A PETROLEUM REFINERY
STORMWATER RUN-OFF STUDY
Richard B. Stalzer, Environmental Engineer
Glenn W. McArdle, Environmental Engineer
Engineering Division
The Standard Oil Company (Ohio)
Cleveland, Ohio 44115
INTRODUCTION
The handling of stormwater run-off at a large petroleum refinery site presents many difficulties
that must be effectively managed to maintain wastewater treatment effluent quality during rainstorms. Adequate diversion and impounding capacity must be available to store excessive storm flows
for treatment after run-off subsides. It is the purpose of this paper to present a case history of upgrading a petroleum refinery wastewater treatment system to efficiently manage stormwater run-off while
maximizing wastewater treatment effectiveness.
The primary objectives of the stormwater run-off study were as follows: (1) Estimate the peak
flow rate and total impounding volume required for design storm events using stormwater run-off
computer modeling; (2) Install automatic flow recorders to obtain data that can be used for calibrating the computer model and improve simulation of stormwater run-off; (3) Develop a conceptual
design for an improved diversion and impounding system; and (4) Prepare a stormwater management
plan that summarizes all aspects of the study.
To meet these objectives, key elements of the stormwater management plan were outlined at the
beginning of the study. These included: identify all areas contributing stormwater run-off to the refinery's oily sewer system; establish the sewer system and subbasin characteristics and hydraulics; determine the maximum flow rate allowable to the wastewater treatment system during a storm event;
select the design storm events for estimating peak flow and total required impounding capacity needed
for conceptual design purposes; use stormwater run-off computer modeling to develop design hydro-
graphs; calibrate the model with data from a sewer monitoring program using automatic flow recorders; and develop a conceptual plan of an improved diversion and impounding system. The major
aspects of the study will be presented here.
SYSTEM LAYOUT AND HYDRAULICS
Figure 1 shows a plot plan of the refinery site with the areas contributing run-off to the oily sewer
system highlighted. The total refinery area encompasses over 500 acres of which almost 400 acres
drain to the oily sewers. Because the plant is about 65 years old, the sewer system is nonsegregated,
collecting both process wastewater and stormwater run-off. Approximately 150 acres of tank dike
area do not contribute stormwater until precipitation has subsided, while 35 acres of process area and
over 200 acres of nonprocess area contribute to the sewers during a storm event, including some adjacent non-refinery property.
The first major task involved gathering all information available on the sewer system. We were
fortunate in that about 80% of the information needed existed in the refinery's files. This greatly
reduced the time needed to compile all the sewer data necessary. As shown in Figure 2, an overall
sewer map was sketched out. For each sewer segment a pipe diameter, slope and pipe material was
determined. Based on a field survey and past sewer surveys, dry flow rates were established as well as
extent of sludge deposition and backwater conditions. Due to downstream conditions and substantial
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