Stormwater Report 1

STORMWATER MANAGEMENT REPORT FOR THE ESTATE BLOCK 151 LOT 17.01 TOWNSHIP OF WEST ORANGE ESSEX COUNTY, NEW JERSEY SUBMITTED TO: TOWNSHIP OF WEST ORANGE PLANNING BOARD PREPARED FOR: THE ESTATE 111 PROSPECT AVENUE WEST ORANGE, NEW JERSEY 07052 PREPARED BY: PETRY ENGINEERING, LLC 155 PASSAIC AVENUE FAIRFIELD, NEW JERSEY 07004 973-227-7004

STORMWATER MANAGEMENT REPORT FOR THE ESTATE BLOCK 151 LOT 17.01 TOWNSHIP OF WEST ORANGE ESSEX COUNTY, NEW JERSEY SUBMITTED TO: TOWNSHIP OF WEST ORANGE PLANNING BOARD PREPARED FOR: THE ESTATE 111 PROSPECT AVENUE WEST ORANGE, NEW JERSEY 07052 PREPARED BY: PETRY ENGINEERING, LLC 155 PASSAIC AVENUE FAIRFIELD, NEW JERSEY 07004 973-227-7004 J. Michael Petry J. MICHAEL PETRY, PE NJ PROFESSIONAL ENGINEER # 36662 DECEMBER 27, 2024 1

TABLE OF CONTENTS Introduction ..................................................................................................................................... 3 Proposed Improvements.................................................................................................................. 3 Methodology ................................................................................................................................... 4 Existing Conditions......................................................................................................................... 5 Drainage area 1 (DA-1) .............................................................................................................. 5 Curve Numbers ........................................................................................................................... 5 Peak Flows .................................................................................................................................. 5 Post-Development Runoff Target ..................................................Error! Bookmark not defined. Proposed Conditions ....................................................................................................................... 6 Drainage area 1 (DA-1) .............................................................................................................. 6 Curve Numbers ........................................................................................................................... 6 Peak Flows .................................................................................................................................. 6 Water Quality .................................................................................................................................. 7 Groundwater Recharge ................................................................................................................... 7 Storm Sewer Computations ............................................................................................................ 7 Conclusion ...................................................................................................................................... 7 Existing Conditions Hydrographs Proposed Conditions Hydrographs Appendix - Web Soil Survey - Essex County Soils Information - New Jersey 24 Hour

..................................................... 7 Existing Conditions Hydrographs Proposed Conditions Hydrographs Appendix - Web Soil Survey - Essex County Soils Information - New Jersey 24 Hour Rainfall Frequency Data - Table 2-2a Runoff Curve Numbers for Urban Data - Figure 10-B Rainfall Intensity – Duration Frequency Curve – Northern Region - Table 7 – Existing Vs. Proposed Runoff Rates – Current Adjusted Rainfall - Table 8 – Existing Vs. Proposed Runoff Rates – Future Projected Rainfall - Time of Concentration Calculations - Storm Sewer Calculations - Drainage Area Maps (Fig.-1 – Fig.-3) 2

INTRODUCTION The subject property is located at 111 Prospect Avenue, at the corner of Prospect Avenue and Woodland Avenue in the Township of West Orange, NJ. The property consists of 8.29± acres of land. It is located within the B-2 General Business Zone. The adjacent properties to the south and west are residential. To the north of the property is the Residence Inn. Finally, to the east of the property, across Prospect Avenue, is the Eagle Rock Reservation. Currently, the site contains a catering hall and restaurant consisting of 3 buildings and multiple paved parking lots that service the buildings. The property slopes from elevation 555 to elevation 505, from the southeast to the northwest. The main building has a footprint of approximately 36,100 square feet and contains 2 stories. There are also 2 smaller buildings on the lot, located in the center and rear of the site. Three large parking lots are located throughout the site. An employee parking lot is located at the southwestern corner. A valet parking lot is located to the east of the main building, and a public parking lot is located to the north. The public parking lot is also partially contained by a cross-access easement and connects to the Residence Inn parking lot. The NRCS Websoil survey mapping indicates that the portion of the site subject to development contains Hydrologic Group “D” soils, Urban land, Boonton Substratum, (URBONB) with Urban Land. The stormwater analysis considers this soil group type D. (See attached Websoil Survey Mapping.) PROPOSED IMPROVEMENTS The proposed improvements call for the renovation of the main building, the front garden area, and the reconstruction of the valet parking lot. Also, a new porte cochere will be constructed at the main entrance. A new storm sewer system is proposed throughout the parking lot to capture stormwater more effectively. The new parking lot will contain substantially more landscape islands throughout which will help to guide traffic as well as allow for improved plantings. Subsequently, the proposed development will reduce the overall impervious on the site. The existing impervious coverage for the site is 5.12 acres and the existing motor vehicle surface is 3.48 acres. The proposed impervious coverage for the site is 5.02 acres and the proposed motor vehicle surface is 3.39 acres. The entirety of the proposed disturbance is limited to

vehicle surface is 3.48 acres. The proposed impervious coverage for the site is 5.02 acres and the proposed motor vehicle surface is 3.39 acres. The entirety of the proposed disturbance is limited to previously developed areas. 3

METHODOLOGY The USDA Natural Resources Conservation Service (NRCS) methodology described in the Technical Release 55 – Urban Hydrology for Small Water Sheds (TR-55) is used for computing stormwater runoff rates, volumes, and hydrographs for both existing and proposed conditions. In computing stormwater runoff from all design storms, the relative stormwater runoff rates and volumes of pervious and impervious surfaces are analyzed separately. The rainfall-durationfrequency data was taken from the NOAA National Weather Service. (See attached.) The NRCS Type D Design Storm Rainfall Distribution was used to analyze both pre- and post-conditions for both current adjusted and future projected rainfall projections. Hydraflow Hydrographs Extension 2024 Modeling Software was used to compute the site's pre- and post-development runoff of the site. Table 1 – Rainfall Data Current Rainfall Current Adjusted Storm Event (in) Rainfall (in) 2-Yr 3.44 3.47 10-Yr 5.22 5.38 100-Yr 8.66 9.18 Future Rainfall (in) 4.09 6.37 11.52 According to the Township of West Orange Stormwater Management Rules and the NJDEP Stormwater Management regulations, the proposed development is considered a major development since there is more than one acre of disturbance. For major developments, stormwater management measures designed to provide groundwater recharge, stormwater runoff quantity control, and stormwater runoff quality treatment, utilizing green infrastructure. The development does not have to meet the groundwater recharge requirement since it is located within the Metropolitan Planning Area. Also, since the proposed development does not result in a net increase of ¼ of an acre or more of impervious surface, the water quality aspect of the Stormwater Management Rules is not required. Therefore, the stormwater management measures have been designed to meet only the stormwater runoff quantity requirements. According to Section 7:8-5.6(b)1. the design must “demonstrate through hydrologic and hydraulic analysis that for stormwater leaving the site, post-construction runoff hydrographs for the 2, 10 and 100-year storm events do not exceed, at any point in time, the pre-construction runoff hydrographs for the same storm events.” The proposed development calls for a decrease in the amount of impervious on the site, the amount of runoff will be reduced. Since the stormwater quantity is

ff hydrographs for the same storm events.” The proposed development calls for a decrease in the amount of impervious on the site, the amount of runoff will be reduced. Since the stormwater quantity is satisfied through the use of non-structural strategies, green infrastructure requirements are not required. 4

EXISTING CONDITIONS The existing site has been modeled as one drainage area totaling 4.68 acres. (See Fig.1 Existing Drainage Area Map.) The point of analysis for this drainage area is the Type Double “B” Inlet at the rear of the site, which connects to the municipal storm sewer system within Deerfield Drive. The drainage area includes all areas of disturbance, as well as any other areas that drain to the point of analysis. DRAINAGE AREA 1 (DA-1) Drainage Area 1 consists of 4.68 acres of both pervious and impervious surfaces. The impervious area, 3.32 acres, consists of the existing parking lot and associated improvements. The pervious area, 0.27 acres, is comprised of landscaped and lawn areas that are in good condition. Two times of concentration have been calculated for this drainage area, one based on the current adjusted rainfall total and one for the future projected rainfall total. The times of concentration are 13.6 and 12.7 minutes, respectively. CURVE NUMBERS The CN values used have been taken from the TR-55 Manual “Urban Hydrology for Small Watersheds,” Table 2-2a and Table 2-2c, based on land cover and hydrologic soil groups. Table 2 – Curve Number (Existing Conditions) Description Hydrologic Group Curve Number Landscaped Islands D 80 (Open Space-Good Conditions) Impervious D 98 PEAK FLOWS Using the information described above, the peak flows during the 2-, 10-, and 100-year storm events where calculated. Table 2 below summarizes the peak flows during each storm event. (See attached Hydraflow Output for Existing Conditions Hydrographs, CN Values, and Time of Concentration Calculations.) Table 3 – Existing Peak Runoff Rates Current Adjusted Rainfall Future Projected Rainfall Existing Site Existing Site Existing Site Existing Site Storm Event Peak Runoff Runoff Volume Peak Runoff Runoff Volume 2 Year 9.339 cfs 44,031 cf 11.28 cfs 53,349 cf 10 Year 15.35 cfs 73,038 cf 18.49 cfs 88,329 cf 100 Year 27.41 cfs 132,192 cf 34.83 cfs 169,002 cf 5

PROPOSED CONDITIONS The proposed site has been modeled as one drainage area totaling 4.68 acres. (See Fig.2 Proposed Drainage Area Map.) The point of analysis for this drainage area is the Type Double “B” Inlet at the rear of the site, which connects to the municipal storm sewer system within Deerfield Drive. DRAINAGE AREA 1 (DA-1) Drainage Area 1 consists of 4.68 acres of both pervious and impervious surfaces. The impervious area, 3.32 acres, consists of the existing and proposed parking lot and associated improvements. The pervious area, 0.27 acres, is comprised of landscaped and lawn areas that are in good condition. Two times of concentration have been calculated for this drainage area, one based on the current adjusted rainfall total and one for the future projected rainfall total. The times of concentration are 12.6 and 11.7 minutes, respectively. CURVE NUMBERS The CN values used have been taken from the TR-55 Manual “Urban Hydrology for Small Watersheds,” Table 2-2a and Table 2-2c, based on land cover and hydrologic soil groups. Table 4 – Curve Number (Proposed Conditions) Description Hydrologic Group Curve Number Landscaped Islands D 80 (Open Space-Good Conditions) Impervious D 98 PEAK FLOWS Using the information described above, the peak flows during the 2-, 10-, and 100-year storm events where calculated. Table 4 below summarizes the peak flows during each storm event. (See attached Hydraflow Output for Proposed Conditions Hydrographs, CN Values, and Time of Concentration Calculations.) As shown in this table, the proposed runoff rates and volumes are reduced from the existing to proposed conditions. Since this regulation requires that we show reductions at each time interval, we have included Table 7 in the appendix of this report which shows the minute-by-minute flows leaving the site for each storm event and compares existing and proposed conditions. Table 5 – Overall Peak Runoff Rates – Current Adjusted Rainfall Existing Site Proposed Site Proposed Site Existing Site Storm Event Peak Runoff Runoff Volume Peak Runoff Runoff Volume 2 Year 9.339 cfs 44,031 cf 9.179 cfs 43,147 cf 10 Year 15.35 cfs 73,038 cf 15.19 cfs 71,995 cf 100 Year 27.41 cfs 132,192 cf 27.27 cfs 130,994 cf 6