Palm_Harbor_Eng_Design_Rpt.pdf

Palm Harbor Recreation Center 1500 16th Street

Section 01, Township 28S, Range 15E

Unincorporated Pinellas County, Florida

Engineering Design Report

Prepared By:

Vickstrom Engineering Services, Inc.

April 2025

Unincorporated Pinellas County, Florida

Engineering Design Report

Engineers Certification:

I HEREBY CERTIFY THAT THE ATTACHED CALCULATIONS

HAVE BEEN PERFORMED UNDER MY DIRECT SUPERVISION

Daniel M. Vickstrom, P.E.

State of Florida P.E. No. 46090

PALM HARBOR RECREATION CENTER

TABLE OF CONTENTS

Section 1 Project Location

Section 2 Project Scope

Section 3 Hydrologic Analysis & Pond Volume Calculations

Section 4 Water Quality Volume Check

Appendix o Hydrologic Calculations o Pond Volume Calculation o HydroCAD Models (Input & Output)

10 Year, 24 Hour Existing Conditions Model 10 Year, 24 Hour Proposed Conditions Model 25 Year, 24 Hour Existing Conditions Model 25 Year, 24 Hour Proposed Conditions Model 100 Year, 24 Hour Proposed Conditions Model o MODRET Input and Model o Geotechnical Report

SECTION 1 PROJECT LOCATION

The proposed project involves the demolition of an existing building and the construction of a recreational facility on an occupied parcel in Pinellas County within Section 01, Township 28S, and Range 15E. The site is located on the northeast corner of Pennsylvania Avenue and 16 th Street. See Sheet 1 of the Construction Plans for a location map. The proposed recreational facility with new parking will create approximately 0.86 acres of new impervious surface.

SECTION 2 PROJECT SCOPE

The proposed project involves the demolition of the existing building to the north and the construction of a recreation facility on the 8.59-acre parcel. Additional parking and drive aisles will be added to the existing parking lot as part of this project. Access to the site will remain along 16th street.

The existing dry pond on the south side of the site will be modified to accommodate the increase in impervious area. Drainage inlets will collect runoff from the site and direct it to the pond for treatment and attenuation. The pond system will be designed to provide water quality treatment to meet Presumptive Criteria for Pinellas County per table 6.10.4 of Pinellas County Stormwater Manual, and storm runoff attenuation for the 10 year and 25 year, 24 hour storm events. The 100 year, 24 hour storm event was also analyzed to ensure that the pond will not overtop and no buildings will flood.

See the Construction Plans showing the location of the proposed construction and stormwater pond.

In its current condition, the site is developed. No wetlands currently exist on the site. Therefore, no wetlands will be impacted as part of this project.

Based on the geotechnical report, and site observations, it is estimated that the seasonal high water elevation at the pond will be El 49.3 ft NAVD. The bottom of the pond is set eight feet above the SHGW elevation at El 57.3 ft NAVD.

SECTION 3 HYDROLOGIC ANALYSIS & POND VOLUME CALCULATION

Runoff from the site will be directed to the proposed pond via a piped storm drainage system.

The proposed pond, located at the southern area of the site, will discharge into the County drainage system (ditch) at the southwest corner of the site if the pond overtops.

A control structure is provided within the proposed pond, and is designed to retain the runoff from the 10 year, 25 year and 100 year storms with no discharge. The water quality treatment volume will be retained and percolated into the ground.

Unincorporated Pinellas County, Florida

Engineering Design Report

Engineers Certification:

I HEREBY CERTIFY THAT THE ATTACHED CALCULATIONS

HAVE BEEN PERFORMED UNDER MY DIRECT SUPERVISION

Daniel M. Vickstrom, P.E.

State of Florida P.E. No. 46090

TABLE OF CONTENTS

Section 1 Project Location

Section 2 Project Scope

Section 3 Hydrologic Analysis & Pond Volume Calculations

Section 4 Water Quality Volume Check

Appendix o Hydrologic Calculations o Pond Volume Calculation o HydroCAD Models (Input & Output)

▪ 10 Year, 24 Hour Existing Conditions Model

▪ 10 Year, 24 Hour Proposed Conditions Model

▪ 25 Year, 24 Hour Existing Conditions Model

▪ 25 Year, 24 Hour Proposed Conditions Model

▪ 100 Year, 24 Hour Proposed Conditions Model o MODRET Input and Model o Geotechnical Report

SECTION 1 PROJECT LOCATION

The proposed project involves the demolition of an existing building and the construction of a recreational facility on an occupied parcel in Pinellas County within Section 01, Township 28S, and Range 15E. The site is located on the northeast corner of Pennsylvania Avenue and 16th

Street. See Sheet 1 of the Construction Plans for a location map. The proposed recreational facility with new parking will create approximately 0.86 acres of new impervious surface.

SECTION 2 PROJECT SCOPE

The proposed project involves the demolition of the existing building to the north and the construction of a recreation facility on the 8.59-acre parcel. Additional parking and drive aisles will be added to the existing parking lot as part of this project. Access to the site will remain along 16th street.

The existing dry pond on the south side of the site will be modified to accommodate the increase in impervious area. Drainage inlets will collect runoff from the site and direct it to the pond for treatment and attenuation. The pond system will be designed to provide water quality treatment to meet Presumptive Criteria for Pinellas County per table 6.10.4 of Pinellas County Stormwater

Manual, and storm runoff attenuation for the 10 year and 25 year, 24 hour storm events. The 100 year, 24 hour storm event was also analyzed to ensure that the pond will not overtop and no buildings will flood.

See the Construction Plans showing the location of the proposed construction and stormwater pond.

In its current condition, the site is developed. No wetlands currently exist on the site. Therefore, no wetlands will be impacted as part of this project.

Based on the geotechnical report, and site observations, it is estimated that the seasonal high water elevation at the pond will be El 49.3 ft NAVD. The bottom of the pond is set eight feet above the SHGW elevation at El 57.3 ft NAVD.

SECTION 3 HYDROLOGIC ANALYSIS & POND VOLUME CALCULATION

Runoff from the site will be directed to the proposed pond via a piped storm drainage system.

The proposed pond, located at the southern area of the site, will discharge into the County drainage system (ditch) at the southwest corner of the site if the pond overtops.

A control structure is provided within the proposed pond, and is designed to retain the runoff from the 10 year, 25 year and 100 year storms with no discharge. The water quality treatment volume will be retained and percolated into the ground.

The hydrologic analysis for this project was performed using SCS Methods per TR-55. Values for Runoff Curve Numbers (RCNs) and Times of Concentration (Tc) were computed following TR-55 procedures. For the attenuation routing analysis, the starting elevation in the pond was started at the bottom of the pond, El. 57.3.

An RCN was determined for the existing and proposed conditions. In the natural condition, the site contains mostly Astatula soils, and some Basinger, Holopaw, and Samsula soils which are HSG type A soils. Because the groundwater is shallow in this area, the HSG A soil was used to determined the RCN for the runoff routing modeling and pond routing. This assessment is also supported by the exfiltration rates determined in the Geotechnical report, attached.

The time of concentration was estimated based on a runoff velocity under both existing and post development conditions.

These values were input into the HydroCAD model to create 10 year and 25 year runoff hydrographs for the existing and proposed conditions. The proposed runoff hydrograph was routed through the pond to determine the release rate and verify it will retain the conditions design storms for the 10 year and 25 year storms with no discharge.

The pond will retain both the 10 year and the 25 year storms with 6 inches of freeboard. In addition, the 100 year, 24 hour model was run to demonstrate that the pond will not overtop.

The pond top of bank is El 61.3 ft.

Peak Stages in Pond

10 Yr-24 Hr Elevation 58.9 ft 25 Yr-24 Hr Elevation 59.4 ft 100 Yr-24 Hr Elevation 59.9 ft

Computations for the hydrologic parameters for proposed conditions are contained in the appendix. The calculations for the pond volume and the HydroCAD models are provided in the appendix.

SECTION 4 WATER QUALITY VOLUME CHECK

The water quality volume for the proposed pond is based on the requirement to capture and retain sufficient treatment volume to meet the County’s water quality requirements. To verify the treatment volume, the presumptive criteria in section 6.10.7 was used. Per table 6.10.4, (as shown in the appendix) the retained water quality volume is 1.59” x (Area of site draining to pond = 138,996 S.F.) = 18,417 C.F. Because the pond is a retention facility designed to retain up to and including the 100 year storm, this water quality volume is achieved well below the crest of the weir.

A MODRET model was developed to determine the water quality volume drawdown from the water quality pool level (EL 58.55 ft NAVD) to the pond bottom elevation of El 57.3 ft NAVD.

Based on the DRI test results in geotechnical report, the soils have a Kv of 29 in/hr. The

MODRET model determined that the retained water quality volume will exfiltrate in less than 3 hours. The results are provided in the appendix. Due to there being no outflow from the 100 year storm, a MODRET model was also used to find the volume drawdown. The MODRET model determined that the retained weir level volume will exfiltrate in less than 8 hours. The MODRET analysis is included in the Appendix.

APPENDIX

• Hydrologic Calculations

• Pond Volume Calculation

• HydroCAD Models (Input & Output)

10 Year, 24 Hour Existing Conditions Model

10 Year, 24 Hour Proposed Conditions Model

25 Year, 24 Hour Existing Conditions Model

• MODRET Input and Model

• Geotechnical Report

Hydrologic Calculations

POND DRAINAGE SUMMARY

EX. POND DRAINAGE AREA= 90,213 S.F. ~ 2.07 AC.

EX. IMPERVIOUS

EX. PERVIOUS

TOTAL EX. POND DRAINAGE AREA

50,150 S.F.

40,063 S.F.

90,213 S.F.

PROP. POND DRAINAGE AREA= 138,996 S.F. ~ 3.19 AC.

PROP. IMPERVIOUS 87,539 S.F.

PROP. PERVIOUS 51,457 S.F.

TOTAL PROP. POND DRAINAGE AREA 138,996 S.F.

1.15 AC.

0.92 AC.

2.07 AC.

2.01 AC.

1.18 AC.

3.19 AC.

REQ'D W.Q. VOLUME = 1.59" X 138,996 S.F. = 18,419 C.F.

Pond Volume Calculation

Project: Palm Harbor 3/25/2025 Calc by: FWM

Proposed Pond Volume Calculation

Elevation

NAVD

Elevations Area

Average Area

D Volume (ft³)

Volume

58.00 57.30 13,458

59.00 58.30 15,418 14,438 14,438 14,438

60.00 59.30 17,949 16,684 16,684 31,122

61.00 60.30 19,535 18,742 18,742 49,864

62.00 61.30 21,971 20,753 20,753 70,617

HydroCAD Models (Input & Output)

• 10 Year, 24 Hour Existing Conditions Model

• 10 Year, 24 Hour Proposed Conditions Model

• 25 Year, 24 Hour Existing Conditions Model

• 25 Year, 24 Hour Proposed Conditions Model

• 100 Year, 24 Hour Proposed Conditions Model

10 Year, 24 Hour Existing Conditions Model

Type II FL 24-hr Rainfall=7.50"SWFWMD Palm Harbor Printed 1/22/2025Prepared by {enter your company name here}

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Subcatchment 1S: Existing Site

Runoff = 3.27 cfs @ 12.64 hrs, Volume= 0.735 af, Depth= 4.26"

Runoff by SCS TR-20 method, UH=SWFWMD-256, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type II FL 24-hr Rainfall=7.50"

Area (sf) CN Description

* 50,150 98 Building and Parking

40,063 39 >75% Grass cover, Good, HSG A 90,213 72 Weighted Average 40,063 44.41% Pervious Area 50,150 55.59% Impervious Area

Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs)

30.0 Direct Entry, Type II FL 24-hr Rainfall=7.50"Palm Harbor 10 yr Printed 4/2/2025Prepared by {enter your company name here}

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Pond 2P: Existing Pond

Inflow Area = 2.071 ac, 55.59% Impervious, Inflow Depth = 4.26" Inflow = 3.27 cfs @ 12.64 hrs, Volume= 0.735 af Outflow = 1.08 cfs @ 14.33 hrs, Volume= 0.876 af, Atten= 67%, Lag= 101.1 min Discarded = 1.08 cfs @ 14.33 hrs, Volume= 0.876 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Starting Elev= 58.30' Surf.Area= 12,810 sf Storage= 6,063 cf Peak Elev= 58.62' @ 14.33 hrs Surf.Area= 13,394 sf Storage= 10,301 cf (4,238 cf above start)

Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated: outflow precedes inflow)

Volume Invert Avail.Storage Storage Description #1 57.80' 52,501 cf Custom Stage Data (Prismatic) Listed below (Recalc)

Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet)

57.80 11,441 0 0

58.30 12,810 6,063 6,063

59.30 14,615 13,713 19,775

60.30 16,311 15,463 35,238

61.30 18,214 17,263 52,501

Device Routing Invert Outlet Devices #1 Primary 60.30' 3.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #2 Discarded 57.80' 2.900 in/hr Exfiltration over Surface area

Conductivity to Groundwater Elevation = 54.00'

Discarded OutFlow Max=1.08 cfs @ 14.33 hrs HW=58.62' (Free Discharge) 2=Exfiltration ( Controls 1.08 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=58.30' (Free Discharge) 1=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)

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10 Year, 24 Hour Proposed Conditions Model

Type II FL 24-hr Rainfall=7.50"SWFWMD Palm Harbor

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Subcatchment 3S: Proposed Site

Runoff = 5.94 cfs @ 12.62 hrs, Volume= 1.334 af, Depth= 4.93"

Runoff by SCS TR-20 method, UH=SWFWMD-256, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type II FL 24-hr Rainfall=7.50"

Area (sf) CN Description

* 93,396 98 Building and Parking

47,985 39 >75% Grass cover, Good, HSG A 141,381 78 Weighted Average 47,985 33.94% Pervious Area 93,396 66.06% Impervious Area

Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs)

30.0 Direct Entry, Type II FL 24-hr Rainfall=7.50"Palm Harbor 10 yr Printed 3/26/2025Prepared by {enter your company name here}

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Pond 4P: Proposed Pond

Inflow Area = 3.246 ac, 66.06% Impervious, Inflow Depth = 4.93" Inflow = 5.94 cfs @ 12.62 hrs, Volume= 1.334 af Outflow = 1.31 cfs @ 14.79 hrs, Volume= 1.334 af, Atten= 78%, Lag= 130.3 min Discarded = 1.31 cfs @ 14.79 hrs, Volume= 1.334 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 58.92' @ 14.79 hrs Surf.Area= 16,977 sf Storage= 24,413 cf

Plug-Flow detention time= 185.4 min calculated for 1.331 af (100% of inflow) Center-of-Mass det. time= 185.2 min ( 1,054.8 - 869.7 )

Volume Invert Avail.Storage Storage Description #1 57.30' 70,617 cf Custom Stage Data (Prismatic) Listed below (Recalc)

Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet)

57.30 13,458 0 0

58.30 15,418 14,438 14,438

59.30 17,949 16,684 31,122

60.30 19,535 18,742 49,864

61.30 21,971 20,753 70,617

Device Routing Invert Outlet Devices #1 Primary 60.30' 3.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #2 Discarded 57.30' 2.900 in/hr Exfiltration over Surface area

Conductivity to Groundwater Elevation = 48.00'

Discarded OutFlow Max=1.31 cfs @ 14.79 hrs HW=58.92' (Free Discharge) 2=Exfiltration ( Controls 1.31 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=57.30' (Free Discharge) 1=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)

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25 Year, 24 Hour Existing Conditions Model

Type II FL 24-hr Rainfall=9.00"SWFWMD Palm Harbor

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Subcatchment 1S: Existing Site

Runoff = 4.29 cfs @ 12.63 hrs, Volume= 0.963 af, Depth= 5.58"

Runoff by SCS TR-20 method, UH=SWFWMD-256, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type II FL 24-hr Rainfall=9.00"

Area (sf) CN Description

* 50,150 98 Building and Parking

40,063 39 >75% Grass cover, Good, HSG A 90,213 72 Weighted Average 40,063 44.41% Pervious Area 50,150 55.59% Impervious Area

Tc Length Slope Velocity Capacity Description

Type II FL 24-hr Rainfall=9.00"Palm Harbor 25 yr Printed 4/2/2025Prepared by {enter your company name here}

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Pond 2P: Existing Pond

Inflow Area = 2.071 ac, 55.59% Impervious, Inflow Depth = 5.58" Inflow = 4.29 cfs @ 12.63 hrs, Volume= 0.963 af Outflow = 1.21 cfs @ 14.50 hrs, Volume= 1.105 af, Atten= 72%, Lag= 112.2 min Discarded = 1.21 cfs @ 14.50 hrs, Volume= 1.105 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Starting Elev= 58.30' Surf.Area= 12,810 sf Storage= 6,063 cf Peak Elev= 59.00' @ 14.50 hrs Surf.Area= 14,065 sf Storage= 15,402 cf (9,339 cf above start)

Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 1.1 min ( 877.0 - 875.9 )

Volume Invert Avail.Storage Storage Description #1 57.80' 52,501 cf Custom Stage Data (Prismatic) Listed below (Recalc)

Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet)

57.80 11,441 0 0

58.30 12,810 6,063 6,063

59.30 14,615 13,713 19,775

60.30 16,311 15,463 35,238

61.30 18,214 17,263 52,501

Device Routing Invert Outlet Devices #1 Primary 60.30' 3.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #2 Discarded 57.80' 2.900 in/hr Exfiltration over Surface area

Conductivity to Groundwater Elevation = 54.00'

Discarded OutFlow Max=1.21 cfs @ 14.50 hrs HW=59.00' (Free Discharge) 2=Exfiltration ( Controls 1.21 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=58.30' (Free Discharge) 1=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)

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Type II FL 24-hr Rainfall=9.00"SWFWMD Palm Harbor

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Subcatchment 3S: Proposed Site

Runoff = 7.60 cfs @ 12.61 hrs, Volume= 1.710 af, Depth= 6.32"

Runoff by SCS TR-20 method, UH=SWFWMD-256, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type II FL 24-hr Rainfall=9.00"

Area (sf) CN Description

* 93,396 98 Building and Parking

47,985 39 >75% Grass cover, Good, HSG A 141,381 78 Weighted Average 47,985 33.94% Pervious Area 93,396 66.06% Impervious Area

Tc Length Slope Velocity Capacity Description

Type II FL 24-hr Rainfall=9.00"Palm Harbor 25 yr

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Pond 4P: Proposed Pond

Inflow Area = 3.246 ac, 66.06% Impervious, Inflow Depth = 6.32" Inflow = 7.60 cfs @ 12.61 hrs, Volume= 1.710 af Outflow = 1.46 cfs @ 14.94 hrs, Volume= 1.710 af, Atten= 81%, Lag= 139.5 min Discarded = 1.46 cfs @ 14.94 hrs, Volume= 1.710 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 59.44' @ 14.94 hrs Surf.Area= 18,177 sf Storage= 33,717 cf

Plug-Flow detention time= 238.6 min calculated for 1.710 af (100% of inflow) Center-of-Mass det. time= 238.5 min ( 1,100.4 - 861.9 )

Volume Invert Avail.Storage Storage Description #1 57.30' 70,617 cf Custom Stage Data (Prismatic) Listed below (Recalc)

Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet)

57.30 13,458 0 0

58.30 15,418 14,438 14,438

59.30 17,949 16,684 31,122

60.30 19,535 18,742 49,864

61.30 21,971 20,753 70,617

Device Routing Invert Outlet Devices #1 Primary 60.30' 3.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #2 Discarded 57.30' 2.900 in/hr Exfiltration over Surface area

Conductivity to Groundwater Elevation = 48.00'

Discarded OutFlow Max=1.46 cfs @ 14.94 hrs HW=59.44' (Free Discharge) 2=Exfiltration ( Controls 1.46 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=57.30' (Free Discharge) 1=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)

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Type II FL 24-hr Rainfall=12.00"SWFWMD Palm Harbor

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Subcatchment 3S: Proposed Site

Runoff = 10.93 cfs @ 12.60 hrs, Volume= 2.481 af, Depth= 9.17"

Runoff by SCS TR-20 method, UH=SWFWMD-256, Weighted-CN, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Type II FL 24-hr Rainfall=12.00"

Area (sf) CN Description

* 93,396 98 Building and Parking

47,985 39 >75% Grass cover, Good, HSG A 141,381 78 Weighted Average 47,985 33.94% Pervious Area 93,396 66.06% Impervious Area

Tc Length Slope Velocity Capacity Description

Type II FL 24-hr Rainfall=12.00"Palm Harbor 100 yr

HydroCAD® 10.00-26 s/n 08021 © 2020 HydroCAD Software Solutions LLC

Summary for Pond 4P: Proposed Pond

Inflow Area = 3.191 ac, 62.98% Impervious, Inflow Depth = 8.90" Inflow = 10.46 cfs @ 12.61 hrs, Volume= 2.366 af Outflow = 2.65 cfs @ 14.55 hrs, Volume= 2.366 af, Atten= 75%, Lag= 117.0 min Discarded = 2.65 cfs @ 14.55 hrs, Volume= 2.366 af Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af

Routing by Stor-Ind method, Time Span= 0.00-30.00 hrs, dt= 0.05 hrs Peak Elev= 59.96' @ 14.55 hrs Surf.Area= 18,992 sf Storage= 43,273 cf

Plug-Flow detention time= 182.9 min calculated for 2.366 af (100% of inflow) Center-of-Mass det. time= 182.8 min ( 1,037.6 - 854.8 )

Volume Invert Avail.Storage Storage Description #1 57.30' 70,617 cf Custom Stage Data (Prismatic) Listed below (Recalc)

Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet)

57.30 13,458 0 0

58.30 15,418 14,438 14,438

59.30 17,949 16,684 31,122

60.30 19,535 18,742 49,864

61.30 21,971 20,753 70,617

Device Routing Invert Outlet Devices #1 Primary 60.30' 3.0' long Sharp-Crested Rectangular Weir 2 End Contraction(s) #2 Discarded 57.30' 2.900 in/hr Exfiltration over Surface area

Conductivity to Groundwater Elevation = 55.30'

Discarded OutFlow Max=2.65 cfs @ 14.55 hrs HW=59.96' (Free Discharge) 2=Exfiltration ( Controls 2.65 cfs)

Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=57.30' (Free Discharge) 1=Sharp-Crested Rectangular Weir ( Controls 0.00 cfs)

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MODRET Input and Model

Water Quality Volume

MODRET INPUT WATER QUALITY

Pond Bottom Area = 13,458 s.f.

Volume Between Bottom and Water Quality Elevation = 18,417 s.f.

Pond Length to Width Ratio = 144 / 100 = 1.4

SHW Elevation = 50

Pond Bottom Elevation = 57.3

Control Structure Top (Overflow Elevation) = 58.55

From Geotech Report:

Field Measured Infiltration Rate (KVS) = 29 in/hr = 58 ft/day

KVU = 2/3 (58 ft/day) = 38.67 ft/day

KHS = 1.5 (58 ft/day) = 87 ft/day

Recovery Time = 2 hours

MODRET

SUMMARY OF UNSATURATED & SATURATED INPUT PARAMETERS

PROJECT NAME : Palm Harbor Rec Center

POLLUTION VOLUME RUNOFF DATA USED

UNSATURATED ANALYSIS EXCLUDED

Pond Bottom Area 13,458.00 ft²

Pond Volume between Bottom & DHWL 18,417.00 ft³

Pond Length to Width Ratio (L/W) 1.40

Elevation of Effective Aquifer Base 35.00 ft

Elevation of Seasonal High Groundwater Table 50.00 ft

Elevation of Starting Water Level 57.30 ft

Elevation of Pond Bottom 57.30 ft

Design High Water Level Elevation 58.55 ft

Avg. Effective Storage Coefficient of Soil for Unsaturated Analysis 0.10

Unsaturated Vertical Hydraulic Conductivity 38.67 ft/d

Factor of Safety 2.00

Saturated Horizontal Hydraulic Conductivity 87.00 ft/d

Avg. Effective Storage Coefficient of Soil for Saturated Analysis 0.20

Avg. Effective Storage Coefficient of Pond/Exfiltration Trench 1.00

Hydraulic Control Features:

Top Bottom Left Right

Groundwater Control Features - Y/N N N N N Distance to Edge of Pond 0.00 0.00 0.00 0.00 Elevation of Water Level 0.00 0.00 0.00 0.00

Impervious Barrier - Y/N N N N N Elevation of Barrier Bottom 0.00 0.00 0.00 0.00

Analysis Date: 3/26/2025

TIME - RUNOFF INPUT DATA

PROJECT NAME: PALM HARBOR REC CENTER

STRESS

PERIOD

NUMBER

INCREMENT

OF TIME

(hrs)

VOLUME

OF RUNOFF

(ft³)

Unsat 0.00 0.00

1 1.00 18,417.00

2 1.82 0.00

3 1.82 0.00

4 1.82 0.00

5 1.82 0.00

6 1.82 0.00

7 1.82 0.00

8 1.82 0.00

9 1.82 0.00

10 1.82 0.00

11 1.82 0.00

12 1.82 0.00

13 1.82 0.00

14 1.82 0.00

15 1.82 0.00

16 1.82 0.00

17 1.82 0.00

18 1.82 0.00

19 1.82 0.00

20 1.82 0.00

21 1.82 0.00

22 1.82 0.00

23 1.82 0.00

24 1.82 0.00

25 1.82 0.00

26 1.82 0.00

27 1.82 0.00

28 1.82 0.00

29 1.82 0.00

30 1.82 0.00

SUMMARY OF RESULTS

PROJECT NAME : Palm Harbor Rec Center

CUMULATIVE

TIME

(hrs)

WATER

ELEVATION

(feet)

INSTANTANEOUS

INFILTRATION

RATE (cfs)

AVERAGE

INFILTRATION

RATE (cfs)

CUMULATIVE

OVERFLOW

(ft³)

Analysis Date: 3/26/2025

00.00 - 0.00 50.000 0.000 * 0.00000

0.00 50.000 3.56525 3.08310

1.00 57.797 2.60095 0.00 1.72319

2.18 57.300 1.44083 0.00 1.15847

4.64 56.515 1.01966 0.00 0.88085

6.46 56.123 0.79920 0.00 0.71754

8.28 55.804 0.66309 0.00 0.60864

10.10 55.533 0.56931 0.00 0.52998

11.92 55.297 0.49992 0.00 0.46986

13.74 55.088 0.44604 0.00 0.42222

15.56 54.901 0.40281 0.00 0.38341

17.38 54.730 0.36717 0.00 0.35094

19.21 54.574 0.33719 0.00 0.32344

21.03 54.430 0.31159 0.00 0.29974

22.85 54.297 0.28941 0.00

PROJECT NAME : Palm Harbor Rec Center

CUMULATIVE

TIME

(hrs)

WATER

ELEVATION

(feet)

INSTANTANEOUS

INFILTRATION

RATE (cfs)

AVERAGE

INFILTRATION

RATE (cfs)

CUMULATIVE

OVERFLOW

(ft³)

Analysis Date: 3/26/2025

0.27907

24.67 54.173 0.27001 0.00

0.26095

26.49 54.056 0.25289 0.00

0.24483

28.31 53.948 0.23766 0.00

0.23050

30.13 53.845 0.22405 0.00

0.21759

31.95 53.748 0.21174 0.00

0.20588

33.77 53.657 0.20054 0.00

0.19520

35.59 53.570 0.19040 0.00

0.18561

37.41 53.487 0.18115 0.00

0.17669

39.23 53.409 0.17258 0.00

0.16846

41.05 53.334 0.16472 0.00

0.16098

42.87 53.262 0.15746 0.00

0.15393

44.69 53.194 0.15069 0.00

0.14745

46.51 53.128 0.14442 0.00

0.14138

48.33 53.065 0.13854 0.00

PROJECT NAME : Palm Harbor Rec Center

CUMULATIVE

TIME

(hrs)

WATER

ELEVATION

(feet)

INSTANTANEOUS

INFILTRATION

RATE (cfs)

AVERAGE

INFILTRATION

RATE (cfs)

CUMULATIVE

OVERFLOW

(ft³)

Analysis Date: 3/26/2025

0.13569

50.15 53.005 0.13308 0.00

0.13046

51.97 52.947 0.12797 0.00

0.12547

53.79 52.891 0.12311 0.00

0.12076

55.62 52.837 0.11857 0.00

0.11638

57.44 52.785 0.11431 0.00

0.11225

59.26 52.736 0.11029 0.00

0.10833

61.08 52.687 0.10647 0.00

0.10461

62.90 52.641 0.10286 0.00

0.10111

64.72 52.596 0.09944 0.00

0.09776

66.54 52.552 0.09622 0.00

0.09468

68.36 52.510 0.09314 0.00

0.09161

70.18 52.470 0.09020 0.00

0.08878

72.00 52.430 0.00

Maximum Water Elevation: 57.797 feet @ 1.00 hours Recovery @ 2.180 hours

* Time increment when there is no runoff Maximum Infiltration Rate: 18.080 ft/day

INFILTRATION : PALM HARBOR REC CENTER

Total Volume Infiltrated = 18,417 ft³

Time (hrs)

V o lu m e I n fi lt ra te d ft ³)

18,000

17,500

17,000

16,500

16,000

15,500

15,000

14,500

14,000

13,500

13,000

12,500

12,000

11,500

11,000

10,500

10,000

9,500

9,000

8,500

8,000

7,500

7,000

6,500

6,000

5,500

5,000

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

Max Water Elevation = 57.80 ft

Time (hrs)

W a te r E le v a ti o n ft

57.5

Weir Volume

MODRET INPUT WEIR VOLUME

Pond Bottom Area = 13, 458 s.f.

Volume Between Bottom and Water Quality Elevation = 49, 864 s.f.

Pond Length to Width Ratio = 188 / 145 = 1.4

SHW Elevation = 50

Pond Bottom Elevation = 57.3

Control Structure Top (Overflow Elevation) = 60.3

From Geotech Report:

Field Measured Infiltration Rate (KVS) = 29 in/hr = 58 ft/day

KVU = 2/3 (58 ft/day) = 38.67 ft/day

KHS = 1.5 (58 ft/day) = 87 ft/day

Recovery Time = 7.5 hours

SUMMARY OF UNSATURATED & SATURATED INPUT PARAMETERS

PROJECT NAME : Palm Harbor Rec Center

POLLUTION VOLUME RUNOFF DATA USED

UNSATURATED ANALYSIS EXCLUDED

Pond Bottom Area 13,458.00 ft²

Pond Volume between Bottom & DHWL 49,864.00 ft³

Pond Length to Width Ratio (L/W) 1.40

Elevation of Effective Aquifer Base 35.00 ft

Elevation of Seasonal High Groundwater Table 50.00 ft

Elevation of Starting Water Level 57.30 ft

Elevation of Pond Bottom 57.30 ft

Design High Water Level Elevation 60.30 ft

Avg. Effective Storage Coefficient of Soil for Unsaturated Analysis 0.10

Unsaturated Vertical Hydraulic Conductivity 38.67 ft/d

Factor of Safety 2.00

Saturated Horizontal Hydraulic Conductivity 87.00 ft/d

Avg. Effective Storage Coefficient of Soil for Saturated Analysis 0.20

Avg. Effective Storage Coefficient of Pond/Exfiltration Trench 1.00

Hydraulic Control Features:

Top Bottom Left Right

Groundwater Control Features - Y/N N N N N Distance to Edge of Pond 0.00 0.00 0.00 0.00 Elevation of Water Level 0.00 0.00 0.00 0.00

Impervious Barrier - Y/N N N N N Elevation of Barrier Bottom 0.00 0.00 0.00 0.00

TIME - RUNOFF INPUT DATA

PROJECT NAME: PALM HARBOR REC CENTER

STRESS

PERIOD

NUMBER

INCREMENT

OF TIME

(hrs)

VOLUME

OF RUNOFF

(ft³)

Unsat 0.00 0.00

1 1.00 49,864.00

2 1.82 0.00

3 1.82 0.00

4 1.82 0.00

5 1.82 0.00

6 1.82 0.00

7 1.82 0.00

8 1.82 0.00

9 1.82 0.00

10 1.82 0.00

11 1.82 0.00

12 1.82 0.00

13 1.82 0.00

14 1.82 0.00

15 1.82 0.00

16 1.82 0.00

17 1.82 0.00

18 1.82 0.00

19 1.82 0.00

20 1.82 0.00

21 1.82 0.00

22 1.82 0.00

23 1.82 0.00

24 1.82 0.00

25 1.82 0.00

26 1.82 0.00

27 1.82 0.00

28 1.82 0.00

29 1.82 0.00

30 1.82 0.00

PROJECT NAME : Palm Harbor Rec Center

CUMULATIVE

TIME

(hrs)

WATER

ELEVATION

(feet)

INSTANTANEOUS

INFILTRATION

RATE (cfs)

AVERAGE

INFILTRATION

RATE (cfs)

CUMULATIVE

OVERFLOW

(ft³)

Analysis Date: 3/26/2025

00.00 - 0.00 50.000 0.000 * 0.00000

0.00 50.000 4.18985 3.71960

1.00 59.494 3.24934 0.00 2.39325

2.82 58.551 1.96246 0.00 1.53167

4.64 57.947 1.34869 0.00 1.16570

6.46 57.487 1.05789 0.00 0.95008

7.37 57.300 0.87827 0.00 0.80647

10.10 56.795 0.75462 0.00 0.70278

11.92 56.517 0.66327 0.00 0.62376

13.74 56.271 0.59237 0.00 0.56099

15.56 56.050 0.53547 0.00 0.50994

17.38 55.849 0.48864 0.00 0.46733

19.21 55.665 0.44924 0.00 0.43115

21.03 55.495 0.41554 0.00 0.39994

22.85 55.337 0.38640 0.00

PROJECT NAME : Palm Harbor Rec Center

CUMULATIVE

TIME

(hrs)

WATER

ELEVATION

(feet)

INSTANTANEOUS

INFILTRATION

RATE (cfs)

AVERAGE

INFILTRATION

RATE (cfs)

CUMULATIVE

OVERFLOW

(ft³)

Analysis Date: 3/26/2025

0.37285

24.67 55.190 0.36089 0.00

0.34893

26.49 55.053 0.33831 0.00

0.32770

28.31 54.923 0.31828 0.00

0.30886

30.13 54.802 0.30034 0.00

0.29181

31.95 54.687 0.28410 0.00

0.27639

33.77 54.578 0.26941 0.00

0.26242

35.59 54.474 0.25605 0.00

0.24967

37.41 54.376 0.24379 0.00

0.23792

39.23 54.282 0.23252 0.00

0.22712

41.05 54.192 0.22218 0.00

0.21724

42.87 54.107 0.21263 0.00

0.20802

44.69 54.025 0.20371 0.00

0.19940

46.51 53.946 0.19536 0.00

0.19132

48.33 53.871 0.18765 0.00

PROJECT NAME : Palm Harbor Rec Center

CUMULATIVE

TIME

(hrs)

WATER

ELEVATION

(feet)

INSTANTANEOUS

INFILTRATION

RATE (cfs)

AVERAGE

INFILTRATION

RATE (cfs)

CUMULATIVE

OVERFLOW

(ft³)

Analysis Date: 3/26/2025

0.18397

50.15 53.798 0.18044 0.00

0.17692

51.97 53.728 0.17365 0.00

0.17039

53.79 53.661 0.16730 0.00

0.16421

55.62 53.596 0.16129 0.00

0.15838

57.44 53.534 0.15566 0.00

0.15294

59.26 53.474 0.15032 0.00

0.14770

61.08 53.415 0.14524 0.00

0.14278

62.90 53.359 0.14050 0.00

0.13822

64.72 53.305 0.13598 0.00

0.13373

66.54 53.252 0.13167 0.00

0.12960

68.36 53.201 0.12759 0.00

0.12558

70.18 53.151 0.12368 0.00

0.12179

72.00 53.103 0.00

Maximum Water Elevation: 59.494 feet @ 1.00 hours Recovery @ 7.371 hours

* Time increment when there is no runoff Maximum Infiltration Rate: 19.335 ft/day

Total Volume Infiltrated = 49,864 ft³

Time (hrs) 76543210

V o lu m e I n fi lt ra te d ft ³)

48,000

46,000

44,000

42,000

40,000

38,000

36,000

34,000

32,000

30,000

28,000

26,000

24,000

22,000

20,000

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

Max Water Elevation = 59.49 ft

Time (hrs) 76543210

W a te r E le v a ti o n ft

58.5

57.5

Geotechnical Report