City_of_Gainesville_Engineering_&_Design_Construction_Manual_2022.pdf

2022 Edition

Engineering Design & Construction Manual

City of Gainesville Engineering Design & Construction Manual i

TABLE OF CONTENTS

1. Introduction

1.1 Purpose and Applicability

1.2 Enforcement

1.3 Conflicts with Governing Documents

1.4 Definitions and Terms

1.5 Amendments

1.6 Design Exceptions or Variances

1.7 Interpretation

1.8 Omissions

2. Technical References

3. Stormwater Management

3.1 Objective

3.2 Evaluation Criteria

3.3 Permitting Thresholds

3.4 Minimum Requirements

3.5 Water Quality Standards

3.6 Stormwater Quantity Criteria

3.7 Floodplains and Floodways

3.8 Stormwater Conveyance

3.9 Geotechnical Criteria

3.10 Water Management District Criteria

3.11 Stormwater Pollution Prevention Plan

3.12 Erosion and Sedimentation Control

3.13 Karst Areas and High Aquifer Vulnerability Areas

3.14 Stormwater Management Utility

3.15 Operation and Maintenance

4. Roadway Design

4.1 Objective

4.2 Governing Standards

4.3 Roadway Classification

4.4 Lane Widths

Table of Contents

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4.5 Drainage

4.6 Intersection Design

4.7 Pavement Designs

4.8 Driveways

4.9 Bicycle Facilities

4.10 Sidewalks and Shared-use Paths

4.11 Pedestrian Crossings

4.12 Curb Ramps and Sidewalk Connections

4.13 Signage

4.14 Pavement Markings

4.15 Traffic Calming

4.16 On-Street Parking

4.17 Lighting

4.18 Utilities

4.19 Landscaping

4.20 Transit

4.21 Mailboxes

4.22 Temporary Traffic Control

5. Site Design

5.1 Driveways

5.2 Utility Service

5.3 Refuse Collection and Dumpster Pads

5.4 Parking (off street)

5.5 Public Right-of-Way and Maintenance

5.6 Public Sidewalks

6. Traffic Study Guidelines

6.1 Study Thresholds

6.2 Methodology Letter

6.3 Required Information

7 Submittal Requirements

7.1 Site Plans

7.2 Subdivision Development

7.3 Interim Stormwater As-built Survey

Table of Contents

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7.4 As-built Survey

8 Construction

8.1 Objective

8.2 ROW Permits

8.3 Construction Activities

8.4 Stormwater

8.5 Stormwater As-built Survey

8.6 Utility Work

8.7 Earthwork

8.8 Asphaltic Concrete

8.9 Concrete

8.10 Signals

8.11 Signs & Markings

8.12 Landscaping

8.13 Lighting

APPENDIX A Definitions and Terms

APPENDIX B Standard Details B-1 Parking Dimensions B-2 Brick B-3 Traffic Calming: Speed Table B-4 Traffic Calming: Raised Crosswalk B-5 Traffic Calming: 3-Way Raised Intersection B-6 Traffic Calming: 4-Way Raised Intersection

Chapter 1 - Introduction

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1. Introduction

1.1 Purpose and Applicability

The City of Gainesville Engineering Design & Construction Manual (hereafter referred to as the EDCM or this manual) is approved and adopted by Ordinance Number 210572 on October 20, 2022, pursuant to the authority granted by the City of Gainesville Comprehensive Plan. The EDCM further complements the requirements of the Land Development Code, Chapters 23, 26 and 30, City of Gainesville Code of Ordinances.

The EDCM is intended to implement City policy as outlined in the City’s Comprehensive Plan for the provision of transportation facilities that promotes a safe and well-connected, multi-modal transportation system.

The EDCM establishes engineering design standards and specifications for the development of site plans, subdivisions, redevelopment projects, permits and capital projects within the City of Gainesville as part of the City’s responsibility to provide for the health, safety and welfare of the public.

When real property within the City of Gainesville is developed and/or redeveloped or any work is proposed within the City’s right-of-way (ROW) or easement, the infrastructure facilities contained within said property, serving said property or activities within the City’s ROW or easement shall comply with the requirements set forth in this manual and the City of Gainesville Code of Ordinances.

1.2 Enforcement

The Public Works Department, through their designated representatives, shall have the right to inspect the land and constructed facilities addressed by this manual and to issue “Notices to Comply” for violations of the Code of Ordinances or of approved plans reviewed under this manual, an extension of the Code of Ordinance.

1.3 Conflicts with Governing Documents

Where more stringent standards are imposed by federal, state and other local agencies, the more stringent standards having jurisdiction shall apply. Where the standards and specifications included in the City of Gainesville Code of Ordinances and this manual conflict, the City of Gainesville Code of Ordinances shall prevail. Where the Code of Ordinances conflict with the Comprehensive Plan, the Comprehensive Plan shall prevail.

All construction must comply with the EDCM / Code of Ordinances, Chapter 30, Land Development Code unless a design variance or exception is approved in accordance with Chapter

1.6 by Public Works.

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1.4 Definitions and Terms

The definitions of the terms used in this manual have the meanings respectively ascribed to them by common usage or specifically defined in those publications identified by reference, except in those instances where the text clearly indicates a different meaning. The definitions or terms contained herein are not intended to alter definitions expressly specified in any other City of Gainesville ordinance, policy, regulation or code, but are provided for the purpose of making clear and distinct the intention of the language used in a specific section of this document.

1.5 Amendments

The City of Gainesville shall amend the contents of this manual as may be required by ordinance adopted by the City Commission.

1.6 Design Exceptions or Variances

Design Exceptions or Variances from the standards contained in this manual may be approved when such exceptions or variances are not contrary to the public interest where, owing to special conditions, a literal enforcement of the provisions of this manual would result in unnecessary hardship in order to allow for implementation of an innovative design practice.

Design Exceptions are required when the Controlling Design Elements as specified in Chapter 14 of the Manual of Uniform Standards for Design, Construction and Maintenance for Streets and Highways (aka “Florida Greenbook”) cannot be met.

Design Exceptions shall be submitted in writing by the Professional Engineer responsible for the design and justified as described in Chapter 14 of the Florida Greenbook. The FDOT’s Utility Accommodation Manual provides guidance on exceptions with respect to utilities. The City Engineer has the authority to approve Design Exceptions that meet the requirements of this section.

When proposed design elements other than the Controlling Elements do not meet the requirements contained in this manual, sufficient detail and justification of such deviations must be documented by the Responsible Professional Engineer as a Design Variation and shall be submitted to the City. Design Variation shall include the following:

1. Design Criteria versus the proposed criteria

2. Reason the design criteria are not appropriate

3. Justification for the proposed criteria.

4. Review and evaluation of the most recent 5-years of crash history where appropriate

5. Background information which documents or justifies the request

6. Demonstration that the proposed design variations would be in harmony with the general intent and purpose of the Land Development Code, Comprehensive Plan, EDCM and the Manual for Uniform Minimum Standards for Design, Construction and Maintenance (Florida Greenbook), would not be injurious to surrounding properties, and would not otherwise be detrimental to the interest, safety, health, and welfare of the public.

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7. Demonstration that the proposed alternative treatment will meet the intent of the City’s specifications and not pose an undue or significant burden upon the City or any other party.

The City Engineer has authority to approve Design Variances that meet the requirements of this section.

1.7 Interpretation

The Public Works Director, if the incumbent is a registered Professional Engineer, shall provide the final interpretation of the contents of this manual; otherwise, the City Engineer shall provide the final interpretation of the contents of this manual.

As interpretations or corrections of this manual are made by the Public Works Director or City Engineer, the development community will be informed through the use of a Design Memo. The Design Memos will be posted on the Public Works Development Review webpage. The tracking of all design memos will be shown in a Revision Log, which will also be provided on the aforementioned webpage.

1.8 Omissions

Logical, accountable, and generally accepted design standards and engineering judgment shall apply where not specifically addressed in this manual.

Chapter 2 - Technical References

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2. Technical References

Standards and guidelines that are referenced in most recent version of the following technical publications shall be considered part of this manual including subsequent updates or revisions to these publications. In the event of a conflicting standard imposed by the City, federal, state or other local agencies, the more stringent jurisdictional standard shall apply.

American Association of State Highway and Transportation Officials (AASHTO) – A Policy on Geometric Design of Highways and Streets

Americans with Disabilities Act (ADA) – Uniform Federal Accessibility Standards (UFAS); ADA Standards for Accessible Design (ADAAG); Public Rights of Way Accessibility Guidelines (PROWAG)

ASCE - ASCE 24 Flood Resistant Design and Construction

Florida Department of Environmental Protection (FDEP) – Chapter 62-302, F.A.C., Surface Water Quality Standards

FDEP – Chapter 62-621, F.A.C., Generic Permits

FDEP – Chapter 62-624, F.A.C., Municipal Separate Storm Sewer Systems

FDEP – Chapter 62-330, F.A.C., Environmental Resource Permitting

FDEP – The Florida Stormwater Erosion and Sedimentation Control Inspector’s Manual

FDEP and Water Management Districts Environmental Resource Permit (ERP) Applicant’s Handbook Volume I (General and Environmental)

Florida Department of Transportation (FDOT) – “Accessing Transit: Designing Handbook for Florida Bus Passenger Facilities”.

FDOT Design Manual

FDOT Standard Specifications for Road and Bridge Construction

FDOT Standard Plans for Road Construction

FDOT Procedures Manual for Flexible Pavement Design

FDOT Drainage Manual

FDOT Drainage Design Guide

FDOT Utility Accommodations Manual

FDOT Florida Erosion and Sediment Control Designer and Reviewer Manual

Chapter 2 - Technical References

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Federal Highway Administration (FHWA) – Manual on Uniform Traffic Control Devices (MUTCD)

Florida Greenbook – also known as the FDOT Manual of Uniform Minimum Standards for Design, Construction and Maintenance for Streets and Highways

Gainesville Regional Utilities (GRU) Approved Electric System Materials Manual

GRI Lighting Catalog

Institute of Transportation Engineers (ITE) – Curbside Management: Practitioners Guide

ITE – Context Sensitive Solutions in Designing Major Walkable Urban Thoroughfares: A Context Sensitive Approach Major Urban Thoroughfares for Walkable Communities

National Association of City Transportation Officials (NACTO) – Urban Bikeway Design Guide

NACTO – Urban Street Design Guide

National Cooperative Highway Research Program (NCHRP) Report 672

SJRWMD – Permit Information Manual (includes Applicant’s Handbook Volume II)

SRWMD – ERP Applicant’s Handbook Volume II

United States Department of Agriculture/National Resource Conservation Service (USDA/NRCS) – Technical Release 55 (TR-55) Urban Hydrology for Small Watersheds

Chapter 3 - Stormwater Management

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3. Stormwater Management

3.1 Objective

The objective of this section of the EDCM is to provide the design and performance standards necessary for the conservation and improvement of the quality of the surface waters, as well as, the control of stormwater runoff volume and rate and floodplain elevations in the City of Gainesville.

3.2 Evaluation Criteria

Applicants must provide reasonable assurance that the construction, alteration, operation, or maintenance of a project, or removal or abandonment of an existing stormwater management system, will not cause adverse water quality impacts, water quantity impacts, or flooding impacts to on-site or off-site property.

Key documents to be utilized as reference for this section are the FDOT Drainage Manual, the FDOT Drainage Design Guide, the SJRWMD Permit Information Manual (includes Applicant’s Handbook Volume II), and the SRWMD ERP Applicant’s Handbook Volume II.

3.3 Permitting Thresholds

3.3.1 Cumulative Development

All development of a particular lot or site governed by final approved development plans shall be cumulative from October 1, 2013. For example, a site adding 850 sf of new impervious would not trip the New Development Threshold of 1,000 sf. If the site then added additional 150 sf or greater the following year, stormwater requirements would be triggered for the cumulative area.

3.3.2 Definition of Redevelopment of Vehicular Use Area or Building For the purposes of applying permitting thresholds and exemption criteria, redevelopment is any demolition or reconstruction of the vehicular use area (excluding maintenance of pavement such as resurfacing and restriping) or building. Any proposal for a site on which the proposed redevelopment of building(s) or vehicular use area involves the demolition and reconstruction of more than 80 percent of the area devoted to existing building and vehicular use area shall be considered new development, and shall be required to meet the standards for new development.

All redevelopment of a particular lot or site governed by a final development order shall be cumulative from October 1, 2013. Note that the 80% threshold applies to the impervious on the site versus project area.

Example 1:

5 acre site with 4 acres of total impervious, 3.5 acres of which are attributed to building and vehicular use area. If the redevelopment project involves more than 2.8 acres of the 3.5 acres attributed to building and vehicular use area, it will require water quality and quantity.

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Example 2:

5 acre site with 4 acres of total impervious, 3.5 acres of which are attributed to building and vehicular use area. If the redevelopment project involves 2.8 acres or less of the 3.5 acres attributed to building and vehicular use area, it will require water quality. Note that the applicant must demonstrate the project is not impacting adjacent properties.

Only one set of permitting thresholds (new development versus redevelopment) will apply to a proposed project and will be determined by the City Engineer or designee.

3.3.3 Exemptions

1. New development < 1,000 sf of impervious area; or

2. Redevelopment < 4,000 sf of impervious area on an existing improved site.

3. Maintenance of Pavement

a. Activities such as milling, resurfacing, surface overlay, and minor (as determined by Public Works) limerock base replacement are potentially exempt from stormwater requirements.

b. Exemption status will be determined on a site-by-site basis.

c. A sketch or narrative must be provided to describe the proposed activity. Plan(s) may be necessary for review to confirm changes to existing grades and drainage patterns are not proposed, as well as, to demonstrate no impact to adjacent or downstream properties.

4. Accessible parking space improvements associated with Building Permits for ADA compliance.

a. Exemption status will be determined on a site-by-site basis.

b. A sketch or narrative must be provided to describe the proposed activity. Plan(s) may be necessary for review to confirm changes to existing grades and drainage patterns are not proposed, as well as, to demonstrate no impact to adjacent or downstream properties.

3.3.4 Water Quality Required

1. New development between 1,000 sf and 1,999 sf of net new impervious area.

2. Redevelopment of 4,000 sf and greater, but less than or equal to 80% as described in

Section 3.3.2.

3. Demonstrate the project is not impacting adjacent properties by ensuring discharge is not directed onto a neighboring property but to a city street, landscaped area or stormwater retention area.

3.3.5 Water Quality and Quantity Required

1. New development of 2,000 sf and greater of net new impervious area; or

2. Redevelopment of 4,000 sf and greater, and greater than 80% as described in Section

3.3.2.

3.4 Minimum Requirements

3.4.1 Drainage Narrative

See Section 7.1.2 for detailed information on what is required to be included in the drainage report.

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3.4.2 General Design Standards

1. All drainage facilities shall provide a positive outfall to existing watercourses, water bodies, wetlands or storm sewer systems unless it can be proven that it is a closed system or acting as a closed basin.

2. Stormwater management facilities shall be designed to minimize the need for maintenance in accordance with this manual.

3. All stormwater management facilities shall be landscaped in such a manner as to promote safety and to integrate with the overall design of the site as required by the

LDC.

4. Insofar as possible, the contour of stormwater management facilities should promote aesthetically pleasing site design and increased wildlife habitat.

5. The design and operation of stormwater management facilities shall discourage the breeding of mosquitoes.

6. The design of stormwater management facilities shall promote joint uses for habitat, open space, passive recreation, and the establishment and integration of trails.

7. Features that are identified as “Design by Others” shall demonstrate support of the overall stormwater management system and conformance with its design. A review of the features identified as designed by others during the development review process must submit for Public Works Stormwater and Constructability review prior to construction.

8. Underground utilities within the footprint of a stormwater basin are to be reviewed and approved on a case-by-case basis by the City Engineer. Underground utilities are prohibited within underground stormwater facilities. Underground utilities are discouraged from being located within a stormwater basin. Where there are existing utilities within the footprint of a stormwater basin, relocation is encouraged.

3.4.3 Technical Standards

1. The area of the top elevation of all proposed stormwater management facilities shall be considered to have a CN = 100 or C = 0.95 for applicable stormwater calculations.

The top elevation is set at the control elevation of a wet pond and the design high for a dry pond.

2. Stormwater Basins

a. Fill Material.

i. Fill material used for undercut or backfill within the stormwater basin must not exceed 10% passing of 200 sieve.

b. Dry Retention Ponds.

i. Initial basin excavation should be within one foot of the final elevation of the basin floor.

ii. Final excavation should be deferred until all contributing areas of the drainage basins have been stabilized.

iii. Light equipment should be used to remove accumulated sediments and achieve final grade without compacting the basin bottom. The bottom of the pond shall be tested in the field using a double-ring infiltrometer test to demonstrate that it is not less than the design infiltration.

c. Underground/ Exfiltration Systems

i. Design permeability data collected in appropriate flow zones.

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ii. The underground facilities must be designed so that the invert elevation of the system is at least two feet above the seasonal high ground water table elevation unless the engineer of record or geotechnical engineer affirmatively demonstrates based on geotechnical information that an alternative design is appropriate for the specific site conditions.

iii. Provide location of building support beams and footers in relation to the underground facility.

iv. Provide percolation link perimeters on a scaled map. Applicable when using ICPR stormwater modeling software. Basins with shared boundaries and modeled in Ponds are to be consistent with technical memorandums supplied by Devo Engineering.

v. Provide mounding analysis.

vi. Freeboard demonstrated as identified in Section 3.4.3 paragraph 4.

vii. Provide location of roof drain connections. Underground facilities that are individually identified with a drainage basin delineated will have to provide documentation that justifies the design assumptions made.

viii. Provide location of cleanout ports.

ix. An isolation row or chamber that effectively filters sediment and other contaminants, which can be systematically removed using cleanout ports, shall be incorporated into designs that are not open vault style systems.

x. For underground facilities utilizing a geotextile, specify and provide specifications that demonstrate the proposed geotextile will not be a limiting factor in infiltration.

xi. The insitu material under proposed underground facilities shall be tested in the field after preparation but prior to placement of bedding material using a double-ring infiltrometer test to demonstrate that it is not less than the design infiltration.

xii. If utilizing a compacted backfill material, it too must be tested in the field after placement to demonstrate that it is not a limiting factor in infiltration.

xiii. Provide a visual “failure” indicator that would provide the O&M entity some indication that the system is not functioning as intended and requires maintenance or repair.

xiv. The design shall incorporate a way to perform a full visual inspection of the underground facility.

xv. Operation and maintenance guidance document provided.

3. Slope Stability Analysis

a. A slope stability analysis shall be performed for berms, dams, or embankments that provide any storage above surrounding grade. Underground facilities that have the potential to daylight onto an embankment or side slope are included.

Documentation of the slope stability factor shall be provided with the stability analysis. Seepage and piping through the berm or dam and erosion should be of major concern when specifying fill/soil type, placement methods, and compaction.

i. The City Engineer or designee shall require field density tests and these tests shall be made in accordance with FDOT standards and reported in writing to the City Engineer or designee.

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ii. Avoid planting woody species with developed root structures on embankment berms, as this can cause piping and geotechnical failures.

4. Freeboard

a. A minimum freeboard of 6 inches shall be provided for all retention/detention areas.

b. Underground stormwater facilities can utilize areas within the project watershed to accommodate the 6 inches of required freeboard if this freeboard area is at least 5 feet from the property boundary.

i. If freeboard is being provided within the project watershed, identify where the storage will occur on a scaled plan, the volume of that storage, and the maximum depth of staged water that will occur in those areas.

ii. The freeboard area depicted must include enough grade information to demonstrate that the area of storage is occurring at a distance of at least 5 feet from the property line. In addition, the plans must provide enough grading detail to show where discharge would occur in the event freeboard is exceeded.

5. Finished Floor Elevation Finished floor elevations of structures adjacent to or that could potentially be impacted by the stormwater management facility as determined by the City Engineer shall be elevated at least one foot above the design high water elevation or base flood elevation (whichever is higher) so that the structure is adequately protected from a basin overtopping event. All stormwater management systems shall be evaluated for the 100-year critical storm event to establish the minimum finished floor elevation.

6. Sumps

a. Sumps within stormwater management facilities are discouraged. Sumps within stormwater management facilities will only be allowed due to cover issues and minimum pipe slope/velocities. The bottom elevation of the sump shall be a minimum of 12 inches above the seasonal high-water table. When sumps are utilized for dry detention facilities, the bottom elevation of the sump shall be placed up to one foot below the control elevation.

i. Sumps within stormwater management facilities intended to be dedicated to the City for any type of maintenance will not be accepted.

7. Retaining Walls

a. The following requirements apply to retaining walls or near-vertical soil retaining structures used to form stormwater management facilities or portions of stormwater management facilities:

i. Fencing or protective barriers may be required as determined by the City Engineer or designee.

ii. The wall shall be designed with materials that prevent sediment seepage into the stormwater management facility and that do not require regular maintenance to function properly.

iii. Railroad ties, wooded planks, and other similar materials should not be used within stormwater management facilities.

iv. Sufficient access for maintenance equipment is required in accordance with the requirements of this chapter.

b. For “Designs by Others”, retaining walls constructed with a drain shall ensure that the drain is at minimum two (2) feet away from stormwater basins to ensure water quality criteria is met.

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8. Stabilization All sloped areas within stormwater basins and swales/ditches, 3:1 or greater, shall be sodded.

9. Pre-Treatment Best Management Practice (BMP) Oil/water separator or comparable BMP technology is required for pre-treating runoff from vehicular traffic areas associated with the following practices:

a. Car washes;

b. Auto or marine paint and body shops;

c. Auto, recreational vehicle, commercial truck, tractor-trailer, farm tractor, heavy machinery, or small engine parts, service and repair operations;

d. Automotive fleet operations;

e. Junkyards and salvage yards; and

f. Gas stations, including convenience stores with gas pumps.

10. Chlorinated Pool Discharges Chlorinated pool water is not allowed to be discharged into stormwater management systems connected to the City’s storm sewer system.

3.5 Water Quality Standards

Developments within the City of Gainesville shall follow the water quality treatment volume criteria in Table 3-1.

3.5.1 Water Quality Treatment Volume

Table 3-1. Water Quality Treatment Volume Criteria

Facility Off-line On-line

Dry Retention, Underground, Exfiltration Systems)

Greater of 0.5" of runoff from Drainage Area or 1.25" of runoff from impervious area

Off-line + 0.5" of runoff from Drainage

Area

Dry Detention Greater of 1" of runoff from Drainage Area or 2.5" of runoff from impervious area

N/A

Wet Detention Greater of 1" of runoff from Drainage Area or 2.5" of runoff from impervious area.

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3.5.2 Water Quality Recovery

1. The water quality treatment volume shall be recovered within 72 hours for dry systems and one-half of the volume shall be drawn down within 24 to 30 hours for wet systems.

2. All percolation rates shall have a Factor of Safety of 2 applied for all stormwater calculations and modeling.

3. A mounding analysis of the 100-year critical events must be provided for all systems using infiltration to demonstrate recovery.

3.6 Stormwater Quantity Criteria

3.6.1 Design Storm Events

Developments within the City of Gainesville shall use the design rainfall in Table 3-2 in the design of stormwater management systems. The FDOT Zone 5 rainfall curves shall be used to determine the rainfall distribution.

3.6.2 Levels of Service for Stormwater Quantity

Developments within the City of Gainesville shall use Design Discharge Conditions Table 3-3 in the 100-year critical events to demonstrate post < pre criteria for rates in open watersheds and rates and volumes in closed watersheds.

Table 3-3. Design Discharge Conditions

Basins Frequency Duration

Discharge Rate Discharge Volume

Open Basin 100-year critical events Post less than or equal to Pre N/A

Closed Basin 100-year critical events Post less than or equal to Pre Post less than or equal to Pre

Table 3-2. Design Storm Events

Return Period (Years)

Design Rainfall (inches) min min min min* hr* hr* hr hr* hr hr*

3 1.05 1.33 1.93 2.6 3.2 3.8 4 4.48 4.68 6

10 1.19 1.54 2.31 3.2 4 4.8 5.1 5.84 6.24 7.92

25 1.34 1.74 2.66 3.6 4.4 5.28 5.76 6.56 6.96 8.64

50 1.43 1.88 2.9 3.95 4.8 5.92 6.48 6.96 7.92 9.6

100* 1.53 2.03 3.11 4.4 5.4 6.72 7.2 8 8.76 11.04 *Storms required for critical event analysis for proposed stormwater basins.

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3.6.3 Volume Requirements – Closed Basin Criteria

Within a closed basin, systems must be designed to retain any increase in volume of runoff over the predevelopment volume for a 72-hour period under all 100-year storm events.

3.6.4 Tailwater

Tailwater condition for the design of the storm drain systems and for stormwater basin outfalls shall be evaluated as part of the design process.

1. Utilize the FDOT Drainage Manual for guidance on accounting for tailwater impacts.

3.6.5 Lane Spread

Lane spread shall be calculated using FDOT criteria considering the 4 inch per hour or 10-year frequency storm as noted in Chapter 3.9.1 of the FDOT Drainage Manual. Spread criteria shall be consistent with the FDOT Drainage Manual except for:

1. Minor/Major Local Roads (Table 4-1).

a. The allowable lane spread can potentially be to the crown of the road on a case by case basis if approved by the City Engineer.

3.6.6 System Recovery

1. Where systems are designed for reducing post-development peak rate discharge and volume, the outlet and regulation schedule should be designed to provide necessary design detention and retention storage within the times specified by the applicable water management district for its design storm events and 30 days following the City’s 100-year critical events.

2. All percolation rates shall have a Factor of Safety of 2 applied for all stormwater calculations and modeling.

3. A mounding analysis must be provided for all systems using infiltration to demonstrate recovery and horizontal extent of mounding. Mounding analysis must account for other adjacent or nearby systems or properties. See previous reference to mounding analysis in Chapter 3.4.3 2. c. iv.

3.7 Floodplains and Floodways

3.7.1 100-year Floodplain In general, a loss of onsite floodplain storage will result in an increase in the offsite floodplain. As such, developments that encroach into a 100-year floodplain as designated by FEMA and the City of Gainesville, or any other determination by a jurisdictional authority shall demonstrate that the loss of onsite storage will not cause adverse offsite impacts to the floodplain. Additionally, the base flood elevation and the finished floor elevations for existing and proposed structures must be identified for projects located within the floodplain. Any development within a 100-year floodplain shall not increase the base flood elevation.

3.7.2 10-year Flood Channel No permanent structures or fills shall be allowed in the 10-year flood channel except structures and fills designed for flood prevention and control, streets, bridges and sanitary sewer lift stations and utility lines. Structures that are permitted in the 10-year flood channel shall demonstrate that no adverse impacts result from placing the structure within the 10-year flood channel (i.e., there

City of Gainesville Engineering Design & Construction Manual 14 is no increase in the elevation and limits of the 10-year flood channel or floodplain and no changes to the upstream or downstream 10-year flood channel or floodplain).

3.7.3 Critical Facilities

New Class III and IV critical facilities, as defined by the Florida Building Code, shall be located outside of areas with a floodplain subject to a 0.2% or greater chance of flooding (or 500 year flood).

3.7.4 Compensating Storage

Land use activities that do not meet the thresholds for a stormwater analysis shall minimally be required to demonstrate one-for-one compensating storage, to be reviewed and approved by the City Engineer.

3.7.5 Letter of Map Change

When proposed improvements associated with site development encroach into a flood hazard zone, it shall be necessary for the applicant to file a letter of map amendment or revision with FEMA. Provide proof of application prior to final site acceptance by Public Works.

3.8 Stormwater Conveyance

All conveyance systems shall conform to the FDOT Drainage Manual and the Level of Service (LOS) Criteria in Table 3-4.

Table 3-4. LOS Criteria

Type of Storm Frequency

Storm Sewer Systems (Internal to Development) 3-year

Minor/Major Local Street Minor Local Collector

10-year

Side Drain / Driveway Culvert 10-year

Major Local Collector 50-year

Minor / Principal Arterials 100-year

Cross Drains (including culverts, bridge-culverts, and bridges)

FDOT Drainage Manual

Open Channel FDOT Drainage Manual

1. Wet piping systems are not allowed in public rights-of-way and discouraged in private systems. The City Engineer must approve wet piping systems.

2. The rainfall intensity will be determined from the IDF curve for Zone 5 at the calculated time of concentration.

3. Hydraulic Grade Line (HGL) Standard: The HGL must be 12” below inlet top of grate or 12” below theoretical gutter elevation as applicable. For Type E or F structures, this is 13.5”.

4. Tailwater condition for the design of the storm drain systems shall be evaluated as part of the design process. Utilize the FDOT Drainage Manual for guidance on accounting for tailwater impacts.

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3.8.1 Subdivisions – Rear lot Drainage

Any subdivision proposed for City maintenance, whether road/storm sewer or road/storm sewer/stormwater pond maintenance, cannot incorporate rear lot drainage. If rear lot drainage is incorporated, the system will be a privately maintained system, including for functionality.

3.8.2 Closed Conveyance Systems

1. Inlets

a. All inlets with grates shall be per FDOT standards.

b. Provide documentation that the inlets selected can receive the calculated flow estimated.

c. Curb inlets are not allowed at pedestrian crossings or within the radius of intersections.

d. A new structure shall be provided at any change in alignment and elevation of pipe.

e. Elliptical pipes are permitted.

f. Ram-neck connections are not permitted.

g. No sumps are allowed on wet piping systems in public rights-of-way.

h. The maximum spacing of manholes and inlets on pipe runs are shown in Table 3-

5 based on operations and maintenance requirements. Spacing of inlets shall be based on spread calculations.

i. Pre-cast structures are preferred. All structures that are delivered in sections shall have gaskets and interlocking sections to minimize seepage.

Table 3-5. Maximum Manhole and Inlet Spacing

Pipe Size Maximum Spacing

15 to 18 inches 300 feet

Greater than 18 inches to 60 inches 400 feet

Greater than 60 inches 500 feet

2. Pipes

a. The minimum pipe size shall be 15 inches or equivalent in all roadways public or private.

b. All pipes within City right-of-way shall be reinforced concrete or polypropylene meeting FDOT specifications (latest edition), have a 100-year design service life, and be from an FDOT-approved production facility.

c. Stormwater pipes shall have a minimum separation of 3 inches from outside of the pipe to any other utility pipe or structure.

3.8.3 Open Conveyance Systems

1. Roadside swales may be provided in lieu of curb and gutter as long as all the specific requirements this manual can be met.

2. Minimum allowable ditch and swale grades shall be in accordance with the FDOT

Drainage Manual.

3. Maximum side slopes on all ditches are 4:1(H:V). Front and back slopes shall also be in compliance with the Florida Greenbook. Steeper slopes may be reviewed and approved on a case-by-case basis by the City Engineer.

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4. To prevent erosion in ditches all swales shall be sodded to one foot past the top of bank in addition to meeting the requirements in the FDOT Drainage Manual.

5. Roadway spread within gutter and travel lane shall conform to the FDOT Drainage Manual and the LOS criteria in Table 3-4.

6. Drainage easements in addition to ROW width shall be sufficient to accommodate all portions of the public stormwater management system facilities and to provide access for the facility maintenance. Such easements shall be dedicated to the City of Gainesville or to a recognized entity that shall be responsible for the maintenance of the easement. Where drainage facilities serve private streets, the easement or designated area reserved for stormwater management facilities shall be sufficient in width to accommodate all portions of the stormwater management system facility and to provide for access to maintain the facility. Such easements shall be dedicated to a responsible private maintenance entity.

7. Open drainageways (ditches) will not be permitted in or within 100 feet of any land designated as a residential district as defined in the Land Development Code, Sections 30-2.1 and 30-4.1, and any land in actual use or zoned for use as a school, unless it can be established to the satisfaction of the City Engineer that the open drainage way will appear and function as a natural watercourse and will not require significant maintenance. Any permitted open drainageways shall be designed to present no unreasonable hazard to life, the health of the public and nearby property residents, and to be protected against scour and erosion.

3.9 Geotechnical Criteria

All basins shall require geotechnical borings. Documentation of the geotechnical parameters shall be submitted to the City by a licensed geotechnical engineer. Methods of testing should be done in accordance with the appropriate water management district standards (SJRWMD Permit Information Manual or the SRWMD Applicant’s Handbook Volume II). The number of borings required shall be in accordance with Section 26.4 of the SJRWMD Applicant’s Handbook:

Regulation of Stormwater Management Systems Chapter 40C-42 F.A.C.

If a basin’s percolation occurs over different soil layers, each layer must be tested for permeability.

A soil cross section must be provided that shows the stormwater basin top, bottom modeled seasonal high groundwater table and modeled base of aquifer.

See Section 8.7 for additional geotechnical criteria during construction.

3.10 Water Management District Criteria

All stormwater basins shall be designed in accordance with the criteria of the appropriate water management district. See SJRWMD Permit Information Manual or SRWMD Applicant’s Handbook Volume II. Applications must include demonstration the criteria are met.

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3.11 Stormwater Pollution Prevention Plan

An erosion and control plan shall be developed and submitted in accordance with the Florida Department of Environmental Protection’s requirements of Rule 62-621.300(4) National Pollution Discharge Elimination System (NPDES) Generic Permit for Stormwater Discharge from Large and Small Construction Activities.

3.12 Erosion and Sedimentation Control

3.12.1 Key Criteria

Construction plans shall provide notes for the Contractor to outline key criteria including but not limited to:

1. Best Management Practices (BMPs) to be utilized,

2. Timing of BMP Installation,

3. Installation Details for BMPs,

4. Permanent and Temporary Stabilization Measures,

5. Inspection of BMPs,

6. Maintenance of BMPs,

7. Final Site Stabilization and BMP removal.

3.12.2 Additional Requirements

1. Erosion and perimeter controls shall be used to prevent runoff, and/or disposition of sediment from the site and shall be regularly inspected and maintained during construction.

2. Sites are required to control waste such as building materials, concrete truck washouts, chemicals, litter, and sanitary waste.

3. Failure to install or maintain erosion, perimeter, and waste controls shall result in enforcement, up to and including an order to stop all work until site is in compliance.

3.13 Karst Areas and High Aquifer Vulnerability Areas

All stormwater management facilities and systems shall be designed and constructed to ensure that adequate treatment of stormwater runoff is provided prior to this runoff being discharged to the aquifer. The stormwater management facility and system shall be designed to prevent the formation of sinkholes. A map of the most recent Sensitive Karst Area can be obtained from the water management district. SJRWMD provides a map in its Permitting Information Manual (Figure 13.0-3). Section 5.9 of the SRWMD Environmental Resource Permit Applicants Handbook Volume II provides guidance on its Sensitive Karst Area Design Criteria.

Stormwater management facilities and systems located in sensitive karst areas as delineated by the appropriate water management district shall adhere to the minimum following design standards:

1. A minimum of 3 feet of unconsolidated soil material is required between the surface of the limestone bedrock and the bottom and sides of the stormwater management facility. The City Engineer shall approve the type of excavation and backfill material that will be used to meet these criteria.

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2. Stormwater management facilities shall be designed to be as shallow as possible with horizontal bottoms. Deeper areas shall not be allowed in the bottom of the facility unless approved by the City Engineer.

3. To prevent the formation of sinkholes, the maximum facility depth shall be ten (10) feet.

4. The stormwater management facility side slopes, bottoms and areas adjacent to the facility that were disturbed or altered during construction shall be fully vegetated and stabilized.

5. All fill material used onsite shall be free of phosphatic Hawthorn Group sediments or other phosphorous rich materials that may leach phosphorus causing surface water quality degradation and lake eutrophication.

6. Any excavation that would lead to exposure of Hawthorn Group sediments or other phosphorus rich materials that could leach and adversely impact groundwater or surface water shall be mitigated by covering, backfilling or using other techniques to prevent phosphorus leaching.

7. Utility lines shall not be installed beneath stormwater basins in karst sensitive areas unless approved by the City Engineer or designee and GRU. Any lines for temporary irrigation of vegetation in and around stormwater management systems shall be installed to minimize excavation in karst sensitive areas.

3.14 Stormwater Management Utility

All development plans shall include on the cover sheet the following information under the heading “Stormwater Management Utility Data”:

1. Total Project Impervious Area

a. All project impervious located within the project parcel(s) and in the right-of-way

(sidewalks, driveways, etc.).

2. Total Site Impervious Area for SMU Determination

a. Includes all the impervious proposed on the project parcel(s) plus the driveway impervious in the right-of-way.

3. Total Semi-Impervious Area (i.e., grass parking)

4. Table containing the following information for each stormwater management facility:

a. SMF ID

b. Lowest Discharge Elevation (ft)

c. Retention Volume Below Lowest Discharge Elevation (cf)

d. Retention Area at Lowest Discharge Elevation (ft)

3.15 Operation and Maintenance

3.15.1 Accessibility

1. Reasonable maintenance access to all stormwater management facilities shall be provided.

2. The maintenance path shall have a minimum cleared width of 5 feet, a maximum slope of 8H: 1V, and be stabilized with grass.

3. A driveway apron to access into stormwater management facilities for maintenance/ larger equipment is required for ponds intended to be maintained by the City for functionality.

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4. The sidewalk in maintenance access ways to stormwater basins or facilities shall be a minimum of 6 inches thick.

5. Stormwater management facilities within subdivisions or that are maintained by the City shall provide a minimum cleared maintenance path width of 15 feet.

a. This includes facilities in subdivisions that are intended to be maintained by the

City for functionality.

3.15.2 Operation & Maintenance Overview / Manual

1. Maintenance Entity

The entity responsible for all maintenance on the stormwater structures and facilities shall clearly be identified with the following information through a letter to the Public Works Department Director, the subdivision plat or the approved site plan.

a. Name of the entity.

b. Point of contact for the entity. A position title can be used.

c. Address of the entity.

d. Phone number of the entity.

2. Operation & Maintenance Overview / Manual An Operation & Maintenance (O&M) Overview / Manual is to be provided that outline the following:

a. Facility Description

i. Brief description of the stormwater management system.

b. Description of maintenance required for major components of the stormwater management system. Describe routine maintenance for:

i. Stormwater Basins

ii. Erosion Control

iii. Swale/Ditch

iv. Culverts, Pipes and Structures

c. Outline frequency of inspections for major components of the stormwater management system.

d. Provide guidance for sinkhole repairs.

e. Illicit Discharges

i. Outline best management practices (BMPs) for activities on the operational site that could potentially impact the stormwater system or affect downstream water quality. This would include items such as on-site pools, pet waste management, sidewalk or pavement washing activities, a dumpster in disrepair, etc. A reference to the Clean Water Partnership of Gainesville brochures on BMPs can be utilized.

3. Long Term Operation & Maintenance

a. The O&M entity shall provide routine maintenance of all components of the stormwater management system to remove trapped sediments and debris.

Removed materials shall be disposed of in a landfill or other uplands in a manner that does not require a permit under Chapter 62-330, F.A.C., or cause violations of state water quality standards.

b. The O&M entity shall inspect the stormwater or surface water management system after the completion of construction per the Water Management District Requirements and copy the inspection reports to Public Works Stormwater.

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c. Once a system has been constructed and is in its O&M phase, City staff shall be granted access to inspect stormwater management systems to ensure compliance with permitted conditions.

Chapter 4 – Roadway Design

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4. Roadway Design

4.1 Objective

These roadway design standards demonstrate the City’s commitment to the provision and maintenance of a safe, accessible, and integrated transportation system. Road design shall prioritize the implementation of Vision Zero principles to maximize safety and prevent incidence of severe crashes, while balancing the needs of all users including drivers of vehicles, bicyclists, pedestrians, and transit riders. Designs shall be based on functional classification, context classification and design speed. Other mitigating factors such as demand, existing conditions, land use, environment and costs, must also be considered.

4.2 Governing Standards

Roadways shall be designed and constructed in accordance with the applicable sections of the Florida Greenbook, the FDOT Design Manual, FDOT Standard Plans, the MUTCD, the Americans with Disabilities Act and the Public Right-of-Way Accessibility Guidelines “PROWAG” except as modified herein. In the event it is necessary to deviate from the standards referenced in this chapter, a design variance or exception is required.

4.3 Roadway Classification

All streets shall be designed in accordance with the Street Types listed in the Subdivision section of the City’s Land Development Code. For the purposes of this manual, utilize Table 4-1 to correlate Street Types to Functional Classifications listed in the Florida Greenbook. Classifications and Street Types referenced in this manual are defined in accordance with the Florida Greenbook.

Table 4-1. Roadway Classifications

Land Development Code Street Type

ADT

Regulating Florida

Greenbook Classification

Minor local street Less than 800 Local

Major local street 800 to 1,200 Local

Minor local collector 1,201 to 3,200 Local

Major local collector 3,201 to 7,000 Collector

Minor arterial 7,001 to 12,000 Collector

Principal arterial Over 12,000 Arterial

4.4 Lane Widths

Travel lanes shall be designed to safely and cost-effectively accommodate vehicular, transit, and cycle travel. Travel lanes shall be 10’ wide unless mandated otherwise by law. Travel lanes may be reduced to 9’ wide when justified and approved by the City Engineer. Where there are high volumes of transit or other large vehicles, travel lanes may be a minimum of 11’ wide. Travel lanes shall not exceed 11’ wide.

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4.5 Drainage

Stormwater design related to roadways shall adhere to the design criteria established in Chapter 3 Stormwater Management.

4.6 Intersection Design

4.6.1 Type Selection

Roundabouts are the preferred method of intersection control and shall be utilized as opposed to signal control. When new traffic signal is warranted or reconstruction of a traffic signal is necessary, a roundabout shall be constructed unless study is provided in accordance with Chapter 6.

4.6.2 Roundabouts

Roundabouts may be installed in all areas; mini-roundabouts (as defined by NCHRP Report 672) may be installed within roadways projected to carry less than 1,200 ADT.