As part of an effort to upgrade the oil / water separation facilities at a major Southwest refinery, GUERNSEY engineers identified a need to reduce the occurrence of high stormwater flows. By reducing these flows, costs associated with new oil / water separators being built at the plant could be minimized.
The refinery is located in a hilly area. The topography of the site is such that there are steep slopes, deep valleys and significant elevation changes across the site. As a result, storm water falling on the site is quickly focused down several different drainage basins. When high intensity rainfall occurs, the resulting stormwater flow exceeds the normal process flow by several orders of magnitude.
GUERNSEY’s approach included:
- A detailed field evaluation of each sewer hub in and around the refinery process areas to identify major sources of non-contaminated stormwater inflows.
- Evaluation of the very extensive sewer system to identify opportunities to reroute flows to minimize process stormwater.
- Development of 22 low cost modifications to the process sewer system that, taken together, would reduce stormwater flows during a 25-year design storm by approximately 75%.
- Completion of a cost benefit analysis to put each minor modification on a $cost/gpm of stormwater reduced basis. This analysis facilitated prioritization and planning of the implementation of the recommended modifications.
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The results of this study provided the refinery with the detailed information needed to dramatically reduce the overall costs of their planned primary wastewater treatment system upgrades.
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