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Home My WebLink AboutSea Level Change notes rev3a FINAL - jkPage | Sea Levels, Climate Change and Flooding - 1 SEA LEVELS, CLIMATE CHANGE AND FLOODING The DEIS scope calls for the DEIS to describe the potential adverse impact on the Project parcel resulting from climate change and sea level rise, with special attention to flooding, rising groundwater, and increases in precipitation (DEIS scope p. 7). Flooding The DEIS scope calls for the DEIS to include “the potential impacts associated with coastal flooding, storm events, and rising sea levels” (p. 10). It also calls for the “future physical climate risk due to storm surge (including sea level rise) and flooding [to] be considered in project design” (p.10). In 2019 Suffolk County approved legislation that requires the county department of public works to take sea level rise into consideration when planning major roadwork to alleviate flooding and prevent future damage. Newsday has reported that this would apply to CR 48 in Southold which is part of the Project truck route.1 The potential for flooding at the Project site is readily apparent in the attached photograph (COMMENT FIGURE SL-1) showing conditions at the Old Mill Inn, located adjacent to the Project site, during a high- tide storm surge event in 2022. The DEIS concludes that “[S]ea level rise projections . . . would not inundate the subject property and impacts from sea level rise and storm inundation are concentrated at the bulkhead” (DEIS p. 179, Table 30; p. 182 Table 31). However, the DEIS evaluates only a single, Applicant-selected, scenario. The DEIS has based its analysis of the adverse impact of sea level rise on a potential sea level rise of 16 inches by 2050 which, per 6 NYCRR 490 is considered a “medium”2 projection. The DEIS states that “pursuant to 6 NYCRR Part 490 . . . [this], is considered a reasonable analysis” (pp. ix, 110). This language is misleading. Nothing in state regulations sets forth what constitutes a “reasonable” analysis in regard to evaluating the impacts of sea level changes. What constitutes reasonable analysis should be determined by the Planning Board—not the Applicant or his consultants. More conservative analyses using a “'high-medium” projection assuming, a sea level rise of 21 inches, and a “high” projection of 30 inches, representing a possible “worst-case” scenario should have been included. While these alternate scenarios, which are set forth in 6 NYRR 490.4, are noted in the DEIS 1 https://www.newsday.com/long-island/environment/climate-change-sea-levels-bay-tides-long-island-s1hsx81r 2“Medium projection” is the amount of sea-level rise that is about as likely as not (the mean of the 25th and 75th percentiles of ClimAID model outputs) to be exceeded by the specified time interval (6 NYCRR 490.3[n]). “High-medium projection” is the amount of sea-level rise that is unlikely (the 75th percentile of ClimAID model outputs) to be exceeded by the specified time interval (6 NYCRR 490.3[h]). “High projection” is the amount of sea-level rise that is associated with high rates of melt of land- based ice and is very unlikely (the 90th percentile of ClimAID model outputs) to be exceeded by the specified time interval (6 NYCRR 490.3[i]). Page | Sea Levels, Climate Change and Flooding - 2 (p.105, Table 16), potential impacts under these scenarios are not evaluated. In fact, “[S]ea level rise, which has averaged about 1.2 inches a decade in the past century, could accelerate to as much as an inch per year over the next several decades, according to numerous reports issued in recent years.”3 This is consistent with the “high” projection. The DEIS also employed the NYS Energy Research and Development Authority’s (NYSERDA) Future Coastal Floodplain Mapper (the Mapper). The Mapper exhibits how the existing mapped floodplain could be modified in scenarios where 12, 18, 24, 36, 48, 60, and 72 inches of sea level rise are experienced under 10-year, 50-year, 100-year, and 500-year storm conditions. “When analyzing the project area’s susceptibility to sea level rise using the Mapper, the median scenario from CRRA for the 2050s was applied, 18 inches” (p.107).4 The DEIS analyzed two mapped storm scenarios “(1) 18 inches of sea level rise in the 2050s and a 10-year storm event; and (2) 18 inches of sea level rise in the 2050s and a 100-year storm event. At a 10-year recurrence interval (see Figure 24 in Appendix A) with 18 inches of sea level rise (2050s), storm inundation could occur at existing Buildings 2, 7 and 8, and the eastern portions of existing Buildings 3 through 6 could be affected. The existing Building 1 would be unaffected. At a 100-year recurrence interval (see Figure 24 in Appendix A) with 18 inches of sea level rise (2050s), storm inundation could occur across the SYC property, with Building 1 unaffected” (DEIS p.107). No mention is made in the analysis of how the proposed new boat storage buildings would be affected by sea level rise. The references to Figure 24 in DEIS Appendix A are misleading. That figure is a reproduction of a Mapper-generated graphic showing the assumed 18-inch sea level rise/100-year occurrence scenario. Figure 24 shows the approximate location of the proposed boat storage buildings as asterisks. According to Figure 24, these locations would be unaffected by sea level rise. This is misleading and contradicts the DEIS text. The DEIS states that “sea level rise with storm inundation were evaluated at the subject property, under the post-development condition” (emphasis added) (pp. ix, 107). However, the Mapper graphic, on which Figure 24 is based, depicts existing elevations and does not take into account the fact that the post-construction elevations of the marked locations will be up to 40 feet lower than the elevations used by the Mapper to generate Figure 24. No mention is made in the analysis of how the 50-ton travelift to the south of Building 2, and the 85- ton travelift east of Building 7, would be impacted by sea level rise. This is a significant omission. Even if the proposed boat storage structures are not directly impacted, should the travelifts, which are located at a lower elevation, be rendered inoperative, the new storage structures would become useless. Even if the travelifts are rendered inoperative only during a storm inundation event, should such events occur during the limited fall window when yachts are expected to arrive for storage, they 3 https://www.newsday.com/long-island/environment/climate-change-sea-levels-bay-tides-long-island-s1hsx81r 4 The 2014 Community Risk and Resiliency Act. 6 NYCRR 490 are the implementing regulations for the CRRA. Page | Sea Levels, Climate Change and Flooding - 3 would have to reschedule their arrival (if possible), wait for the travelifts to become operative, or depart. All of these possibilities have associated potential environmental impacts which the DEIS fails to address. Sea Level Change and Groundwater The DEIS scope calls for the DEIS to “specifically analyze the effect of rising groundwater on upland resources.” As the DEIS notes, “[D]ue to location of the subject property along the Mattituck Creek, sea level rise is expected to have an equal rise in groundwater elevation (i.e., a 16-inch rise in sea level would cause an equal 16-inch rise in groundwater elevation)” (p.107). Based on the assumed 16-inch rise in sea level, groundwater modeling (DEIS Appendix L) conducted for the Project as “shown on the Utility Plan, [shows the] the top elevation of both Sanitary Systems Nos.1 and 2 would be 9.4± feet AMSL and the base of the leaching galleys would be 4.4 feet AMSL. Based on existing conditions, the distance between the bottom of the leaching pool and groundwater for Sanitary System No. 1 is approximately 3.2 feet and Sanitary System No. 2 is approximately 3.0 feet. When applying a projected 1.31-foot [16 inch] rise in groundwater elevation in the 2050s, this separation distance would decrease to 1.7± feet and 1.9± feet for System Nos. 1 and 2, respectively” (pp. x, 113). The DEIS states that the “recommended separation distance to groundwater for sanitary leaching fields is three feet. As such, should sea level rise occur as projected, the system would be non-compliant with current design requirements” (emphasis added) (pp. x, 114).5,6 In fact, if one were to apply the high- medium (21-inch) or high (30-inch) estimates for sea level rise (see above), all four of the proposed drainage leaching fields, not just the two identified in the DEIS, would be non-compliant, and would become non-compliant sooner. The DEIS dismisses the anticipated future non-compliance of the Project’s new sanitary system. It states that “in the 2050 condition, modifications to the leaching field could be implemented by elevating and installing a pump station. However, the manufacturer lifespan of the I/A OWTS is 30 years, and thus, by the 2050s, new systems could be expected. Should the projections of sea level rise be realized, the new systems to be installed would be required to comply with the regulations at that time” (pp. x, 114). This is speculation as there is no guarantee that this issue would be addressed at some unspecified time in the future. Furthermore, the analysis of the relationship between rising groundwater and the proposed sanitary system only concludes that under, the single scenario considered, the system would be non- 5 Table 17 in the DEIS indicates that proposed Sanitary System No.2 and drainage leaching fields 1.0 and 3.0 will all be separated from current groundwater levels by 3 feet. This is the minimum required separation distance. In other words, the system, as designed, would barely be compliant on day one of operation. 6 The DEIS cites the SCDHS’ Standards for Approval of Plans and Construction for Sewage Disposal Systems for Other Than Single-Family Residences, July 2020, and the New York State Stormwater Management Design Manual, January 2015. The SCDHS Standards (p.51) are clear that the three-foot separation is not a recommendation—it is a requirement. Page | Sea Levels, Climate Change and Flooding - 4 compliant by 2050. This does not address when the system would become non-compliant, which could be considerably sooner than 2050. As noted above, the groundwater modeling performed for the Project is based on a single scenario. It does not include worst case scenarios. It is unclear whether appropriate estimates of precipitation increase over time were integrated into the model (see below). The groundwater report states that “[P]recipitation records going back over the past 70 years show an average annual total precipitation off 49 inches per year. . . [and that the] groundwater model [was] calibrated . . . based on the annual average precipitation rate of 49 inches/year . . .” (DEIS Appendix L p.20). However, the source for this this figure is not provided, and it does not appear to be consistent with data from NOAA for Suffolk County (see below). Precipitation Increase The DEIS scope requires the DEIS to “consider the effects of intensifying precipitation-- including more seasonal precipitation and higher rates and more total precipitation during storms-- both during construction and operation.” The DEIS is not responsive to this requirement. The DEIS has not accurately assessed how future increases in precipitation could affect sea levels. The DEIS states that “between 1940-2000 at New York (LaGuardia), which is also on the North Shore of Long Island along the Long Island Sound similar to the location of the proposed action, the average monthly precipitation was 3.97± inches” (p. 109).7 The choice to use the New York (LaGuardia) data is also inappropriate, given that Suffolk County data is available.8 While the 1940-2000 data for New York (LaGuardia) (COMMENT FIGURE SL-2a) shows no change in average annual precipitation over time (0.0 in/decade), the comparable data set for Suffolk County (COMMENT FIGURE SL-2b) shows that average annual precipitation is trending upward (+0.68 in/decade). The DEIS, again citing NOAA data, goes on to state that “Since 2017, there has been an overall downward trend in annual precipitation” (p.108). It is initially unclear why the DEIS preparers chose 2017 as the starting point from which the trend in the change of precipitation increase should be measured. The NOAA data for the 2017-2021 period is shown in COMMENT FIGURE SL-3a. It does show a downward trend in annual precipitation. However, a closer examination of the NOAA data indicates that this is misleading. If one extends the period for which data is used to establish the trend of change in precipitation by only one year—to 2016--the trend is seen to be increasing—not decreasing 7 The original DEIS indicated that the yearly precipitation was 3.97± inches. This error was noted by the Planning Board’s consultant during the adequacy review of the original DEIS, and corrected in the revised DEIS. While not significant, it is another example of the carelessness with which the DEIS was prepared. 8 This is another example of the DEIS basing analyses on data that minimizes impacts, while ignoring data supporting a greater impact. Page | Sea Levels, Climate Change and Flooding - 5 as stated in the DEIS (COMMENT FIGURE SL-3b).6 In addition, according to Suffolk County data displayed on the USGS National Climate Change Viewer 9, 80% of 20 climate change models predict that precipitation will be greater during the 2025-2049 period than during the 1981-2010 period. The DEIS’ multiple attempts to characterize the trend in annual precipitation as decreasing when, in fact the data indicates the opposite, have compromised all of the climate-change modeling done for the Project, especially as it relates to impacts to changes in groundwater levels over time. 9 https://www.usgs.gov/tools/national-climate-change-viewer-nccv. See also: U.S. Geological Survey - National Climate Change Viewer- Summary of Suffolk County, New York, May 5, 2021 Page | Sea Levels, Climate Change and Flooding - 6 COMMENT FIGURE SL-1 Page | Sea Levels, Climate Change and Flooding - 7 COMMENT FIGURE SL-2a https://www.ncdc.noaa.gov/cag/city/time-series/USW00014732/pcp/ytd/12/1940- 2000?base_prd=true&begbaseyear=1940&endbaseyear=2000&trend=true&trend_base=10&begtrendyear=1940&endtrendyea r=2000 COMMENT FIGURE SL-2b https://www.ncdc.noaa.gov/cag/county/time-series/NY-103/pcp/ytd/12/1940- 2000?trend=true&trend_base=10&begtrendyear=1940&endtrendyear=2000 Page | Sea Levels, Climate Change and Flooding - 8 COMMENT FIGURE SL-3a https://www.ncdc.noaa.gov/cag/county/time-series/NY-103/pcp/ytd/12/2017- 2022?trend=true&trend_base=10&begtrendyear=2017&endtrendyear=2022 COMMENT FIGURE SL-3b https://www.ncdc.noaa.gov/cag/county/time-series/NY-103/pcp/ytd/12/2016- 2022?trend=true&trend_base=10&begtrendyear=2016&endtrendyear=2022