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STORMWATER MANAGEMENT REPORT

STORMWATER MANAGEMENT REPORT

GOLDEN GLADES INTERCHANGE PD&E STUDY From SR 826/Palmetto Expressway Eastbound to I-95 Northbound

Miami-Dade County, Florida

Financial Management Number: 428358-1-22-01 Efficient Transportation Decision Making (ETDM) Number: 11300

Prepared for Florida Department of Transportation - District Six

Miami, Florida

Prepared by:

Stantec Consulting Services, Inc.

901 Ponce de Leon Boulevard, Suite 900 Coral Gables, Florida 33134

Stantec.com

April 2014

Golden Glades Interchange PD&E Study

From SR 826/Palmetto Expressway Eastbound to I-95 Northbound

Golden Glades Interchange – Stormwater Management Report ii

EXECUTIVE SUMMARY

This report provides the drainage documentation required to support the Project

Development and Environment (PD&E) Study prepared for the Golden Glades Interchange

(GGI) project area. This report identifies possible locations for stormwater treatment

ponds. In addition, it also evaluates the Right-of-Way (R/W) needed to accommodate the

stormwater management facilities.

The purpose of this project is to provide a system-to-system connection for the SR

826/Palmetto Expressway eastbound to I-95 northbound movement and to improve the

Turnpike southbound to I-95 southbound connection. The ultimate phase will evaluate a

system-to-system connection between new express lanes on SR 826/Palmetto Expressway

and the existing 95 Express Lanes System. The GGI is located in northeastern Miami-Dade

County, Florida. The study area covers approximately 512 Acres and is located in Section

13, Township 52 South and Range 41 East.

Discharge from the study area is bifurcated by the South Florida Rail Corridor (SFRC).

Runoff from the area north of the SFRC ultimately drains northwesterly, within the Turnpike

swales, towards the C-9 Canal. The area south of the SFRC generally drains south, within

2-72” asphalt coated ultra-flow metal pipes under I-95, towards the C-8 Canal. The project

area was divided into seven main drainage systems. The naming convention was chosen so

that the first two characters represent the receiving water body followed by an abbreviation

of the general location of the system. The western portion of the study corridor is within

the Anodyne contamination plume. A one-mile buffer around the contamination plume

covers most of the study area. The Florida Department of Environmental protection (FDEP)

discourages the use of wet ponds or exfiltration trenches within one mile of a superfund

site. As such, water treatment facilities proposed by this study, which fall within the 1-mile

Anodyne buffer, consist of dry-retention and/or dry-detention.

Stormwater management systems proposed by this study meet current water quality

standards as set forth in Chapter 62-302 of the Florida Administrative Code. The approach

to meeting water quality requirements is to provide treatment for the increase in impervious

area and restore or replace existing treatment facilities impacted by this project. This

approach was discussed with SFWMD during an interagency monthly meeting held on

September 20th 2012.



Golden Glades Interchange – Stormwater Management Report iii

TABLE OF CONTENTS

SECTION PAGE

EXECUTIVE SUMMARY ............................................................................................ ii

TABLE OF CONTENTS .............................................................................................. iii

LIST OF TABLES ..................................................................................................... vi

1. INTRODUCTION ................................................................................................. 1

1.1 Project Description and Location .................................................................... 1

2. DATA COLLECTION ............................................................................................ 2

2.1 Vertical Datum ............................................................................................ 2

2.2 Regional Watershed and Receiving Waterbodies ............................................... 2

2.3 Seasonal High Ground Water Table ................................................................. 3

2.4 Soil Properties ............................................................................................. 4

2.5 Wellfields .................................................................................................... 5

2.6 Existing Drainage Concerns ........................................................................... 5

3. DESIGN CRITERIA ............................................................................................. 6

3.1 Standards ................................................................................................... 6

3.2 Water Quality .............................................................................................. 8

3.3 Discharge Limitations ................................................................................. 10

4. PRELIMINARY DRAINAGE ANALYSIS ............................................................... 11

4.1 Stormwater Management Systems ............................................................... 11

4.2 System C8_I95-S ...................................................................................... 12

4.2.1 Existing Condition ............................................................................ 12

4.2.2 Ultimate Build Alternative ................................................................. 13

4.2.3 Interim Build Alternatives ................................................................. 14

4.3 System C8_PR ........................................................................................... 15




4.4 System C8_GGI ......................................................................................... 17



Golden Glades Interchange – Stormwater Management Report iv




4.5 System C8_I95-N ...................................................................................... 20




4.6 System C9_GGI ......................................................................................... 22




4.7 System C9_TPK ......................................................................................... 25




4.8 System C8_NW17th ................................................................................... 27




4.9 Drainage Analysis Summary ........................................................................ 29

5. FLOODPLAIN ................................................................................................... 31

6. CROSS DRAINS ................................................................................................ 32

7. WATERBODY CROSSINGS ................................................................................ 32

7.1 I-95 over C-8 Canal (Bridge No. 870348) ...................................................... 32

7.2 NW 167th Street over NW 17th Avenue Canal (Culvert Extension) ...................... 33

7.3 NW 165th Street over NW 17th Avenue Canal (Proposed Culvert) ....................... 34

8. PERMITTING ................................................................................................... 35

8.1 Existing Permits ......................................................................................... 35

8.2 Proposed Permits ....................................................................................... 37

9. CONCLUSIONS ................................................................................................. 37

10. REFERENCES ................................................................................................... 38



Golden Glades Interchange – Stormwater Management Report v

LIST OF FIGURES

FIGURE PAGE

Figure 1-1 Project Location ........................................................................................ 1

Figure 2-1 Regional Watersheds ................................................................................. 3

Figure 3-1 Anodyne Superfund Site Contamination Plume & Buffer ................................ 10

Figure 4-1 Stormwater Management Systems ............................................................ 12

Figure 4-2 Drainage System C8_I95-S ...................................................................... 13

Figure 4-3 Drainage System C8_PR .......................................................................... 15

Figure 4-4 Drainage System C8_GGI ........................................................................ 18

Figure 4-5 Drainage System C8_I95-N ...................................................................... 20

Figure 4-6 Drainage System C9_GGI ........................................................................ 22

Figure 4-7 Drainage System C9_TPK ........................................................................ 26

Figure 4-8 Drainage System C8_NW17th ................................................................... 28

Figure 5-1 FEMA Floodplain Map ............................................................................... 31

Figure 7-1 Bridge No. 870348 (I-95 over C-8 Canal) ................................................... 33

Figure 7-2 Culvert Extension (NW 167th ST Over NW 17th Ave. Canal) ............................ 34

Figure 7-3 Proposed Culvert (NW 165th ST Over NW 17th Ave. Canal) ........................... 35



Golden Glades Interchange – Stormwater Management Report vi

LIST OF TABLES

TABLE PAGE

Table 2-1 Datum Conversion from NGVD 29 to NAVD 88 ............................................... 2

Table 2-2 Percolation Rates within Project Area ............................................................ 4

Table 2-3 Soil Corrosion Properties ............................................................................. 4

Table 2-4 Miami-Dade County Soil Types within Project Area .......................................... 5

Table 3-1 Design Criteria .......................................................................................... 6

Table 3-3 SFWMD Water Quality ................................................................................ 9

Table 4-1 Drainage System Characteristics ................................................................ 29

Table 4-2 Preliminary Calculation Summary ............................................................... 30



Golden Glades Interchange – Stormwater Management Report vii

LIST OF APPENDICES

Appendix A: Figures and Maps

A-1: Project Aerial

A-2: USGS Quad Map

A-3: NRCS Soil Survey Maps

A-4: Miami-Dade County Average October Ground Water Level Map

A-5: Miami-Dade County Wellfield Map

A-6: FEMA Flood Insurance Rate Map

A-7: Vertical Datum Conversion

Appendix B: Calculations

B-1: Drainage Areas

B-2: Water Quality Treatment Calculations

B-3: Water Quality Impact Evaluation

Appendix C: Project Correspondence and Meeting Minutes

C-1: RER exemption email January 13th 2012

C-2: SFWMD Interagency Meeting April 19th 2012

C-3: SFWMD Interagency Meeting September 20th 2012

C-4: RER Meeting October 15th 2012

C-5: FDOT Maintenance Teleconference October 24th 2012

Appendix D: Geotechnical Data

D-1: Geotech Structural Report Excerpts

D-2: Geotech Percolation and Infiltration Report

Appendix E: Excerpts from Previous Projects

E-1: Drainage Map from SPN 87270-3418



E-4: Drainage Report from SPN 87270-3419



Golden Glades Interchange – Stormwater Management Report viii

Appendix E: Excerpts from Previous Projects (Continued)

E-5: Drainage Report from FPID 422796-2-52-01

E-6: Drainage Plans from SPN 87270-3451

E-7: Drainage Plans from FPID 415462-2-52-02

Appendix F: Excerpts from Previous Permits

F-1: SFWMD Permit 85-00070-S, Application X000013200

F-2: SFWMD Permit 85-00070-S, Application 090225-2

F-3: SFWMD Permit 13-01013-P, Application 070314-4

F-4: DERM Permit OF 401



Golden Glades Interchange – Stormwater Management Report 1

1. INTRODUCTION

This report provides the drainage documentation required to support the Project

Development and Environment (PD&E) Study prepared for the Golden Glades Interchange

(GGI) project area. Possible locations for stormwater treatment ponds, Right-of-Way (R/W)

needed to accommodate the stormwater management facilities and a preliminary hydraulic

analysis of the area are contained in this report.

1.1 Project Description and Location

The purpose of this project is to provide a system-to-system connection for the

SR 826/Palmetto Expressway eastbound to I-95 northbound movement and to improve the

Turnpike southbound to I-95 southbound connection. The ultimate phase will evaluate a

system-to-system connection between new express lanes on SR 826/Palmetto Expressway

and the existing I-95 Express Lanes system. The Golden Glades Interchange (GGI) is

located in northeastern Miami-Dade County, Florida (See Figure 1-1). The study area

covers approximately 512 Acres and is located in Section 13, Township 52 South and Range

41 East. A USGS quadrangle map of the study corridor is located in Appendix A.

Figure 1-1 Project Location




2. DATA COLLECTION

2.1 Vertical Datum

The primary vertical datum used in this report and the calculations is NGVD 29. This datum

was chosen due to the fact that all existing data for the interchange is in NGVD 29.

Moreover, government agencies such as the Army Corps of Engineers (ACOE), Federal

Emergency Management Agency (FEMA), South Florida Water Management District

(SFWMD) and Miami-Dade Department of Regulatory and Economic Resources (RER)

currently use NGVD 29. Where practical, elevations are shown in both NGVD 29 and NAVD

88 since NAVD 88 is the Florida Department of Transportation (FDOT) standard datum. The

vertical datum shift was identified for the approximate centroid of the study area by using

the National Geodetic Survey VERTCON online tool. Coordinates of the centroid are shown

below in Table 2-1. The datum shift used to convert NGVD 29 to NAVD 88 within the study

area is (-)1.562 feet. See Appendix A for National Geodetic Survey VERTCON datum shift.

Table 2—1: Datum Conversion from NGVD 29 to NAVD 88

Location Latitude Longitude Shift (ft)

Study Area Centroid 25° 55’ 40” 80° 12’ 37” (-)1.562

2.2 Regional Watershed and Receiving Waterbodies

The study corridor lies within South Florida Water Management District (SFWMD) Basins

C-7, C-8, and C-9 East (See Figure 2-1). Discharge from the study area is bifurcated by

the South Florida Rail Corridor (SFRC). Runoff from the area north of the SFRC ultimately

drains northwesterly, within the Turnpike swales, towards the C-9 Canal. The area south of

the SFRC generally drains south, within 2-72” asphalt coated ultra-flow metal pipes under

I-95, towards the C-8 Canal. An exception to this statement is the southwestern corner of

the project, which is north of the SFRC but drains into a local canal that runs along NW 17th

Avenue and discharges into the C-8 Canal.




Figure 2-1 Regional Watersheds

2.3 Seasonal High Ground Water Table

Geotechnical information provided by HR Engineering Services states that test borings,

conducted during 2012, showed groundwater levels varying from elevation 2.1 to 2.6 ft-

NGVD 29 (0.5 to 1.0 ft-NAVD 88). The geotechnical report recommended a Seasonal High

Ground Water Table (SHGWT) of 4.6 ft-NGVD 29 (3.0 ft-NAVD 88). A review of the

Miami-Dade County Design Standards indicates that the average elevation of the October

ground water table for the project area is approximately 2.5 ft-NGVD (0.9 ft-NAVD). As

such, the SHGWT value of 4.6 ft-NGVD 29, recommended by the geotech report, is

considered conservative and will be used in the preliminary drainage design for this study.

See Appendix D for the geotech reports and Appendix A for Miami-Dade County average

October ground water level.




2.4 Soil Properties

Five percolation tests (Exfiltration) and seven double ring infiltrometer tests (Infiltration)

were performed, during the geotechnical exploration, to estimate the hydraulic conductivity

of the soils within the project area. Two additional percolation tests, from the nearby

Turnpike Connector project, were also provided in the geotechnical report. Test results

indicate that the percolation rates are poor to moderate and increase with depth, as shown

in Table 2-2. The effective infiltration rate varies from 0.04 to 3.5 inches/hour for an

average of 1.5 inches/hour. Calculations conducted to support the preliminary drainage

analysis described in this report consider exfiltration trenches to be installed at a depth of

20-ft having a hydraulic conductivity of 1.5E-05 cfs/ft2-ft of head. Dry-retention pond

recovery will be estimated using an infiltration rate of 1.5 inches/hour. These values were

chosen as they are expected to yield reasonably conservative results.

Table 2—2: Percolation Rates within Project Area

Depth (ft) Hydraulic Conductivity (cfs/ft2-ft of head)

0 - 10 2.6E-06 to 3.2E-04

10 - 15 1.6E-06 to 2.3E-03

15 - 20 1.7E-05 to 2.4E-04

As an element of the geotechnical evaluation, soil and water samples were obtained to

identify the soil corrosion properties outlined in Table 2-3. Testing of the soil and water

samples revealed that drainage culverts will be subject to a moderately aggressive

environment.

Table 2—3: Soil Corrosion Properties

Resistivity (ohms-cm) pH Sulfates

(ppm) Chlorides

(ppm)

1,460-3,860 7.3-7.8 9-61 4-12




The geotechnical report for this project suggests that unsuitable materials are not

anticipated within the project area based on a review of the soil map published by the

United States Department of Agriculture (USDA). There are four general mapping units (soil

types), as shown below in Table 2-4. See Appendix D for the geotech reports and

Appendix A for the project soils map.

Table 2—4: Miami-Dade County Soil Types within Project Area

Map Unit

Symbol Map Unit Name Typical Profile

10 Udorthents, limestone substratum-

Urban land

0 to 55 inches: Extremely Gravely Loam

55 to 59 inches: Unweathered Bedrock

15 Urban land N/A

40 Pomello sand 0 to 80 inches: Sand

99 Water 100 percent Water

2.5 Wellfields

There are no wellfields within the project area. See Appendix A for a wellfield map of

Miami-Dade County.

2.6 Existing Drainage Concerns

The Study Team contacted FDOT District Six maintenance personnel to discuss maintenance

concerns as they relate to drainage. Items of particular concern were localized ponding in

the swales/infields or flooding in the travel lanes. Based on information obtained, incidents

of flooding have been reported at the NW 7th Avenue extension to US 441. Flooding at this

location has been reported as early as 2004 and as late as 2010. Most of the flooding

issues seem to be attributed to deficiencies in the drainage system as well as clogged

drainage inlets. See teleconference notes and correspondence located in Appendix C.

FDOT District Six drainage personnel have been made aware of the reoccurring ponding

taking place at the NW 7th Avenue extension to US 441. During the Final Design stage of

this project, drainage design engineers are advised to further explore existing flooding

conditions to ensure that they are corrected as part of the interim improvements proposed

for the interchange.




3. DESIGN CRITERIA

3.1 Standards

Drainage design and construction criteria for the proposed improvements will adhere to

FDOT Standards for the design of such roadways and will comply with the recommended

standard practices as set forth in Table 3-1.

Table 3—1 Design Criteria

DESIGN ELEMENT CRITERIA SOURCE

Design Frequency

Storm Sewer

- 10-Year design frequency standard (1, 8, 24-hour)

- Check 100-Year storm (1,8, 24 hour)

- 50-Year design frequency for interstate facility sag

vertical curves which have no outlet other than a

storm drain system

D.M. Section 3.3

Cross Drains 50-Year design frequency D.M. Section 4.3

Design Tailwater

All Conditions Conditions vary with outfall D.M. Section 3.4

Time Of Concentration (TOC) Minimum T.O.C. of 10 Minutes

Other T.O.C calculations to follow NRCS TR-55 D.M. Section 3.5.1

Pipe Slopes

Minimum Min. slope to produce v=2.5 ft/sec flowing full D.M. Section 3.6.1

Manning's "n" Coefficient

Pipes 0.012 (smooth pipes) 0.024 (corrugated pipe) D.M. Section 3.6.4

Asphalt (rough texture) 0.016 Asphalt Pavement S.D. Table 3-2

Grades

Longitudinal Gutter Grade minimum gutter grade is 0.3% D.M. Section 3.8.1

Spread Standards

Design Speed ≤ 45 Keep ½ lane clear D.M. Section 3.9

45 < Design Speed ≤ 55 Keep 8-ft of lane clear

Design Speed >55 No encroachment

Pipe Size And Length

Trunk Line 18-in Minimum Diameter. D.M. Section 3.10.1

Length Between Structure 18-in Pipe=300ft., 24in – 36in=400ft,>42-in =500ft D.M. Section 3.10.1

Exfiltration Trench

Pipe Diameter 24-in minimum D.M. Section 3.10.1






Exfiltration Trench (continued)

Pipe Lengths

Access through both ends: 300-ft 24-in to 30-in pipes;

400-ft for 36-in and larger pipes.

Access through only one end: 150ft 24-in to 30-in

pipes; 200-ft 36-in and larger pipes

D.M. 3.10.1

Pipe Perforations Perforated pipes preferred in District 6

E.T.R.M Section 3.1

Skimmers/Baffles Required at each entrance to exfiltration trench

Trench Width Minimum 4-ft , maximum 8-ft

Trench Depth Maximum of 20-ft

Drainage Structures 2-foot sediment sump for inlets and catch basins

Other District 6 Preferences FDOT District 6 Exfiltration Trench Reference Manual

Ground Water Clearance

Dry Retention Pond bottom minimum 1-ft above SHGWT B.M.P. Section VIII

Freeboard

Storm Drain

Hydraulic Gradeline Minimum 1-ft below theoretical

gutter elevation

1.13-ft below E.O.P. for Types E & F curb and gutter

1-ft below grate elevation for inlets Standard Index,

S.D. Section 5.0

Ponds Minimum 1-ft above peak design stage, measured

from the inside edge of the maintenance berm.

D.M. Section 5.3.4.2

Permanent Pool Pond Depth

Wet Detention 4-ft minimum depth, 8-ft maximum depth S.M.F. Section 3.1.1

Stormwater Management System

Water Quality Water quality standards, as set forth in Chapter 62-

302, Florida Administrative Code. V - IV Section 5.0

Discharge Limitations Historic Discharges, Post <= Pre V - IV Section 6.1

Bridge Clearances

Horizontal Center span – 25 feet clear bent spacing, measured

perpendicular to the channel.

Approach bents – 20 feet between faces of bents. V - V Section IX B

Vertical

6 feet above seasonal high optimum water control

elevation, or 2 feet above the design water surface,

whichever produces the greater elevation.

7 feet above mean high water for Miami-Dade Canals RER Meeting 10/15/2012






Bridge Clearances (continued)

Vertical 2 feet minimum clearance between design flood stage

and the low member of bridge to allow for debris

passage. 6 feet above Normal High Water for

controlled canals

P.P.M. 2.10.1

Abbreviations

D.M. FDOT Drainage Manual; January 2013

E.T.R.M FDOT District 6 Exfiltration Trench Reference Manual; January 2008

P.P.M. Plans Preparation Manual Volume 1, January 2012

S.D. FDOT Storm Drain Handbook; January 2012

S.M.F. FDOT Stormwater Management Facility Handbook; January 2004

V-IV SFWMD Permit Information Manual Volume IV; 2012

V-V SFWMD Permit Information Manual Volume V; 1999

B.M.P SFWMD Best Management Practices for South Florida Urban Stormwater Management Systems; April 2002

3.2 Water Quality

Stormwater management systems proposed by this study meet existing water quality

standards as set forth in Chapter 62-302 of the Florida Administrative Code. The approach


area and restore or replace existing permitted treatment facilities impacted by this project.

Table 3-2 summarizes the methodology used to calculate the treatment volume. An

emphasis was placed on providing treatment for the increase in impervious area rather than

providing treatment for the entire project area since the project is geometrically constrained

due to the linear nature of the facility and heavily urbanized areas surrounding the study

area. This approach will be followed for the increase in impervious area as it relates to the

total project area and not dependent on whether the increase in impervious area is due to

roadway widening or total road reconstruction, as discussed in the South Florida Water

Management District (SFWMD) interagency monthly meeting held on September 20th 2012.

See Appendix C for meeting minutes.




Table 3—2: SFWMD Water Quality

Type of Treatment Treatment Volume*

Wet-detention 2.5 inches times the increase in impervious area

Dry-detention 75% of wet detention volume

Dry-retention 50% of wet detention volume

*Note: SFWMD agreed to this approach due to corridor constraints.

During the development of the Contamination Screening Evaluation Report (CSER) for this

PD&E, a superfund site named Anodyne was identified. There is evidence that waste from

this site was discharged directly onto the ground. Furthermore, a 90-foot deep injection

well was allegedly used to dispose of spent solvents during the manufacturing phase of the

facility’s operation. The Anodyne contamination plume, as estimated in 2010 by the

TerranearPMC groundwater remediation study, extends into the western portion of the

study corridor. A one-mile buffer around the contamination plume covers most of the study

area, as shown below in Figure 3-1. The Florida Department of Environmental protection

(FDEP) discourages the use of wet ponds or exfiltration trenches within one mile of a

superfund site. As such, this study proposes dry-retention and/or dry-detention stormwater

treatment facilities for areas which fall within the 1-mile Anodyne buffer. The use of solid

pipe is FDEP’s preferred method of conveyance through contaminated areas. A Phase II

contamination study is recommended by the CSER to further quantify impacts to the project

due to the contamination from the Anodyne superfund site as well as other smaller

contamination sites within the study area. The CSER is prepared as part of the PD&E Study.




Figure 3-1 Anodyne Superfund Site Contamination Plume & Buffer

3.3 Discharge Limitations

As mentioned earlier in Section 2.2, the main receiving water bodies for this project are

the C-8 and C-9 Canals. According to the South Florida Water Management District

(SFWMD) Permit Information Manual, Volume IV, the allowable off-site discharge is

essentially unlimited by gravity connection for both the C-8 and C-9 Canals. Given the

preliminary nature of this study, the post development peak discharge has been attenuated

to predevelopment levels in order to avoid impacting adjacent land uses. This is particularly

important for systems discharging into the C-9 Canal, which must first flow through the

Turnpike’s existing system. The peak discharge for this project was estimated by using the

SCS runoff curve number method as described in Technical Release 55 (TR-55), published in

1986 by the United States Department of Agriculture (USDA).




4. PRELIMINARY DRAINAGE ANALYSIS

The preliminary drainage analysis conducted for this study consisted of evaluating the

project area to estimate the stormwater treatment and conveyance needs. The term

stormwater treatment is used throughout this section to refer to both the water quality and

peak attenuation requirements for a particular system. Typically the greater of the two is

provided to insure both requirements are met. Preliminary calculations show that for most

of the drainage systems in this project, the water quality and peak attenuation

requirements are very close. Preliminary calculations are located in Appendix B.

A summary of the analysis is provided in this Section. It follows the general format of

identifying existing conditions and then providing recommended improvements that would

be needed to accommodate additional runoff expected from the increase in impervious area

(pavement) in the post development condition. The analysis was conducted for the

roadway Ultimate Build Alternative and Interim Build Alternatives 3A, 3B, 3C, and 4 as

described in the Preliminary Engineering Report.

4.1 Stormwater Management Systems

The project area was divided into six main drainage systems, as shown below in

Figure 4-1. A seventh system around NW 17th Street was delineated based on potential

connectivity mitigations to SR 826/Palmetto Expressway; this is further explained in

Section 4.8. System limits were determined using existing drainage divides, which included

changes in elevation, transportation facilities and water bodies. The naming convention was

chosen so that the first two characters represent the receiving water body followed by an

abbreviation of the general location of the system. These systems combined have a total

area of 310 Acres.




Figure 4-1 Stormwater Management Systems

4.2 System C8_I95-S

4.2.1 Existing Condition

System C8_I95-S covers the area of I-95 between SR 916/NW 135th Street/Opa-Locka

Boulevard and the C-8 Canal. It is slightly over a mile long and within the 1-mile buffer of

the Anodyne contamination plume. Most of the drainage system consists of a network of

inlets and closed pipes connecting to a main outfall trunk line, which discharges into the C-8

Canal. There is, nonetheless, a segment of the southbound lanes, between NW 151st Street

and the C-8 canal, which has a small swale system with a 24-inch outfall pipe into the

canal. The main outfall trunk line in this system consists of concrete culverts, which

progress in size from 30-inch to 42-inch. The trunk line runs the length of the basin and is

on the west side of I-95 from Opa-Locka Boulevard to just south of NW 151st Street. It then

crosses under I-95 to connect to a 54-inch trunk line running east towards the canal. A

desktop review of the limited plans available for the area indicates that the 54-inch trunk

line services both I-95 and the adjacent residential community. The existing stormwater

management system, for this segment of I-95, appears to be a direct discharge system with

no formal water treatment being provided.




Figure 4-2 Drainage System C8_I95-S

4.2.2 Ultimate Build Alternative

Most of the proposed roadway work within Drainage System C8_I95-S, under the Ultimate

Build Alternative, is focused on the southbound lanes of I-95. Impervious area (pavement)

is being added in order to provide direct managed lane connections between Florida’s

Turnpike and I-95 Express southbound managed lanes. The new pavement will add

2.0 Acres of impervious area and increase the roadway footprint towards the west.

Preliminary calculations indicate that 0.21 Ac-ft of additional dry-retention will be needed to

meet water quality requirements. Several parcels, in the vicinity of NW 6th Court between

NW 146th Street and NW 151st, will be acquired to accommodate the roadway

improvements. A review of the proposed roadway geometry suggests that 1.8 Acres will be

available for storm water treatment in the area where parcels will be acquired. This area

can be used to accommodate a dry-retention pond with a bottom area of 1.2 Acres and a

depth of 1.0 ft to provide a dry-retention treatment volume of 1.2 Ac-ft. The pond would




provide 1.0 Ac-ft of surplus treatment since only 0.2 Ac-ft of treatment is required for this

system. Surplus treatment provided in this pond could be used to compensate for required

treatment in adjacent systems that also outfall into the C-8 Canal. This pond will need to

be connected to the system trunk line in order to provide an outfall for overflows into the

pond. A connection will have to be made to the trunk line before it crosses to the east side

of I-95 in order to avoid needing to Jack & Bore or needing to open trenching across both

lanes of I-95. It is anticipated that the surface drainage for the roadway can be

accomplished by extending the existing closed pipe system and placing inlets as needed to

control the spread. A note is made that contamination has been identified in the general

vicinity of the proposed dry-retention pond. The site is identified as Jimmy’s Shell located

at 14601 NW 7th Avenue and it poses a minimal potential of environmental impacts if

dewatering is needed during construction activities. See environmental documents for

specific contamination issues along the corridor.

4.2.3 Interim Build Alternatives

Under Build Alternative 3A, there is minor work occurring within Drainage System C8_I95.

The increase in impervious area is limited to the southbound lanes of I-95 between

NW 151st Street and the C-8 Canal. Preliminary calculations indicate that the impervious

area will increase by 0.4 Acres and will require 0.04 Ac-ft of dry-retention. This amount of

treatment is small enough that it can easily be accommodated in an adjacent system. In

the event that surplus treatment is not available in a nearby system, a small dry-retention

pond can be placed in the western swale of I-95, just north of NW 151st Street, to provide

the required water quality treatment. The western swale can accommodate a dry retention

pond with a bottom area of 0.3 Acres and retention depth of 1-ft to provide a dry-retention

treatment volume of 0.3 Ac-ft. Overflows into the pond can be discharged by using a

control structure connected to the existing 24-inch outfall pipe, which discharges into the

C-8 Canal.

Under Build Alternatives 3B and 3C, the proposed improvements are the same, within this

system, as in the Ultimate Build Alternative. As such, drainage improvements needed to

meet water quality requirements for Build Alternatives 3B and 3C are the same as what is

needed for the Ultimate Build Alternative in this drainage system.

For Build Alternative 4, the proposed improvements and added impervious area are the

same, within this system, as in Build Alternative 3A.




4.3 System C8_PR


System C8_PR consists of the Park & Ride, Municipal Parking facility and SR 9. The system

is bound by the South Florida Rail Corridor (SFRC) on the north and the Turnpike Connector

on the east, as shown in Figure 4-3. It is partially within the Anodyne contamination

plume and completely within the 1-mile buffer of the plume. Stormwater runoff from this

system is generally conveyed southeasterly through the Municipal Parking facility’s piped

drainage system. Ultimately, the runoff is discharged through a 42-inch culvert into the

adjacent drainage system (C8_GGI), which outfalls into the C-8 Canal. See Appendix E for

the Municipal Parking Facility drainage map (SPN 87270-3454-414). The existing

stormwater management system appears to be a direct discharge system with no formal

water treatment being provided.

Figure 4-3 Drainage System C8_PR





Roadway improvements proposed within Drainage System C8_PR, under the Ultimate Build

Alternative, are geared towards providing a direct connection between SR 9 and I-95 in the

northbound direction as well as widening the I-95 connector to facilitate movements from

the Turnpike and SR 826 onto I-95 southbound. The new pavement will add 2.3 Acres of

impervious area. Preliminary calculations indicate that 0.24 Ac-ft of dry-retention will be

needed to meet water quality requirements. The required treatment can be provided

through compensation in System C8_I95, which outfalls into the same receiving water body

and is anticipated to have surplus treatment capacity when the Ultimate Build Alternative is

constructed. In the event that surplus treatment is not available in C8_I95 or a nearby

system, a 1-ft ditch block can be provided before runoff enters the Municipal Parking

facility’s piped drainage system. This would result in the retention of runoff within the

southbound and northbound lanes of SR-9. Two small dry-retention ponds would be created

that would have a combined bottom area of 1.6 Acres and a treatment volume of 1.6 Ac-ft,

which exceeds the treatment volume of 0.24 Ac-ft required for this drainage system.

A surplus of 1.36 Ac-ft would be available to be used as compensation in an adjacent

system. Excess runoff into the ponds would overtop the ditch block and outfall through the

Municipal Parking facility’s piped drainage system. The minor stage, created in the

retention ponds, is not anticipated to impact the existing roadway base clearance since the

roads in this area are several feet above the existing ground level.


Within Drainage System C8_PR, Interim Build Alternatives 3A, 3B and 3C will widen the

Turnpike connector. Interim Build Alternative 3A will add 1.9 Acres of impervious area and

require 0.20 Ac-ft of dry-retention while both Interim Build Alternatives 3B and 3C will add

2.2 Acres of impervious area and require 0.23 Ac-ft of dry-retention. For Build Alternative

4, the proposed improvements and added impervious area are the same, within this system,

as in Build Alternative 3A. In all cases, the potential stormwater treatment methods

described for the Ultimate Build Alternative are applicable. Namely, using surplus treatment

in an adjacent drainage system or providing a 1-ft ditch block to create a treatment volume

of 1.6 Ac-ft.




4.4 System C8_GGI


System C8_GGI consists of the southern part of the Golden Glades Interchange (GGI). The

system is bound by the South Florida Rail Corridor (SFRC) on the north and the C-8 Canal

on the south, as shown in Figure 4-4. Most of this drainage system is within the 1-mile

buffer of the Anodyne contamination plume. This drainage system receives runoff from

System C8_PR as described in Section 4.3.1. A review of available plans and permit

information indicates that stormwater in this system is being collected and treated via

dry-retention in the various infield areas between ramps before being discharged to the

C-8 Canal.

The I-95 northern segment of this drainage system has two concrete storm sewer trunk

lines, which direct runoff south towards the GGI infield areas. One trunk line is located

under each of the outside shoulders. Both trunk lines begin as an 18-inch round culvert

near the northern limits of the drainage system and transition through several sizes of

elliptical pipe before discharging into the GGI areas. The trunk line, located under the

northbound outside shoulder ends as a 54-inch round culvert near NW 2nd Avenue while the

trunk line under the southbound outside lane ends as a 36-inch round culvert near the

infield area between I-95 and SR 9. Excess runoff generated within the interchange portion

of the system is generally conveyed south towards a double 72-inch asphalt coated metal

trunk line that is located under the southbound shoulder of I-95 between the Park & Ride

ramp and the C-8 Canal. See the drainage map for State Project 87270-3418

(Appendix E) for more information on the existing trunk lines.

The drainage report submitted to the Miami-Dade Department of Regulatory and Economic

Resources (RER), to obtain permit OF 401 for project 87270-3419, states that 15.97 Ac-ft of

retention/detention is being provided in the aforementioned infield areas. Improvements

that have occurred in this drainage system, since the RER permit was issued, have had little

impacts to the amount of impervious area or treatment volume. See Appendix F for

permit excerpts.




Figure 4-4 Drainage System C8_GGI


Proposed roadway improvements within Drainage System C8_GGI, under the Ultimate Build

Alternative, facilitate connections between the major roadways within this drainage system.

A new flyover ramp to connect SR 826 eastbound to I-95 northbound as well as various

widening and roadway realignments are being provided to meet this goal. The Ultimate

Build Alternative will add 6.0 Acres of impervious area to the drainage system. This will

require 0.63 Ac-ft of dry-retention to meet water quality. In the southern end of the

project, improvements to the I-95 southbound lanes will move the travel lanes towards the

west, which will result in the double 72-inch outfall pipes, and corresponding manholes,

being in the travel lanes. Relocation of the double 72-inch outfall pipes (appx. 1,400-ft) is

recommended to avoid having manholes in the travel lanes. Likewise, in the northern end

of the drainage system, a portion of the 54-inch trunk line (appx. 2,800-ft) will also need to




be relocated for the same reason since the I-95 northbound lanes will be shifted towards

the east to create a median area that will accommodate the managed lanes.

The control elevation for one of the existing dry-ponds, near the proposed flyover ramp, can

be raised by 0.5-ft to increase the treatment volume from 0.95 Ac-ft to 1.67 Ac-ft in order

to provide 0.72 Ac-ft of treatment volume, exceeding the required volume needed. The dry

pond is identified as Area 20 in the plans for project 87270-3419. A ditch block is currently

being used to provide the control elevation. It can be raised by adding more earth to the

ditch block and providing a concrete topping per SFWMD requirements. During final design,

a detailed infiltration analysis will be required to ensure the pond recovers within 24-hours

using the in-situ soil since an exfiltration trench to aid in pond recovery will not be allowed

because the dry pond is within the Anodyne 1-mile buffer. The roadway base clearance is

not anticipated to be impacted by the minor stage increase in Area 20.

An alternative approach to meet water quality requirements for this drainage system, under

the Ultimate Build Alternative, is to provide a dry retention pond within the infield area that

will be created between NW 7th Ave and the I-95 ramp. This approach would require a

careful review of existing contamination since the adjacent parcels in this area are currently

industrial. Should contamination be identified in the immediate area, a dry retention pond

poses a potential of displacing the contamination plume.


Within Drainage System C8_GGI, Interim Build Alternatives 3A, 3B, 3C, and 4 will add 0.4,

1.1, 3.6, and 1.0 Acres of impervious area, respectively. Interim Build Alternative 3A will

require 0.04 Ac-ft of dry retention. This small amount of treatment can easily be

accommodated in a nearby drainage system. Interim Build Alternatives 3B, 3C, and 4 will

require dry-retention treatment of 0.13, 0.38, and 0.13 Ac-ft respectively. The drainage

solutions discussed in Section 4.4.2 to meet water quality requirements for the Ultimate

Build Alternative would be applicable to Build Alternatives 3B, 3C, and 4. Any surplus

storage created during these interim phases would be available for the Ultimate Build

Alternative. All four Interim Build Alternatives would require the relocation of the double

72-inch outfall pipes, located in the southern end of the drainage system.




4.5 System C8_I95-N


System C8_I95-N spans from just south of NE 1st Avenue to NE 183rd Street (Miami Gardens

Drive). It is slightly less than a mile long and is outside of the Anodyne 1-mile buffer. This

drainage system consists of roadside swales on both sides of the roadway with equalizer

pipes connecting them and a retention area located in the western swale where I-95 turns

away from the South Florida Rail Corridor (SFRC). The retention area provides 0.35 Ac-ft of

dry-retention treatment. See the drainage report excerpts from FPID 422796-2-52-01,

located in Appendix E for more information on the existing retention area. In general

runoff is conveyed from the eastern swale to the western swale, which abuts the SFRC, and

runs south towards Drainage System C8_GGI. A note is made that the drainage report for

FPID 422796-2-52-01 states that the area served by this drainage system ultimately

discharges to the C-9 Canal; however a review of existing plans did not show a connection

to move runoff across NE 183rd Street. As such, the study team concluded that this

drainage system ultimately discharges south along the SFRC swale towards the C-8 Canal

rather than across NE 183rd Street towards the C-9 Canal.

Figure 4-5 Drainage System C8_I95-N





Under the Ultimate Build Alternative, within Drainage System C8_I95-N, proposed roadway

improvements provide an additional lane in each direction for the I-95 express lanes located

between the northbound and southbound lanes of the I-95 mainline. The express lanes are

accommodated by shifting out the mainline by approximately 14-ft on the west side and

19-ft on the east side. The Ultimate Build Alternative will add 2.2 Acres of impervious area

to the drainage system. In order to meet water quality, 0.23 Ac-ft of dry-retention will be

needed to account for the increase in impervious area and 0.18 Ac-ft will be needed to

offset encroachments into the existing retention area for a total of 0.41 Ac-ft of

dry-retention needed for this drainage system. Proposed roadway improvements will

greatly reduce or eliminate the existing swales being used for conveyance. A drainage trunk

line (appx. 2,500-ft of 42-inch) will be needed to replace the function of the swales.

Preliminary calculations indicate that the required 0.41-Ac-ft of dry-retention can be

provided by installing 2,000-ft of 20-ft deep exfiltration trench in series with the new trunk

line. The use of exfiltration trench in this drainage basin is acceptable because there is

limited R/W available for a dry pond, the drainage system is outside of the 1-mile Anodyne

contamination buffer and the anticipated exfiltration rate is 1.7E-05 cfs/ft2-ft of head.

A note is made that this basin is located near several isolated contaminated sites, according

to RER and FDEP records. See the Contamination Screening Evaluation Report (CSER) for

details of these sites.


Interim Build Alternatives 3A, 3B, 3C, and 4 will not add any additional impervious area to

Drainage System C8_I95-N. As such, no improvements are needed to this drainage system

under the interim build alternatives.




4.6 System C9_GGI


System C9_GGI consists of the northern part of the Golden Glades Interchange (GGI) and

an adjacent section of SR 826 (Palmetto Expressway), as shown in Figure 4-6. It is

partially within the Anodyne contamination plume and completely within the 1-mile buffer of

the plume. Stormwater runoff from the SR 826 segment of this system is conveyed east,

through trunk lines along both sides of the roadway, towards the GGI interchange infield

area. Runoff from the SR 826 southern swale is conveyed through a 24-inch x 38-inch

cross drain under SR 826 to unite with runoff from the northern swale and flows north along

the outside western Turnpike swale. In general, runoff generated within this drainage

system is directed towards the GGI infield areas and then north towards the Turnpike

(Drainage System C9_TPK) where it is conveyed by a 36-inch culvert through the Toll Plaza

area and ultimately into the C-9 Canal. Based on a review of available construction plans

and permitting information, the existing stormwater management system was not designed

to provide a specific amount of water quality treatment.

Figure 4-6 Drainage System C9_GGI





Proposed roadway improvements within Drainage System C9_GGI, under the Ultimate Build

Alternative, facilitate connections between the major roadways within this drainage system.

A new flyover ramp to connect SR 826 eastbound to I-95 northbound as well as widening of

the Turnpike connector to I-95 southbound are being provided to meet this goal. The

Ultimate Build Alternative will add 7.3 Acres of impervious area to the drainage system.

This will require 0.78 Ac-ft of dry-retention to meet water quality.

Proposed right-of-way acquisition of the warehouse area located in the Sunshine Industrial

Park found in the southwest quadrant of the Golden Glades Interchange (GGI) can provide

an appropriate location for water quality treatment. The proposed right-of-way acquisition

area is part of Interim Build Alternative 4, which will be used to provide for the NW 12th

Avenue on-ramp to SR 826 that continues connecting to I-95 southbound. This potentially

acquired area can accommodate a 4.2-Acre dry-retention pond. A depth of 0.5-ft can yield

2.10 Ac-ft of dry-retention treatment in the pond, thereby providing surplus treatment since

only 0.78 Ac-ft of treatment is required for this system. Surplus treatment provided in this

pond could be used to compensate for required treatment in adjacent systems that also

outfall into the C-9 Canal.

In order to get runoff from SR 826 to the proposed pond, trunk lines along both sides of

SR 826 will need to be extended (Appx. 1000-ft) and increased in size from 24-inch to

36-inch pipes. The north trunk line would need to cross under SR 826 and connect to the

south trunk line before reaching the SR 826/I-95 ramp. The final discharge point, of the

extended southern trunk line, would then be on the eastern side of the pond by the

SR 826/I-95 ramp. Excess runoff into the pond could be discharged using the existing

24-inch x 28-inch cross drain under SR 826 and then continue to flow north along the

outside western Turnpike swale towards the Turnpike Toll Plaza and eventually into the

C-9 Canal.

The required treatment volume for this drainage system can also be provided by creating a

dry-retention pond in the FDOT owned vacant lot, folio 34-2112-000-0083, located just

north of the railroad and bordered by both the SR 826 and Turnpike Connectors. This

vacant lot can accommodate a 3.6-Acre dry-retention pond while avoiding impacting the

Intelligent Transportation System (ITS) existing building on the site. A depth of 0.5 ft will

yield 1.80 Ac-ft of dry-retention treatment in the pond thereby providing surplus treatment




for this system. As mentioned before, available surplus treatment could be used to

compensate for required treatment in adjacent systems that also outfall into the C-9 Canal.

The aforementioned vacant parcel has been used in the recent past as a debris staging area

to facilitate disaster recovery after hurricanes. If the parcel is used as a stormwater

treatment pond, it will no longer be available for use as a debris staging area. See

Appendix C for notes of a teleconference held with the FDOT Maintenance Department.

In order to get runoff from SR 826 to the proposed pond, trunk lines will be needed along

both sides of the roadway to get the runoff to the Turnpike Connector infield area. The

trunk line on the north side will need to cross under the SR 826 mainline with a 42-inch

culvert (Appx. 300-ft). The trunk line on the south side will need to cross under the

SR 826/I-95 ramp with a 42-inch culvert (Appx. 150-ft). A 54-inch culvert (Appx. 250-ft)

will need to be installed under the Turnpike Connector to get the runoff from the infield area

to the pond. Given the relative height of the roadways to the surrounding ground, the Jack

& Bore installation method will likely be the most economical way to install the needed

culverts. Excess runoff into the pond can be discharged using the existing culverts to

convey runoff towards the Turnpike Toll Plaza and into the C-9 Canal.

A review of plans for proposed improvements to the Turnpike Toll Plaza (FPID 415462-2-52-

02) indicates that the existing 36-inch culvert, used as this systems outfall and described in

Section 4.7.1, will remain in operation after the improvements are constructed. See

Appendix E for excerpts from the plans for the Toll Plaza improvements.


Within Drainage System C9_GGI, Interim Build Alternatives 3A, 3B and 3C are focused on

widening the Turnpike Connector. Interim Build Alternative 4 also focuses on the Turnpike

Connector widening but is more distinctly concerned with maintaining the NW 12th St

on-ramp open, to SR 826. Interim Build Alternative 3A, 3B, 3C, and 4 will add 3.3, 3.6, 3.8,

and 3.5 Acres of impervious area, respectively. In all cases, the increase in impervious area

is roughly half of the increase estimated for the Ultimate Build Alternative. As such, the

potential stormwater treatment methods described for the Ultimate Build Alternative are

applicable. However, the dry-retention pond potentially available due to the prospective

right-of-way acquisition is only a viable treatment alternative for Interim Build Alternative 4.

A note is made that there is a potential of encountering contamination during pond

excavation due to the proximity of the Anodyne contamination plume and localized fuel




spills from traffic accidents in the interchange. Final designers of the selected interim build

alternative may want to limit excavation of the pond to the amount needed to meet water

quality requirements for the interim design rather than excavating the pond for the Ultimate

Build Alternative.

4.7 System C9_TPK


System C9_TPK covers the area of the Turnpike between the Toll Plaza and the Golden

Glades Interchange (GGI) loop ramps. It is approximately half a mile long and is within the

1-mile buffer of the Anodyne contamination plume. In general, runoff from this system is

conveyed along the Turnpike swales towards the C-9 Canal. This drainage system receives

runoff from Drainage System C9_GGI.

For the purposes of quantifying the increase in impervious area, the existing condition in

Drainage System C9_TPK was considered as the condition that will result once project FPID

415462-2-52-02 is constructed. A review of the proposed plans indicates that the existing

36-inch culvert, used as this system’s outfall, will remain in operation after the

improvements are constructed. See Appendix E for excerpts from the plans for the Toll

Plaza improvements.

Project FPID 415462-2-52-02 will convert the Toll Plaza to an All Electronic Tolling (AET)

facility. Consequently, the facility’s impervious footprint will be reduced allowing water

quality treatment to be provided in the roadside swales. Documentation for permit

13-01013-P, Application 070314-4, indicates that the water quality treatment provided in

the widened swales is to compensate future improvements to the Turnpike mainline. See

Appendix F for excerpts from permit 13-01013-P.


Proposed roadway improvements within Drainage System C9_TPK, under the Ultimate Build

Alternative, focus on widening the Turnpike connector to I-95 southbound. The Ultimate

Build Alternative will add 0.9 Acres of impervious area to the drainage system. This will

require 0.09 Ac-ft of dry-retention to meet water quality. The treatment volume

requirement for this system can be met by providing compensating treatment in Drainage

System C9_GGI, which has surplus capacity in its dry retention pond.




Figure 4-7 Drainage System C9_TPK


In this drainage system, roadway improvements proposed for Interim Build Alternatives 3A,

3B, 3C, and 4 are the same as the improvements proposed for the Ultimate Build

Alternative. As such, the potential stormwater treatment methods described for the

Ultimate Build Alternative are applicable for the interim build alternatives.




4.8 System C8_NW17th

This drainage system was delineated due to potential considerations in closing the NW 12th

Avenue on-ramp to SR 826. To maintain connectivity to SR 826, NW 17th Avenue would be

widened at the intersections to provide additional turn lanes and a new bridge at NW 165th

Street crossing the NW 17th Avenue Canal would be provided.


System C8_NW17th covers the area of NW 17th Avenue from NW 163rd Street to the

SR 826. It is slightly less than half a mile long and within the 1-mile buffer of the Anodyne

contamination plume. NW 17th Avenue is a County owned two lane undivided rural road

with no dedicated drainage system. There are, however, a few drainage inlets mostly along

the western swale area, as shown in Figure 4-8, but there is no formal conveyance system

to get runoff to the inlets. Construction plans for NW 17th Avenue were unavailable from

Miami-Dade County at the time of this study. The assumption is made that each of the

sparsely placed drainage inlets is connected to an exfiltration trench of undetermined length

and condition. The roadway is crowned such that runoff from the southbound lane

sheet-flows into a flat swale area shared with a residential neighborhood while runoff from

the northbound lane sheet-flows into a 15-ft wide flat strip of sod before overflowing into

the NW 17th Avenue canal. In general, runoff generated within this system overtops NW

17th Avenue and flows into the NW 17th Avenue canal, which discharges into the C-8 Canal.


In the Ultimate Build Alternative, the NW 12th Avenue on-ramp to SR 826 will remain open,

thus not requiring alternative connectivity to SR 826. There are no roadway improvements

proposed within Drainage System C8_NW17th under the Ultimate Build Alternative.


Roadway improvements proposed within this drainage system, under Interim Build

Alternatives 3A, 3B, and 3C will add 1.2 Acres and 0.13 Ac-ft of dry-retention will be needed

to meet water quality requirements. There are no roadway improvements proposed within

Drainage System C8_NW17th under Interim Build Alternative 4.

Options to meet water quality needs within this system are limited by the NW 17th Avenue

Canal on the east side and residential development along the west side. The geometric

constraints of the system area leave little room for stormwater treatment outside of the




roadway R/W. Furthermore, the use of exfiltration trench in this system is discouraged by

FDEP because it is within the 1-mile buffer of the Anodyne contamination plume. The

approach to meeting water quality is to provide as much treatment within the existing R/W

and provide compensating treatment in adjacent system to balance any shortcomings in this

drainage system.

A review of the potential roadway typical section for this system indicates a shallow ditch

that can be utilized as a dry-retention swale for the southbound lane. The ditch is divided

into two separate swales by NW 166th Street. Each swale would need an outfall into the NW

17th Avenue Canal and it would be beneficial to have an equalizer pipe connecting the

swales under NW 163rd Street. The ditches would have side slopes of 1H:3V, average width

of 5.5-ft, a combined length of 1,100-ft and a retention depth of 0.5-ft to provide 0.07 Ac-ft

of dry-retention treatment. The remaining 0.06 Ac-ft of dry-retention treatment would need

to be provided in an adjacent drainage system with surplus capacity. Coordination with

Miami-Dade Department of Regulatory and Economic Resources (RER) will be needed to

obtain a permit for construction of an outfall into the NW 17th Avenue Canal.

Figure 4-8 Drainage System C8_NW17th




4.9 Drainage Analysis Summary

Preliminary water quality and attenuation calculations performed for the study are located in

Appendix B. They are also summarized in Table 4-1 and Table 4-2, shown below. The

treatment/storage quantity provided for each receiving water body exceeds the required

amount for each Build Alternative.

Table 4—1: Drainage System Characteristics

Drainage

System

Build Alternatives

Existing Ultimate Interim

3A Interim

3B Interim

3C Interim

4

TA EI EP PI PP PI PP PI PP PI PP PI PP

C8_I95-S 39.4 30.7 8.7 2.0 6.7 0.4 8.3 2.0 6.7 2.0 6.7 0.4 8.3

C8_PR 36.3 18.7 17.6 2.3 15.3 1.9 15.7 2.2 15.5 2.2 15.5 1.9 15.7

C8_GGI 118.8 64.8 54.0 6.0 48.0 0.4 53.6 1.1 52.9 3.6 50.4 1.0 53.0

C8_I95-N 18.6 13.7 4.9 2.2 2.7 0.0 4.9 0.0 4.9 0.0 4.9 0.0 4.9

C8_NW17 4.0 2.0 2.0 0.0 2.0 1.2 0.8 1.2 0.8 1.2 0.8 0.0 2.0

C9_GGI 72.4 40.8 31.6 7.3 24.3 3.3 28.3 3.6 28.0 3.8 27.8 3.5 28.1

C9_TPK 19.9 11.1 8.9 0.9 8.0 0.9 8.0 0.9 8.0 0.9 8.0 0.9 8.0

NOTES:

1. TA = Total Area in drainage system (Ac).

2. EI = Existing Impervious Area (Ac).

3. EP = Existing Pervious area (Ac).

4. PI = Proposed Increase in impervious area (Ac).

5. PP = Proposed Pervious area (Ac).




Table 4—2: Preliminary Calculation Summary

Drainage

System

Build Alternatives

Ultimate Interim 3A Interim 3B Interim 3C Interim 4

WQ ATT PRV WQ ATT PRV WQ ATT PRV WQ ATT PRV WQ ATT PRV

C8_I95-S 0.21 0.20 1.20 0.04 0.04 0.30 0.21 0.20 1.20 0.21 0.20 1.20 0.04 0.04 0.30

C8_PR 0.24 0.23 1.60 0.20 0.20 1.60 0.22 0.23 1.60 0.22 0.23 1.60 0.24 0.23 1.60

C8_GGI 0.63 0.63 0.72 0.04 0.00 0.00 0.12 0.13 0.72 0.38 0.38 0.72 0.10 0.13 0.72

C8_I95-N 0.41 0.22 0.41 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 C8 NW17 0.00 0.00 0.00 0.13 0.11 0.07 0.13 0.11 0.07 0.13 0.11 0.07 0.00 0.00 0.00

C9_GGI 0.78 0.69 1.80 0.34 0.31 1.80 0.38 0.31 1.80 0.39 0.31 1.80 0.36 0.31 1.80

C9_TPK 0.09 0.08 0.00 0.09 0.08 0.00 0.09 0.08 0.00 0.09 0.08 0.00 0.09 0.08 0.00

Receiving Water

Body

Build Alternatives

Ultimate Interim 3A Interim 3B Interim 3C Interim 4

WQ ATT PRV WQ ATT PRV WQ ATT PRV WQ ATT PRV WQ ATT PRV C-8 Canal 1.48 1.28 3.93 0.41 0.35 1.97 0.67 0.67 3.59 0.94 0.92 3.59 0.34 0.37 2.62 C-9 Canal 0.88 0.77 1.80 0.43 0.39 1.80 0.47 0.39 1.80 0.49 0.39 1.80 0.45 0.39 1.80

NOTES:

1. WQ = Required treatment volume to meet water quality requirements (Ac-ft).

2. ATT = Required storage volume to attenuate peak discharge (Ac-ft).

3. PRV = Treatment/storage volume provided by proposed design (Ac-ft).

4. Treatment/storage quantity provided for each receiving water body exceeds the required amount.




5. FLOODPLAIN

According to the Flood Insurance Rate Maps published by the Federal Emergency

Management Agency (FEMA), a portion of the study area is within Special Flood Hazard

Zone AE while the remainder of the study area is outside of the floodplain. See Figure 5-1

below. The 1% annual chance flood (100-year or Base Flood) in Zone AE is estimated to

range from Elevation 6.0-ft to 7.0-ft NGVD. Areas identified within Zone X or Zone X-500

are estimated to have less than one foot or no flooding at all during the Base Flood.

Roadway improvements proposed by this project are estimated to be no lower than

elevation 9.0 NGVD, based on elevations extrapolated from limited As-built plans. As such,

the facility is anticipated to be open to traffic during the Base Flood. There are no regulated

floodways within the project limits. See Appendix A, for the Location Hydraulics

Memorandum.

Figure 5-1 FEMA Floodplain Map




6. CROSS DRAINS

There are no major cross drains in this project.

7. WATERBODY CROSSINGS

Roadway improvements proposed by this study will involve work within the C-8 Canal and

the NW 17th Avenue Canal. The C-8 Canal is under the jurisdiction of South Florida Water

Management District (SFWMD) and the Army Corp of Engineers and the NW 17th Avenue

Canal is under the jurisdiction of Miami-Dade Department of Regulatory and Economic

Resources (RER).

7.1 I-95 over C-8 Canal (Bridge No. 870348)

Existing Bridge 870348, shown below in Figure 7-1, carries I-95 northbound and

southbound traffic over the C-8 Canal. Interim Build Alternative 3A widens the bridge while

Interim Build Alternatives 3B, 3C and the Ultimate Build provide a new bridge for

southbound traffic. In Build Alternative 3A, improvements to the Bridge will widen the

footprint towards the west and require piles in the C-8 Canal. Preliminary calculations

indicate that the existing bridge low member elevation of 7.66 ft-NGVD 29 (6.10 ft-NAVD

88) can be maintained for the widening in Build Alternative 3A as it meets the 2.0-ft

minimum vertical clearance over the Normal High Water of the Canal. For the partial bridge

replacements for Build Alternatives 3B, 3C and the Ultimate Build, the bridge will need to be

raised to meet minimum vertical clearance requirements, as the anticipated widening for

these alternatives would reduce the vertical clearance below acceptable limits if maintained

at the existing elevation. The portion of the existing bridge carrying northbound traffic will

remain for the aforementioned alternatives. New piles placed in the C-8 Canal will be

aligned with existing piles to minimize hydraulic impacts (head loss) in the Canal. For more

information on improvements to this bridge, see the Bridge Analysis Report-Interim Build

Alternatives and the Bridge Analysis Report-Ultimate Build Alternative prepared as part of

the PD&E Study.




Figure 7-1 Bridge No. 870348 (I-95 over C-8 Canal)

7.2 NW 167th Street over NW 17th Avenue Canal (Culvert Extension)

Potential considerations in closing the NW 12th Avenue on-ramp to SR 826 will require

improvements to the NW 17th Avenue interchange with SR 826 that will widen it towards the

north and south. This will require extending the existing culvert in the NW 17th Avenue

Canal by approximately 15-ft on the northern end and 10-ft on the southern end to

accommodate the widened footprint of NW 167th Street. See Figure 7-2 below. Existing

plans show that the culvert at this location was built in the early 60’s and consists of 10-in

reinforced concrete walls with inside dimensions of 10-ft by 10-ft. In general, RER agreed

to allow culvert extension at this location. The culvert extension proposed for this location

will have dimensions of 10-ft by 10-ft to match the existing culvert. See Appendix C for

notes of the meeting held on 10/15/2012.




Figure 7-2 Culvert Extension (NW 167th ST Over NW 17th Ave. Canal)

7.3 NW 165th Street over NW 17th Avenue Canal (Proposed Culvert)

A new roadway connection from NW 165th Street to NW 17th Avenue, across the NW 17th

Avenue Canal, is proposed by this study to provide alternate connectivity and mitigate the

potential removal of the NW 12th Avenue on-ramp to SR 826. The Bridge Analysis Report,

prepared as a part of this PD&E study, recommends a culvert for the NW 17th Avenue Canal

crossing and approximately 500 linear feet of bulkhead along the western bank of the canal.

The Study Team met with RER on October 15th 2012 to confirm that a culvert crossing

would be acceptable at this location. In general, RER agreed to allow a culvert at this

location as long as certain requirements are met such as providing a maintenance access

pad on either side of the culvert and hydraulic modeling as needed. See Appendix C for

meeting notes.

N CULVERT EXTENSION NW 17TH AVENUE




Existing plans show that the culvert (SR 826 crossing), just north from NW 165th Street,

was built in the early 60’s and consists of 10-in reinforced concrete walls with inside

dimensions of 10-ft by 10-ft. For the purposes of estimating a project cost, two Alternatives

based on the existing upstream culvert were considered for the proposed culvert.

Alternative 1 provides a single 10-ft x 10-ft culvert while Alternative 2 provides two

10-ft x 10-ft culverts, as shown in Figure 7-3 below. If this crossing is needed, the actual

dimensions of the proposed culvert will be determined during the design phase of this

project when the Bridge Hydraulics Report is prepared for this crossing.

Figure 7-3 Proposed Culvert (NW 165th ST Over NW 17th Ave. Canal)

8. PERMITTING

8.1 Existing Permits

The South Florida Water Management District (SFWMD) and Miami-Dade Department of

Regulatory and Economic Resources (RER) were contacted to obtain existing permits within

the study area. Relevant permits are summarized below. See Appendix F for excerpts

from these permits.

SFWMD Permit 6P79-103, Application X000006257

Issued 1979.




Connector ramp provided from Turnpike to SR 826 West. Designers felt extra pavement width would not “contribute greatly to existing conditions or contribute to the degradation of water quantity.” Receiving waterbody is C-9 Canal.

SFWMD Permit 85-00070-S, Application X000013200

Issued 1985

No documentation available.

SFWMD Permit 85-00070-S, Application 090225-2

Issued 2009.

Modification of surface water management system to serve an additional 6.8 acres of impervious area for the I-95 Managed Lanes. Project site is a section of I-95 from north of Golden Glades Interchange to the Miami-Dade/Broward County boundary line.

SFWMD Permit 85-00070-S, Application 120327-2

Issued 2012.

Modification of surface water management system to serve an additional 10.62 acres of impervious area for the I-95 Express Lanes. Project site is a section of I-95 from north of Golden Glades Interchange to the Miami-Dade/Broward County boundary line. Receiving waterbody is C-9 Canal.

SFWMD Permit 13-01013-P, Application 110713-6

Issued 2011.

Modification of surface water management system to serve Turnpike Golden Glades Toll Plaza area. Proposed improvements include conversion of toll plaza to All Electronic Tolling (AET). This resulted in a reduction of existing impervious area by 3.57 acres. Existing storage was not impacted and additional storage is was provided for future use by the Turnpike.

RER Permit OF 401

Issued 1991

Improvements of the existing drainage system serving I-95 from NW 151st Street to approximately one mile south of SR 860. Work done as part of SPN 87270-3419




8.2 Proposed Permits

The Study Team has coordinated with SFWMD and RER to identify permits related to the

stormwater management system for this project. See Appendix C for documentation

related to those meetings. The following drainage related permits will be required for this

project.

Stormwater Management System

SFWMD has stated that they will make the final determination of whether a permit modification or new permit will be required when the project proceeds to the permitting phase. The reason for this is because there are portions of the interchange that have been permitted incidental to roadway work but there is no cohesive permit for the interchange itself.

RER has indicated that they will not require a permit for the stormwater management systems that serves FDOT roadways since they are being permitted through SFWMD. However, if work along NW 17th Avenue is required due to the closing of the NW 12th Avenue on-ramp to SR 826, then RER will require a Class II permit since the roadway is County owned and it has existing outfalls into the NW 17th Canal.

Right of Way (R/W) Occupancy

A R/W occupancy permit, from SFWMD, will be needed for proposed improvements to the I-95 Bridge over the C-8 Canal.

If the NW 12th Avenue on-ramp to SR 826 is closed and work is done in the NW 17th Avenue Canal, a Class III permit, from RER, will be needed for the work. The permit would include bulkheading, the culvert extension at NW 167 Street and a proposed culvert at NW 165th Street.

9. CONCLUSIONS

Based on preliminary calculations, the stormwater management systems proposed by this

study meet existing water quality standards as set forth in Chapter 62-302 of the Florida

Administrative Code. In addition, the treatment/storage quantity provided for each

receiving water body exceeds the required amount for each Build Alternative. The approach


area and restore or replace existing permitted treatment facilities impacted by this project.

Following this approach, Right-of-Way acquisition is not needed to meet current permitting




requirements. However, any Right-of-Way acquired as part of the roadway improvements

may prove to be advantageous in providing water treatment.

10. REFERENCES

1. FDOT 2013 Drainage Manual

2. FDOT 2012 Storm Drains Handbook

3. FDOT 2012 Plans Preparation Manual

4. FDOT 2013 Design Standards

5. FDOT 2008 District 6 Exfiltration Trench Reference Manual

6. FDOT 2004 Stormwater Management Facility Handbook

7. SFWMD 2012 Permit Information Volume IV

8. SFWMD 1999 Permit Information Manual Volume V

9. SFWMD 2002 Best Management Practices for South Florida Urban

Stormwater Management Systems

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