TO:	EPA Docket No. EPA-HQ-OAR-2003-0146

		

FROM:	Brenda Shine, EPA/SPPD 

DATE:	August 21, 2007

SUBJECT:	Cooling Tower Risk analysis

I.	Purpose

The purpose of this memorandum is to document the potential risk impacts
of cooling tower emissions reductions.

II.	Background 

Following the approach described in the memorandum entitled, “Risk
Estimates for Alternate Emissions Scenarios” an estimate of the risk
reductions is provided for the proposed Cooling Tower Options 1 and 2. 
Cooling tower Option 1 is a surrogate parameter monitoring leak
detection and repair program and results in 29 TPY benzene reduction. 
Option 2 requires monthly direct monitoring of cooling tower return for
leaks, and the same repair requirements as Option 1 and results in 129
TPY benzene reduction.

III.	Emission Assessment

Emissions of benzene under the baseline case and a hypothetical
alternative baseline are presented in the Table 1 below, along with
reductions anticipated from the suite of options under consideration.  

 

Table 1 -   Benzene Emissions Scenarios



	Benzene Emission Totals, TPY 

	RTR Baseline	Alternate Baseline1	Cooling Tower Option 1	Cooling Tower
Option 2

Cooling towers 	17	302	273	173

Fugitives	194	194	194	194

Tanks	200	200	200	200

Vessel Loading 	16	16	16	16

Marine Vessels 	13	13	13	13

Wastewater 	136	388	388	388

Other	142	142	142	142

Total	717	1255	1226	1126

1 Alternate baseline includes addition of hypothetical non inventoried 
emissions from cooling towers and wastewater operations



Cooling tower option 1 reduces benzene by 29 TPY and Option 2 reduces
benzene emissions by 129 TPY.  

Table 2 -   Control Option Risk Estimates



 	RTR Baseline	Alternate Baseline	Cooling Tower Option 1	Cooling Tower
Option 2

Benzene Emission Ratio 	1	1.75	1.71	1.57

MIR (in a million)	70	70	70	70

Number of people

> 1-in-100 million	0	0	0	0

> 1-in-10 million	         6,000 	10,500                   	10,300	9,300

> 1-in-1 million	      460,000 	    805,000       	790,000	720,000

Number of Facilities

> 1-in-100 million	0	0	0	0

> 1-in-10 million	21	41	41	36

> 1-in-1 million	96	108	108	104

Cancer Incidence2	0.04 - 0.09	0.07 – 0.16	0.07 – 0.16	0.06 – 0.14







	1 “Population Risks” and “Plant Risk Bin Estimates” are based
on utilizing the high end of the reported cancer URE range for benzene. 
These estimates may be as much as 30% lower when estimated using the
lower end of the benzene URE range.

2 The cancer incidence range is based on extrapolation of 22 refineries
as provided by the American Petroleum Institute as well as considering
the reported cancer URE range for benzene.



Technical Memorandum –Cooling Tower Risk Analysis

August 21, 2007

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Technical Memorandum

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