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5.0 Assessment of Baseline and Natural Conditions

Under Section 169A(b)(2)(B) of the Clean Air Act, the initial Regional Haze SIPs must contain measures to make reasonable progress toward the goal of achieving natural visibility. Comparing natural visibility levels to current baseline conditions helps determine how much progress should be made in the next five to 10 years. Determining natural visibility conditions is a SIP element and each state containing a Class I area (in consultation with Federal Land Managers and other states) was required to estimate natural visibility levels. New York State contains no Class I areas and, as such, this assessment is not required. However, it is presented here for informational purposes.

Additionally, Section 51.308(d)(4)(iii) of the EPA's Regional Haze Rule, 40 CFR 51.308 requires the inclusion in the SIP of a description of procedures by which monitoring data and other information are used in determining the contribution of emissions from within the state to regional haze visibility impairment at mandatory Class I Federal areas both within and outside the state. The Interagency Monitoring of Protected Visual Environments (IMPROVE) program was developed in 1985 to establish current visibility conditions, track changes in visibility, and help determine the causes and sources of visibility impairment in Class I areas.

IMPROVE data was used to calculate baseline and natural conditions for MANE-VU Class I areas. Data from the following IMPROVE monitors (see Table 5-1 below) is representative of Class I areas in and near MANE-VU.

Source: VIEWS (http://vista.circa.colostate.edu/views/), prepared on 7/06/06

5.1 Natural Conditions

In September 2003, the EPA issued guidance for a calculation of natural background and baseline visibility conditions. EPA guidance gives states a "default" method to estimate natural visibility. Natural visibility represents the visibility for each Class I area that is representative of existing conditions before human activities affected air quality in the area. MANE-VU estimated natural visibility using the default method for the 20% best and worst days, and also evaluated ways to refine the estimates. Potential refinements included increasing the multiplier used to calculate impairment attributed to carbon, adjusting the formula used to calculate the 20% best and worst visibility days, and accounting for visibility impairment due to sea salt at coastal sites. However, MANE-VU found that these refinements did not significantly improve the accuracy of the estimates and MANE-VU states desired a consistent approach. Therefore, default estimates were used.

Once the technical analysis was complete, MANE-VU provided an opportunity to comment to federal agencies and stakeholders. After serious consideration of the comments that were received, in December 2006, MANE-VU recommended adoption of the alternative reconstructed extinction equation for use in the Regional Haze SIPs. Therefore, default estimates were used with the understanding that this would be reconsidered as better scientific understanding warranted.

Notwithstanding the above, New York State does not contain any Class I areas and so is not required to estimate reasonable progress goals. However, as described in Section 3, the Department has coordinated with states containing Class I areas which are affected by emissions from sources located in New York as those states assessed baseline, natural and current visibility conditions in their respective Class I areas. The results of this work were used to determine the control measures whose implementation would be necessary by New York and other contributory states to meet reasonable progress goals for each Class I area.

5.2 Baseline Visibility

A five-year average (2000 to 2004) baseline visibility in deciviews was calculated by MANE-VU for each Class I Area for the 20 percent best and 20 percent worst days in accordance with 40 CFR 51.308(d)(2) and as detailed in Appendix L of the document entitled Baseline and Natural Background Visibility Conditions (NESCAUM, December 2006). The deciview visibility for these worst and best days are based on calculations and data included in Appendix C, Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Rule of this SIP submission.

Table 5-2 presents the IMPROVE program calculations for the 20 percent worst and best baseline (2000-2004) visibility conditions for each IMPROVE monitoring site at MANE-VU Class I Areas. These values are posted on the Visibility Information Exchange Web System (VIEWS) operated by the Regional Planning Organizations (available online at http://vista.cira.colostate.edu/views/).

*Data does not exist for the Great Gulf Wilderness Area IMPROVE site for the year 2000, however, according to the EPA document entitled, Guidance for Tracking Progress Under the Regional Haze Rule, states that, "...a minimum of three years of data meeting these completeness requirements is sufficient to calculate the 5-year averages within each 5-year period...the three year completeness criterion allows for the calculation of baseline conditions at sites with less than five years of data."

Source: VIEWS (http://vista.circa.colostate.edu/views/), prepared on 10/16/07

5.3 Comparison of Natural and Baseline Conditions

Table 5-3 compares the baseline visibility for the 20 percent worst and the 20 percent best visibility days based on the five-year average for 2000-2004, natural visibility for the 20 percent worst and the 20 percent best visibility days, and the difference between baseline and natural visibility conditions for each MANE-VU Class I area. These differences provide the beginning and endpoints of the "glide path" that indicates the progress that must be made over the term of the Regional Haze Program out to 2064. This information is also useful in determining the reasonable progress goals (RPGs) that will be established for the term of this SIP extending out to 2018, as well as the control measures that contributing states like New York will need to implement to meet these goals.

Reasonable progress goals are discussed in detail in Section 9 of this SIP.

Source: VIEWS (http://vista.cira.colostate.edu/views/) prepared on 6/22/2007