APPENDIX B

Developing Values for Natural Background and Progress Goals for the Class IArea of the Virgin Islands National Park, St. John, Virgin I slands

Th e Federal Implementation Plan for Regional Haze for the Virgin Islands is designed to take the first steps in improving visibility of the view in the Virgin Islands National Park by reducing emissions of substances that scatter light

. Emitting mo re light scattering aerosols in the air make it harder to se e distant objects; these reductions are caused b y human

- caused emissions and emissions from natural causes. This Plan will include the first ten years of visibility improvements through 2018 that will lead, by 20 64 , to no visibility impairment due to human emissions.

The prospect of clear skies

- scenic vistas unmarred by human interference

- go along with the Virgin Islands’ reputation for clear water with magnificent coral reefs and underwater marine life. Th e FIP has a goal of protecting scenic views visible to the people of the I slands and their many

visitors . The Clean Air Act gives special protection to the pristine areas like the Virgin Islands National Park on St. John.
Overall, a goal in the Clean Air Act is to develop a plan that reduces human interference with seeing the view. Somet imes dust from human activities reduces the abilit y to see the view. Motor traffic, especially

on dirt roads, throws dust into the air. Making concrete or working with gravel emits dust. Emissions from combustio n
- electric generators, water heaters, industrial boilers, ships, power plants, open burning and refineries add sulfate, nitrates and carbon to the haz y mix. Sometimes, particles from nature spoil our view. Dust travels from the Sahara Desert, plankton can give off sulfur particles ; and once in a while, the Montserrat Volcano sends ash toward the Islands. We can’t control the sources of these particles. Some day s, the ir effects on visibility can be very

n oticeable, especiall y because there are not as many human sources of air pollution in the I slands as opposed to the more built

- up megalopolis es in the continental United States.
**Natural Background and Baseline Data** The Interagency

Monitoring of Protected Visual Environments (IMPR OVE) program was initiated in 1985 to establish current visibility conditions, track changes in visibility , and help determined the causes of visibility impairment in Class IAreas We can use information from the ty pes and amounts of particles captured in particulate samplers to calculate the effect the particles have on visibility

. The IMPROVE network collects particles at the air monitoring site in the Virgin Islands National Park every three day s. Since different particles scatter light in different w ay s, they have different effects on visibility . Scientists have developed equations to quantify the obscuration of visibility from the particulates. These calculations also take into account the humidity in the air, which can make some particles swell up and increase their ability to reduce visibility . Then modelers can project the effect of reducing particle emissions on visibility by calculating the change in the amounts of the various particles and the amount of change in visibility that will occur.The Clean Air Act stipulates that states should improve visibility to reach natural conditions. The Act say s that states should do this by improving the visibility

on the worst day s while making sure visibility

does not get worse on the best day s. To address this requirement, we calculate the average visibility impairment over the worst one

- fifth (top twenty percent) day s and the best one

- fifth ( lowest twent y percent) days. The Table below compares the average visibility impairment for the best and wor st day s for Class Iareas that represent various parts of the country . Brigantine and Acadia represent the ‘pristine’ areas in the urban northeastern corridor of the United States. Everglades has a tropical climate like the Virgin Islands, but has more s ources of pollution nearb y than the Virgin Islands. Grand Canyon is representative of the dry deserts of the western United States, remote from major urban areas and sources of pollution. While the Virgin Islands are remote from major urban areas and hav e less industry nearb y, like the western United States, its more humid climate allows particulates, especially sulfates, to have a greater effect on reducing visibility

.

Figure 1. Visibility

impairment for selected National Parks and Wilderness Areas Virgin Islands Brigantine,

NJ Acadia, ME Everglades, FL Grand

Canyon, AZ Worst 20% 17.02 29.01 22.89 22.30 11.66 Average 12.20 21.14 14.59 16.04 6.58 Best 20% 8.54 14.33 8.77 11.69 2.16 Notes: Units are amount of visibility impairment in deciviews. Lower values of deciviews mean better visibility . Higher numbers indicate more impairment to visibility . Brigantine is representative of sites in the urban corridor of the eastern United St ates. Acadia is a more rural location on the east coast. The Everglades are representative of tropical conditions in the Continental United States. Grand Can yon is a representative of the dry desert regime in the western United States.

Sidebar: What is a deciview? A deciview is a unit of visibility reduction. More deciviews indicate lower visibility , or, a decrease in how far away you can see objects

. The deciview scale was developed as a measure of visibility that is linear; to make it easier to do calculations needed to compare improvements to visibility . Ty picall y, a change of one deciview is large enough of a change to the noticeable to the human ey e. The following figure shows the different way s visibility is quantified, with w orst visibility on the right side and clearer air on the left.

Virgin Islands’ visibility

is better than ty

pical locations in the eastern United States. But even the best day s in the Virgin Islands have more obscuration than most day s in dry western l ocations like the Grand Canyon. Higher humidity in the tropics results in more obscurationwhen sulfates are in the air, since sulfates scatter more light, and decrease visibility , as the

humidity increases. Thus sites in the western United States have much better visibility than more humid places in the eastern United States and the Virgin Islands.

We can use information from the ty pes and amounts of particles captured in particulate samplers to calculate the effect the particles have on visibility

. The IMPROVE network collects partic les at air monitoring sites in the Virgin Islands National Park and other Class I areas every

three day s. Since different particles scatter light in different way s, they have different effects on visibility . Scientists have developed equations to quantify the obscuration of visibility

from the particulates. These calculations also take into account the humidity in the air, which can make some particles swell up and increase their ability to reduce visibility . Then mod elers can project the effect of reducing particle emissions on visibility by calculating the change in the amounts of the various particles and the amount of change in visibility

that will occur. The Clean Air Act stipulates that states should improve vis ibility to reach natural conditions. The Act say s that states should do this by improving the visibility

on the worst day s while making sure visibility

does not get worse on the best day s. To address this requirement, we calculate the average visibility impairment over the worst one

- fifth (top twenty percent) day s and the best one

- fifth (best twenty percent) day s. Baseline and Natural Visibility In September 2003, EPA issued guidance for the calculation of natural background and baseline visibility

co nditions. The guidance provided a default method and describes certain refinements that states may wish to evaluate to tailor these estimates to a specific Class I area if it is poorly

represented by

the default method. EPA’s Region 2 office met with rep resentatives of the Federal Land Manager for the Virgin Islands National Park in 2008 to discuss the calculation of baseline and natural background conditions in the Virgin Islands National Park. The FLM agreed with the calculation of the baseline conditi ons and the estimate of progress needed to reach natural conditions. EPA noted that the default calculation of natural background conditions did not include the large impact of non

- anthropogenic impacts from Sahara Dust and biogenic emissions. The FLM ag reed that the information presented (and described in this Plan) showed the large influence of Sahara Dust on visibility in the Park. However, the FLM noted that more work would need to be done on more precisel y calculate the impact on natural sources on visibility in the Park. They

suggested that a Plan that strove for implementing reasonable controls on sources that affect visibility

in the Park would be the most important element of this Plan that covers the first ten years of improving visibility for the Park. The issues of the impact of natural sources on visibility

in the Virgin Islands National Park needs additional research the needs to be done before the next iteration of this Plan, due in 201 8 , is prepared.

Natural visibility

represents the visibility

for each Class Iarea representative of the conditions before human activities affected air quality in the area. Certain natural phenomenacan reduce visibility . The Clean Air Act goal is to remedy visibility impairment resulting from human activit y. Natural visibility , without anthropogenic emissions, is calculated to provide a target level to meet the Act’s goal of no anthropogenic obscuration of visibility . This natural visibility is based on formulas that ar e specific to various parts of the country . It does not include the impact of locall y important natural obscurers of visibility . In the Virgin Islands, for example, Saharan Dust can noticeably reduce visibility . Less obvious are biologically produced
s ulfates from marine life, which may also contribute to obscuring the view. Using data from the IMPRO VE program, we can calculat e the baseline (2000

- 2004) twent y percent worst visibility and natural visibility conditions for the IM PROVE monitoring site in the Class Iarea in Virgin I slands National Park. These values are computed from the Visibility Information Exchange Web S ys tem (VIEWS) operated b y the Regional Planning Organizations (available online at http://vista.cira.colostate.edu/views/). The VIEWS site lists the worst visibility

day s as a five

- ye ar average for 200 0

- 2004 using the alternative IMPROVE algorithm approved in 2006 b y the IMPROVE Steering Committee. Also listed are the natural backgro und visibility for the twent y percent worst and the twenty percent best visibility day s. Since one of the baseline years, 2000, has incomplete data, EPA guidance allows the use of calculations based on four y ear of data, from 2001

- 2004 1 . The resulting data are listed in the t able below. Table 2. Calculations of visibility for natural conditions for selected National Parks and Wilderness Areas.

Virgin Islands Brigantine,

NJ Acadia, ME Everglades, FL Grand

Canyon, AZ Worst 20% 10.68 12.24 12.43 12.15 7.04 Average 7.10 8.48 7.88 7.77 3.20 Best 20% 4.41 5.51 4.65 5.22 0.31 This Table lists the amount of visibility reduction due to natural causes only , calculated based on t ypical background concentrations of pollutants, with assumed average local meteorological conditions. Note that natural visibility calculations for the Virgin Islands are numerically similar to natural visibility

calculations for eastern United States sites.

1 A ccording to the EPA document entitled, Guidance for Tracking Progress Under the Regional Haze Rule , states that, “...a minimum of 3 y ears of data meeting these completeness requirements is sufficient to calculate the 5

- ye ar averages within each 5 ye ar period...the 3 year completeness criterion allows for the calculation of baseline conditions at sites with less than 5 y ears of data. ”Figure 1. Actual and natural visibility statistics from selected National Parks and Wilderness Areas compared with the Virgin Islands. Note that the goal for these areas is for all day s to achieve the natural background by 2064. To calculate the natural and basecase actual visibility for the twent y percent worst day s, we used the data from the IMPROVE site to calculate the impairment for eac h portion of the particulate data. Table 3. Calculations of Natural and Actual Visibility Reductions for the Virgin Islands National Park, b y Parameter

Parameter Natural

worst 20% estimated by formula Actual

worst 20% calculated from data Description

aBext 18.52803 44.85217 Bext is the amount of visibility reduction for all particles

bCM 3.27672 15.70808 Visibility reduction from coarse particulate ma tter bEC 0.27781 1.545539 Visibility reduction from elemental carbon bNO3 0.947763 2.075003 Visibility reduction from nitrates bOMC 1.744017 1.836166 Visibility reduction from organic carbon bSO4 1.483411 10.30606 Visibility reduction from sulfates bSoil 1.394714 5.901773 Visibility reduction from fine soil bSs 9.403591 7.479546 Visibility reduction from sea salt

dv 10.68113 17.02366 Total visibility reduction from all particles, converted to deciviews. Source: VIEWS ( http://vista.cira.colostate.edu/views/), prepared on 05/12/08 Calculated from IMPROVE data using the most recent set of calculation equations. Data, except for the final row, is in Mm

- 1, which is light extinction per million meters, commonly

said as units of ‘inverse megameters’Then we combined all the visibility impairment from each contributor to the reduced

visibility

– the result is in the last row of Table 3. To reach the calculated natural background of 10.68 dv by

2064 , visi bility

will need to improve by

6 .34dv from the present actual 17.02dv.

According to EPA’s Regi onal Haze Rule, a reduction of 6 .34 dv by 2064 is to be accomplished b y reducing visibility impairment by

at least the rate of uniform reduction in each ten

- year period covered b y the haze plans. A target for 2018 results from 6 .34 divided b y the number of years from 2004 to 2064 and multiplied by the number of years from 2004 to 2018 to get the target of visibility improvement for each ten

- ye ar period of at least 1. 48 dv. Are the Calculations Accurate for the Virgin Islands?

Based on the wo rk of Tombach, concentrations of fine soil in summer average 7.54 ug/m3 (likely to be mostl y Saharan Dust in the Virgin Islands’ summer

– which is prime season for Sahara Dust). This calculated natural background of fine soil of 7.54 ug/m3 is much higher than the 0.5ug/m3 assumed in the calculations of natural visibility or even the recorded concentrations of about 3 ug/m3 in the southeastern United States. This is important to note that in order to be on track to improve visibility to the Clean Air Act g oal of reaching natural visibility levels, this plan estimates the amount of progress needed by 2018 based on the calculated natural level of visibility . If possible, emission reductions should meet the reasonable progress goal line for 2018. However, th e amount of progress estimate for 2018 may

be an overestimate due to the underestimation of natural visibility conditions. This calculation does not include the full impact of Saharan Dust and other natural emissions that interfere with visibility

. Whi le there is uncertainty in estimating how much of the Virgin Islands’ visibility impairment is due to natural sources, the amount of emission reduction s for the first ten ye ars’ plan will still be based on the application of reasonably available emission r eductions from sources that affect visibility in the Virgin Islands National Park on St. John , U. S. Virgin Islands

.