Doral_PD_HQ_SD_NARRATIVE_Civil_Utilites_&_Enviromental_.pdf

City of Doral Police Headquarters

Programing and Schematic Design

Civil Design / Drainage, Utilities & Environmental Narrative

S ta n te c A rc h it e c tu re I n c

Prepared for:

City of Doral

Prepared by:

Stantec

Date:

November 19, 2025 Rev1: January 9, 2026

Project/File:

219421076

The conclusions in the Report titled City of Doral Police Headquarters are Stantec’s professional opinion, as of the time of the Report, and concerning the scope described in the Report. The opinions in the document are based on conditions and information existing at the time the scope of work was conducted and do not take into account any subsequent changes. The Report relates solely to the specific project for which Stantec was retained and the stated purpose for which the Report was prepared. The Report is not to be used or relied on for any variation or extension of the project, or for any other project or purpose, and any unauthorized use or reliance is at the recipient’s own risk.

Stantec has assumed all information received from City of Doral (the “Client”) and third parties in the preparation of the Report to be correct. While Stantec has exercised a customary level of judgment or due diligence in the use of such information, Stantec assumes no responsibility for the consequences of any error or omission contained therein.

This Report is intended solely for use by the Client in accordance with Stantec’s contract with the Client.

While the Report may be provided by the Client to applicable authorities having jurisdiction and to other third parties in connection with the project, Stantec disclaims any legal duty based upon warranty, reliance or any other theory to any third party, and will not be liable to such third party for any damages or losses of any kind that may result.

Table of Contents

Project: 219421076 i

Table of Contents

1 Drainage Review

1.1 Existing Conditions

1.2 Site Data

1.3 Proposed Conditions

1.4 Water Quality

1.5 Water Quantity

1.6 Nutrient Analysis

1.7 Recommendations

2 Utilities Review

2.1 Water

2.2 Sewer

3 Environmental Review…………………………………………………………………………….…..……7

3.1 Environmental Compliance…………………………………………………………………………………..7

3.2 Permittin Status………………………………………………………………………………………………. 7

3.3 Agency-Specific Mitigation Requirements………………………………………………………………… 8

3.4 Mitigation Options……………………………………………………………………………………………. 9

3.5 SFWMD Site Visit Summary………………………………………………………………………………. . 9

3.6 Next Steps…………………………………………………………………………………………………… 10

Appendix A A.1 SFWMD Site visit 12/06/2025 - Chapter 62-340, F.A.C. Data Form and site photographs………….11

Drainage, Utilities, and Environmental Review

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1 Drainage Review

1.1 Existing Conditions

The project site is located at 3719 NW 97th Avenue, Doral, FL 33178, within Section 28, Township 53S, Range 40E. The property currently houses the City of Doral Police Training and Community Center, along with associated parking areas and open space.

The existing stormwater drainage system consists of:

• Catch basins that collect surface runoff from paved areas.

• A network of storm drainage pipes connected to approximately 320 linear feet of exfiltration trenches located within the parking lot. These trenches are designed to capture and treat stormwater runoff, providing infiltration into the underlying soils.

• A 0.9-acre dry retention area situated at the southeast corner of the property, serving as additional storage and treatment for stormwater.

This configuration reflects a zero-discharge approach, meaning stormwater is managed entirely on-site without direct discharge to off-site conveyance systems.

1.2 Site Data

Floodplain

According to FEMA Flood Insurance Rate Map (FIRM) Panel 12086C0286L, most of the site lies within

Flood Zone X, which represents areas outside the 100-year floodplain with an annual flood risk of less than

0.2%.

However, a portion of the site falls within Flood Zone AE, which has a Base Flood Elevation (BFE) of 6 feet NAVD. Zone AE indicates areas with a 1% annual chance of flooding, requiring compliance with federal and local floodplain management regulations.

Miami Dade County Flood Criteria

According to the Miami Dade County Flood Criteria Map, 2022, the minimum elevations of the site is 7’

NAVD. The purpose of the County Flood Criteria is to determine the minimum ground surface elevation of developed properties, crown/grade of roads, and secondary canal banks based on a 10-year, 24-hour storm event, 2060 scenario with SLR. These criteria are used to ensure developments can withstand flooding by defining required minimum ground surface elevations and top elevations for seawalls.

Groundwater

The average October groundwater level in the area is approximately 3.6 feet NGVD, as reported by Miami-

Dade County Water Control Section 2.2. This information is critical for designing infiltration/exfiltration systems.

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Soils

According to the USDA Web Soil Survey, the site primarily consists of Hallandale fine sand–Urban land complex. Previous subsurface investigations indicate the presence of fill soils in the northeast corner, with predominant fine sand and limestone layers.

A geotechnical subsurface investigation will be required to:

• Confirm soil composition.

• Determine infiltration and exfiltration rates per South Florida Water Management District (SFWMD) requirements.

1.3 Proposed Conditions

The City of Doral is proposing the construction of an additional three-story building along with associated amenities.

The proposed improvements will include the addition of a +/- 0.53 Ac building and a new parking lot with an added impervious cover of 2.18 Acres. Table 1 provides a comparison of the land use cover for site in existing and proposed conditions.

Table 1 – Land Use Summary

Existing (Ac) Proposed (Ac)

Impervious 2.67 4.85 + 2.18 Ac

Pervious 7.07 4.36 - 2.71 Ac

Building 0.30 0.83 + 0.53 Ac

Wetlands

Approximately 2 acres of wetlands exist on-site. No formal delineation has been completed. Any impacts to wetlands will require mitigation measures in accordance with regulatory requirements.

1.4 Water Quality

Miami-Dade DRER requires a minimum of 1-inch retention for rainfall over the site area. SFWMD Water

Quality criteria states that drainage management system must treat the higher of the first inch of runoff from the site or 2.5 inches times the percent impervious. According to the SFWMD AH VOL II, Section 4.2.1(a)3:

"Retention volume shall be provided equal to 50 percent of the above amounts computed for wet detention". Since exfiltration/infiltration is used, 50% WQV should be provided. However, since the proposed system is designed to provide zero discharge, 100% of the WQV will be captured and treated.

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Water Quality Volume:

Water quality volume for the site has been provided by the existing exfiltration trench system. Water quality treatment will be required for the addition of impervious cover and new structure.

Existing conditions water quality volume was calculated to 0.9 Ac.ft. The required quality detention volume in the proposed condition was calculated to 1.10 Ac.ft. The existing exfiltration system can be expanded to capture and treat the additional water quality requirements. Alternatively, detention or retention facilities could be utilized to capture and treat the water quality volume.

Pre-treatment:

According to the SFWMD AH VOL II, Section 4.2., all projects other than single family residential projects are required to provide ½” of dry pretreatment. This dry pretreatment may be used towards meeting the overall water quality treatment requirements.

1.5 Water Quantity

The stormwater management plan will utilize a zero-discharge approach since there is no point source discharge, similar to the existing condition. Storm volume computations and peak stage elevation comparison for pre-development and post development conditions shall provide evidence that peak stage elevations for design storms have not been adversely affected with the proposed improvements.

The following design parameters have been used per SFWMD ERP Applicant’s Handbook Volume II, Part

III, Section 3.5.

Permitting/Design Criteria

Storm Event Criteria

10 Yr – 24 Hrs Parking and Road Centerlines

25 Yr – 72 Hrs Perimeter Berm

100 Yr – 72 Hrs Finish Floor Elevation

Finish Floor Elevation:

The minimum finished floor elevation shall be set at the highest of the following criteria:

1. The base flood elevation indicated on the FIRM map,

2. The 100-year 3-day storm stage (zero discharge)

3. 8-inches above the crown of road elevation fronting the property for residential properties and 4-inches above the crown of road elevation fronting the property for non-residential structures.

On-site Storage

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Onsite storage is the volumetric capacity of the site to store rainfall. The proposed parking lot will encroach onto the existing wetlands. The minimum elevation for the parking lot will result in decreased storage capacity on-site as existing wetlands elevations of 4-5’ will need to be raised to a minimum of 7’ per the

County Flood Criteria

Additionally, the area of the proposed structure that will occupy a portion of the existing parking lot is considered storage areas lost since roofs and structures are excluded from on-site stage storage calculation.

The proposed improvements will also encroach onto the existing dry retention area at the southwest corner of the site and therefore also reduce the on-site storage

Water Use

No dewatering activities are anticipated for the construction of the proposed site improvements. In the case dewatering is required for the construction of the project, or for an irrigation system, contractor shall be responsible to obtain the appropriate Water Use permits.

1.6 Nutrient Analysis

The South Florida Water Management District (SFWMD) has updated its Environmental Resource Permit

(ERP) rules to require projects to meet performance-based nutrient reduction targets instead of just design-based solutions. New rules effective June 28, 2024, stipulate that post-development nutrient loads (Total

Nitrogen and Total Phosphorus) cannot exceed pre-development loads, necessitating nutrient loading calculations to prove a net improvement.

1.7 Recommendations

Preliminary indicate that 3.5 Ac.ft. of on-site storage will need to be compensated for due to the proposed improvements. On-site storage can be compensated for by multiple options such as:

1. Underground stormwater detention such as storm chambers or r-tanks. It is to be noted that underground detention/retention systems shall be designed with the bottom elevation 1 foot higher than the season high groundwater table to receive water quality credit

2. An expanded retention pond in the wetlands area to provide storage and satisfy the nutrient loading requirements.

3. Expanding the storm drainage pipe network and the addition of exfiltration trenches. It is to be noted that per DERM and SFWMD requirements, the exfiltration trenches can be sized up to 3.28” of rainfall. This should attenuate the water quality volume for the entire site.

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2 Utilities Review

2.1 Water

The existing potable water and fire protection supply for the site is provided by a 16-inch Ductile Iron Pipe

(DIP) water main located along NW 97th Avenue. This main serves as the primary source for both domestic water and fire suppression needs.

Existing Connections

• A 12-inch water main has been extended from the site entrance along the southern edge and continues approximately 280 feet north into the property, terminating at a fire hydrant.

• A separate connection to the 16-inch DIP main provides:

o Two (2) 2-inch domestic water service lines, each equipped with individual meters.

o One (1) 6-inch fire line, fitted with a 6-inch double detector check valve assembly, supplying fire protection to the existing building.

• Additionally, a 4-inch DIP fire line branches from the 6-inch fire main and is available for future building connections.

Future Considerations

Water demand and fire flow calculations must be performed to confirm whether the existing infrastructure can accommodate the additional requirements of the proposed development. These calculations will consider:

• Domestic water demand for the new building.

• Fire flow requirements per NFPA standards and local jurisdiction criteria.

It is anticipated that Miami-Dade Water and Sewer Department (WASD) will require the existing fire line to be looped around the site and reconnected to the 16-inch water main. This improvement would enhance system reliability and meet WASD standards for redundancy.

The proposed loop extension is estimated to require approximately 960 linear feet of new water main installation.

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2.2 Sewer

The site is currently served by an 8-inch sanitary sewer main located along NW 97th Avenue. This main provides gravity sewer service to the property.

Existing Connections

• A 6-inch lateral extends from the 8-inch main into the site, providing sanitary service to the existing building.

• A 4-inch lateral, branching from the 6-inch lateral, is available for future building connections.

Future Considerations

Sewer demand calculations will be required to verify whether the existing sanitary infrastructure can handle the additional flow generated by the proposed building. These calculations will be based on:

• Anticipated occupancy and fixture counts.

• Peak flow conditions per Miami-Dade WASD design criteria.

If the existing system is determined to be insufficient, a new sanitary sewer main will need to be extended to the proposed building. The existing invert elevation of the sanitary main along NW 97th Avenue is approximately 10 feet below grade, which is favorable for maintaining gravity flow.

In the event of a new extension, approximately 570 linear feet of additional sewer main will be required.

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3 Environmental Review

3.1 Environmental Compliance Summary

This section addresses the permitting requirements for the City of Doral Police Headquarters project, which involves wetlands subject to regulatory oversight. The permitting pathway is contingent upon a jurisdictional determination by the South Florida Water Management District (SFWMD). If SFWMD retains jurisdiction, the project will be governed by the Environmental Resource Permit (ERP) program, requiring mitigation based on the Uniform Mitigation Assessment Method (UMAM) and compliance with stormwater management standards. Alternatively, if authority is delegated to Miami-Dade County Department of Environmental

Resources Management (DERM), mitigation will be addressed through a bioassessment report and contribution to the County’s Wetland Trust Fund, resulting in a substantially different cost structure.

In addition to jurisdictional clarification, the project team is awaiting confirmation from Miami-Dade DERM regarding any existing covenant on the wetland area.

This section outlines the regulatory requirements of SFWMD, DERM, and the U.S. Army Corps of Engineers

(USACE), including permit types, mitigation standards, monitoring obligations, and recent updates. It also presents mitigation options, on-site restoration, off-site mitigation, and mitigation banking, and provides a comparative analysis of agency requirements to inform strategic planning and cost considerations.

3.2 Permitting Status

The project team is currently awaiting a jurisdictional determination from the SFWMD regarding the wetlands associated with the City of Doral Police Headquarters project. This determination is critical because it will establish the applicable permitting pathway and directly influence project requirements.

If SFWMD elects to retain jurisdiction, the project will be subject to the requirements of the ERP program.

This includes compliance with mitigation standards based on the UMAM, as well as stormwater management obligations such as nutrient loading analysis and adherence to updated treatment criteria. Conversely, if regulatory authority is deferred to the Miami-Dade County DERM, mitigation will be addressed through a bioassessment report and a contribution to the County’s Wetland Trust Fund, which represents a substantially different cost structure compared to SFWMD’s functional mitigation requirements.

In parallel, the project team is awaiting confirmation from the Wetlands Section of Miami-Dade DERM regarding whether any covenant exists on the existing wetland area. Although the wetlands have been surveyed, formal delineation has not yet been completed.

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3.3 Agency-Specific Mitigation Requirements

Miami-Dade County (DERM)

Any dredging, filling, or construction within wetlands requires a Class IV Permit from DERM, even if state or federal permits have already been obtained. Applicants must demonstrate avoidance and minimization of impacts before proposing mitigation. When mitigation is necessary, on-site restoration or enhancement is generally preferred; however, off-site mitigation or mitigation banking may be allowed if on-site options are not feasible. Ratios typically exceed 1:1, commonly reaching 1.5:1 or higher depending on habitat quality.

DERM applies its own ecological evaluation criteria, emphasizing native vegetation, hydrology restoration, and long-term maintenance plans rather than relying exclusively on UMAM. Post-mitigation monitoring is required for a minimum of five years, with annual reporting and financial assurance such as a bond or escrow to ensure project success.

South Florida Water Management District (SFWMD)

SFWMD regulates wetland impacts through its ERP program. Applicants must first demonstrate avoidance and minimization of impacts. When mitigation is required, options include on-site restoration or creation, off-site mitigation within approved regional areas, or the purchase of credits from state-approved mitigation banks. Mitigation requirements are determined using UMAM, which evaluates ecological value and calculates functional loss and gain. Ratios typically start at 1:1 but may increase for high-value wetlands or when mitigation quality is lower. Monitoring and maintenance obligations are included in ERP conditions, and financial assurance may be required. A recent update (July 2025) allows mitigation credits to be used across

Water Management District boundaries with appropriate justification.

U.S. Army Corps of Engineers (USACE)

USACE regulates wetland impacts under Section 404 of the Clean Water Act, which applies to activities that discharge dredged or fill material into Waters of the United States. A Section 404 permit is required even if state or local permits have been obtained. Applicants must demonstrate avoidance and minimization of impacts before mitigation is considered. When mitigation is necessary, USACE allows on-site restoration, off-site mitigation, or the purchase of credits from federally approved mitigation banks. Mitigation requirements are typically based on functional assessments such as UMAM or an equivalent method, ensuring that ecological losses are fully offset. Ratios often start at 1:1 but may increase for high-value wetlands or when mitigation quality is uncertain. Post-mitigation monitoring and financial assurance are generally required, with compliance periods often extending beyond five years.

Based on current desktop analysis and prior environmental reports, the wetlands in question do not appear to be jurisdictional; therefore, a USACE Section 404 Permit may not be required. This information is provided for reference only.

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3.4 Mitigation Options

Mitigation may be achieved through one or more of the following approaches:

• On-site mitigation, involving restoration or creation of wetlands at the project site;

• Off-site mitigation, utilizing nearby areas for restoration; or

• Mitigation banking, through the purchase of credits from approved banks.

Comparison of Regulatory Requirements

Aspect DERM (Miami-Dade) SFWMD USACE

Permit Type Class IV Permit ERP Section 404 Permit

Avoidance &

Minimization Required Required Required

Mitigation Options On-site preferred; off-site or banking allowed

On-site, off-site, or mitigation banking

On-site, off-site, or federally approved banking

Mitigation Ratios >1:1 (commonly 1.5:1 or higher)

Typically 1:1 (UMAM-based)

Varies; often aligned with state standards

Assessment Method DERM ecological criteria UMAM UMAM or equivalent

Approved Areas Within Miami-Dade or approved regional area

Regional mitigation banks or ROMAs

Federally approved banks or in-kind areas

Monitoring &

Maintenance

5 years minimum; annual reports; financial assurance

Per ERP conditions;

financial assurance

5+ years; financial assurance required

Recent Updates No major changes July 2025: Cross-district credit use allowed No major changes

3.5 SFWMD Site Visit Summary

On December 16, 2025, two wetland biologists from the SFWMD conducted a site visit to evaluate wetland conditions. Their assessment confirmed the presence of wetlands on the property, though they are considered low in ecological quality. These findings were documented in the Chapter 62-340, F.A.C. Data

Form and supported by site photographs. Refer to attachments in Appendix A for a copy of this report.

At this stage, mitigation credits cannot be calculated because additional information is required. The next step is to perform a formal wetland delineation and establish survey boundaries. Once this is complete, a UMAM analysis will be prepared to determine wetland quality and calculate mitigation requirements. Preliminary estimates indicate approximately 1.38 acres of wetlands on-site.

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3.6 Next Steps

The District has verified the presence of wetlands and provided a completed Chapter 62-340, F.A.C. Data

Form. Below is a summary of the next steps required to ensure regulatory compliance.

1. Wetland Boundary Delineation: The Chapter 62-340, FAC Data Form provided by the District, confirms wetland points but does not define the full boundary. A formal wetland delineation will need to be conducted in the field to establish the wetland edge and calculate impact acreage. This will provide the information needed to complete the UMAM form (required for mitigation).

2. Survey and Mapping: After delineation, a surveyor will tie flagged points to the property boundary.

A wetland map will then be prepared showing the delineated polygon, property lines, and proposed impact areas.

3. Formal Determination (Optional): If the City wants regulatory certainty, submitting a petition for a

Formal Wetland Determination to SFWMD is suggested. This provides an official wetland boundary valid for five years.

4. ERP Application: Once the boundary is finalized, survey and wetland maps have been created, preparation of the ERP application can begin.

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Appendix A

A.1 SFWMD Site visit 12/06/2025 - Chapter 62-340, F.A.C.

Data Form and site photographs.

Doral Police Station Site Visit 12/16/2025

Site Visit Notes:

Heavily wooded and overgrown with invasive exotic plant species throughout.

Muck present at different points within the wetland.

Area very disturbed and has a low-quality wetland.

Nettle and elephant grass are present within the south edge of wetland.

Ear-leaf acacia, cabbage palm and myrsine within the north edge of the wetland where it starts transitioning to upland.

Soil is sandier near the north portion as well.

Muck also presents within wetland at 25.8066821, -80,3526561.

Saw grass, pennywort and other hydrophytic vegetation located within pockets of the wetland.

WL Point – 25.8070646, -80.3528754

UP Point - 25.807514865085395, -80.3529116257898

Wetland Point #1

North

South

East

West

Soil profile of 0-5”

Soil cut at 2.5”

Close up of soil from the surface

Also muck presence at another location

Upland Point #2

South

East

North

West

Canopy

Soils at upland point – losing dark surface and muck presence

Soil plug not possible due to heavy roots and compaction

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