10-2: Water

RESPONSE 10-2:

The significant impact zone is an area that the emissions levels are above a threshold called the Significant Impact Levels (“SILs”) that if exceeded a more detailed analysis must be performed that includes emissions from other nearby sources.  The SILs are much lower than the National Ambient Air Quality Standards (“NAAQS”),  and the air quality in an area where the modeled concentration is greater than the SIL is still considered safe with regard to human health and public welfare.  Modeled impacts above the SILs are considered safe by the EPA and therefore there is no potential impact to anyone residing within the radius, the only issue is more detailed modeling is required.

As required by the Clean Air Act (“CAA”), the EPA has established NAAQS for six commonly found (criteria) pollutants: carbon monoxide (“CO”), lead (“Pb”), nitrogen dioxide (“NO_2”), ozone (“O_3”), particulate matter (less than 10 microns in diameter (“PM_10”) and less than 2.5 microns in diameter (“PM_2.5”) and sulfur dioxide (“SO_2”). 

The United Stated Environmental Protection Agency (“EPA”) has established two types of NAAQS.  The primary standards protect public health, including the health of sensitive populations such as asthmatics, children and the elderly.  The secondary standards protect public welfare, including protection against decreased visibility and damage to animals, crops, vegetation and buildings.

Based on the most recent monitoring data, Rhode Island is an attainment area with regard to the NAAQS.  Therefore, any new proposed source, such as the CREC, must demonstrate that the maximum air quality impacts resulting from its operation, when combined with existing background air quality concentrations and the maximum air quality impacts resulting from the operation of other nearby sources, will not cause an exceedance of the NAAQS. 

Such a demonstration has been made for the CREC, as detailed in the Air Dispersion Modeling Report submitted to RIDEM on October 30, 2015.  The results of the air dispersion modeling analysis have demonstrated that the maximum air quality impacts resulting from its operation, when combined with existing background air quality concentrations and the maximum air quality impacts resulting from the operation of other nearby sources, will result in criteria pollutant ambient air quality concentrations which will remain at levels which are protective of human health and public welfare.

The EPA has also established Significant Impact Levels (“SILs”) for each of the criteria pollutants.  The SILs are much lower than the NAAQS and represent the impact concentration levels at which the ambient air impacts from nearby sources must be considered.  Because the SILs are lower than the NAAQS, the air quality in an area where the modeled concentration is greater than the SIL is still considered safe with regard to human health and public welfare; however, a more in-depth air quality analysis is required.  Modeled impacts below the SILs are considered by the EPA to be insignificant, and therefore the ambient air impacts from nearby sources are not required to be considered in the modeling analysis.

The results of the CREC air dispersion modeling analysis, which included the modeled impacts from the Algonquin Compressor Station, Ocean State Power, and the Tennessee Gas Compressor Station, indicated maximum CO, annual NO₂, annual PM₁₀ and SO₂ impacts below their respective SILs, and therefore insignificant.  The maximum modeled 1-hour NO₂ and 24-hour PM₁₀ impacts exceeded their respective SILs.  The PM_2.5 SILs have been vacated by the EPA as a result of a court order.            

Figure 8 of the Major Source Permit Application (attached as Exhibit 1) graphically depicts the areas where the maximum modeled impacts exceeded their respective SILs.  The concentrations are above the SIL threshold, however the resulting air quality concentrations will remain well below the NAAQS, and thus at levels still protective of human health and the public welfare.  Any increases in criteria pollutant ambient air concentrations in all other areas resulting from the operation of the CREC will be insignificant, as defined by the EPA.

The air quality impact analysis completed for the CREC Project has demonstrated that the air quality both within the Significant Impact Area and as far away as 50 kilometers in every direction, will remain at levels deemed protective of human health and the public welfare by the EPA during CREC operation.

DATE:

June 13, 2016