Appendix 7 Acute Impacts Refined Analysis Figures1 Refined Acute Modeling Approach

Initial acute screening risk calculations were performed with the HEM3 model using the maximum hourly emissions estimates described in the memorandum Methodology for Estimation of Maximum Hourly Emissions for Ferroalloy Sources
, which can be found in Appendix 1 to this report . HEM3 estimates acute (1

- hour) impacts at both polar and census block receptors. It is assumed for this short period of time that an exposed individual could be located at any off

- site location. T he lack of readily available detailed property boundary information for many of the facilities evaluated made it difficult to determine whether receptors were on

- or off

- site. In the absence of such information, t he first ring of polar receptors was place d 100 meters from the plant center for many facilities. However, these polar rings often transected on

- site locations, restricting public access to exposures at these levels and thereby overestimating exposures

.

The screening approach used by HEM 3 to es timate maximum 1

- hour exposures also likely overestimate s exposures . To estimate maximum 1

- hour concentrations at each

re ceptor, HEM3 sums the maximum concentrations attributed to each source, regardless of whether those maximum concentrations occurred du ring the same hour. In other words, HEM3 assum es that t he maximum impact from each source at each receptor occurs at the same time. In actuality

, maximum impacts from different sources may occur at different times.

This appendix addresses refinements to determine the maximum offsite values by plot ting the HEM3 polar grid results on aerial photographs of the facilities for those facilities and pollutants that exceeded short

- term health benchmarks

. Th ese photograp h s were examined to determine off

- site locations that may be accessible to the public ( e.g., roadways and public buildings.). The attached f igures present the estimated property lines of the facilities and the estimate d hazard quotient values (the modeled 1

- hour concentration of a pollutant d ivided by its short

- term health benchmark) at the polar receptors near the facil ities. Table 1 provides the resulting change in acute risks taking into account these off

- site locations for the baseline modeling scenario

. There were no hazard quotients greater than 1 in the post

- control modeling scenario.

Table 1

. Refined Acute Risks Due to Off

- site Receptors

– Baseline Modeling Scenario

Facility NEI ID Pollutant Criteria Original Acute Hazard Quotient Off

- site Hazard Quotient

54053NEIWV053FELMAN Nickel compounds REL 40 10 54053NEIWV053FELMAN Arsenic compounds REL 40 9 39167NEI11660 Arsenic compounds REL 4 2

# Ferroalloys Facilities

## Figure 1

– Estimated Eramet Fenceline

## Figure 2

– Estimated Felman Fenceline

# Ferroalloys Facilities

– Baseline Modeling Scenario

## Figure 3

– NEIWV053FELMAN Acute Nickel HQ (REL)

## Figure 4

– NEIWV053FELMAN Acute Arsenic HQ (REL)

## Figure 7

– NEI11660 Acute Arsenic HQ (REL)

# Ferroalloys Facilities

– Post

- Control Modeling Scenario

## Figure 10

– NEWV053FELMAN Acute Nickel HQ (REL)

## Figure 11

– NEIWV053FELMAN Acute Arsenic HQ (REL)