**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]{.underline}**

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

**II. [Background ]{.underline}**

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]{.underline}**

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     Cooling    Cooling Tower
                                       Baseline^1^   Tower      Option 2
                                                     Option 1   

  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        | A        | Cooling  | Cooling  |   |
|                    | Baseline   | lternate | Tower    | Tower    |   |
|                    |            | Baseline | Option 1 | Option 2 |   |
+--------------------+------------+----------+----------+----------+---+
| Benzene Emission   | 1          | 1.75     | 1.71     | 1.57     |   |
| Ratio              |            |          |          |          |   |
+--------------------+------------+----------+----------+----------+---+
| MIR (in a million) | 70         | 70       | 70       | 70       |   |
+--------------------+------------+----------+----------+----------+---+
| Number of people   |            |          |          |          |   |
+--------------------+------------+----------+----------+----------+---+
| \> 1-in-100        | 0          | 0        | 0        | 0        |   |
| million            |            |          |          |          |   |
+--------------------+------------+----------+----------+----------+---+
| \> 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        | 0          | 0        | 0        | 0        |   |
| million            |            |          |          |          |   |
+--------------------+------------+----------+----------+----------+---+
| \> 1-in-10 million | 21         | 41       | 41       | 36       |   |
+--------------------+------------+----------+----------+----------+---+
| \> 1-in-1 million  | 96         | 108      | 108      | 104      |   |
+--------------------+------------+----------+----------+----------+---+
| Cancer             | 0.04 -     | 0.07 --  | 0.07 --  | 0.06 --  |   |
| Incidence^2^       | 0.09       | 0.16     | 0.16     | 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.           |            |          |          |          |   |
+--------------------+------------+----------+----------+----------+---+