2022 08 Drainage Report

STORMWATER MANAGEMENT, GROUNDWATER RECHARGE AND WATER QUALITY ANALYSIS For SHI Builders Proposed Residential Subdivision Block 80.03, Lots 21 & 10 2 & 10 Ridge Road Township of West Orange Essex County, New Jersey Prepared by: ip) DYNAMIC ENGINEERING 1904 Main Street Lake Como, NJ 07719 (732) 974-0198 Robert P. Freud, P.E., P.P. NJ Professional Engineer License #41938 August 2022 DEC# 4266-99-001

Ix. XL Site Description. Design Overview. Existing Drainage Conditions .... Proposed Drainage Conditions. Design Methodology. TABLE OF CONTENTS Stormwater Management System Design & Green Infrastructure Compliance....... 5 Runoff Rates . Water Quality Groundwater Recharge... Standards for Off-Site Stability Conclusion. NRCS Web Soil Survey Hydrograph Summary Reports — Existing & Proposed Conditions 2, 10, 25, & 100-year Hydrograph Summary Reports — Water Quality Storm Stormwater Collection System Calculations (Pipe Sizing) Overflow Spillway Calculations Report of Preliminary Geotechnical and Stormwater Basin Area Investigation, prepared by Dynamic Earth, LLC (Attached Separately) Drainage Area Maps

I. SITE DESCRIPTION The subject site is located at 2 & 10 Ridge Road in the Township of West Orange, Essex County, New Jersey. The site is identified as Block 80.03, Lot 21 & 10 on the Township of West Orange Tax Map Sheet #32. The subject site is currently undeveloped with overgrown wooded areas. The existing conditions of the site have been verified by the ALTA/NSPS Land Title Survey as prepared by Dynamic Survey, LLC, dated 05/11/2022. The scope of the study includes the proposed which consists of subdividing into four total lots and developing each parcel with four new single-family houses with a prototypical footprint size of 40’x60’ totaling approximately 9,600 SF with accompanying driveways. II. DESIGN OVERVIEW This report has been prepared to define and analyze the stormwater drainage conditions that would occur as a result of the development of the subject site into four subdivided lots with four new single-family residential houses on Block 80.03, Lots 21 & 10 in the Township of West Orange, Essex County, New Jersey. The scope of the study includes the proposed which consists of subdividing into four total lots and developing each parcel with four new single-family houses with assumed footprint sizes totaling approximately 9,600 SF (2,400 SF each) with accompanying driveways as well as stormwater management facilities as shown on the accompanying engineering drawings. Based upon the fact that the proposed development will result in more than one (1) acre of land disturbance, this project is classified as a “major development”. Therefore, the proposed development has been designed to meet the stormwater runoff quantity, quality, and groundwater recharge standards, set forth by the Township of West Orange Land Use Ordinance and NJAC 7:8. Accordingly, the following items are addressed within this report: Groundwater recharge standards (7:8-5.4) Stormwater runoff quality standards (7:8-5.5) Stormwater runoff quantity standards (7:8-5.6) Calculation of stormwater runoff and groundwater recharge (7:8-5.7) A hydrological evaluation is provided for the NJDEP Water Quality, 2, 10, 25, and 100-year storm events utilizing the Urban Hydrology for Small Watershed TR55 method. SHI Builders August 2022 DEC# 4266-99-001 -1-

The Township of West Orange and NJAC 7:8 flow reduction requirements are as follows: 2-year: 50% reduction 10-year: 25% reduction 25-year: Maintain existing flow (no reduction requirement) 100-year: 20% reduction It is the intention of the design of this facility to comply with the Stormwater Management Best Management Practices Manual. Ill. EXISTING D GE CONDITI! The area to be analyzed consists of approximately 3.71 acres and is comprised of impervious, brush and wooded areas. Currently, the majority of stormwater runoff generated by the subject site drains to Mount Pleasant Avenue at the south-east corner of the site through overland flow. The subject site has been evaluated with the following drainage sub-watershed areas as depicted on the Existing Drainage Area Map included within the Appendix of this report. Study Area Mount Pleasant Avenue: This area consists of the entire site to be disturbed, which includes impervious, brush and wooded areas. As noted above, under existing conditions, stormwater runoff generated by this area is ultimately tributary to Mount Pleasant Avenue via overland flow. SOIL TYPE SOIL TYPE NAME Ecce BogCc Boonton loam, 8 to 15 percent slopes, extremely stony € HanBe Haledon silt loam, 0 to 8 percent slopes, extremely stony Cc YaobBe Yalesville — Boonton — Holyoke complex, 0 to 8 percent slopes, c extremely stony USBONB [1] Urban land, Boonton substratum — Boonton complex, 0 to 8 percent slopes [1] No soil group was provided by NRCS, therefore B rating was assumed for existing conditions while D rating soils were assumed for proposed conditions. SHI Builders August 2022 DEC# 4266-99-001 -2-

IV. PROPOSED SITE CONDITIONS As noted above, the proposed development includes the development of four new single-family residential houses with assumed footprint sizes totaling approximately 9,600 SF (2,400 SF each) with accompanying driveways. Additional site improvements include constructing stormwater management facilities for each subdivided lot. The stormwater management system includes four (4) aboveground small-scale bioretention basins also known as rain gardens to detain stormwater runoff generated by the development in order to meet the stormwater management requirements set forth by the Township of West Orange and NJAC 7:8. The proposed site conditions have been evaluated using the following drainage sub-watershed areas as depicted on the Proposed Drainage Area Map included within the Appendix of this report. Study Area asant Avenue Undetained: This area consists of a small portion of the northern-most and easterly disturbed portions of the subject area which includes open grass cover for which stormwater runoff is undetained. Stormwater runoff from this area flows via overland flow to the east, ultimately tributary to Mount Pleasant Avenue located east of the site. Study Area Basin A: This area consists primarily of the stormwater runoff associated with the development of improvements associated with the proposed Lot 1 located at the south-west portion of the tract, which includes the proposed single-family residential house, driveway, a small portion of Ridge Road, and open grass/lawn cover. Stormwater runoff from this area will flow overland to the proposed bioretention basin located at the east side of the proposed lot. Stormwater runoff generated within this area is ultimately tributary to Mount Pleasant Avenue located at the east of the site. Study Area Basin B: This area consists primarily of the stormwater runoff associated with the development of improvements associated with the proposed Lot 2 located at the south-west portion of the tract, which includes the proposed single-family residential house, driveway, a small portion of Ridge Road, and open grass/lawn cover. Stormwater runoff from this area will flow overland to the proposed bioretention basin located at the east side of the proposed lot. Stormwater runoff generated within this area is ultimately tributary to Mount Pleasant Avenue located at the east of the site. Study

bioretention basin located at the east side of the proposed lot. Stormwater runoff generated within this area is ultimately tributary to Mount Pleasant Avenue located at the east of the site. Study Area Basin C: This area consists primarily of the stormwater runoff associated with the development of improvements associated with the proposed Lot 3 located at the north-west portion of the tract, which includes the proposed single-family residential house, driveway, a small portion of Ridge Road, and open grass/lawn cover. Stormwater runoff from this area will flow overland to the proposed bioretention basin located at the east side of the proposed lot. Stormwater runoff generated within this area is ultimately tributary to Mount Pleasant Avenue located at the east of the site. SHI Builders August 2022 DEC# 4266-99-001 -3-

Study Area Basin D: This area consists primarily of the stormwater runoff associated with the development of improvements associated with the proposed Lot 4 located at the north-west portion of the tract, which includes the proposed single-family residential house, driveway, a small portion of Ridge Road, and open grass/lawn cover. Stormwater runoff from this area will flow overland to the proposed bioretention basin located at the east side of the proposed lot. Stormwater runoff generated within this area is ultimately tributary to Mount Pleasant Avenue located at the east of the site. V. DESIGN METHODOLOGY The intention of the design of the proposed stormwater management facilities for this development is to provide measures as required to address the applicable aspects of the Township of West Orange Land Use Ordinance and NJAC 7:8. In order to prepare the stormwater management design for the subject site, extensive initial investigation of the property and topography was performed. On-site review of the tract was initially performed by Dynamic Engineering Consultants, PC to verify existing site conditions and land cover characteristics. Dynamic Survey, LLC was contracted to prepare the ALTA/NSPS Land Title Survey with topography to depict the existing site conditions. Furthermore, Dynamic Earth, LLC performed test pits within the site to establish the seasonal high-water table and soil permeability rates. Based on our review of the existing site conditions and survey, the Drainage Area Maps for the existing and proposed site conditions as defined within this report were established. A grading plan was developed for the proposed site improvements with consideration to the existing drainage patterns. The plan was designed to ensure runoff from the proposed development could be directed to stormwater management facilities in order to address the applicable sections of the Township of West Orange Land Development Ordinance and NJAC 7:8. The rainfall data utilized for the analysis of the existing and proposed drainage conditions is based upon the New Jersey 24 Hour Rainfall Frequency Data for Essex County as published by the USDA NRCS utilizing the NOAA Region D rainfall distribution. Under proposed conditions, the stormwater runoff from the subject site and surrounding areas is conveyed by overland flow for collection by the proposed aboveground

AA Region D rainfall distribution. Under proposed conditions, the stormwater runoff from the subject site and surrounding areas is conveyed by overland flow for collection by the proposed aboveground small-scale bioretention basins with underdrains. The proposed basins are designed to detain and infiltrate through the planted vegetation in the soil bed to the underdrains and be released at a controlled rate through outlet control structures in order to satisfy the runoff peak rate reductions (quantity requirement) set forth by the Township of West Orange and NJAC 7:8. The overall stormwater management design for the subject site has been evaluated by Dynamic Engineering Consultants to ensure that the overall development satisfies the standards set forth in the Township of West Orange Land Use Ordinance and NJAC 7:8. SHI Builders August 2022 DEC# 4266-99-001 -4-

VI. STORMWATER MANAGEMENT SYSTEM DESIGN & GREEN INFRASTRUCTURE COMPLIANCE As detailed above, in order to meet the stormwater runoff quantity requirements for the proposed development, the stormwater management system design includes four (4) proposed aboveground small-scale bioretention basins with underdrains. The proposed development is not subject to quality or groundwater recharge requirements — More information will be detailed in the following sections of this report. The stormwater management design utilizes four (4) small scale bioretention systems with underdrains. The systems will accept runoff via overland flow. The collected stormwater runoff will infiltrate through the planted vegetation in the soil bed to the underdrain and be released at a controlled rate through outlet control structures in order to satisfy the runoff peak rate reductions (quantity requirement). Although quality requirements are not required, the basins will also provide 80% TSS removal. The stormwater runoff from yard areas and impervious surfaces will be conveyed to the basins via overland flow and discharged at a controlled rate using outlet control structures. In accordance with the New Jersey Stormwater Best Management Practices Manual, the following design considerations have been satisfied: * Bottom of gravel layer must be a minimum of one (1) foot above Seasonal High-Water Table + System must fully drain volume within 72 hours * Bottom of system must be as level as possible * Construction of system must be done to avoid compaction of sub-grade soils + Minimum design permeability rate of 0.5 Inches/hour + — System must be designed to safely convey overflow volume + System may not be used where there is risk of basement flooding, etc. Green Infrastructure Design Standards Compliance — Small Scale Bioretention Basins BMP Criteria Requirement Basin A Basin B Basin C Basin D lear 2.5 Ac 0.669Ac | 0.831Ac | 0.821Ac } 0.422 Ac Drainage Area [1] Max. Drain Time 72 Hrs 25.95 Hrs | 26.30Hrs | 25.90Hrs | 25.50 Hrs Min. Subsoil Design : 7 . . , P ability Rate 0.5 in/hr 0.5 in/hr 0.5 in/hr 0.5 in/hr 0.5 in/hr Min. Separation between 1.0 FT with Additional | Additional | Additional | Additional SHWT & BMP Bottom ° F soils testing | soils testing | soils testing | soils testing underdrain Fi A : : A 7 . is required is required is required is required [1] Does not

al | Additional | Additional SHWT & BMP Bottom ° F soils testing | soils testing | soils testing | soils testing underdrain Fi A : : A 7 . is required is required is required is required [1] Does not include area of BMP SHI Builders August 2022 DEC# 4266-99-001 -5-