IFB_26-012-HG_Attachment_B_-_5th_Street_Parking_Lot_Drainage_Report.pdf

Prepared by: GAI Consultants, Inc.

Orlando Office

618 East South Street, Suite 700 Orlando, Florida 32801

Prepared for: City of Leesburg PO Box 490630

Leesburg, FL, 34749-0630

Drainage Calculations

Leesburg 5th Street Parking Lot 429 W. Magnolia St.

City of Leesburg, Florida, 34748

GAI Project Number: R240665.01

August 2025

Revised December 2025

Drainage Report

429 W. Magnolia Street Leesburg, FL 34749

Page i

R240665.01 / August 2025

SJRWMD Drainage Report

Leesburg 5th Street Parking

429 W. Magnolia Street Leesburg, Florida

GAI Project Number: R240665.01

August 2025

Prepared for:

City of Leesburg PO Box 490630

Leesburg, Florida 34749-0630

St. Johns River Water Management District 601 South Lake Destiny Road, Suite 200

Maitland, Florida 32751

Prepared by:

GAI Consultants, Inc.

Orlando Office

618 East South Street Orlando, Florida 32801

Jacob Crabtree, E.I.

Senior Engineering Intern

Aimee Shields, P.E.

Senior Project Manager

STATE OF

No. 68011

PRO

FE S S ION A L EN G IN

E E R

A IMEE J. SHIEL DS

FLORIDA

429 W. Magnolia Street

Page ii

Table of Contents

1.0 Introduction

1.1 Purpose and Scope

2.0 Existing Conditions

2.1 Description

2.2 Historic Drainage Features

2.2.1 Basins

2.3 Existing Storm Water Management System

2.4 Geotechnical Analysis

3.0 Proposed Conditions

3.1 Description

3.2 Proposed Drainage Features

3.2.1 Sub-Basin 1A

3.2.2 Sub-Basin 1B

3.3 Basin Characteristics Table

4.0 Stormwater Management System

4.1 Description

4.2 Treatment Volume Calculations

4.3 Exfiltration System

4.4 Recovery Analysis

4.5 Exfiltration System Summary Table

4.6 Stormwater Quantity and Attenuation Requirements

4.6.1 SJRWMD

4.6.2 City of Leesburg

4.6.3 Stormwater Discharge

4.7 Nutrient Loading

4.8 Maintenance and Operation

4.8.1 Periodic Maintenance

4.8.2 Corrective Maintenance

Appendix A

A-1: Location Map A-2: Aerial Photography A-3: USGS Quadrangle Map A-4: NRSCS Soils Map A-5: FEMA Map A-6: Pre-Development Basin Map A-7: Post-Development Basin Map Appendix B

B-1: Treatment Volume Calculations B-2: Stage vs. Storage Calculations B-3: Recovery Analysis B-4: Pollutant Analysis Appendix C

C-1: Sample Inspection Log

429 W. Magnolia Street

1.0 Introduction

1.1 Purpose and Scope

The City of Leesburg proposes to construct a parking lot, two (2) stormwater management exfiltration systems, and associated site improvements located at 429 West Magnolia Street, Leesburg, Florida. Refer to Appendix A-1 for the location map.

The site has not been previously permitted under the St. Johns River Water Management District (SJRWMD). This submittal will be for the approval of a SJRWMD Environmental Resource Permit according to Section 62-330 F.A.C., as well as review and approval through the City of Leesburg.

2.0 Existing Conditions

2.1 Description

The existing site consists of 2.09 acres and is located within a highly urban environment. The site was previously developed in historic conditions and is currently owned and used by the City of Leesburg as several surface parking lots. Using historical data to determine the impervious ratio shows a condition of 91%. At the time of permitting, the sub-basin to the south of the project site is used as surface parking every weekday by the Leesburg Water Department. For this reason, we have considered the impervious area to be high in this region, but the nutrient loading to be lower than that of the surrounding paved surface parking areas. Refer to Appendix A-6 for the Basin Characteristics, which are also shown in the Table in Section 3.3.

2.2 Historic Drainage Features

Runoff from the existing drainage basin sheet flows from the site into the existing stormwater conveyance system along South 6th Street, South 5th Street, and West Magnolia Street. Please refer to Appendix A-6 for the Pre-Development Basin Map.

2.2.1 Basins

Basin 1 contains 2.09 acres and consists of developed area; the impervious area ratio is 91%.

The stormwater runoff from Basin 1 currently sheet flows into the City of Leesburg’s storm sewer system, with ultimate outfall to Lake Harris. Refer to historic aerial in Appendix A-2.2.

2.3 Existing Storm Water Management System

There is no existing stormwater management system on site.

2.4 Geotechnical Analysis

The seasonal high groundwater table was estimated based on Geotechnical data for the project site. The estimated seasonal high-water table (SHWT) elevation is around 81.35’ (NAVD88).

429 W. Magnolia Street

3.0 Proposed Conditions

3.1 Description

As the majority of the project site will remain a parking lot as it is today, with a lower impervious surface ratio, stormwater treatment is only provided for those areas that were historically building areas. Sub- Basin 1A consists of the area previously occupied by the Leesburg Arts Center building. Sub-Basin 1B consists of the area previously occupied by an auxiliary Leesburg Water Department building. The remainder of the site will remain as it does during the existing conditions, and therefore won't be analyzed in our calculations. The total site area is 2.09 acres. The total project area is 0.97 acres (Sub-Basins 1A and 1B).

3.2 Proposed Drainage Features

3.2.1 Sub-Basin 1A

Sub-Basin 1A contains 0.42 acres with an impervious ratio of 88%. The basin consists of a surface parking and sidewalks. Refer to Appendix A-7.

The stormwater runoff from Sub-Basin 1A will drain by sheet flow to a drain with discharge to the proposed exfiltration system. Once the exfiltration system has collected the treatment volume, the remaining water will be discharged to the North of the site. The outfall of the system is the City of Leesburg’s stormwater conveyance system on West Magnolia Street, as in the existing conditions. The stormwater management system has been designed as an on-line system.

3.2.2 Sub-Basin 1B

Sub-Basin 1B contains 0.55 acres with an impervious ratio of 84%. The basin consists of a surface parking and sidewalks. Refer to Appendix A-7.

The stormwater runoff from Sub-Basin 1B will drain by sheet flow to a drain with discharge to the proposed exfiltration system. Once the exfiltration system has collected the treatment volume, the remaining water will be discharged to the West of the site. The outfall of the system is the City of Leesburg’s stormwater conveyance system on South 6th Street, as in the existing conditions. The stormwater management system has been designed as an on-line system.

3.3 Basin Characteristics Table

Table 3.1

Pre-Development Basins

Basin Name Pervious Area

(ac) Impervious Area

(ac) Total Area

(ac) % Of

Imperviousness

“Basin 1” 0.20 1.89 2.09 90

Table 3.2 Post-Development Basins

Basin Name Pervious Area (ac)

Impervious Area (ac)

Total Area (ac)

% Of Imperviousness

“Basin 1” 0.30 1.79 2.09 86

429 W. Magnolia Street

Table 3.3 Post-Development TREATMENT Sub-Basins

Basin Name Pervious Area

(ac) Impervious Area

(ac) Total Area

(ac) % Of

Imperviousness

“Sub-Basin 1A” 0.05 0.37 0.42 88

“Sub-Basin 1B” 0.09 0.46 0.55 84

4.0 Stormwater Management System

4.1 Description

The existing project site area is 0.97 +/- acres and is located within an existing commercial environment. The site consists of commercial buildings and surface parking.

The proposed project area will include two (2) drainage sub-basins: Sub-Basin 1A and Sub-Basin 1B.

Sub-Basin 1A will include the proposed parking lot, sidewalks, and the stormwater management area.

Sub-Basin 1A drains to proposed stormwater pond 1A, with ultimate outfall at the West Magnolia Street stormwater conveyance system. Sub-Basin 1B will include the proposed parking lot, sidewalks, and the stormwater management area. Sub-Basin 1B drains to proposed stormwater pond 1B, with ultimate outfall at the South 6th Street stormwater conveyance system.

The proposed improvements associated with this project result in a direct reduction in stormwater runoff. Existing conditions contribute 1.89 acres of impervious area. Proposed conditions contribute

1.79 acres of impervious area.

The pre-development basin map is presented in Appendix A. The post-development basin map is presented in Appendix B.

4.2 Treatment Volume Calculations

The exfiltration system has been designed as an on-line system and must treat the greater of 1.25” over the impervious area or 0.5” over the added impervious area. While the site grading limits the proposed stormwater management system from capturing the entire project area, the required treatment volume was calculated to accommodate the project area. Treatment Volume (TV) Sub-Basins 1A and 1B represent the new areas of impervious surface required to be treated by the WMD. Runoff Sub-Basins 1A and 1B represent the drainage basin limits actually available to be collected by the exfiltration fields for treatment. When comparing the total treatment required by the TV Sub-Basins to that provided by the Runoff Sub-Basins, the proposed exfiltration fields provide treatment for the entire project in excess of the amount required. The remainder of the site will remain existing parking surfaces. Refer to Appendix B-1 for treatment volume calculations.

After developing the treatment volume calculation, it has been determined that impervious governs. The proposed system for Sub-Basin 1A will be required to provide treatment for 4,443 ft3 of stormwater for the proposed project. The water quality control elevation has been set at 93.35’ (NAVD88) per the stage

vs. storage calculations. The proposed system for Sub-Basin 1B will be required to provide treatment for 3,093 ft3 of stormwater for the proposed project. The water quality control elevation has been set at 87.20’ (NAVD88) per the stage vs. storage calculations. Refer to Section 4.5 – Exfiltration System Summary Table.

429 W. Magnolia Street

4.3 Exfiltration System

The on-line exfiltration system has been designed to treat stormwater runoff from the new impervious area in Sub-Basins 1A and 1B. The Estimated Seasonal High Groundwater Table (ESHWT) is at elevation 81.35’ (NAVD88), per the geotechnical report provided under separate cover.

The exfiltration system consists of an underground exfiltration system with 36” perforated pipe with gravel and filter fabric envelope. The proposed bottom of the pond 1A system has been set 84” above the ESHWT at elevation 81.35’, which meets the recovery requirements for SJRWMD. The proposed bottom of the pond 1B system has been set 30” above the ESHWT at elevation 81.35’, which meets the recovery requirements for SJRWMD. Refer to Section 4.4 – Recovery Analysis.

Note that the runoff area collected by the exfiltration system will accommodate the treatment volume required by the project area. See the post-development basin map in Appendix B for details on the runoff area captured by the exfiltration field(s).

4.4 Recovery Analysis

PONDS software was used to perform a recovery analysis of the proposed exfiltration system. The separation from the bottom of the exfiltration system and the ESHWT is 84” for pond 1A and 30” for pond 1B. The model result shows that the provided water quality volume was recovered within 72 hours with a factor of safety of 2, which meets the SJRWMD requirements. Refer to Recovery Analysis, Appendix B-3.

4.5 Exfiltration System Summary Table

Table 4.1

Exfiltration System (Pond 1A) Summary Table

Required Provided

Water Quality Storage (cu-ft) 4,443 4,799

Recovery Time (hrs) 72 6

Water Quality Elevation -- 93.35

Bottom of the System -- 88.35

Estimated Seasonal High Water Table Elevation (ft) -- 81.35

Clearance from ESHWT to the Bottom of the pond (ft) -- 7.0

429 W. Magnolia Street

Table 4.2 Exfiltration System (Pond 1B) Summary Table

Required Provided

Water Quality Storage (cu-ft) 3,093 3,141

Recovery Time (hrs) 72 24

Water Quality Elevation -- 87.20

Bottom of the System -- 83.85

Estimated Seasonal High Water Table Elevation (ft) -- 81.35

Clearance from ESHWT to the Bottom of the pond (ft) -- 2.5

4.6 Stormwater Quantity and Attenuation Requirements

4.6.1 SJRWMD

The project is within the Ocklawaha River Special Regulatory Basin, which requires attenuation of the 10 and 25-year design storm events. The proposed project reduces the impervious area.

Therefore, the post-development peak discharge will be less than the pre-development rates.

4.6.2 City of Leesburg

The City of Leesburg requires the stormwater management facility to be designed to attenuate the post-development peak discharge, which must be less than the pre-development condition for the 25-Year/24-Hour, 10-Year/24-Hour, and MEAN ANNUAL/24-Hour storm events.

The pre-development condition has less impervious area than the post-development condition.

Therefore, the peak discharge rates will be reduced.

4.6.3 Stormwater Discharge

At present, the project site contains no stormwater management facilities. The proposed improvements will reduce impervious surface area—and therefore runoff—from 1.89 acres under existing conditions to 1.79 acres post-development. Accordingly, the volume and rate of stormwater discharged from the site in the proposed condition will be lower than under existing conditions.

429 W. Magnolia Street

Rational Method:

Rainfall Intensity1 = 7.41 in/hr

Pre-Development

Basin ID Basin Area (ac)

Impervious Area (ac)

Pervious Area (ac)

Composite Runoff

Coefficient (C)

Percent Impervious

Peak Discharge

Q = C x A x I

(CFS)

1 2.091 1.894 0.197 0.834 91% 12.91

Pre-Development

Basin ID Basin Area (ac)

Impervious Area (ac)

Pervious Area (ac)

Composite Runoff Coefficient (C)

Percent Impervious

Peak Discharge

Q = C x A x I

(CFS)

1 2.091 1.788 0.303 0.799 86% 12.36

Note 1) Rainfall Zone: 7

4.7 Nutrient Loading

Per the Florida Department of Environmental Protection (FDEP), Lake Harris has been listed as an impaired waterbody. This waterbody is impaired by nutrients.

Pursuant to Rule 67-330-055, FAC, the developed project will demonstrate a net positive benefit in pollutant loading generated by the basin for nitrogen and phosphorus. BMP Trains software was used to determine the developed project pollutant loading.

The result from BMPTrains simulation results in a net reduction of nitrogen and phosphorus contributed to the basin. Refer to Appendix B-4 for the Pollutant Analysis / BMPTrains results.

429 W. Magnolia Street

4.8 Maintenance and Operation

The exfiltration system will be owned and maintained by the applicant.

The exfiltration system should be inspected at regular intervals and maintained as necessary to ensure optimum performance. The rate at which the system collects pollutants will determine the frequency of inspection. These inspections will determine if only periodic maintenance is required, or corrective maintenance is required. The corrective maintenance is primarily for the maintenance of the filtration gravel of the exfiltration chamber system.

Inspection is the key to effective maintenance. A quarterly inspection of the accumulated sediment is recommended. Sediment deposition and transport may vary from year to year and quarterly inspections will help to ensure that the system is cleaned at appropriate times. Inspections should be performed more often during the spring and summer months where rapid accumulation of debris may occur due to the frequency of storm events. A sample inspection log is included for reference in Appendix C-1.

4.8.1 Periodic Maintenance

For periodic maintenance, the system should be thoroughly cleaned when inspection reveals accumulated sediment. The system is provided with manhole access. Should it be necessary to enter the system to perform maintenance activities, all appropriate precautions regarding confined space entry and current OSHA regulations should be followed.

4.8.2 Corrective Maintenance

Corrective maintenance is defined as the full removal and replacement of failed portions of the stormwater management system.

A well-maintained system should be capable of percolation of the retained water within 72-hours after the last rain event. Should the system be found deficient, the permittee has been advised to seek services from a qualified professional to evaluate the level of corrective maintenance required.

429 W. Magnolia Street

APPENDIX A-1

Location Map

Map data (c) OpenStreetMap contributors, Microsoft, Facebook, Google, Esri Community Maps contributors, Map layer by Esri Powered by Esri

NTS

SHEET NO.:

PROJECT NO.:

SCALE:

DATE:

A-1

North

5TH STREET PARKING LOT

LEESBURG, FL

R240665.01

AUGUST, 2025

618 E. South Street Suite 700

Orlando, Florida 32801 Phone: 407.423.8398 gai consultants

LOCATION MAP

APPENDIX A-2

Aerial Photography

SHEET NO.:

PROJECT NO.:

SCALE:

DATE:

A-2.1

North

5TH STREET PARKING LOT

LEESBURG, FL

R240665.01

NTS

AERIAL MAP

618 E. South Street Suite 700

Orlando, Florida 32801 Phone: 407.423.8398

AUGUST, 2025

APPENDIX A-3

USGS Quadrangle Map

SCALE:

DATE:

A-2

North

5TH STREET PARKING LOT

LEESBURG, FL

R240665.01

NTS

USGS QUADRANGLE MAP

618 E. South Street Suite 700

Orlando, Florida 32801 Phone: 407.423.8398

APPENDIX A-4

NRSCS Soils Map

A-4

North

MAP SYMBOL MAP UNIT NAME

LEGEND

8 CANDLER SANDS, 0 TO 5

PERCENT SLOPLES

5TH STREET PARKING LOT

LEESBURG, FL

NRCS SOILS MAP

SHEET NO.:

PROJECT NO.:

SCALE:

DATE:

R240665.01

NTS

618 E. South Street

Suite 700 Orlando, Florida 32801 Phone: 407.423.8398

APPENDIX A-5

FEMA Map

SCALE:

DATE:

A-5

North

5TH STREET PARKING LOT

LEESBURG, FL

R240665.01

NTS

FEMA FLOOD MAP

618 E. South Street Suite 700

Orlando, Florida 32801 Phone: 407.423.8398

APPENDIX A-6

Pre-Development Basin Map

CONSULTANTS

PROJECT

SHEET NUMBER

SHEET TITLE

REVISIONS:

PROJECT NUMBER

REGISTRATION

DRAWN:

CHECKED:

R240665.01

DATE: 08/19/2025

APPROVED:

5TH STREET

PARKING LOT

A GAI CONSULTANTS, INC SERVICE GROUP

257 SOUTH 5TH STREET

LEESBURG FL, 34748

CDA

JTC

618 E. SOUTH STREET

SUITE 700

ORLANDO, FL 32801

407 423-8398

CERTIFICATE OF AUTHORIZATION: EB9951

gai consultants

AJS

DP

KO

KO

0 20' 40'

FULL SCALE: 1"=20'

HALF SCALE: 1"=40'

EX-1

PRE BASIN

MAP EXHIBIT

BASIN 1:

TOTAL = 91084.48 SF / 2.09 AC

IMP. = 82510.52 SF / 1.89 AC

APPENDIX A-7

Post-Development Basin Map

SHEET NUMBER

SHEET TITLE

REVISIONS:

PROJECT NUMBER

REGISTRATION

DRAWN:

CHECKED:

R240665.01

DATE: 08/19/2025

APPROVED:

5TH STREET

PARKING LOT

A GAI CONSULTANTS, INC SERVICE GROUP

257 SOUTH 5TH STREET

LEESBURG FL, 34748

CDA

JTC

618 E. SOUTH STREET

SUITE 700

ORLANDO, FL 32801

407 423-8398

CERTIFICATE OF AUTHORIZATION: EB9951

gai consultants

AJS

0 20' 40'

FULL SCALE: 1"=20'

HALF SCALE: 1"=40'

EX-2

PROP. BASIN

MAP EXHIBIT

T.V. SUB-BASIN 1A:

TOTAL = 18437.68 SF / 0.42 AC

IMP. = 16195.80 SF / 0.37 AC

RUNOFF AREA SUB-BASIN 1A:

TOTAL = 32126.62 SF / 0.74 AC

IMP. = 29777.66 SF / 0.68 AC

T.V. SUB-BASIN 1B:

TOTAL = 24011.53 SF / 0.55 AC

IMP. = 20142.01 SF / 0.46 AC

RUNOFF AREA SUB-BASIN 1B:

TOTAL = 13802.84 SF / 0.32 AC

IMP. = 12468.32 SF / 0.29 AC

BASIN 1:

TOTAL = 91084.48 SF / 2.09 AC

TV IMP. = 36337.81 SF / 0.83 AC

RUNOFF IMP. = 42,245.98 / 0.97 AC

TOTAL IMP. = 77869.04 SF / 1.79 AC

APPENDIX B-1

Treatment Volume Calculations

GAI Project No. R240665.01 Curve Number Calc. by: JTC

Soil A CN= 49 Soil B CN= 69 Soil C CN= 79 Soil D CN= 84

CN=98 CN=100 % % % %

1 2.091 1.894 0.000 0.197 100 0 0 0 93.4

1 2.091 1.788 0.000 0.303 100 0 0 0 90.9

1A TV 0.423 0.372 0.000 0.051 100 0 0 0 92.0

1A Runoff 0.738 0.684 0.000 0.054 100 0 0 0 94.4

1B TV 0.551 0.462 0.000 0.089 100 0 0 0 90.1

1A Runoff 0.317 0.286 0.000 0.031 100 0 0 0 93.3

0.000 0.000

0.031 0.000 0.000 0.000

P o st

0.303 0.000 0.000 0.000

0.197 0.000 0.000 0.000P re

Area (ac) Total Area

(ac) Area (ac)

Leesburg 5th Street Parking Runoff Curve Number Calculations

Basin Total Area (ac)

Imperv.

Area (ac)

Pond Area (ac)

Pervious Weighted

CNArea (ac) Area (ac)

0.051 0.000 0.000 0.000

0.089 0.000 0.000 0.000

0.054 0.000

12/24/2025 Page 1 of 9

GAI Project No. R240665.01 Treatment Volume Calc. by: JTC

Site Basin-Basin 1A (TV)

Treatment Volume Requirements

SJRWMD requirements for retention will govern and are as follows:

Retention volume shall be provided for the greater of

1. One half inch of runoff over the drainage area

2. 1.25 inches times the impervious area (excluding water bodies)

3. An additional 0.5 inch of runoff over the drainage area is needed for online systems

Area Breakdown - SUB-BASIN 1A

Total Area 0.423 Acres Impervious Area 0.372 Acres Pervious Area 0.051 Acres

Treatment Volume

1. Compute one half inch of runoff from the entire basin.

Treatment Volume = (0.5")(Total Site Area)(1'/12") = 0.018 Ac-Ft

2. Compute 1.25 inches of runoff times the impervious site area.

Treatment Volume = (1.25")(Impervious Site Area)(1'/12") = Treatment Volume = 0.039 Ac-Ft

The percentage of impervious area governs, therefore the treatment volume is

0.039 Ac-Ft.

3. Compute an additional 0.5 inch of runoff over the entire developed basin.

Is the system online? Yes

Treatment Volume = (0.5")(Total Site Area) + TV = 0.057 Ac-Ft

∆ The Required Treatment Volume for Water Quality is 0.057 Ac-Ft Volume Provided is 0.11 Ac-Ft

Leesburg 5th Street Parking

12/24/2025 Page 2 of 9

Site Basin-Basin 1A (Runoff)

Treatment Volume Requirements

SJRWMD requirements for retention will govern and are as follows:

Retention volume shall be provided for the greater of

1. One half inch of runoff over the drainage area

2. 1.25 inches times the impervious area (excluding water bodies)

3. An additional 0.5 inch of runoff over the drainage area is needed for online systems

Area Breakdown - SUB-BASIN 1A

Total Area 0.738 Acres Impervious Area 0.684 Acres Pervious Area 0.054 Acres

Treatment Volume

1. Compute one half inch of runoff from the entire basin.

Treatment Volume = (0.5")(Total Site Area)(1'/12") = 0.031 Ac-Ft

2. Compute 1.25 inches of runoff times the impervious site area.

Treatment Volume = (1.25")(Impervious Site Area)(1'/12") = Treatment Volume = 0.071 Ac-Ft

The percentage of impervious area governs, therefore the treatment volume is

0.071 Ac-Ft.

3. Compute an additional 0.5 inch of runoff over the entire developed basin.

Is the system online? Yes

Treatment Volume = (0.5")(Total Site Area) + TV = 0.102 Ac-Ft

∆ The Required Treatment Volume for Water Quality is 0.102 Ac-Ft Volume Provided is 0.11 Ac-Ft

12/24/2025 Page 3 of 9

Site Sub-Basin 1B (TV)

Treatment Volume Requirements

SJRWMD requirements for retention will govern and are as follows:

Retention volume shall be provided for the greater of

1. One half inch of runoff over the drainage area

2. 1.25 inches times the impervious area (excluding water bodies)

3. An additional 0.5 inch of runoff over the drainage area is needed for online systems

Area Breakdown - SUB-BASIN 1B

Total Area 0.551 Acres Impervious Area 0.462 Acres Pervious Area 0.089 Acres

Treatment Volume

1. Compute one half inch of runoff from the entire basin.

Treatment Volume = (0.5")(Total Site Area)(1'/12") = 0.023 Ac-Ft

2. Compute 1.25 inches of runoff times the impervious site area.

Treatment Volume = (1.25")(Impervious Site Area)(1'/12") = Treatment Volume = 0.048 Ac-Ft

The percentage of impervious area governs, therefore the treatment volume is

0.048 Ac-Ft.

3. Compute an additional 0.5 inch of runoff over the entire developed basin.

Is the system online? Yes

Treatment Volume = (0.5")(Total Site Area) + TV = 0.071 Ac-Ft

∆ The Required Treatment Volume for Water Quality is 0.071 Ac-Ft Volume Provided is 0.072 Ac-Ft

12/24/2025 Page 6 of 9

Site Sub-Basin 1B (Runoff)

Treatment Volume Requirements

SJRWMD requirements for retention will govern and are as follows:

Retention volume shall be provided for the greater of

1. One half inch of runoff over the drainage area

2. 1.25 inches times the impervious area (excluding water bodies)

3. An additional 0.5 inch of runoff over the drainage area is needed for online systems

Area Breakdown - SUB-BASIN 1B

Total Area 0.317 Acres Impervious Area 0.286 Acres Pervious Area 0.031 Acres

Treatment Volume

1. Compute one half inch of runoff from the entire basin.

Treatment Volume = (0.5")(Total Site Area)(1'/12") = 0.013 Ac-Ft

2. Compute 1.25 inches of runoff times the impervious site area.

Treatment Volume = (1.25")(Impervious Site Area)(1'/12") = Treatment Volume = 0.030 Ac-Ft

The percentage of impervious area governs, therefore the treatment volume is

0.030 Ac-Ft.

3. Compute an additional 0.5 inch of runoff over the entire developed basin.

Is the system online? Yes

Treatment Volume = (0.5")(Total Site Area) + TV = 0.043 Ac-Ft

∆ The Required Treatment Volume for Water Quality is 0.043 Ac-Ft Volume Provided is 0.072 Ac-Ft

12/24/2025 Page 7 of 9

APPENDIX B-2

Stage vs. Storage Calculation

GAI Project No. R240665.01 Calc. by: JTC

Pond 1A - Exfiltration System Design

Project: Leesburg 5th Street Parking Location: City of Leesburg System: Exfiltration

Target Water Quality Volume: 4,443 Cu. Ft.

Structure Inside Dimensions No. of Structures Min. Length 0.0 Feet Length Feet

Feet Btm. of Structure 89.35 Feet

OR

Header Inside Dimensions Min. Length 16.0 Feet Length - Feet Min. Width 4.0 Feet Width - Feet

Rock Side/Width: 12 Inches Min. Trench Width: 16.0 Feet Trench Width: - Feet Rock Storage: 40 % Trench Height: 5.0 Feet Round Pipe Size: 36 Inches Pipe Area 7.07 Sq.Ft.

No. of Pipes: 4 Total Area 28.27 Sq.Ft.

Total Trench Storage per Foot: 74.83 Cu. Ft./Ft

Total Trench

53.32 Cu. Ft./Ft

Length of Trench Req'd: 83 Feet Length Provided 90 Feet

Min. Proposed Grade 95.35 Feet 24 - Minimum 18" inches above Top of Pipe Top of Trench 93.35 Feet 6 - Minimum 6" inches above Top of Pipe Top of Pipe 92.85 Feet 36 - Pipe Size in inches Btm. of Pipe 89.85 Feet 18 - Minimum 6" inches above Btm Trench Btm. of Trench/Header 88.35 Feet 84 - Preferably a minimum 24 in above the ESHWT ESHWT 81.35 Feet

Width Min. = Manhole Diameter

Storage per Foot at W.Q. Elevation:

12/24/2025 4 of 9

Stage vs. Storage Analysis

Stage Elevation

(FT)

Structure Storage

(CF)

Header Pipe

Storage

(CF)

Header Gravel

Storage

(CF)

Trench Pipe

Storage

(CF/FT)

Trench Gravel

Storage

(CF/FT)

Net Trench Storage

(CF/FT)

Cumulative System Volume

(CF)

Cumulative System Volume

(AC-FT)

Pipe Area

88.35 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000 0.00

88.85 0.00 0.00 12.80 0.00 3.20 3.20 313.60 0.007 0.00

89.35 0.00 0.00 25.60 0.00 6.40 6.40 627.20 0.014 0.00

89.85 0.00 0.00 38.40 0.00 9.60 9.60 940.80 0.022 0.00

90.35 0.00 12.39 46.24 3.10 11.56 14.66 1436.53 0.033 0.77

90.85 0.00 33.00 50.80 8.25 12.70 20.95 2053.11 0.047 2.06

91.35 0.00 56.55 54.18 14.14 13.55 27.68 2712.87 0.062 3.53

91.85 0.00 80.10 57.56 20.02 14.39 34.41 3372.62 0.08 5.01

92.35 0.00 100.71 62.12 25.18 15.53 40.71 3989.20 0.09 6.29

92.85 0.00 113.10 69.96 28.27 17.49 45.76 4484.93 0.10 7.07

93.35 0.00 113.10 82.76 28.27 20.69 48.96 4798.53 0.11 7.07

Water Quality Treatment Volume Provided @ 93.35 = 4,799 Cu. Ft.

Water Quality Volume Req'd: 4,443 Cu. Ft.

Delta Water Quality Volume Req'd & Provided: 355 Cu. Ft.

Stage vs. Area (for Recovery Analysis)

Stage Elevation

(FT)

Cumulative System Volume

(CF)

Incremental System Volume

(CF)

Cross Sectional Area (SF)

88.35 0.00 0.00 1536.00

88.43 52.27 52.27 627.20

88.85 313.60 261.33 627.20

89.35 627.20 313.60 627.20

89.85 940.80 313.60 627.20

90.35 1436.53 495.73 991.46

90.85 2053.11 616.58 1233.16

91.35 2712.87 659.75 1319.51

91.85 3372.62 659.75 1319.51

92.35 3989.20 616.58 1233.16

92.85 4484.93 495.73 991.46

93.35 4798.53 313.60 627.20

12/24/2025 2 of 2

Pond 1B - Exfiltration System Design

Project: Leesburg 5th Street Parking Location: City of Leesburg System: Exfiltration

Target Water Quality Volume: 3,093 Cu. Ft.

Structure Inside Dimensions No. of Structures Min. Length 0.0 Feet Length Feet

Feet Btm. of Structure 83.85 Feet

OR

Header Inside Dimensions Min. Length 16.0 Feet Length - Feet Min. Width 4.0 Feet Width - Feet

Rock Side/Width: 12 Inches Min. Trench Width: 16.0 Feet Trench Width: - Feet Rock Storage: 40 % Trench Height: 4.0 Feet Round Pipe Size: 36 Inches Pipe Area 7.07 Sq.Ft.

No. of Pipes: 4 Total Area 28.27 Sq.Ft.

Total Trench Storage per Foot: 60.43 Cu. Ft./Ft

Total Trench

41.88 Cu. Ft./Ft

Length of Trench Req'd: 74 Feet Length Provided 75 Feet

Min. Proposed Grade 89.85 Feet 24 - Minimum 18" inches above Top of Pipe Top of Trench 87.85 Feet 6 - Minimum 6" inches above Top of Pipe Top of Pipe 87.35 Feet 36 - Pipe Size in inches Btm. of Pipe 84.35 Feet 6 - Minimum 6" inches above Btm Trench Btm. of Trench/Header 83.85 Feet 30 - Preferably a minimum 24 in above the ESHWT ESHWT 81.35 Feet

Width Min. = Manhole Diameter

Storage per Foot at W.Q. Elevation:

12/24/2025 8 of 9

Stage vs. Storage Analysis

Stage Elevation

(FT)

Structure Storage

(CF)

Header Pipe

Storage

(CF)

Header Gravel

Storage

(CF)

Trench Pipe

Storage

(CF/FT)

Trench Gravel

Storage

(CF/FT)

Net Trench Storage

(CF/FT)

Cumulative System Volume

(CF)

Cumulative System Volume

(AC-FT)

Pipe Area

83.85 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000 0.00

84.35 0.00 0.00 12.80 0.00 3.20 3.20 265.60 0.006 0.00

84.85 0.00 12.39 20.64 3.10 5.16 8.26 685.45 0.016 0.77

85.35 0.00 33.00 25.20 8.25 6.30 14.55 1207.66 0.028 2.06

85.85 0.00 56.55 28.58 14.14 7.15 21.28 1766.43 0.041 3.53

86.35 0.00 80.10 31.96 20.02 7.99 28.01 2325.20 0.053 5.01

86.85 0.00 100.71 36.52 25.18 9.13 34.31 2847.41 0.065 6.29

87.35 0.00 113.10 44.36 28.27 11.09 39.36 3267.26 0.08 7.07

87.85 0.00 113.10 57.16 28.27 14.29 42.56 3532.86 0.08 7.07

Water Quality Treatment Volume Provided @ 87.20 = 3,141 Cu. Ft.

Water Quality Volume Req'd: 3,093 Cu. Ft.

Delta Water Quality Volume Req'd & Provided: 49 Cu. Ft.

Stage vs. Area (for Recovery Analysis)

Stage Elevation

(FT)

Cumulative System Volume

(CF)

Incremental System Volume

(CF)

Cross Sectional Area (SF)

83.85 0.00 0.00 1394.00

83.93 44.27 44.27 531.20

84.35 265.60 221.33 531.20

84.85 685.45 419.85 839.71

85.35 1207.66 522.21 1044.41

85.85 1766.43 558.77 1117.54

86.35 2325.20 558.77 1117.54

86.85 2847.41 522.21 1044.41

87.35 3267.26 419.85 839.71

87.85 3532.86 265.60 531.20

12/24/2025 9 of 9

APPENDIX B-3

Recovery Analysis

PONDS Version 3.3.0315 Retention Pond Recovery - Refined Method

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1A 12-24-2025 14:50:30 Page 1

Project Data

Project Name: Leesburg 5th St Parking Pond 1A

Simulation Description: Exfiltration

Project Number: R240665.01

Engineer : JTC

Supervising Engineer: AJS

Date: 12-24-2025

Aquifer Data

Base Of Aquifer Elevation, [B] (ft datum): 80.85

Water Table Elevation, [WT] (ft datum): 81.35

Horizontal Saturated Hydraulic Conductivity, [Kh] (ft/day): 18.10

Fillable Porosity, [n] (%): 25.00

Unsaturated Vertical Infiltration Rate, [Iv] (ft/day): 8.0

Maximum Area For Unsaturated Infiltration, [Av] (ft²): 1536.0

Geometry Data

Equivalent Pond Length, [L] (ft): 96.0

Equivalent Pond Width, [W] (ft): 16.0

Ground water mound is expected to intersect the pond bottom

Stage vs Area Data

Stage (ft datum)

Area (ft²)

88.35 1536.0

88.43 627.2

88.85 627.2

89.35 627.2

89.85 627.2

90.35 991.5

90.85 1233.2

91.35 1319.5

91.85 1319.5

92.35 1233.2

92.85 991.5

93.35 627.2

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1A 12-24-2025 14:50:31 Page 2

Detailed Results :: Scenario 1 ::

Elapsed Time

(hours)

Instantaneous Inflow Rate

(ft³/s)

Outside Recharge

(ft/day)

Stage Elevation (ft datum)

Infiltration Rate (ft³/s)

Combined Instantaneous

Discharge Rate (ft³/s)

Cumulative Inflow

Volume (ft³)

Cumulative Infiltration

Volume (ft³)

Combined Cumulative

Discharge (ft³) Flow Type

0.000 740.5000 0.00000 81.35000 0.00000 0 0.000 0.0 0 N.A.

0.002 740.5000 0.00000 92.86208 0.14222 0 4443.000 0.9 0 U/P

2.400 0.0000 0.00000 91.83356 0.18452 0 4443.000 1228.8 0 U/P

6.000 0.0000 0.00000 87.05846 0.15501 0 4443.000 4443.0 0 U/S

12.000 0.0000 0.00000 85.37357 0.00000 0 4443.000 4443.0 0 S

24.000 0.0000 0.00000 84.32899 0.00000 0 4443.000 4443.0 0 S

36.000 0.0000 0.00000 83.80962 0.00000 0 4443.000 4443.0 0 S

48.000 0.0000 0.00000 83.49017 0.00000 0 4443.000 4443.0 0 S

60.000 0.0000 0.00000 83.26910 0.00000 0 4443.000 4443.0 0 S

72.000 0.0000 0.00000 83.10444 0.00000 0 4443.000 4443.0 0 S

84.000 0.0000 0.00000 82.97552 0.00000 0 4443.000 4443.0 0 S

96.000 0.0000 0.00000 82.87092 ---- ---- 4443.000 4443.0 0 N.A.

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1A 12-24-2025 14:50:31 Page 3

Summary of Results :: Scenario 1 ::

Time (hours)

Stage (ft datum)

Rate (ft³/s)

Volume (ft³)

Stage Minimum 0.000 81.35 Maximum 0.002 92.86

Inflow Rate - Maximum - Positive 0.002 740.5000 Rate - Maximum - Negative None None Cumulative Volume - Maximum Positive 0.002 4443.0 Cumulative Volume - Maximum Negative None None Cumulative Volume - End of Simulation 96.000 4443.0

Infiltration Rate - Maximum - Positive 2.400 0.1845 Rate - Maximum - Negative None None Cumulative Volume - Maximum Positive 6.000 4443.0 Cumulative Volume - Maximum Negative None None Cumulative Volume - End of Simulation 96.000 4443.0

Combined Discharge Rate - Maximum - Positive None None Rate - Maximum - Negative None None Cumulative Volume - Maximum Positive None None Cumulative Volume - Maximum Negative None None Cumulative Volume - End of Simulation 96.000 0.0

Discharge Structure 1 - inactive Rate - Maximum - Positive disabled disabled Rate - Maximum - Negative disabled disabled Cumulative Volume - Maximum Positive disabled disabled Cumulative Volume - Maximum Negative disabled disabled Cumulative Volume - End of Simulation disabled disabled

Discharge Structure 2 - inactive Rate - Maximum - Positive disabled disabled Rate - Maximum - Negative disabled disabled Cumulative Volume - Maximum Positive disabled disabled Cumulative Volume - Maximum Negative disabled disabled Cumulative Volume - End of Simulation disabled disabled

Discharge Structure 3 - inactive Rate - Maximum - Positive disabled disabled Rate - Maximum - Negative disabled disabled Cumulative Volume - Maximum Positive disabled disabled Cumulative Volume - Maximum Negative disabled disabled Cumulative Volume - End of Simulation disabled disabled

Pollution Abatement:

36 Hour Stage and Infiltration Volume 36.000 83.81 4443.0 72 Hour Stage and Infiltration Volume 72.000 83.10 4443.0

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1A 12-24-2025 14:50:31 Page 4

P lo t o f C u m u la ti v e V o lu m e s a n d

P o n d

S ta g e v s

E la p s e d

T im e S c e n a ri o

Y

A x is

C u m u la tiv e In flo w

C u m u la tiv e In fil tr a tio n C u m u la tiv e

D is ch ar g e

Y

A x is

P o nd S ta g e

E la p s e d

T im e h rs

Cumulative Volumes (ft³) -1

-5

Elevation (ft datum)

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1A 12-24-2025 14:50:32 Page 5

P lo t o f F lo w

R a te s a n d P o n d S ta g e v s E la p s e d T im e

S c e n a ri o

Y

A x is

In flo w R at e

In fil tr a tio n

R a te D is ch ar g e R a te

Y

A x is

P o nd S ta g e

E la p s e d

T im e h rs

Volumetric Rate (ft³/s)

-2

-1

Stage Elevation (ft datum)

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1B 12-24-2025 15:44:38 Page 1

Project Data

Project Name: Leesburg 5th St Parking Pond 1B

Simulation Description: Exfiltration

Project Number: R240665.01

Engineer : JTC

Supervising Engineer: AJS

Date: 12-24-2025

Aquifer Data

Base Of Aquifer Elevation, [B] (ft datum): 80.85

Water Table Elevation, [WT] (ft datum): 81.35

Horizontal Saturated Hydraulic Conductivity, [Kh] (ft/day): 18.10

Fillable Porosity, [n] (%): 25.00

Unsaturated Vertical Infiltration Rate, [Iv] (ft/day): 8.0

Maximum Area For Unsaturated Infiltration, [Av] (ft²): 1394.0

Geometry Data

Equivalent Pond Length, [L] (ft): 82.0

Equivalent Pond Width, [W] (ft): 17.0

Ground water mound is expected to intersect the pond bottom

Stage vs Area Data

Stage (ft datum)

Area (ft²)

83.85 1394.0

83.93 531.2

84.35 531.2

84.85 839.7

85.35 1044.4

85.85 1117.5

86.35 1117.5

86.85 1044.4

87.35 839.7

87.85 531.2

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1B 12-24-2025 15:44:39 Page 2

Detailed Results :: Scenario 1 ::

Elapsed Time

(hours)

Instantaneous Inflow Rate

(ft³/s)

Outside Recharge

(ft/day)

Stage Elevation (ft datum)

Infiltration Rate (ft³/s)

Combined Instantaneous

Discharge Rate (ft³/s)

Cumulative Inflow

Volume (ft³)

Cumulative Infiltration

Volume (ft³)

Combined Cumulative

Discharge (ft³) Flow Type

0.000 515.5000 0.00000 81.35000 0.00000 0 0.000 0.0 0 N.A.

0.002 515.5000 0.00000 87.19794 0.12913 0 3093.000 0.8 0 U/P

2.400 0.0000 0.00000 85.46941 0.14475 0 3093.000 1853.4 0 U/S

6.000 0.0000 0.00000 84.94205 0.03177 0 3093.000 2371.1 0 S

12.000 0.0000 0.00000 84.40443 0.01464 0 3093.000 2763.1 0 S

24.000 0.0000 0.00000 83.81779 0.00382 0 3093.000 3093.0 0 S

36.000 0.0000 0.00000 83.38528 0.00000 0 3093.000 3093.0 0 S

48.000 0.0000 0.00000 83.12082 0.00000 0 3093.000 3093.0 0 S

60.000 0.0000 0.00000 82.93720 0.00000 0 3093.000 3093.0 0 S

72.000 0.0000 0.00000 82.79992 0.00000 0 3093.000 3093.0 0 S

84.000 0.0000 0.00000 82.69212 0.00000 0 3093.000 3093.0 0 S

96.000 0.0000 0.00000 82.60448 ---- ---- 3093.000 3093.0 0 N.A.

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1B 12-24-2025 15:44:40 Page 3

Summary of Results :: Scenario 1 ::

Time (hours)

Stage (ft datum)

Rate (ft³/s)

Volume (ft³)

Stage Minimum 0.000 81.35 Maximum 0.002 87.20

Inflow Rate - Maximum - Positive 0.002 515.5000 Rate - Maximum - Negative None None Cumulative Volume - Maximum Positive 0.002 3093.0 Cumulative Volume - Maximum Negative None None Cumulative Volume - End of Simulation 96.000 3093.0

Infiltration Rate - Maximum - Positive 2.400 0.1448 Rate - Maximum - Negative None None Cumulative Volume - Maximum Positive 24.000 3093.0 Cumulative Volume - Maximum Negative None None Cumulative Volume - End of Simulation 96.000 3093.0

Combined Discharge Rate - Maximum - Positive None None Rate - Maximum - Negative None None Cumulative Volume - Maximum Positive None None Cumulative Volume - Maximum Negative None None Cumulative Volume - End of Simulation 96.000 0.0

Discharge Structure 1 - inactive Rate - Maximum - Positive disabled disabled Rate - Maximum - Negative disabled disabled Cumulative Volume - Maximum Positive disabled disabled Cumulative Volume - Maximum Negative disabled disabled Cumulative Volume - End of Simulation disabled disabled

Discharge Structure 2 - inactive Rate - Maximum - Positive disabled disabled Rate - Maximum - Negative disabled disabled Cumulative Volume - Maximum Positive disabled disabled Cumulative Volume - Maximum Negative disabled disabled Cumulative Volume - End of Simulation disabled disabled

Discharge Structure 3 - inactive Rate - Maximum - Positive disabled disabled Rate - Maximum - Negative disabled disabled Cumulative Volume - Maximum Positive disabled disabled Cumulative Volume - Maximum Negative disabled disabled Cumulative Volume - End of Simulation disabled disabled

Pollution Abatement:

36 Hour Stage and Infiltration Volume 36.000 83.39 3093.0 72 Hour Stage and Infiltration Volume 72.000 82.80 3093.0

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1B 12-24-2025 15:44:40 Page 4

P lo t o f C u m u la ti v e V o lu m e s a n d

P o n d

S ta g e v s

E la p s e d

T im e S c e n a ri o

Y

A x is

C u m u la tiv e In flo w

C u m u la tiv e In fil tr a tio n C u m u la tiv e

D is ch ar g e

Y

A x is

P o nd S ta g e

E la p s e d

T im e h rs

Cumulative Volumes (ft³) -1

-1

-5

Elevation (ft datum)

1.

1.

2.

2.

3.

3.

4.

4.

5.

5.

6.

6.

7.

7.

Copyright 2012 Devo Seereeram, Ph.D., P.E.

Leesburg 5th St Parking Pond 1B 12-24-2025 15:44:40 Page 5

P lo t o f F lo w

R a te s a n d P o n d S ta g e v s E la p s e d T im e

S c e n a ri o

Y

A x is

In flo w R at e

In fil tr a tio n

R a te D is ch ar g e R a te

Y

A x is

P o nd S ta g e

E la p s e d

T im e h rs

Volumetric Rate (ft³/s)

-5

Stage Elevation (ft datum)

1.

1.

2.

2.

3.

3.

4.

4.

5.

5.

6.

6.

7.

7.

APPENDIX B-4

Pollutant Analysis

SHEET NUMBER

SHEET TITLE

REVISIONS:

PROJECT NUMBER

REGISTRATION

DRAWN:

CHECKED:

R240665.01

DATE: 08/19/2025

APPROVED:

5TH STREET

PARKING LOT

A GAI CONSULTANTS, INC SERVICE GROUP

257 SOUTH 5TH STREET

LEESBURG FL, 34748

CDA

JTC

618 E. SOUTH STREET

SUITE 700

ORLANDO, FL 32801

407 423-8398

CERTIFICATE OF AUTHORIZATION: EB9951

gai consultants

AJS

DP

KO

KO

0 20' 40'

FULL SCALE: 1"=20'

HALF SCALE: 1"=40'

EX-1

PRE BASIN

MAP EXHIBIT

SUB-BASIN 1A:

TOTAL = 30730.74 SF / 0.71 AC

IMP. = 30642.19 SF / 0.70 AC

SUB-BASIN 1B:

TOTAL = 13802.84 SF / 0.32 AC

IMP. = 13729.57 SF / 0.32 AC

BASIN 1 [REMAINDER]:

TOTAL = 46550.90 SF / 1.07 AC

IMP. = 37719.10 SF / 0.86 AC

SHEET NUMBER

SHEET TITLE

REVISIONS:

PROJECT NUMBER

REGISTRATION

DRAWN:

CHECKED:

R240665.01

DATE: 08/19/2025

APPROVED:

5TH STREET

PARKING LOT

A GAI CONSULTANTS, INC SERVICE GROUP

257 SOUTH 5TH STREET

LEESBURG FL, 34748

CDA

JTC

618 E. SOUTH STREET

SUITE 700

ORLANDO, FL 32801

407 423-8398

CERTIFICATE OF AUTHORIZATION: EB9951

gai consultants

AJS

0 20' 40'

FULL SCALE: 1"=20'

HALF SCALE: 1"=40'

EX-2

PROP. BASIN

MAP EXHIBIT

SUB-BASIN 1A:

TOTAL = 30730.74 SF / 0.71 AC

IMP. = 28381.79 SF / 0.65 AC

SUB-BASIN 1B:

TOTAL = 13802.84 SF / 0.32 AC

IMP. = 12468.32 SF / 0.29 AC

BASIN 1 [REMAINDER]:

TOTAL = 46550.90 SF / 1.07 AC

IMP. = 37793.02 SF / 0.87 AC

Complete Report (not including cost) Ver 5.3.2 Project: Leesburg 5th Street Parking Date: 12/24/2025 2:50:24 PM

Site and Catchment Information

Analysis: Net Improvement

Catchment Name

Runoff Area Sub- Basin 1A

Runoff Area Sub-Basin 1B Basin 1 [Remainder]

Rainfall Zone Florida Zone 2 Florida Zone 2 Florida Zone 2

Annual Mean Rainfall

50.00 50.00 50.00

Pre-Condition Landuse Information

Landuse Low-Intensity Commercial:

TN=1.13 TP=0.188

SJRWMD Apopka Open Space/Recreation/Fallow Crop:

TN=1.100 TP=0.050

High-Intensity

TN=2.40 TP=0.345

Area (acres) 0.71 0.32 1.07

Rational Coefficient (0- 1)

0.81 0.81 0.66

Non DCIA Curve Number

39.00 39.00 39.00

DCIA Percent (0-100)

99.70 99.50 81.00

Nitrogen EMC (mg/l)

1.130 1.100 2.400

Phosphorus EMC (mg/l)

0.188 0.050 0.345

Runoff Volume (ac-ft/yr)

2.386 1.073 2.928

Groundwater N (kg/yr)

0.000 0.000 0.000

Groundwater P (kg/yr)

0.000 0.000 0.000

Nitrogen Loading (kg/yr)

3.325 1.456 8.666

Phosphorus Loading (kg/yr)

0.553 0.066 1.246

Post-Condition Landuse Information

Landuse

Commercial:

TN=2.40 TP=0.345

High-Intensity Commercial:

Area (acres) 0.71 0.32 1.07

Rational Coefficient (0- 1)

0.75 0.73 0.66

Non DCIA Curve Number

39.00 39.00 39.00

DCIA Percent (0-100)

92.40 90.30 81.20

Wet Pond Area (ac)

0.00 0.00 0.00

Nitrogen EMC (mg/l)

2.400 2.400 2.400

Phosphorus EMC (mg/l)

0.345 0.345 0.345

Runoff Volume (ac-ft/yr)

2.213 0.975 2.936

Groundwater N (kg/yr)

0.000 0.000 0.000

Groundwater P (kg/yr)

0.000 0.000 0.000

Nitrogen Loading (kg/yr)

6.550 2.886 8.687

Phosphorus Loading (kg/yr)

0.942 0.415 1.249

Catchment Number: 1 Name: Runoff Area Sub-Basin 1A

Project: Leesburg 5th Street Parking Date: 12/24/2025

Exfiltration Trench Design

Pipe Span (in) 36.0

Pipe Rise (in) 36.0

Pipe Length (ft) 360.0

Trench Width (ft) 4.0

Trench Depth (ft) 5.0

Trench Length (ft) 360.0

Aggregate Void (fraction) 0.40

Storage Volume (Ac-ft) 0.10

Retention Depth (in over CA) 1.710

Watershed Characteristics Catchment Area (acres) 0.71

Contributing Area (acres) 0.710

Non-DCIA Curve Number 39.00

DCIA Percent 92.40

Rainfall Zone Florida Zone 2

Rainfall (in) 50.00

Surface Water Discharge Required TN Treatment Efficiency (%) 49

Provided TN Treatment Efficiency (%) 87

Required TP Treatment Efficiency (%) 41

Provided TP Treatment Efficiency (%) 87

Media Mix Information Type of Media Mix Not Specified

Media N Reduction (%)

Media P Reduction (%)

Groundwater Discharge (Stand-Alone) Treatment Rate (MG/yr) 0.000

TN Mass Load (kg/yr) 5.686

TN Concentration (mg/L) 0.000

TP Mass Load (kg/yr) 0.817

TP Concentration (mg/L) 0.000

Load Diagram for Exfiltration Trench (stand-alone)

Load N: 6.55 kg/yr P: 0.94 kg/yr

Treatment N: 87 % P: 87 %

Surface Discharge N: 0.86 kg/yr P: 0.12 kg/yr

↓ Mass Reduction N: 5.69 kg/yr P: 0.82 kg/yr

Load Diagram for Exfiltration ( As Used In Routing)

Upstream Nodes None

Load N: 6.55 kg/yr P: 0.94 kg/yr Q: 2.21 ac-ft

Treatment N: 86.8 % P: 86.8 %

Mass Discharged N: 0.86 kg/yr P: 0.12 kg/yr Q: 0.29 ac-ft

Mass Removed N: 5.69 kg/yr P: 0.82 kg/yr Q: 1.92 ac-ft

Catchment Number: 2 Name: Runoff Area Sub-Basin 1B

Date: 12/24/2025

Exfiltration Trench Design Pipe Span (in) 36.0

Pipe Rise (in) 36.0

Pipe Length (ft) 300.0

Trench Width (ft) 4.0

Trench Depth (ft) 4.0

Trench Length (ft) 301.0

Aggregate Void (fraction) 0.40

Storage Volume (Ac-ft) 0.07

Retention Depth (in over CA) 2.754

Watershed Characteristics Catchment Area (acres) 0.32

Contributing Area (acres) 0.320

Non-DCIA Curve Number 39.00

DCIA Percent 90.30

Rainfall Zone Florida Zone 2

Rainfall (in) 50.00

Surface Water Discharge Required TN Treatment Efficiency (%) 50

Provided TN Treatment Efficiency (%) 95

Required TP Treatment Efficiency (%) 84

Provided TP Treatment Efficiency (%) 95

Media N Reduction (%)

Media P Reduction (%)

TN Mass Load (kg/yr) 2.750

TN Concentration (mg/L) 0.000

TP Mass Load (kg/yr) 0.395

Load Diagram for Exfiltration Trench (stand-alone)

N: 2.89 kg/yr P: 0.41 kg/yr

Treatment N: 95 % P: 95 %

Surface Discharge N: 0.14 kg/yr P: 0.02 kg/yr

↓ Mass Reduction N: 2.75 kg/yr P: 0.40 kg/yr

Load Diagram for Exfiltration ( As Used In Routing)

Load N: 2.89 kg/yr P: 0.41 kg/yr Q: 0.98 ac-ft

Treatment N: 95.3 % P: 95.3 %

Mass Discharged N: 0.14 kg/yr P: 0.02 kg/yr Q: 0.05 ac-ft

N: 2.75 kg/yr P: 0.40 kg/yr Q: 0.93 ac-ft

Catchment Number: 3 Name: Basin 1 [Remainder]

Date: 12/24/2025

None Design

Watershed Characteristics Catchment Area (acres) 1.07

Contributing Area (acres) 1.070

Non-DCIA Curve Number 39.00

DCIA Percent 81.20

Rainfall Zone Florida Zone 2

Rainfall (in) 50.00

Surface Water Discharge Required TN Treatment Efficiency (%)

Provided TN Treatment Efficiency (%)

Required TP Treatment Efficiency (%)

Provided TP Treatment Efficiency (%)

Media N Reduction (%) 0.000

Media P Reduction (%) 0.000

TN Mass Load (kg/yr) 0.000

TN Concentration (mg/L) 0.000

TP Mass Load (kg/yr) 0.000

Load Diagram for None (stand-alone)

N: 8.69 kg/yr P: 1.25 kg/yr

Treatment N: % P: %

Surface Discharge N: 8.69 kg/yr P: 1.25 kg/yr

↓ Mass Reduction N: 0.00 kg/yr P: 0.00 kg/yr

Load Diagram for None ( As Used In Routing)

Load N: 8.69 kg/yr P: 1.25 kg/yr Q: 2.94 ac-ft

Treatment N: 0.0 % P: 0.0 %

Mass Discharged N: 8.69 kg/yr P: 1.25 kg/yr Q: 2.94 ac-ft

N: 0.00 kg/yr P: 0.00 kg/yr Q: 0.00 ac-ft

Summary Treatment Report Version: 5.3.2

Project: Leesburg 5th Street Parking

Analysis Type: Net Improvement BMP Types:

Catchment 1 - (Runoff Area Sub-Basin 1A) Exfiltration Trench Catchment 2 - (Runoff Area Sub-Basin 1B) Exfiltration Trench Catchment 3 - (Basin 1 [Remainder]) None Based on discharge load to 2 decimal places

Date:12/24/2025

Routing Summary Catchment 1 Routed to Outlet Catchment 2 Routed to Outlet Catchment 3 Routed to Outlet

Total nitrogen target removal met? Yes Total phosphorus target removal met? Yes

Summary Report Nitrogen

Surface Water Discharge

Total N pre load 13.45 kg/yr

Total N post load 18.12 kg/yr

Target N load reduction 25.8 %

Target N discharge load 13.45 kg/yr

Percent N load reduction 46.55 %

Provided N discharge load 9.69 kg/yr 21.36 lb/yr

Provided N load removed 8.44 kg/yr 18.6 lb/yr

Phosphorus

Surface Water Discharge

Total P pre load 1.865 kg/yr

Total P post load 2.605 kg/yr

Target P load reduction 28.41 %

Target P discharge load 1.865 kg/yr

Percent P load reduction 46.55 %

Provided P discharge load 1.392 kg/yr 3.07 lb/yr

Provided P load removed 1.213 kg/yr 2.674 lb/yr

APPENDIX C-1

Sample Inspection Log

DATE

Depth of Sediment

(inches)

Accumulated

Trash

Maintenance

Performed

Maintenance

Personnel Comments

02/01/14 1" None Removed Sediment B. Johnson Example

06/01/14 0.5" Some Removed Sediment and Trash B. Johnson Swept Parking Garage

Inspection and Maintenance Log Citi Tower at Eola Park - Stormwater Management System

East SDG Cititower, LLC Orlando Florida

Alta At Health Village 500 E Colonial Dr, Orlando, FL 32803

02/01/25

06/01/25

Quest Academy - Stormwater Management SystemLeesburg 5th Street Parking Lot - Stormwater Management System 429 W. Magnolia St.

Leesburg, FL 34748