REGULATORY USE OF BROWARD COUNTY S FUTURE GROUNDWATER ELEVATION MAP

Transcription

1 REGULATORY USE OF BROWARD COUNTY S FUTURE GROUNDWATER ELEVATION MAP CARLOS ADORISIO, P.E. ENVIRONMENTAL ENGINEERING AND PERMITTING DIVISION ENVIRONMENTAL PROTECTION AND GROWTH MANAGEMENT DEPARTMENT

2 Goal To understand which groundwater (water table) maps should be used when applying for a Broward County Surface Water Management License for new or modified projects

3 Overview Understanding the Significance of Groundwater Elevations Old Groundwater Elevation Map vs. New Groundwater Elevation Map Regulatory Requirements for Antecedent Conditions Understanding Code Requirements and Definitions Practical Examples

4 Application Groundwater (water table) elevation affects the design of stormwater management systems: Wet or dry retention areas, stage/storage curve (on-site storage), allowable discharge, etc. Permitting process requires the use of appropriate groundwater elevations

5 Water Management Plate WM 2.1 (Water Table Map) Adopted in 2000 Average Wet Season Water Table Based on groundwater and surface water measurements Limited data (e.g., along coast line) requires use of site-specific measurements of groundwater

6 Rising Historic Groundwater Levels

7 New Challenge - Future Conditions Sea level rise: National Research Council Curve 3 (NRC3)

8 Water Management Plate WM 2.1-Future Conditions (Future Conditions Average Wet Season Groundwater Elevations)

9 Water Management Plate WM 2.1-Future Conditions (Future Conditions Average Wet Season Groundwater Elevations) The map represents the expected future average wet season groundwater elevations for Broward County. The average is based on model outputs for the months of May through October over the period of The models used are The Broward County Inundation Model and the Broward County Northern Variable Density model, both developed by the United States Geological Survey (USGS) and MODFLOW based. The future conditions that are modified in the models are both precipitation and sea level rise. The future precipitation pattern is based on the Center for Ocean-Atmospheric Prediction Studies (COAPS) downscaled Community Climate System Model (CCSM) global model and represents an increase of 9.1% rainfall from the base case of (53.4 in/yr to 58.2 in/yr). Sea level rise was based on the United States Army Corps of Engineers (USACE) National Research Council Curve 3 (NRC3) curve which equates to an increase of 26.6 to 33.9 inches to the future period from 1992 levels. Final results are presented in 1988 North American Vertical Datum (NAVD 88).

10 Water Management Plate WM 2.1-Future Conditions (Future Conditions Average Wet Season Groundwater Elevations) Establishes a Future Conditions Average Wet Season Water Level Map representing conditions predicted in Ensures the resiliency of current and future infrastructure investments by providing the necessary level of flood protection and water quality treatment during their expected useful lifespan (Cannot rely solely upon historic and current environmental conditions as the basis for infrastructure planning, design, and permitting)

11 Plate WM 2.1 vs. Plate WM 2.1-Future Conditions Minor changes in Western Broward More significant increases in tidally influenced Eastern Broward

12 Broward County Code Requirements Chapter 27, Volume V - WATER RESOURCE MANAGEMENT

13 Design Criteria Section (b)(5)a.3.b) Antecedent conditions: Ground water and surface water stages antecedent to a design event shall be the higher of the average wet season water levels or the applicable control elevations. Plate WM 2.1 may be used for determining the average wet season ground water levels for use in calculating a design event for existing projects, except for applications for major redevelopment as defined in Section or for a major modification to a surface water management license. Plate WM Future Conditions shall be used for determining the average wet season ground water levels for use in calculating a design event for new applications for a surface water management license, applications for major redevelopment of existing sites, and applications for major modifications to existing surface water management licenses submitted after June 30, 2017.

14 Design Criteria Section (b)(5)a.3.b) Antecedent conditions: Ground water and surface water stages antecedent to a design event shall be the higher of the average wet season water levels or the applicable control elevations. If the applicable control elevation (CE) is higher than the average wet season ground water elevation shown in Plate WM 2.1 and/or Plate WM 2.1- Future Conditions, then that CE will be used in the design

15 Design Criteria Section (b)(5)a.3.b) Antecedent conditions:... Plate WM 2.1 may be used for determining the average wet season ground water levels for use in calculating a design event for existing projects, except for applications for major redevelopment as defined in Section or for a major modification to a surface water management license. Plate WM Future Conditions shall be used for determining the average wet season ground water levels for use in calculating a design event for new applications for a surface water management license, applications for major redevelopment of existing sites, and applications for major modifications to existing surface water management licenses submitted after June 30, 2017.

16 Definitions Modifications: Major Modification Letter Modification Redevelopment: Major Redevelopment Minor Redevelopment

17 Modifications Section (d)(2)d.1.b Section 198(d)(2)d.1.b allows for modifications to a surface water management license by letter (or Letter Modification) provided the request modification does not: Substantially alter the license authorization, or any license conditions Increase the authorized off-site discharge Adversely impact the environmental features of the project Decrease the required retention/detention Increase the required flood elevations for roads or buildings Decrease pollution removal efficiency All other modifications are deemed Major Modifications

18 Major Redevelopment Section Definition Major redevelopment means construction activities which involve the demolition or removal of the principal structure on a site or of more than fifty percent (50%) of the impervious surface of a developed area on a site. Major redevelopment also means minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site or greater than or equal to two (2) acres over a period of ten (10) years.

19 Major Redevelopment Construction which involve the demolition or removal of the principal structure on a site Construction activities which involve the demolition or removal of more than fifty percent (50%) of the impervious surface of a developed area on a site Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Minor redevelopment with the cumulative expansion of developed area greater than or equal to two (2) acres over a period of ten (10) years

20 Major Redevelopment (Example 1) Construction which involve the demolition or removal of the principal structure on a site Site 20 acres: 2.6 ac. of buildings, 10 ac. of parking, and 7.4 ac. of pervious areas. The buildings include a 1-acre principal structure and 8 satellite structures (each 0.2- ac. in area) If the 1.0-ac. principal structure is removed, then the project will be deemed as major redevelopment

21 Construction which involve the demolition or removal of the principal structure on a site Example 1 Site 20 acres: 2.6 ac. of buildings, 10 ac. of parking, and 7.4 ac. of pervious areas. The buildings include a 1-acre principal structure and 8 satellite structures (each 0.2-ac. in area) 1 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 7.4 ac. 10 ac.

22 Construction which involve the demolition or removal of the principal structure on a site Example 1 (cont d) 0.2 ac. 0.2 ac. 1 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 0.2 ac. 7.4 ac. 10 ac.

23 Major Redevelopment (Example 2) Construction activities which involve the demolition or removal of more than fifty percent (50%) of the impervious surface of a developed area on a site A site has a building area and a pavement area. Both areas are impervious. Therefore, the building area is a developed area and the pavement area is also a (another) developed area Site 10 acres: 3 ac. of buildings, 5 ac. of parking, and 2 ac. of pervious areas If the 1.51 ac. of the building area are removed, then the project will be deemed as major redevelopment If the 2.51 ac. of the parking area are removed, then the project will be deemed as major redevelopment

24 Construction activities which involve the demolition or removal of more than fifty percent (50%) of the impervious surface of a developed area on a site Example 2 Site 10 acres: 3 ac. of buildings, 5 ac. of parking, and 2 ac. of pervious areas 3 ac. 2 ac. 5 ac.

25 Construction activities which involve the demolition or removal of more than fifty percent (50%) of the impervious surface of a developed area on a site Example 2 (cont d) 1.51 ac. 3 ac. 2 ac. 5 ac.

26 Construction activities which involve the demolition or removal of more than fifty percent (50%) of the impervious surface of a developed area on a site Example 2 (cont d) 2.51 ac. 3 ac. 2 ac. 5 ac.

27 Major Redevelopment (Example 3) Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Site 20 acres: 6 ac. of buildings, 10 ac. of parking, and 4 ac. of pervious areas If a project in Year 1 involves construction over 5.0 ac. of the site, it will be deemed major redevelopment If a project in Year 1 involves construction over 4.5 ac. of the site and does not include more than 3.0 acres of the existing building, it will be deemed minor redevelopment; Then a project in Year 10 involves construction over 0.5 acres of the site, the project in Year 10 will be deemed major redevelopment

28 Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Example 3A Site 20 acres: 6 ac. of buildings, 10 ac. of parking, and 4 ac. of pervious area 6 ac. 4 ac. 10 ac.

29 Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Example 3A (cont d) 5 ac. 6 ac. 4 ac. 10 ac.

30 Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Example 3A (cont d) 5 ac. 6 ac. 4 ac. 10 ac.

31 Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Example 3B 6 ac. 4 ac. 10 ac.

32 Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Example 3B (cont d) YEAR ac. 6 ac. 4 ac. 10 ac.

33 Minor redevelopment with the cumulative expansion of developed area greater than or equal to twenty-five percent (25%) of the existing developed area of a site over a period of ten (10) years Example 3B (cont d) YEAR ac. YEAR ac. 6 ac. 4 ac. 10 ac.

34 Major Redevelopment (Example 4) Minor redevelopment with the cumulative expansion of developed area greater than or equal to two (2) acres over a period of ten (10) years Site 100 acres: 30 ac. of buildings, 50 ac. of parking, and 20 ac. of pervious areas. If a project in Year 1 involves expanding the site drainage area to ac., it will be deemed major redevelopment If a project in Year 1 involves expanding the site drainage area to ac., it will be deemed minor redevelopment; Then a project in Year 10 involves expanding the site drainage area further by 0.5 acres, the project in Year 10 will be deemed major redevelopment

35 Minor redevelopment with the cumulative expansion of developed area greater than or equal to two (2) acres over a period of ten (10) years Example 4A Site 100 acres: 30 ac. of buildings, 50 ac. of parking, and 20 ac. of pervious areas 30 ac. 20 ac. 50 ac.

36 Minor redevelopment with the cumulative expansion of developed area greater than or equal to two (2) acres over a period of ten (10) years Example 4A (cont d) 2 ac. 30 ac. 20 ac. 50 ac.

37 Minor redevelopment with the cumulative expansion of developed area greater than or equal to two (2) acres over a period of ten (10) years Example 4B 30 ac. 20 ac. 50 ac.

38 Minor redevelopment with the cumulative expansion of developed area greater than or equal to two (2) acres over a period of ten (10) years Example 4B (cont d) YEAR ac. 30 ac. 20 ac. 50 ac.

39 Minor redevelopment with the cumulative expansion of developed area greater than or equal to two (2) acres over a period of ten (10) years Example 4B (cont d) YEAR ac. 30 ac. 20 ac. 50 ac.

40 SMW Licensing Exemptions Section (c) Section (c) describes exemptions and other considerations in surface water management licensing Water management works for major redevelopment of land that had originally been developed prior to the requirement of operating licenses or in accordance with operating licenses shall be accomplished utilizing the licensing provisions currently in effect Water management works for minor redevelopment of land that had originally been developed in accordance with operating licenses shall be accomplished utilizing the licensing provisions in effect at the time of original licensing If the existing construction or operation SWM license is expired, or if the approved works are not in compliance with the conditions of the license, minor redevelopment of land shall be accomplished utilizing the licensing provisions currently in effect

41 Design Criteria Section (b)(5)a.3.b) Type of Project New Project 1.- Major Redevelopment: a) Major Modification to existing SWM license b) No prior licensing 2.- Minor Redevelopment: a) Existing construction or operation SWM license is expired b) Approved works are not in compliance with the conditions of the SWM license Minor Redevelopment (Existing construction or operation SWM license is not expired, and approved works are in compliance with the conditions of the SWM license Design Criteria Plate WM 2.1-Future Condition will be used to determine water quality and water quantity requirements. Entire site needs to comply with current code requirements. Plate WM 2.1-Future Condition will be used to determine water quality and water quantity requirements. Plate WM 2.1 will be used to determine water quality and water quantity requirements.

42 Modification to Conceptual Approval (Letter of Conceptual Approval or Master License/Permit) Conceptual license should not be expired Modification request will be reviewed and evaluated based on the degree of information detail and criteria in effect at the time of application and issuance of the initial conceptual approval If the modification request requires information details which were not submitted with the initial application, then that information will be reviewed and evaluated pursuant to the criteria in effect at the time of the subsequent application

43 Conceptual Approval License Duration 2 years from date of issuance May be granted a one-year extension if requested 180 days prior to the expiration date and a reasonable justification is provided Each subsequent construction phase of the project is granted 5 years to finish construction Construction License will become invalid 2 years from date of issuance if work has not begun unless other provisions have been made with EPGMD

44 Substantial Improvement If a project is determined to be a substantial improvements by the Municipality s Building Official, all buildings within the site may need to comply with the current Florida Building Code. If this additional requirement results in additional work that deems the project a major redevelopment, Plate WM 2.1-Future Condition will be used to determine water quality, water quantity, and minimum FFE requirements.

45 Questions?

46 Surface Water Management System Redesign Examples

47 Surface Water Management System Redesign Example 1

48 Surface Water Management System Redesign Example 1

49 Surface Water Management System Redesign Example 1 Impacts to drainage system resulting from 2 increase in groundwater: Exfiltration trench lost 37.5% of capacity (reduced water quality) and drainage well lost 34% of discharge capacity (higher peak 100-yr, 3- day elevation) Drainage system re-design: Increase exfiltration trench from 70 feet to 110 feet and add pump to drainage well

50 Surface Water Management System Redesign Example 2

51 Surface Water Management System Redesign Example 2

52 Surface Water Management System Redesign Example 2 Impacts to drainage system resulting from 2 increase in groundwater: Dry retention areas no longer provide water quality, perimeter berm no longer contains 25-yr, 3-day runoff, and offsite discharge through orifice becomes negligible due to submergence (higher tail water) Drainage system re-design: Provide 85 feet of exfiltration trench, raise perimeter berm, and raise orifice

53 Surface Water Management System Redesign Example 3 AREA DESIGNED LOWER THAN BUILDING AND ADJACENT PROPERTY

54 Surface Water Management System Redesign Example 3 THROUGHOUT

55 Surface Water Management System Redesign Example 3 Impacts to drainage system resulting from 2 increase in groundwater: Exfiltration trench lost 58% of capacity (reduced water quality), higher 100-yr, 3-day peak elevation, parking lot flooded during 5-yr, 1 hour storm event Drainage system re-design: Raise parking lot (stem walls allow for raising) and add drainage well

56 Questions?