To help ensure assets are maintained to high standards, a 20-year service contact between the City of Stockton and OMI/Thames Water required a condition assessment of all managed assets. Due to the size and complexity of the system, it was not possible to test all assets as part of the condition assessment. A methodology was developed to prioritize assets to be subjected to further testing based on an initial inspection and a risk evaluation based on age, condition, and criticality of all assets. This approach enabled the owners and system managers to obtain relevant testing results for the most critical infrastructure assets while minimizing the associated testing costs and thereby efficiently established the baseline condition and value of utility assets.
In 2003, the City of Stockton entered into a 20-year service contract with OMI/Thames Water for operation and maintenance of the City’s water, wastewater, and stormwater utilities, consisting of over 140 facilities and including about 1,500 individual assets. As part of this agreement, OMI/Thames Water is responsible for asset management, including all maintenance and capital repair and replacement of all managed facilities and equipment. To help ensure these managed assets are maintained to high standards and returned to the City in acceptable condition (95% of the weighted average useful life of the Managed Asset), the contract included criteria for the condition of managed assets at the end of the contract period based, in part, on the condition of these assets at the start of the agreement.
The Stockton - OMI/Thames agreement required identification of the “weighted average useful life of the Managed Asset Equipment, as determined through a Baseline Asset Evaluation,” at the start of the contract term. In order to achieve this objective, the City of Stockton and OMI/Thames Water retained Carollo Engineers to serve as an Independent Evaluator to document the condition of these assets at the start of the agreement.
Several notable challenges needed to be addressed as part of the initial condition assessment. In particular, it would be difficult to inspect and evaluate assets that were below ground, submerged, and/or in-service at the time of evaluation. This process was further complicated because the initial condition assessment was not started until two years after the start of the operating contract. Analytical testing of assets, using methods such as vibration analysis, oil analysis, temperature measurements, and strength testing is frequently applied in such assessments to fully document otherwise undetectable deficiencies. Unfortunately, given the size and complexity of the Stockton system, resource constraints limited the ability to conduct analytical testing of all managed assets.