Walden Develops a Tank Coating Renewal and Improvement Prioritization Program

Working for a mid western U.S.A Investor-Owned Utility company, Walden developed a renewal and improvement prioritization program for tank coatings.  The utility provides drinking water to over 650,000 people in 46 cities and towns. With more than 125 tanks spread throughout the separate distribution systems, and limited funds for improvements, the need for a prioritization system was necessary. A Tank Improvement Prioritization System (TIPS) was developed and implemented by Walden to effectively rank tank coating condition. 

The Tank Improvement Prioritization System (TIPS) was created to aid the development of a ranking of tank coating renewal and other improvement needs.  TIPS is combined with other engineering, economic and managerial information and influences to determine the number, selection, scope and schedule of tank coating renewal and other improvements.  The features of TIPS include:

  1. Included within existing spreadsheet.
  2. Scoring completed in-house using contracted inspections.
  3. Includes absolute, relative and intangible elements.
  4. Scoring ‘ages’ automatically.
  5. Differentiates among ground or elevated tanks.
  6. Results that can be effectively communicated.

TIPS is a nested spreadsheet within the overall storage tank computerized file which lists and tracks comprehensive information on all tanks within the utilities system.

The TIPS included the following ranking methodology components:

  1. Coating System Effectiveness

This component combined a raw score obtained during time of inspection and a time added value based on assumed deterioration of the coating over time. Inspection data is obtained from inspection firms and evaluated by the scorer utilizing a ranking system; 0-1 for newer systems in excellent condition and 2-5 to translate results of periodic maintenance or pre-bid inspections where findings may reveal fair or poor conditions.  Time-added value is calculated from time elapsed since a prior inspection, a raw score from the time of the last inspection and a generalized half-life of the existing coating system. The sum of both the raw score and time added value calculation provides the resulting Component 1 tank coating score.

  1. ‘S-Five’ Components

“S-Five’ stands for Site Conditions, Structural Conditions, Safety Conditions, Sanitary Conditions, Security Conditions and Specialized Deficiencies. It includes metrics from Component 1 raw score and time added value. Deficiencies in each of the five sub-factor categories are listed with suggested point values. The scorer assigns point values using suggested guidelines to remain consistent. The total points obtained by each S-Five sub-category is written on a scoring sheet and presented in the TIP system.

  1. Coating System Scoring

This component asks questions defining intangible characteristics of the tanks. These questions are translated into points which are then totaled. Some of the questions include the following; Does the tank have current lettering and logo or nothing at all? Is the tank in a highly visible location? Is it difficult to take the tank out of service? Is the estimated cost of the recommended improvements significant?

Tank Scoring and Ranking

Once the TIPS assessment components have been completed, a comprehensive score is assigned using a weighted function and combining the scores of all three components. The comprehensive score determines the draft ranking of the tank coating renewals as well as other improvements for the planned year. Each TIPS report is reviewed to determine and confirm project scope and estimated cost.

The Tank Improvement Prioritization System is an effective tool for helping municipal, regional districts, public utilities or investor-owned utilities prioritize tank coating system renewal. The Walden designed and implemented system creates an innovative and comprehensive tank system list, which enables further review, investigation and evaluation. This project was published and presented at the Infrastructure Conference of the American Water Works Association.

TIPS is another example of how Walden Environmental Engineering leverages its experience and industry know-how to provide cost saving solutions to our clients.


Posted on

June 14, 2021