2,000-5,000 Very Severe <2,000 pH Acidic <6 Neutral 6-9 Basic >9
Chlorides (mg/L)* Low <100
Moderate 100-500 Severe >500
Sulfates (mg/L)*
Low <1,000 Moderate 1,000-2,000
Severe 2,000-20,000 Very Severe >20,000 cc: FCCO-725 (C. Beyer), 86-68320 (T. Lewis), 86-68540 (D. Little), 86-68550 (T. Chatfield)
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APPENDIX A
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