Permitting_and_Calculation_Report.pdf

PRW GROUP, LLC

PLANNING • DESIGN • UTILITIES • STORMWATER • LEACHATE • WASTEWATER • WATER • REUSE

17337 Kennedy Drive, North Redington Beach, Florida 33708• (407) 721-6954 • rwilson@wilscbs.com

PERMITTING AND CALCULATION REPORT

Seminole County Solid Waste Management Division Osceola Road Landfill (OLF)

Dry Hydrant System Updated January 2025

This report has been prepared to document the calculations and design of a dry hydrant for fire protection at the Osceola Road Landfill (OLF). The report includes information and calculations regarding existing conditions, details of the proposed project, water availability and design of the facilities.

The following reference documents were used in the development of the report and the calculations.

References

1. Survey of the Pond (including bottom contours) prepared by Southeastern Surveying and

Mapping Corporation, Drawing Number 52343002, dated 9/30/2020.

2. Seminole County Landfill – Firewater Supply Analysis prepared by Neptune Fire Protection

Engineering dated July 31, 2020.

3. NFPA 1142 – Standard on Water Supplies for Suburban and Rural Fire Fighting, 2017

Edition.

4. Input from the Seminole County Fire Department regarding details of the dry hydrant fire protection system.

BACKGROUND AND EXISTING CONDITIONS

The project is at the Seminole County Osceola Road Landfill (OLF) which is located at 1930 East Osceola Road in Geneva, Florida.

The existing on-site fire suppression tank is not in compliance and a new fire suppression water supply is necessary. Since the OLF does not have an adequate or reliable water distribution system for fire protection, the code allows other methods (approved by the AHJ) to provide an onsite water source, including a dry hydrant that would be supplied by an on-site pond. Key permitting requirements for a dry hydrant system include demonstrating that sufficient water is available on a year-round basis (drought with a 50-year return period) and that the system can provide a minimum flow of 1,000 gpm at draft.

This report was previously submitted and accepted by the Fire Department under an approved site plan in 2022 (Project number: 21-06000054). The project and report have been modified to eliminate a Seminole County Landfill water truck fill station; however, the dry hydrant remains as provisionally permitted. Attachment C provides responses to the previously permitted project regarding compliance with NFPA 1.

Permitting and Calculation Report Seminole County Solid Waste Management Division Osceola Road Landfill (OLF) Dry Hydrant System

PROPOSED PROJECT AND BASIS FOR DESIGN/PERMITTING

Municipal water supply (and fire protection) is not available at the OLF; consequently, on-site water storage must be used for firewater applications. This supply will be provided from an on-site stormwater pond (designated as “Pond B”) and a dry hydrant for withdrawal. Pond B is a 24-acre pond located north of the main access road.

Pond volume calculations and system design will document compliance with NFPA 1142 requirements for fire protection. The concept is summarized as follows:

1. Fire trucks will use the existing roadway and parking area for access to the dry hydrant. In the future, truck parking will not be allowed in the area.

Per NFPA 1, Section 18.2.3.4, The landfill is designed to accommodate large transfer trailer access. The roads are over 20-ft wide, and most are much wider.

2. The paved area in front of the dry hydrant will be stripped and marked “No Parking “.

DRY HYDRANT SYSTEM DESIGN

Since there is no adequate and reliable water supply available on site for fire-fighting purposes in this rural area, the FFPC, Section 13.5.2 requires the application of NFPA 1142. The Pond must provide a sufficient volume to meet the required water supply during a drought with an average 50-year frequency. In addition, the dry hydrant system must comply with the minimum flow requirements (i.e. 1,000 gpm) and other design criteria in NFPA 1142.

Dry Hydrant Required Water Supply The detailed Firewater Supply Analysis presented is presented in Attachment A (Reference 2) -referred to this reference document for additional details. In accordance with NFPA 1142 Section 4.2 the minimum water supply for structures without exposure hazards, (structures within 50 feet), is calculated using the following equation:

where, WSmin is the minimum water supply in gallons, VStot is the total volume of the structure in cubic feet, and OHC is the occupancy hazard classification number CC is the construction classification number as determined in NFPA 1142 Chapters 5 and 6 respectively.

The largest water supply required is to protect Building #1, the Administration/Maintenance Garage Building. The VStot for this building is 188,232 cubic feet.

The OHC has been determined to be four (4) for a repair garage as determined by NFPA 1142, 5.2.2.2(11).

The CC has been determined to be 0.75 for Type II construction per NFPA 1142, Table 6.2.1.

Osceola Road Landfill (OLF) Dry Hydrant System

When the above equation is applied, the required water supply is 35,294 gallons.

50-Year Drought Level and Water Availability Water availability from Pond B was determined for a drought with an average 50-year return period using stage-storage analysis, as well as historical rainfall and pond level data. Once the available volume of water was determined, then the dry hydrant minimum design flow rate of 1,000 gpm was determined using the worksheet approach and tables in NFPA 1142. The calculations are documented as follows:

1. Stage-storage volumes for the pond were determine based on the survey of the pond bottom (Reference 1). Table 1 shows the stage storage volume for the Pond.

Table 1 - Pond Stage-Storage Analysis

Contour Elevation (NAVD88), ft Contour Area, sf Volume, cf

Cumulative Volume, cf

6 258,183.30 0 0 7 741,494.40 479,073 479,073 8 864,981.30 802,446 1,281,518 9 913,522.60 889,142 2,170,660 10 964,710.60 939,000 3,109,660 11 1,028,457.50 996,414 4,106,074 12 1,099,030.20 1,063,549 5,169,623 13 1,218,831.50 1,158,414 6,328,037

14.5 1,365,638.80 1,937,309 8,265,347

2. Historical rainfall data (from the landfill and the Sanford Airport), as well as limited pond water elevation data was used to estimate the water level of the Pond during a drought with an average 50-year return period. The available data was for a period of record from 1957 to 2001. The data was ranked, then the probability of occurrence and associated return period were calculated. Figure 1 shows the historical data and the drought with a return period of 50-years.

Osceola Road Landfill (OLF) Dry Hydrant System

As shown in Table 2, which presents the existing pond data (elevations and volumes) and the design elevations for a drought with a 50-year return period, there is over 19 million gallons of water available. The available volume is significantly greater that the required water supply of 35,294 gallons.

Table 2- Available Water in Pond

Item

Elevation (NAVD88) or Distance, ft Volume, gal

Pond Data Total Pond Volume --- 65,031,120 Pond Bottom 6 --- Average Water Level 14.9 --- Discharge Weir Elevation 14.8 ---

Design for 50-Year Drought Pond bottom @ Pipe/Strainer 9 --- Pipe Invert Above Bottom 2 --- Pipe Invert 11 --- 8" Pipe Diameter 0.67 --- Top of Pipe 11.67 35,921,000 Allowance Above Pipe 2.2 --- Pond Level (50-Year Drought) 13.9 55,853,000 Available Volume --- 19,932,000

Ra in fa ll, in ch

Year

Figure 1 Historical Rainfall and Estimated 50-Year Drought

Rainfall, inch 50-Yr Drought

Osceola Road Landfill (OLF) Dry Hydrant System

3. The dry hydrant minimum design flow rate of 1,000 gpm was determined using the worksheet approach and tables in NFPA 1143, Annex I. An 8-inch suction pipe (intake screen, pipe and fittings) provides positive pressure at the connection. The worksheet and fitting tables are provided in Attachment B and the attached drawing (Drawing C-2 in Attachment D) shows the layout of the proposed system.

Prepared By PRW Group, LLC 17337 Kennedy Drive North Redington Beach, Florida 33708

(407) 721-6954

COB 27490

Richard D. Wilson, P.E.

Florida License No. 42807