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Item S10ELj » °o � i G�, BOARD OF COUNTY COMMISSIONERS C ounty of M onroe r i ��� Mayor Heather Carruthers, District 3 The Florida. Ke Se I Mayor Pro Tem George Neugent District 2 y Danny L. Kolhage, District I David Rice, District 4 Sylvia J. Murphy, District 5 County Commission Meeting November 22, 2016 Agenda Item Number: S.10 Agenda Item Summary #2370 BULK ITEM: No DEPARTMENT: Sustainability TIME APPROXIMATE: STAFF CONTACT: Rhonda Haag (305) 453 -8774 10:00 a.m. AGENDA ITEM WORDING: Review and discussion of the draft Final Report of the tidal flooding roads demonstration projects. ITEM BACKGROUND: The King Tides in 2015 provided a preview of what the County can expect as sea level rise becomes a reality. The impacts exemplify flooding from events but also from more regular tidal intervals that would be expected to be more impactful with higher sea levels. Knowing that the County would be addressing increased flooding from either King Tides, storm events or general sea level rise countywide, the County decided to move forward with a "Pilot effort" to test methodologies for determining future flood risk scenarios and the policy framework for making these decisions relative to ongoing roadway improvement projects. Two communities were chosen for this study (where impacts from the King Tides in 2015 were highest), one in Key Largo and one in Big Pine Key. Specific roadway areas within those communities were further defined as the Shaw, Crane, Adams area in Key Largo area as well as Father Tony Way and the Avenues in Big Pine Key. Pilot Roads Proiect Linkage to GreenKeys Earlier this year, Monroe County accepted the GreenKeys Sustainability Action Plan which had several recommendations related to infrastructure planning in light of future sea level rise projections. The GreenKeys plan showed that approximately 150 miles of County roadways may be exposed to intermittent flooding by 2030, so the recommendations design criteria will need to consider this larger county -wide need to assure that further recommendations are developed appropriately. Recommendations from the GreenKeys Plan relevant to this Pilot Study include: 1 -19, "Pilot project to conduct Comprehensive Feasibility Study for Enhanced Stormwater and Tidewater Criteria (prioritizing areas) for near -term areas subject to inundation risk, including nuisance flooding (in two locations). 2 -14, "Conduct a countywide roads analysis to identify near -term roads subject to inundation risk, including nuisance flooding. This will include researching where related green infrastructure would be appropriate. Increase the percentage of funding invested in green infrastructure." 2 -36, "Ensure that all new nuisance flooding data informs future road decisions. These data will also need to be considered for future road decisions. This will require coordination with FDOT for impacts to State Roads (U.S. Highway 1). Pilot Roads Report Overview The Final Report for the Pilot Roads project is currently being drafted for presentation to the County Commission in two parts. A draft of the final report is attached. The two parts are: • Part 1 of the Report and BOCC presentation in November will focus on: • Project Background • Assumptions and Methodology • Results of analysis for design alternatives • Cost Comparisons between alternatives • Part 2 of the Report and BOCC presentation in December will focus on: • Local government responsibilities regarding drainage • Overview of level of service factors considering future flood risk • Case studies in local government approaches • Recommended policy guidance for criteria to consider in road improvements factoring in future sea level rise Summary of Part 1 of Report Part 1 of this draft Report explains the history and technical work to assess the potential response to tidal flooding in the two Pilot communities. The focus of this effort to date has been on developing a method to estimate future flood potential, based on analysis of historical events — and also to develop conceptual design and cost estimates to evaluate alternatives for road and stormwater improvements in the two communities. Final designs recommendations for these two communities will serve as a pilot effort to take lessons learned from this process and extend those to other projects countywide projects considering the following: • What is a reasonable level of service for road projects on County roads for flooding levels and the amount of time a given road is impacted? • How shall the County establish levels of service established in the face of uncertainty with a changing climate and projected levels of sea level rise that are based on a range of future conditions? • What would be considered a cost - effective response given the needs of these communities and the broader needs of the larger Monroe County community? • What is a model policy approach for future decision - making on road level of service countywide? The technical analysis completed for this project used an analytical framework that can help with decisions for future road improvements. An overview of the process was to assess existing flooding in the past, incorporate rising water levels associated with sea level rise, determine how roadway design considerations may have to be modified due to changing future conditions, and then consider how that information could be used to guide county policies moving forward. The following include assumptions and parameters in the alternatives analysis: 1. Sea level rise scenarios- the IPCC AR5 Median and USACE High scenarios are the recommended scenarios for use by the Southeast Regional Climate Compact 2. Planning horizon- the planning horizon is 2040 because the typical design life for a road improvement project is 25 years (from 2015- date of project initiation). 3. Flood levels- are compared among existing conditions (Mean Sea Level and Mean Higher High Water) with future sea level rise predictions and Average and Maximum Fall 2015 Conditions 4. Duration- duration of inundation is also analyzed at the 30, 7 and 1 day flood impact Elevation scenarios were also evaluated to 1) ensure sufficient differences to gauge costs and benefits and 2) compare performance among flood level and duration of event. The elevation scenarios included 6, 12, 18 and 28 ". These elevation scenarios also help identify over and under design considerations which impact alternative costs. Finally, relative costs among elevation alternatives are evaluated based on level of elevation, length of road miles elevated and stormwater features associated with project alternatives. The analysis for this project is meant to be specific to the two pilot communities in the areas defined in Big Pine and Key Largo. However, the outcomes of this project must be taken in context within the broader policy framework for Monroe County which is why a comprehensive policy for consideration of future sea level rise in road design projects is also included in Part II. PREVIOUS RELEVANT BOCC ACTION: 01/20/16: Approval of amendment No. 6 to Erin Deady's contract to authorize a pilot project on integrating design of tidewater, stormwater and road elements in two communities for sea level rise adaptation and to extend the contract. CONTRACT /AGREEMENT CHANGES: N/A STAFF RECOMMENDATION: Not applicable DOCUMENTATION: Final Report for Roads Demo Project - DRAFT FINANCIAL IMPACT: Effective Date: Not applicable Expiration Date: N/A REVIEWED BY: Rhonda Haag Completed 11/05/2016 4:33 PM Pedro Mercado Completed 11/06/2016 1:29 PM Budget and Finance Completed 11/07/2016 9:17 AM Maria Slavik Completed 11/07/2016 9:17 AM Kathy Peters Completed 11/07/2016 12:01 PM Board of County Commissioners Pending 11/22/2016 9:00 AM ��� _ 1 _ � �; II f� • _ 1� m 0 as LL as 0. 0 F— LL as 0- 0 E 0 0 0 CL U- E 0 Monroe County Pilot Roads Project Key Largo and Big Pine Key Final Report a Draft 1 Executive Summary .................................................................................. ..............................1 2 Introduction ............................................................................................. ............................... 2 3 Part I: Methodology and Technical Background .................................... ............................... 6 3.1 Tidal Flooding Assessment ..................................................................................... ............................... 6 3.2 Climate Change and Sea Level Rise ...................................................................... ............................... 9 3.3 Engineering Design Assessment .......................................................................... ............................... 11 4 Recommendations .................................................................................. .............................19 4.1 Establishing a baseline for decision - making ....................................................... ............................... 19 4.2 Example decision - making ..................................................................................... ............................... 20 5 Part II: Legal and Policy Analysis ......................................................... ............................... 23 Figure 1- Communities Selected for the Pilot Project .......................................... ............................... Figure 2 -Study Location -Shaw Drive, Key Largo ............................................... ............................... Figure - Study Area, Big Pine Key ........................................................................ ............................... Figure 4 - Project Technical Work Flow .................................................................. ............................... Figure 5 - Vaca Gauge Water Level - 1996 to 2016 ............................................. ............................... Figure 6 - 2015 Tidal Record for Vaca Key Highlighting 2015 Event .............. ............................... Figure 7 -Sea Level Rise Projections -Southeast Florida Regional Climate Change Compact........ 2 3 3 5 7 8 .10 Table 1- Analysis of Tidal Flood Levels for Vaca Key and Estimated Levels for Two Pilot Communities................................................................................................ ..............................9 Table 2 - Tidal Condition and Flooding Estimates for Two Communities for Two Policy SLR Values....................................................................................................... ............................... 11 Table 3 - Tidal Water Elevations and Recurrence Periods for Big Pine .................. ............................... 13 Table 4 -Tidal Water Elevations and Recurrence Periods for Key Largo ............... ............................... 13 N o v e m b e r 2 0 1 6 m 0 as LL as 0. 0 F— LL as 0- 0 E 0 0 0 CL U- E 0 This report summarizes the preliminary results of a pilot project conducted by Monroe County, Florida to assess the implications of sea level rise on its roadway improvement program. This effort was motivated by two significant events. The first was the release of the County's GreenKeys Sustainability Plan, which outlined the need to refine the County's thinking with regard to long term climate change. The second was the King Tide Event of 2015, which due to a combination of tidal and storm conditions, caused long -term, disruptive flooding. The County conducted a pilot study and technical analysis based on a data - driven method to identify the appropriate design response to potential sea level rise effects on roadways for communities. To conduct this work, the County completed the following activities: • Assess past tidal events in the Keys by analyzing the historic record and determine the statistical probability of flooding for certain events. • Identify how sea level rise might impact the study areas by adding an estimate for IPCC AR5 Median and USACE High predicted rise to the values derived from the analysis of past events. • Identify how various design response strategies could be put in place to address flooding concerns and ensure that roadways remain drivable for various events. • Develop design cost estimates to bound the costs of various policy strategies available to the County. • Made recommendations on implementation strategies for incorporating the material from this document into later project designs. This study concludes that the County will need to carefully consider the implications of various response strategies and issue policy guidance on the actions the County will take to address sea level rise as a part of its regular design and maintenance activities. Packet Pg. 2862 Monroe County Pilot Roads Project - Key Largo and Big Pine Key Final Report - Draft 2 Introduction Monroe County accepted the GreenKeys Plan in early 2016, which made several recommendations concerning infrastructure planning in light of future sea level rise projections. The county also experienced flooding from higher- than - normal King Tides in 2015 and 2016, causing extended periods of flooding in some communities along the Keys. King Tides refer to the higher- than - average annual high tides that occur in the Fall each year when the moon, sun and Earth are aligned in such a way that gravitational forces produce the greatest tidal fluctuations. The King Tides in 2015, in particular, provided a preview of what the county can expect as sea level rise becomes a slowly evolving reality in the future. The event also represented similar future conditions with regular tidal events that would be expected to be more impactful with higher sea levels. Knowing that increased flooding from either King Tides, storm events or just general sea level rise will likely occur in the future, and that the County will have to address this issue countywide, the County adopted a "pilot effort" to test methodologies for determining future flood risk scenarios and to develop a policy framework for making these decisions relative to ongoing roadway improvement projects. Two communities were chosen for this study, one in Key Largo and one in Big Pine Key. Figure 1 below identifies the locations of the two communities chosen. Specific roadway areas within those communities were further defined as the primary area of focus (see Figures 2 and 3). Page 2 I November 2016 Contents Figure 1 - Communities Selected for the Pilot Project Page 3 of 28 Figure 2 - Study Location - Shaw Drive, Key Largo Figure 3 - Study Area, Big Pine Key Monroe County Pilot Roads Project Key Largo and Big Pine Key Final Report a Draft Part I of this report presents the history of, and the technical work for, the assessment of the potential response to tidal flooding in the two county communities. This work reflects pertinent GreenKeys Plan recommendations to better plan for future flood risk associated with roads. The focus of this effort has been on developing a method to estimate future flood potential, based on analysis of historical events - and also to develop conceptual design and cost estimates for road and stormwater improvements in the two communities. Final designs for these two communities will serve as a pilot effort to take lessons learned from this process and extend them to other county road improvement projects that would consider the following questions: • What is a reasonable level of service for county road projects for flooding levels and the amount of time a given road is impacted? • How are levels of service established in the face of uncertainty with a changing climate and projected levels of sea level rise that are based on a range of future conditions? • What would be considered a cost - effective response given the needs of these communities and the broader needs of the larger Monroe County community? • What is a model policy approach for future decision making on road level of service countywide? Part II of this report includes an approach for policy adoption that includes a set of factors for the County to consider in establishing levels of service for future flood risk when implementing road projects. The analysis for this project is specific to the two pilot communities in the areas defined in Big Pine and Key Largo. However, the outcomes of this project must be considered in a broader framework of governance in Monroe County, which is why a comprehensive policy for consideration of future sea level rise in road design projects is also included. The GreenKeys Plan indicated that approximately 144 miles of roadways may be exposed to nuisance flooding by 2030 under the low sea level rise scenario, and that 188 miles of roadways may be exposed by 2030 under the USACE High sea level rise scenario. Thus, design criteria will need to consider a larger countywide need to assure that appropriate sea level rise impacts are considered as part of project decision making. Recommendations from the GreenKeys Plan relevant to this study include: 1 -19, "Pilot project to conduct Comprehensive Feasibility Study for Enhanced Stormwater and Tidewater Criteria (prioritizing areas) for near -term areas subject to inundation risk, including nuisance flooding (in two locations). 2 -14, "Conduct a countywide roads analysis to identify near -term roads subject to inundation risk, including nuisance flooding. This will include researching where related green infrastructure would be appropriate. Increase the percentage of funding invested in green infrastructure." • 2 -36, "Ensure that all new nuisance flooding data informs future road decisions. These data will also need to be considered for future road decisions. This will require coordination with FDOT for impacts to State Roads (U.S. Highway 1). The technical analysis in this project used a framework that can help with future road improvement decisions. The steps taken to complete this work are shown in Figure 4. In essence, the analysis reviewed existing flooding over the past several years, incorporated rising water levels associated Page 4 I November 2016 Packet Pg. 2865 with sea level rise into project considerations, determined how roadway design factors may have to be modified due to changing future conditions, and then considered how that information could be used to guide county policies. HyUre 4 - Project Technical Work Flow Study Past Events and Determine Flooding Recurrence Consider Sea 11 Identify Design Level Rise Engineering Alternatives Estimates for Response Response for the County Strategies w/ Communities Estimated Costs A Note about the Vertical Datum Value Used in this Report A vertical datum is a reference measurement to identify elevations in comparable units from around the world. The units used in this report at for the North American Vertical Datum from 1988 - or the NAVD88 datum. This set of measurements is calculated based on a set of control points, with the result being a set of values for land elevation. One interesting thing to note on the use of this datum is that for many points in the Florida Keys, the measure for Mean Sea Level is less than 0. This makes things a bit challenging to process, but the use of relative change from a baseline point makes the use of this datum more understandable. From this point forward in the report, the reader will note that some values are shown as negative when referencing NAVD 88. Page 5 of 28 Monroe County Pilot Roads Project Key Largo and Big Pine Key Final Report a Draft Part Methodology Background The purpose of the tidal flooding assessment was to conduct an analysis of past tidal events that occurred in the study areas to develop an understanding of how tidal influences and events have affected the two pilot communities. The intent was to develop a data - driven assessment to bound the understanding of past events and inform decisions on how the county should respond to similar events. The assessment focused on determining how past events, including the events that occurred in Fall 2015 and 2016, should be considered in terms of understanding how tidal and other flooding events have impacted Monroe County communities. The water elevation data included a summary of tidal events from the Vaca Key National Oceanic and Atmospheric Administration ( "NOAA ") Tide Gauge 20 year tidal record to complete an analysis of tidal flooding events in the county. The work included an assessment of the extended period of record for the Vaca Gauge, which is shown in Figure 5. Page c I November 2016 Packet Pg. 2867 Figure 5 - Vaca Gauge Water Level -1996 to 2016 Hourly Water Level Vaca Key, Station 8723970 5.5 5.0 4.5 4.0 3.5 3.0 m 2.5 0 2.0 z x 1.5 w 1.0 3 0.5 0.0 -0.5 -1.0 -1.s -2.0 - -2.5 6J V N W Ot N fJ� O The analysis also looked very specifically at the Fall 2015 flooding event, and the factors that went into the flooding caused by that event. The tidal record for that event is included in Figure 6. One primary conclusion of the review of the Fall 2015 event is that the weather conditions in the region resulted in shifting the average tidal conditions significantly higher during that event. This means that during the events noted in the two subject communities, the overall tidal effects shifted higher by a few inches, with the result being the low tides during this period were not low enough to clear the flooding experienced - resulting in extended periods with water on community roadways. While Fall 2016 was a more recent King Tide event, Fall 2015 was chosen because predicted and observed water levels were higher, reflecting a more extreme condition for comparison purposes and alternatives evaluation. Page 7 of 28 Monroe County Pilot Roads Project - Key Largo and Big Pine Key Final Report - Draft Figure 6 - 2015 Tidal Record for Vaca Key - Highlighting 2015 Event De- trended Water Level Vaca Key, Station 8723970 5.s 5.0 4.5 4.a 3.5 3.0 m� 2.5 7 Z 2.0 1.5 v 1.a IL � 0.5 ©.0 -1.a 1.5 -2.a -2.5 - N � N N ✓� N N N rY e-I N N N N Note on the graphic - the graphic above depicts the tidal record for the year 2015. The title of the figure shows "de- trended" data which describes a method applied by the project team to clarify the tidal effects over the 20 year period, in part by removing the incremental sea level rise that occurred during that period. The time period between the two red lines is the start and end points of the 2015 event described throughout this report. A statistical analysis was completed for the 20 -year tidal record to develop an understanding of the effect of past tidal conditions on flooding in Monroe County. This was done to further refine an understanding of how tidal events, even those affected by non - hurricane conditions, have impacted the two communities over the past two decades. This baseline assessment could then be used to project forward into the future while also considering sea level rise effects on these conditions. Table 1 shows the results of the initial analysis performed for this report, outlining the work to identify return period events and flood levels for the two pilot communities. Some notable differences in the table are attributable to the overall tidal effects in each area - with the tidal values being generally higher for Big Pine Key based upon its location, and less for the Key Largo community. The information in Table xx outlines the number of hours of flooding at various elevation levels for the two communities, converting those values into hours of inundation, which is then averaged over Page 8 I November 2016 Contents the 20 -year analysis period to identify flood probabilities. As an example, a flood level of approximately 1.7 feet (NAVD 88) at Vaca Key translates into approximately 7 days of flooding per year (24 hours of flooding), which is used as a metric in later design steps of the project. The values in the table in green are used as input on future design decisions. Table 1 - Analysis of Tidal Flood Levels for Vaca Key and Estimated Levels for Two Pilot Communities Vaca Key Key Largo Big Pine Twenty Year Record Average Per year Flood Flood Flood Number of Inundation Number of Inundation Level Level Level floods floods (in, NAVD88) I (In, NAVD88) (In, NAVD88) H (hr) H (days) -1.3 159 16416 8.1 @35 1.7...x; 45 3600 2.3 @7 4.7 .�; 12 744 0.6 @1.5 7.7 5.0 10.9 2 120 Note: columns 2 and J exempllty the point at wnlcn Hooding occurs In the particular area but due to dltterences In elevation, topography and the inherent difference in tidal levels between the two areas, flooding occurs at different levels Climate change is a term used to describe warming of the Earth's atmosphere, and how that warming will result in changing conditions such as sea level rise or changing weather patterns. There are individual elements of sea level rise such as ice melt, thermal expansion of water, or other factors that are the focus of other research. An obvious concern in Monroe County as a coastal community is the potential long term effects of rising sea levels. This changing condition, combined with porous geology and tropical weather patterns, makes Monroe County unique in its exposure to long -term coastal risks. The challenge will be to develop policies that respond appropriately to these changes while recognizing the timing and uncertainties associated with such future conditions. Monroe County is a part of the Southeast Florida Regional Climate Compact ( SFRCC), which provides information to help guide policy decisions throughout the four (4) county lower east coast region. The SFRCC released in late 2015 a document that outlined sea level rise values for three (3) scenarios in southeast Florida'. These curves are noted in Figure 7. The challenge of using three (3) potential future conditions, particularly with regards to infrastructure planning, is that there is the possibility of overspending or underspending on improvement or protection strategies depending on which scenario is selected. In reviewing Figure 7, one can see that building to NOAA high conditions in 2040 may be overbuilding to conditions not expected for 30 -40 years should the IPCC AR5 1 Unified Sea Level Rise Projections - Southeast Florida, October 2015 Page 9 of 28 Monroe County Pilot Roads Project - Key Largo and Big Pine Key Final Report - Draft Median scenario be the reality. Decisions that recognize this reality and identify how to spend scarce resources appropriately are important in the context of planning for sea level rise, Figure 7 - Sea Level Rise Projections - Southeast Florida Regional Climate Change Compact 80 70 J LL 60 a � v v 50 E 0 40 v v v � J w 30 m � a s ' c 20 ra or 10 0 Unified Sea Level Rise Projection (Southeast Florida Regional Climate Change Compact, 2015) y i t W ! § _ - -- 1992 2000 2010 2020 2030 2040 2050 Ak 2U /U 2060 2090 21UU Year Another primary consideration in making infrastructure decisions is the lifetime of a project. Adopting an expected project "useful or design life" ensures that investments consider how long an asset is expected to be in place before future replacement or improvement cycles are necessary, or to understand how long an asset may have before being impacted by changing environmental conditions. This is an important perspective, as every infrastructure project should consider not only the point of impact, but also the implications of that impact on the facility, or the remaining design life. These are factors that are not a part of traditional facility design. Data analysis was conducted to develop estimates for how sea level rise would potentially change the design approach for raising the roadways in the two communities, primarily by incorporating future sea level rise scenarios into decision making. The Compact generally recommends that the IPCC AR5 Median and USACE High scenarios be used as a range for more common infrastructure planning decisions. Decisions for infrastructure or facilities with a very low tolerance for flood exposure (such as power plants) should utilize the NOAA High scenario as recommended by the Compact. For this analysis (given the routine nature of road improvements), the two recommended estimates for sea level rise of the IPCC AR5 and USACE High were applied to the end of the 25 -year design life used as an estimate for the pilot project. Twenty -five (25) years was chosen as the typical useful or design life for a road improvement project. Estimates of sea level rise increase from the current 2015 levels by 5.4" (2040 Median) and 10.1" (2040 USACE High) and these values were added to information taken from the tidal records to develop a table of water elevations associated with various tidal inundation events that would be considered for a future design response. Table 2 IPCCARS USACE High NOAA High Year Median (inches) (inches) (inches) 2030 6 10 12 2060 14 26 34 2100 31 61 81 y i t W ! § _ - -- 1992 2000 2010 2020 2030 2040 2050 Ak 2U /U 2060 2090 21UU Year Another primary consideration in making infrastructure decisions is the lifetime of a project. Adopting an expected project "useful or design life" ensures that investments consider how long an asset is expected to be in place before future replacement or improvement cycles are necessary, or to understand how long an asset may have before being impacted by changing environmental conditions. This is an important perspective, as every infrastructure project should consider not only the point of impact, but also the implications of that impact on the facility, or the remaining design life. These are factors that are not a part of traditional facility design. Data analysis was conducted to develop estimates for how sea level rise would potentially change the design approach for raising the roadways in the two communities, primarily by incorporating future sea level rise scenarios into decision making. The Compact generally recommends that the IPCC AR5 Median and USACE High scenarios be used as a range for more common infrastructure planning decisions. Decisions for infrastructure or facilities with a very low tolerance for flood exposure (such as power plants) should utilize the NOAA High scenario as recommended by the Compact. For this analysis (given the routine nature of road improvements), the two recommended estimates for sea level rise of the IPCC AR5 and USACE High were applied to the end of the 25 -year design life used as an estimate for the pilot project. Twenty -five (25) years was chosen as the typical useful or design life for a road improvement project. Estimates of sea level rise increase from the current 2015 levels by 5.4" (2040 Median) and 10.1" (2040 USACE High) and these values were added to information taken from the tidal records to develop a table of water elevations associated with various tidal inundation events that would be considered for a future design response. Table 2 identifies the calculated values for a set of events taken from the tidal record, adds the sea level rise estimates, and identifies the water elevations to be considered as a part of roadway design for this project. Table 2 - Tidal Condition and Flooding Estimates for Two Communities for Two Policy SLR Values Note: This table is one of those that highlights the negative values associated with NAVD88 elevations in the study area. Reviewing the data to note changes or differences in elevations and to identify elevations that address certain flood recurrences is the best use of the table. This data formed the basis for design recommendations that were developed and assessed for this project, a process that is outlined in the next section of the report. l An engineering t design t rrn assessment was rrr t performed for this project to � rrrrrrrrrrrrrrrrrrrrrrr identify a set of design scenarios that could address current and potential future conditions as a means of defining the extent and cost of strategies that would address longterm sea level rise and tidal conditions. This was an important consideration given the conditions present in these two communities will be similar to other communities in the county. Flood Levels and Recurrence The study team evaluated not only a particular level of sea level rise by 2040, but also an array of days of flooding annually from a particular flooding level. The goal is to provide information related to each flood level scenario that tracks the amount of time that level will occur in any one year. Flooding on a road for 30 days in one year versus flooding for 7 days or a single day creates a much Page 11 of 28 Existing Future Design Levels Considered Values (inches NAVD88) 2044 Median SLR (in) 2040 High SLR (in) Big Pine Key Largo Big Pine` Key Largo Big Pine Key Largo Mean Sea Level -9.0 -11.0 -3.6 -5.6 1.1 -0.9 Mean Higher High Water -1.1 -7.0 43 -1.6 9.0' 3.0 2015 Event', Avg Elevation 5.3 3.3 10.7 8.7 15.3 13.3 2015 Event' High Elevation 16.1 14.1 21.5 19.5 26.1 24.1 Est. Month Flooding 1.9 -4.0 7.3 1.4 12.0 6.0 Est. Week Flooding' 4.9 -1.0 10.3 4.4 15.0 9.0 Est. Day Flooding 7°9 2.0 13.3 7.4 18.0 12.0 Note: This table is one of those that highlights the negative values associated with NAVD88 elevations in the study area. Reviewing the data to note changes or differences in elevations and to identify elevations that address certain flood recurrences is the best use of the table. This data formed the basis for design recommendations that were developed and assessed for this project, a process that is outlined in the next section of the report. l An engineering t design t rrn assessment was rrr t performed for this project to � rrrrrrrrrrrrrrrrrrrrrrr identify a set of design scenarios that could address current and potential future conditions as a means of defining the extent and cost of strategies that would address longterm sea level rise and tidal conditions. This was an important consideration given the conditions present in these two communities will be similar to other communities in the county. Flood Levels and Recurrence The study team evaluated not only a particular level of sea level rise by 2040, but also an array of days of flooding annually from a particular flooding level. The goal is to provide information related to each flood level scenario that tracks the amount of time that level will occur in any one year. Flooding on a road for 30 days in one year versus flooding for 7 days or a single day creates a much Page 11 of 28 Monroe County Pilot Roads Project Key Largo and Big Pine Key Final Report a Draft different impact on the community, so the "days of impact" is also considered over a range of options. King Tides of 2015 and 2016 In the fall of 2015, both Big Pine and Key Largo saw levels of inundation for numerous days due to multiple factors. The primary effect was just the time of the year in that October typically brings the King Tides. Additionally, this effect can also be compounded by wind - related impacts or surge from events such as tropical storms or hurricanes. In terms of comparing known flooding conditions in both the Fall of 2015 and 2016 within the two communities, NOAA data from the Vaca Key tide gauge shows that flooding levels in the Fall of 2015 were on average greater than 2016, so the Fall 2015 was chosen for a comparison between sea level rise scenarios and a recent event - driven impact. Anecdotal information supplied by area residents noted that the Fall 2015 condition had not been seen before (the extended period of flooding) and historical data shows that level had a very low probability of occurring (less than 3% in any given year). But given the fact that people got to see firsthand the impact of that level of event, scenarios were compared to this condition as well as future sea level rise scenarios. Design Scenarios The focus of the engineering assessment was to look at multiple design scenarios for raising the roadway to address tidal flooding issues. The intent of identifying varying roadway elevation scenarios that would address a few inundation levels was in part to develop a stronger understanding of the differences in costs for identified design alternatives. The team selected elevations that would be sufficiently different as to enable comparison of options to address flooding and to compare project costs associated with addressing the different flood levels. For this exercise the following design elevations were tested - 6 ", 12 ", 18" and 28" (NAV88 elevations), meaning the roadways would be elevated to these various levels for analytical purposes. These values were loosely based on the various water elevations associated with different current and future inundation levels. Tables 3 and 4 represent the range of conditions based upon the use of the 2040 sea level rise scenarios for the IPCC AR5 Median and USACE High estimates. A number of considerations are important when looking at this table: • The table was reoriented from those developed for earlier tasks for ease of use and comparison. • The columns represent the duration of water elevation conditions for the scenarios shown. Mean Sea Level and Mean Higher High Water represent a general sea condition and average high tide respectively. This is followed by the calculated analysis results of recurrence of flooding elevation ranges from 30 days down to 1 day annually. • The Average Fall 2015 event column shows the calculated average level of flooding that occurred over the duration of the "King Tide" event in 2015 from September 24th to October 31St • The Max Fall 2015 event column shows the highest level the water was recorded around October 4th during the 2015 King Tide event. • Rows represent the following: Page 12 1 November 2016 Packet Pg. 2873 o Row 1 - current estimated flood levels from the 2015 Tidal Record, providing a "base condition" for comparison with the IPCC AR5 Median and USACE High sea level rise scenarios. o Row 2 - those same calculated flood levels, but with each value having been increased by the sea level rise estimate to occur between now and 2040 for Median SLR (5.4 " ?) o Row 3 - flood levels in row 1 increased by 10.1 ", which is the estimated sea level rise value from between now and 2040 for USACE High SLR Numbers within the tables represent the inches in elevation of the water levels, in the tidal datum NAVD 88 values. Negative values are presented as noted throughout the report due to the NAVD 88 reference and the fact that many areas of coastal Florida are at a level below that base elevation. Table 3 - Tidal Water Elevations and Recurrence Periods for Big Pine Big Pine Key Community All Elevations Shown in Inches (water levels) NAVD88 All Elevations Shown in Inches (water levels) NAVD88 MSL MHHW 30 Days Annually 7 Days Annual 1 Day Annually Avg Fall 2015 Event Max Fall 2015 Event 2015 -Tidal Record -9.0 -1.1 1.9 4.9 7.9 5.3 16.1 2040 Med SLR ( +5.4 ") -3.6 4.3 7.3 10.3 13.3 10.7 21.5 2040 High SLR ( +10.1 ") 1.1 9.0 12.0 15.0 18.0 15.3 26.1 Table 4 - Tidal Water Elevations and Recurrence Periods for Key Largo Shaw Drive Community - Key Largo All Elevations Shown in Inches (water levels) NAVD88 MSL MHHW 30 Days Annually 7 Days Annually 1 Day Annually Avg Fall 2015 Event Max Fall 2015 Event 2015 -Tidal Record -11.0 -7.0 -4.0 -1.0 2.0 3.3 14.1 2040 Med SLR ( +5.4 ") -5.6 -1.6 1.4 4.4 7.4 8.7 19.5 2040 High SLR ( +10.1 ") -0.9 3.0 6.0 9.0 12.0 13.3 24.1 A Note Here on How to Read the Tables - the tables show those values for some key conditions or return period events that were used to derive potential roadway design levels that matched predicted water levels. It is similar material as what is presented above, but reoriented to show various water levels. Negative values, as noted throughout, are a result of the elevation datum applied on this project. The reader can review the table to note conditions that would be addressed through building the roadway to a certain elevation. As an example, building the roadway to an elevation of 6" NAVD88 would be high enough to be higher than the calculated average 2015 event elevation in both communities (3.3 inches in Key Largo and 5.3 inches in Big Pine) - meaning the low tides would enable the water to clear from the roadway. Page 13 of 28 Monroe County Pilot Roads Project Key Largo and Big Pine Key Final Report a Draft The recommendations for roadway design elevations were based on input received from the technical advisory team. The shading shown in Table 5 identifies the tidal conditions and return period events that would be "covered" by the design roadway elevations identified for consideration. The implications of these design elevations will be important to consider when the analysis of these design methods are discussed further in terms of benefits gained for additional costs associated with raising the roadway to higher elevations. Table 5 - Elevations for Various Return Periods - And Identified Roadway Design Elevation Scenarios Shaw Drive Community - Key Largo All Elevations Shown in Inches NAVD88 MSL MHHW 30 Days Annually 7 Days Annually 1 Day Annually Avg Fall 2015 Event Max Fall 2015 Event Key to Color Scheme 2015 -Tidal Record -11.0 -7.0 -4.0 -1.0 2.0 3.3 14.11 6" Roadway Elevation 2040 Med SLR ( +5.4 ") -5.6 -1.6 1.4 4.4 7.4 8.7 19.5 12" Roadway Elevation 2040 High SLR ( +10.1 ") -0.9 3.0 6.0 9.0 12.0 13.3 24.1 18" Roadway Elevation 28" Roadway Elevation Development of Estimated Costs Estimated costs for raising the roadways were based on cost data maintained by both the County and FDOT for local roadway construction projects. It is important to note that the two communities have areas that are higher or lower in elevation along the roadways in question, that is the effort to raise roadways to meet a desired elevation would be in sections, not as one continuous effort.. Figures 8 and 9 were prepared as working products and have been included to depict this condition in the two communities. The maps have been prepared to show the elevations in the community to match the chosen design scenarios (- 6 ", 12 ", 18 "; and 28 ") to indicate the elevations in each community that are higher or lower than these values (note: the color schemes differ due to the need for more specificity in the Big Pine Key community). This means that the changes in water elevations have implications for both the depth of roadway, and also the extent of roadways that would need to be raised to achieve the final preferred design elevation. Or more clearly stated, elevating the roadway to certain design level may require more length as well as height, depending on the local neighborhood conditions. This condition is represented simply in Figure 10, showing how incremental increases in design heights also have increases in the lengths of roadways that would need to be reconstructed to address those identified flood elevations. Page 14 1 November 2016 Packet Pg. 2875 Figure 8 - Current Elevations in the Key Largo Community - Denoting NAVD 88 Elevations by Design Category Page 15 of 28 A 0 a� w ca v _ a� H N D h _ O w N W a _ J co co Z _ O _ N O I w _ O O U a� _ 'a m w w W a 0 a� W w _ a a U I �s O Figure 10 - Conceptual Representation of Elevation and Extent of Roadway Design Changes 28" 18" 12" 6 Note: this table demonstrates the relationship between increasing elevation and increasing roadway length required to get all roadways to that elevation within each community Estimated costs for elevating the roadways in the two communities were developed based on information provided by Monroe County and a review of construction costs for other similar local projects. Table 6 summarizes the cost estimates for raising the roadway profiles for the roads in identified within the study area for those communities, to ensure that the project consistently addresses the given flood level and all roads in the study areas are at the noted design elevation identified in the left column of the table. The engineering work to develop the estimates for construction are noted in the attached appendices and are included for reference. The expectation is that this material is presented to the County oversight team for review and comment. Once approved by the County, this material will November 2016 Table 6 - Cost Estimates for Re onstnicting Roadways in the Ti,vo StUdy C OMMUllitieS Monroe County Pilot Roads Project Key Largo and Big Pine Key Final Report a Draft form the basis for identifying the estimated costs associated with addressing the design policy recommendations and enable a dialogue on a potential response to the issue of long -term community tidal flooding. The cost estimate includes a full range of construction - oriented costs including: • Maintenance of Traffic • Mobilization • Design • Construction • 15% of costs for Construction Engineering and Inspection • A 25% Cost Contingency • Stormwater measures Page 18 Nove Packet Pg. 2879 Recently, the County has begun factoring sea level rise considerations into decisions related to road improvement projects. The factors already being considered on a project -by- project basis include tide levels at the location of the project, tide elevation seen on average or during the Fall 2015 King Tide event, and the projected sea level rise for a 2040 scenario. These efforts have occurred in response to public comment and were driven primarily by the events of 2015. They represent an effort that the County wanted to assess as a means of ensuring that any design response be based on an analysis framework. While these changes have already been incrementally made, the County should adopt a more comprehensive policy that takes into account site - specific conditions as warranted. From a policy perspective, while the BOCC may decide upon a particular level of projected sea level rise to drive design decisions, other considerations may prevent that projection from being achieved. Regardless whether a 2040 USACE High or IPCC AR5 Median sea level rise projection is considered, the following site - specific conditions should be factored into the design process: • The elevation of private parcels alongthe roadway • Environmental considerations such as sensitive land and mitigation requirements • Right of way availability • Current road conditions • Available space for required Stormwater features • Access for private parcels • Future maintenance costs of stormwater features including staffing resources Design alternatives should be based on a number of considerations, including those from governance, data and engineering perspectives. These are more fully outlined below: • From a Policy/Governance Perspective November 2016 Monroe County Pilot Roads Project Key Largo and Big Pine Key Final Report a Draft • The issue of sea level rise will be one with implications county -wide so the effort to identify an appropriate design elevation in these two communities will be important. • Given the broader recognition of county needs and the fact that (to date) the 2015 Fall event can be considered an anomaly, the focus of the County should be on delivering future flooding levels of service for more regular conditions than only those conditions noted in 2015. This is why a future sea level rise scenario should be chosen to guide road design considerations as a primary consideration rather than responding and designingto the Fall 2015 event. • The impacts of the 2015 event cannot be ignored despite the low probably of occurrence over the period of record evaluated. With a future sea level rise scenario, comparison can still be made to determine how an alternative would perform under Fall 2015 conditions. • Use of scenarios should be tied to the useful life of a project per Policy 1502.1.1 of the Comprehensive Plan. For that reason, the study team focused on the use of 2040 sea level rise projections to reflect the 25 -year life of a road improvement project. • From a data analysis perspective • An evaluation has been completed for impacts project for each sea level rise scenario and recurrence interval, which translates into a specific elevation for segments of the identified roads in each community. This information can be used to drive policy decisions. • Should the 2040 IPCC AR5 Median projection be used, the level of relief over an extended period of time would be realized even if the high SLR rate were to occur. And the opposite is true, should the high projection be used, the level of relief may carry over to a future maintenance cycle or longer potential project life. • Scenarios have also been compared to the Fall 2015 event to show the level of relief anticipated both from future 2040 conditions as well as what was seen last year. This information can be used to inform the public of design scenarios. • From an engineering and implementation perspective: • Designing to any scenario should raise the current roadway profile reducing the level and duration of flooding resulting in what would be a passable roadway under most current and future estimated conditions. • Under - design and over - design considerations translate to fiscal trade -offs that must be considered in the context of future risk for the County. As an example of the options available for design - two approaches to the level of sea level rise can be considered given the uncertainties of future SLR values and whether the IPCC AR5 Median or USACE High sea level rise projections are realized over time. 2 Prior to incorporating a new project to the Capital Improvements Element, Monroe County shall assure that it is reviewed for recommendations to increase resiliency and account for the impacts from climate change, including but not limited to, sea level rise and storm surge. Monroe County shall evaluate financial expenditures to fund repairs, reconditioning of deteriorating infrastructure and new infrastructure improvements within or proximate to vulnerable areas to manage public investments appropriately. Monroe County shall focus on level of service standards, as one of the points of analysis, to assure that infrastructure useful life and service expectations can be met in the face of climate change impacts. Page 20 Nove Packet Pg. 2881 Approach #1 uses the 2040 IPCC AR5 Median sea level rise projection of the Compact, which allows for targeting a future level of sea level rise, but also allows incremental improvements should projections track the 2040 USACE High scenario. The risk is that the road project could be considered "under- designed" and will show impacts before the end of the life of the project (after 2030), but the road project could still be constructed near term providing some level of relief. The concept is that the base material could support additional pavement in the future to accommodate a few additional inches of elevation, allowing for more flexible adaptation design based on what real sea level rise impacts occur versus those projected to occur. Approximately 3 -4" of additional pavement could be added on top of the installed pavement as an overlay to further raise the profile of the road should actual sea level rise track the higher end of the 2040 range. This incremental process is supported by the Compact's Unified Sea Level Rise Projection (2015). Approach #2 would be to use the 2040 USACE High projection. Designing to 2040 USACE High might be considered a "no regrets" adaptation strategy if the higher levels of sea level rise are realized. If future sea level rise impacts track more along the IPCC AR5 Median end of the range, using the 2040 USACE High projection could result in overdesign and a higher upfront cost to achieve a 2040 sea level rise condition. But if the road has already been elevated to a higher level this could reduce the cost of elevation in a future maintenance cycle. The table on the next page identifies how each of these approaches can be considered when combined with a response policy to put parameters around the decisions for the design elevation recommended for community roadways. The table was assembled to highlight the differences between two options so that county officials can understand how different policy decisions can lead to different longterm conditions, and be defined by different potential costs. 3 The designer of a type of infrastructure that is easily replaced, has a short lifespan, is adaptable, and has limited interdependencies with other infrastructure or services must weigh the potential benefit of designing for the upper blue line with the additional costs. Should the designer opt for specifyingthe lower curve, she /he must consider the consequences of under - designing for the potential likely sea level condition. Such consequences may include premature infrastructure failure. Additionally, planning for adaptation should be initiated in the conceptual phase. 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