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06-17-24 Joint Workshop between the City Commission and CDB - Amended AgendaCity of Atlantic Beach Amended Agenda Joint Workshop between the City Commission and the Community Development Board Monday, June 17, 2024 - 6:00 p.m. City Hall, Commission Chamber 800 Seminole Road, Atlantic Beach, FL 32233 INVOCATION AND PLEDGE TO THE FLAG Page(s) CALL TO ORDER 1. INTRODUCTIONS 2. PUBLIC COMMENT 3. OVERVIEW: STORMWATER MANAGEMENT PROGRAM AND ONSITE STORAGE HISTORY — STEVE SWANN, CITY ENGINEER SW Workshop Presentation 3-23 4. PRESENTATION —JONES EDMUNDS ENGINEERING AND CONSULTING SERVICES 5. QUESTIONS AND DISCUSSION — CITY COMMISSION ADJOURNMENT This meeting will be live -streamed and videotaped. The video recording will be posted within four business days on the City's website. To access live or recorded videos, visit www.coab.us/live. Any person wishing to speak to the City Commission on any matter at this meeting should submit a request to the City Clerk. For your convenience, forms for this purpose are available at the entrance to the Commission Chamber. In accordance with the Americans with Disabilities Act and Section 286.26, Florida Statutes, persons with disabilities needing special accommodation to participate in this meeting should contact the City Clerk's Office at (904) 247-5821 or at City Hall, 800 Seminole Road, Atlantic Beach, FL 32233, no later than 5:00 PM on the Thursday prior to the meeting. Page 1 of 23 Page 2 of 23 n) CM W 0 NJ W Overview of Stormwater Management in Atlantic Beach Julia Cornrnission & Community Development Board Workshop June 17, 2024 City of Atlantic Beach ➢ 4 square miles of flat & low-lying land ➢ Surrounded by water o ➢ High ground water table W ➢ Typical elevations from 10 FT to over 30 FT in some places a) CM U1 0 NJ W ➢ Few vacant parcels left ) 1/4...►Ly i._ e.5.)tiiiIdlly bulli UM Vacant Parcels 1 Overall Impervious Area Coverage L- .gar.. 1 +ARBOR ➢ Includes Buildings, Roads, Parks, etc. ➢ Impervious Area by Census Block group ➢ 2021 Data from COAB Comprehensive Plan 2O% 0 N 22% 49% 0 NJ W 16000 14000 12000 10000 8000 6000 4000 2000 0 1930 Population Data 1940 1950 1960 1970 1980 1990 2000 2010 2020 ➢ City has grown to —14,000 today ➢ Slower growth projected in the future as the City is essentially built -out Storm Sewer System Overview > System mostly constructed prior to modern regulations for flood protection > Water quality treatment is not provided in most of the system > Design Goal Level of Service for Flood Protection: > Major Streets (4 -lane roads) should be passable with water not exceeding the crown of the road during a 10 -year flood event ➢ Residential streets and other 2 -lane roads should be passable with water not exceeding the crown of the road during a 5 -year flood event CM D as oo Nm o V 3 s- O- N.) N a cu W 3 = N m 3 O N Storm Sewer System Overview Agenda Item # 17 Jun 2024 WaramlErilmorlimPligimIlimElmilmrUNIPAMPalimMarmanal SPIE AMP' 11"11.101111.1.11. OOP rola& P171.""1114112111111111111111. 1111114 4444 f . wit of imito• es of Storm Sewer Pipes E u7 N A Page 9 of 23 r^ Sewer Sy :em 'erview Agenda Item # 17 Jun 2024 laiP.lgllLu1lSrl■rel■E■Irf■11m11rIM1 ildmintiallaimigrallirillgiala. mi=ftliel:- waiivirrn,-_006- wrio,iitrAs ib,_ it Sir"' 4 im IOW nli H sow ,__ dip.- ;r1 iirmizi.._ a Arm 1 ,,„. ,- IA. 1 im.,..", IT a 0 • 1 = im Am.wrif p 1, .L i .. 1 1 ek 4 miles of Ditches & Swales A Page 10 of 23 Agenda Item # 17 Jun 2024 Page 11 of 23 EZ 40 ZZ abed Topography Legend Hopkins Creek Watershed Sherman Creek Watershed City Limits EZ 40 ET abed Sea Level Rise Trends 8720218 Mayport, Florida 2.89 +1- 0.25 mm/yr 0. E.0 - Linear Relative Sea Level Trend 0.-15 — Upper 95% Confidence Interval —Lower 95% Confidence Interval Monthly mean sea level with the 0.30 average seasonal cycle removed 0.15 -0.15 -0.30 -0.45 -0.60 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 ➢ Long-term rate of change = —0.1 inch/yr ➢ "5 inches of sea level rise since 1980 ➢ Predictions are that sea level rise rates are increasing ➢ Drainage system performance degrades as sea levels rise and ground water table rises EZ 40 VZ abed 2 . 0 1.5- 1.0- ' 5- 0.0 - Sea Level Rise Prediction -0.6 l [f -0.5 1970 1980 1990 2000 2010 2020 2030 Tide Gauge Observations — Observation Extrapolation — — — • Extrapolation Confidence Limits Low Intermediate -Low Intermediate NOAA 2022 Southeast Region Sea Level Rise Predictions - 0.0 2640 2050 Intermediate -High High Agenda Item # 17 Jun 2024 .�:��a�a��l•�a .mai■ �'�fl.�i�ltiiriiii�t ry.:, s :1.44ri I• ■ la SLI ■ {{ sy �� is k��l1yyt �J4{i] n9 -• n .��y,J 1 r _ a.-Sti i3y `• rlr•l .k_���«•.s's7���}{pyi: :C4'# ...'•.iiii ff�� ".' - -- ' 70. u, �r5; 5 .} �• ...:L.' '. ii .. s. •. .lxl ,#.. ,. ..#d.— y.�'+' s. ff05 55 .-.w r 'Am 5��.�.R } - . it s;ti l�Fti _•._ .'_ s.. - %a: �.{:.+,� �. tom' -rN VII.: -....,....:4::. f.' i - r`, rvy`g•� CJ t• 1..'.."11..'.."1: �Y • S r r T %} }' SYJM1s' 6'.'2 R +. .�'T• T 'r T. �i ...v7 r v - n . r, i. IT.4 +` •. i �. {'J'' 1',- - - - - ' 2 _ .r...M :.±.....444„: _ ."y!y �..7 w'-.4r1laNfC�:S••?.F. r. Page 15 of 23 Agenda Item # 17 Jun 2024 m. ".'77`.." JGx r� �it L > ii'kl zS"31•i FARC QM17att � ]�'�. �,--- te -ray• Page 16 of 23 EZ 40 LT abed Impervious Area History 1982 — Ord 90-82-74 Impervious Surface included in the definition for Lot Coverage. Lot Coverage included all areas of the lot covered by principal and accessory uses and structures as well as impervious surfaces such as drives, parking areas, walkways, swimming pools, patios, terraces, and the like. ➢ 35% maximum lot coverage for all residential districts ➢ 65% maximum lot coverage for Commercial Limited (CL) ➢ No maximum lot coverage for Commercial General (CG), Commercial Intensive (CI) and Light Industrial (LIW) - Ord 90-85-91 Driveways, parking areas, walkways, swimming pools, terraces and the like removed from lot coverage definition due to prohibition off-street parking in front setbacks which made it nearly impossible to meet the maximum 35% lot coverage requirement. Maximum lot coverage only accounted for areas of the lot covered by principal and accessory uses and structures. ➢ 35% maximum lot coverage for all residential districts ➢ 65% maximum lot coverage for CL ➢ No maximum lot coverage for CG, CI, and LIW Impervious Area History 1986 — Ord 90-86-113 Eliminated maximum lot coverage requirements in all residential zoning districts. It was mentioned by the City Commission that the 35% maximum lot coverage requirement was unnecessary due to new setback requirements that allowed for over 35% lot coverage. The belief was that setback requirements would serve to control the amount of a lot covered by structures. ➢ No definition or restrictions on impervious surfaces existed in the City Code at this time. 1998 — Ord 90-98-167 Due to flooding and stormwater concerns, driveways, patios, decks and the like were added to the definition of lot coverage. Additionally, a 50% maximum lot coverage requirement was created for all residential zoning districts. ➢ 50% maximum lot coverage for all Residential districts ➢ No maximum lot coverage for CG, 0, and LIW EZ 40 81 abed EZ 40 61 abed Impervious Area History 2001— Ord 90-01-172 An independent definition of impervious surface was added to the Code. Definition included rooftops, sidewalks, patios, driveways, parking lots and similar surfaces. Swimming pools were not considered impervious. The definition of lot coverage was changed to "the area of the lot covered by all impervious surfaces." ➢ 25% maximum Impervious Surface for Conservation zoning ➢ 50% maximum Impervious Surface for Residential districts ➢ 70% maximum Impervious Surface for commercial and industrial zoning districts 2003 — Ord 90-03-184 Added "surfaces using pervious concrete or other similar open grid paving systems shall be calculated as 50% impervious" to definition of impervious surface due to advancements in paver and pervious concrete technology. Lot coverage was still defined as the area covered by all impervious surfaces. ➢ 25% Maximum Impervious Surface for Conservation zoning ➢ 50% Maximum Impervious Surface for Residential districts ➢ 70% maximum Impervious Surface for commercial and industrial zoning districts, except that maximum Impervious Surface did not apply to infill development or redevelopment of previously developed sites. Stormwater management requirements were also required for infill development and for redevelopment projects involving exterior site changes. Impervious Area History 2006 — Ord 90-06-188 Due to pavers often being installed in a way that prevented permeability, the following language was added to the definition of Impervious Surface: ➢ "Open grid pavers must be installed on a sand base, without liner, in order to be considered 50% impervious. Solid surface pavers do not qualify for any reduction in impervious area, regardless of type of base material used" To address infill and redevelopment of residential Tots, the language below was also added to the definition of Impervious Surface: ➢ "In such cases where a previously and lawfully developed residential lot or development project exceeds the 50% limit, redevelopment or additions to existing residential development shall not exceed the pre -construction Impervious Surface limit..." EZ 40 OZ abed Impervious Area History 2019 — Ord 90-19-238 In 2018, Commission considered reducing Impervious Area in residential districts to 40% due to concerns from increased flooding potential. Final ordinance included: ➢ 45% maximum lot coverage for all residential districts ➢ Amended definition of Impervious Surface to include swimming pools at 50% ➢ No credit given for pervious pavers EZ 40 ZZ abed Onsite Stormwater Storage History 2002 Stormwater Master Plan Update ➢ Topography of the City makes us sensitive to the volume of runoff discharged ➢ Concluded that new development and redevelopment could result in increases in the volume and rate of stormwater runoff ➢ Modeled Hopkins Creek area with all developable area at 50% Impervious — Result was flood stages in houses and buildings would be higher ➢ Recommended that the City regulate the peak discharge of stormwater from individual lots for a 100 -Year rainfall event ➢ Recommended onsite stormwater storage so that there is no increase in the rate or volume of stormwater runoff offsite ➢ Alternatively, they suggested the City could require a fee -in -lieu of onsite storage. Fee would be based on fair share of capital and annual costs for construction and maintenance of piping & storage facilities. Fee would include cost of land acquisition ➢ Recommended the use of V=CAR/12 with runoff from IA = 100% and undeveloped = 20% EZ 40 ZZ abed EZ 40 EZ abed Onsite Stormwater Storage History 2003 — Ord 90-03-180 ➢ Onsite storage implemented for a 25 -Year rainfall event 2012 Stormwater Master Plan Update ➢ Concluded that by far, the most cost-effective means of controlling stormwater runoff is at its source - onsite storage 2018 Stormwater Master Plan Update ➢ Evaluated redevelopment resulting in partially reaching 50% total IA in residential areas of the city by 2030 and totally reaching 50% IA by 2045. ➢ Concluded that there would be a substantial increase in average and maximum peak stage flood conditions under these scenarios. 2019 — Ord 90-19-238 ➢ All development and redevelopment which result in improvements that exceed 50% percent of the market value of all improvements, if any, on the subject development parcel before the new development or redevelopment project is started shall provide onsite storage of stormwater for all impervious surface on the development parcel. 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