Structures Design Guidelines | July 2005
1 - General Requirements |

## 1.3 Environmental Classifications

A. The District Materials Engineer or the Department’s Environmental/Geotechnical Consultant will environmentally classify all new bridge sites. Environmental classification is required for major widenings (see definitions in Chapter 7
) and may be required for minor widenings. This determination will be made before or during the development of the Bridge Development Report (BDR)/30% Plans Stage and the results will be included in the documents. The bridge site will be tested, and separate classifications determined for superstructures and substructures.

B. In the bridge plans “General Notes,” include the environmental classification for both the superstructure and substructure according to the following classifications:

1.) Slightly Aggressive

2.) Moderately Aggressive

3.) Extremely Aggressive

C. For the substructure, additional descriptive data supplements the environmental classification. After the classification, note in parentheses, the source and magnitude of the environmental classification parameters resulting in the classification.

Commentary: As an example, for a proposed bridge located in a freshwater swampy area where the substructure is determined to be in an Extremely Aggressive environment due to low soil pH of 4.5 and the superstructure to be in a Slightly Aggressive environment, the format on the bridge plans will be:

> ENVIRONMENTAL CLASSIFICATION:

> Substructure: Extremely Aggressive (Soil - pH = 4.5)

> Superstructure: Slightly Aggressive

D. The substructure will not be classified less severely than the superstructure.

E. Bridge substructure and superstructure environments will be classified as Slightly Aggressive, Moderately Aggressive, or Extremely Aggressive environments according to the following criteria.

### 1.3.1 Substructure

For Conditions of soil and water (See Figure 1-1):

A. Slightly Aggressive when all of the following conditions exist:

1.) pH greater than 6.6.

2.) Resistivity greater than 3,000 ohm-cm.

3.) Sulfates less than 150 ppm.

4.) Chlorides less than 500 ppm.

B. Moderately Aggressive: This classification must be used at all sites not meeting requirements for either Slightly Aggressive or Extremely Aggressive Environments.

C. Extremely Aggressive when any one of the following conditions exists:

1.) For concrete structures: pH less than 5.0.

2.) For steel structures: pH less than 6.0.

3.) Resistivity less than 500 ohm-cm.

4.) Sulfates greater than 1,500 ppm.

5.) Chlorides greater than 2,000 ppm.

### 1.3.2 Superstructure

A. Slightly Aggressive: Any superstructure situated in an environment that is not classified as either Moderately or Extremely Aggressive (see Figure 1-1).

B. Moderately Aggressive: Any superstructure located within 2,500 feet. of any coal burning industrial facility, pulpwood plant, fertilizer plant or any other similar industry where, in the opinion of the District Materials Engineer, a potential environmental corrosion condition exists, or any other specific conditions and/or locations described in Figure 1-1.

C. Extremely Aggressive: Any superstructure situated in an area such that a combination of environmental factors indicates that significant corrosion potential exists, or with specific conditions and/or locations described in Figure 1-1.

### 1.3.3 Chloride Content

A. The District Materials Engineer will determine the chloride content of the water and soil at the proposed bridge site.

B. The chloride content of major bodies of water within 2,500 feet of the proposed bridge site will, in most instances, be available in the Department's Bridge Corrosion Analysis database. If chloride values are unavailable, the major body of water must be tested unless it is known to be a freshwater body.

C. Generally, all superstructures that are within line-of-sight and within 2,500 feet of the Atlantic Ocean or the Gulf of Mexico are subject to increased chloride intrusion rates on the order of 0.0016 lbs/cy/year at a 2-inch concrete depth. The intrusion rate decreases rapidly with distance from open waters and/or when obstacles such as rising terrain, foliage or buildings alter wind patterns. In order to optimize the materials selection process, the Designer and/or District Materials Engineer have the option of obtaining representative cores to determine chloride intrusion rates for any superstructure within 2,500 feet of any major body of water containing more than 12,000-ppm chlorides. The District Materials Engineer will take core samples from bridge superstructures in the immediate area of the proposed superstructure. The sampling plan with sufficient samples representing the various deck elevations will be coordinated with the State Corrosion Engineer. The Corrosion Laboratory of the State Materials Office will test core samples for chloride content and intrusion rates.

D. After representative samples are taken and tested, Table 1.1 will be used to correlate the core results (the chloride intrusion rate in lbs/cy/year at a depth of 2-inch) with the classification.

Table 1.1 Chloride Intrusion Rate/Environmental Classification

CHLORIDE INTRUSION RATE | CLASSIFICATION
> 0.0016 lbs/cy/year | Extremely Aggressive
< 0.0016 lbs/cy/year | Moderately Aggressive

### Figure 1-1 Flow Diagram for determining Environmental Classification (07/05)