Structures Design Guidelines | Jan 2008
1 - General Requirements |

## 1.3 Environmental Classifications (07/07) July 2007 - Revised section to differentiate classification process for marine and non-marine environments which eliminates testing for most marine environments. Deleted 6,000 ppm -12,000 ppm chloride range for superstructures, and sulfate criteria for steel substructures. Revised pH criteria for slightly aggressive environments, sulfate criteria for concrete substructures in soil, resistivity thresholds for steel substructures, and flow chart. Added new Table 1.1.

## 1.3.1 General

A. The District Materials Engineer or the Department’s Environmental/Geotechnical Consultant will determine the environmental classifications for 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 (See the PPM Volume 1 Chapter 26) and the results will be included in the documents. The bridge site will be tested, and separate classifications will be determined for both superstructure and substructure.

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.

## 1.3.2 Classification Criteria (01/08) Jan 2008 Table 1.1 Changed Slightly Aggressive Cl for steel from N.A. to <500.

A. Bridge substructure and superstructure environments will be classified as Slightly Aggressive, Moderately Aggressive, or Extremely Aggressive environments according to the following criteria and as shown in Figure 1-1. The superstructure is defined as all components from the bearings upward. Conversely, every element below the bearings is classified as substructure.

B. Marine Structures: Structures located over or within 2500 feet of a body of water containing chloride above 2000 ppm are considered to be marine structures and all other structures will be considered non-marine structures. Only chloride test results are required to determine if a structure is classified as marine. Results of chloride tests for most locations are available on the internet at the following address: http://databases.sm.dot.state.fl.us/bridgeenvironment.htm

NOTE: Access to this database is currently limited to FDOT personnel only. Consultants needing information from this database should contact the appropriate district office for assistance.

Classify superstructure and substructure as follows:

1.) For structures over or within 2,500 feet of a body of water with chloride concentrations in excess of 6000 ppm, both superstructure and substructure will be classified as extremely aggressive.

2.) For structures over any water with chloride concentrations of 2000 to 6000 ppm, the substructure will be classified as extremely aggressive. Superstructures located at 12 feet or less above the mean high water elevation will be classified as extremely aggressive. Superstructures located at an elevation greater than 12 feet above the mean high water elevation will be classified as moderately aggressive.

3.) For structures within 2,500 feet of any of a body of water with a chloride concentration of 2000 to 6000 ppm, but not directly over the body of water, the superstructure will be classified as moderately aggressive. The substructure will follow the non-marine criteria in Table 1.1.

C. Non-Marine Structures: All structures that do not meet the criteria above are considered non-marine structures.

1.) Substructure: Classify all non-marine substructures in contact with water and/or soil as follows:

Table 1.1 Criteria for Substructure Environmental Classifications
Classification | Environmental Condition | Units | Steel | Concrete
Water | Soil | Water | Soil
Extremely Aggressive (If any of these conditions exist) | pH |  | < 6.0 | < 5.0
Cl | ppm | > 2000 | > 2000
SO4 | ppm | N.A. | > 1500 | > 2000
Resistivity | Ohm-cm | < 1000 | < 500
Slightly Aggressive (If all of these conditions exist) | pH |  | > 7.0 | > 6.0
Cl | ppm | < 500 | < 500
SO4 | ppm | N.A. | < 150 | < 1000
Resistivity | Ohm-cm | > 5000 | > 3000
Moderately Aggressive | This classification must be used at all sites not meeting requirements for either slightly aggressive or extremely aggressive environments.
pH = acidity (-log10H+; potential of Hydrogen), Cl = chloride content, SO4 = Sulfate content.

2.) Superstructure: Any superstructure located within 2,500 feet of any coal burning industrial facility, pulpwood plant, fertilizer plant, or any other similar industry classify as Moderately Aggressive. All others classify as Slightly Aggressive.

### 1.3.3 Chloride Content (01/08) Jan 2008. Corrected Chloride Intrusion rate to 0.016 lbs/cy/year.

A. 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 6,000-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.

Commentary:

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 0.016 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.

B. After representative samples are taken and tested, Table 1.2 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 1.2 Chloride Intrusion Rate/Environmental Classification
Chloride Intrusion Rate | Classification
> 0.016 lbs/cy/year | Extremely Aggressive
< 0.016 lbs/cy/year | Moderately Aggressive

See Figure 1-1 Flow Chart for determining Environmental Classification