Drainage Report

a ACS Anderson Consulting Services LLC Drainage Report West Essex Highlands Block 179, Lot 32 West Orange NJ March 12, 2023 Rev 1 April 27, 2023 Rev Sept 7, 2023 Rev Oct 3, 2023 Rev October 24, 2023 Rev 10-30-23 Digitally sigtedby Paul W. Anders SOR Datez: eae £0.29 16:15103°04'00' Paul W. Anderson PE PP CME NJ PE Lic. No. 33410 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ.07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com

Anderson Consulting Services LLC Table of Contents Location Map. Introduction. Methodology. Discussion..... Detention area 1 .. Detention area 2 Detention area 3.. Detention area 4.. Detention area 5.. we Canoe Brook Watershed Analysis. Canoe Brook Tributary Analysis. Basin Infiltration calculations..... Groundwater Recharge Spreadshee' Water Quality Calculation. Culvert Design.. Conclusion....... Appendix Drainage area maps Hydrocad calculations Full Hydrology Basin 1 without exfiltration Basin 2-1 without exfiltration Basin 2-2 without exfiltration Basin 2-3 without exfiltration Basin 2-4 without exfiltration Basin 2-5 without exfiltration Basin 2-6 without exfiltration Basin 3 without exfiltration Basin 4 without exfiltration Basin 5 without exfiltration ®NOAwWNNNS Groundwater recharge routings Basin 1 2yr with exfiltration Basin 2-1 2yr with exfiltration Basin 2-2 2yr with exfiltration Basin 2-3 2yr with exfiltration Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com

Basin 2-4 2yr with exfiltration A f > & Basin 2-5 2yr with exfiltration Basin 2-6 2yr with exfiltration ndersan' Gonsbling Services LLC. Basin 3 2yr with exfiltration Basin 4 2yr with exfiltration Basin 5 2yr with exfiltration Culvert Groundwater Mounding Analysis Contech water quality device sizing Figure 1.1: US.G.S. Map (from 1995 US.G.S. 7.5” Quadrangle: Caldwell, NJ). 12 Location Map 1 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com

Introduction f : The West Essex Highlands property has been designated as the location for muléfam help meet the affordable housing requirements of the Township of West Orange’ Nib" AS HarEuf thes court approved development plan for this property the limit of disturbance on the 120-acre parcel is limited to 30 acres leaving the remainder as open space to be utilized as passive recreation in its natural condition. The project design includes a stormwater management design that meets state stormwater standards for water quality, groundwater recharge and discharge rate. The drainage design has small scale infiltration basins with pre-treatment devices to provide green technology solutions for quantity , quality and recharge. One large scale infiltration basin with NJDEP approved green technology device for water quality throughout the drainage area and two porous pavement systems to provide green technology solutions for quality, quantity and recharge. The stormwater control systems have been routed with exfiltration for the quantity calculation to demonstrate compliance without reliance on exfiltration. The groundwater recharge calculations use exfiltration based on field soil testing with the appropriate factor of safety to demonstrate compliance with the recharge requirement and a calculation is included to demonstrate the basins completely evacuate within 72 hours. The calculations utilize Hydrocad, version 9.10, NJDEP approved intensity curves, and the SCS TR- 20 methodology to calculate the pre-and post-development runoff volumes. Methodology The drainage for the development area of the property is calculated for the existing and proposed conditions for the areas going to each of the 6 detention systems. Overland flow areas that will not drain to the detention system are calculated individually in each of the areas. The existing conditions for the site are considered wooded in good conditions per the ordinance standards. Discharge rates for the existing conditions under the 2, 10 and 100-year storm events are calculated with The Hydrocad drainage program and the SCS TR-20 method. Hydrographs for the proposed conditions for areas detained and un-detained are developed. Allowable discharge rates for the detention system are calculated and the proposed hydrograph is routed through a proposed detention system until the desired discharge rate is

-detained are developed. Allowable discharge rates for the detention system are calculated and the proposed hydrograph is routed through a proposed detention system until the desired discharge rate is achieved for each storm. Discussion Soil Conditions & Groundwater Recharge An extensive geotechnical investigation has been performed on the subject property to establish existing conditions. 15 borings and 27 test pits were performed in the development area in 2021 during the January to April testing window and testing was previously performed with a past development application. The results indicated a fairly uniform soil conditions. The percolation rates onsite indicate primarily a type D soil however due to the published maps indicating C soils onsite the stormwater calculations utilize C soils when selecting curve numbers. 2 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com

The geotechnical investigation found that significant area of the site proposed AY limitations to groundwater recharge in the form of shallow bedrock. Approximately? acres 6fttie-Site where proposed building B and C are located has bedrock located on average 4 ft below grade. This site specific limiting factor make the estimation groundwater recharge of existing conditions with the standard analysis grossly conservative. _ It also limits the project's ability to provide small scale green infrastructure in proximity to the area of disturbance. The proposed design with green technology solutions at the lower section of the site adjacent to the wetlands area then mimics the natural conditions of the site by taking stormwater that does not recharge into bedrock and recharging it into the deeper running permeable soils at the base of the hill. We believe that modeling the natural conditions as proposed meets the intent of the regulations. Additional soil tests we recently performed in the proposed basin areas to verify the soil conditions in the exact location of the stormwater management systems. These tests were found to be very similar to the adjacent ones previously performed. The older tests are within the standards to locate the seasonal high groundwater table and the new testing provided more permeability data within the basin area. Water Quality The project proposes 8 small scale infiltration basins which take the discharge for the proposed developed area of the property. These small scale infiltration basins will have mechanical pretreatment in the form of a Cascade separator which removed 50% of the suspended solid prior to discharge to the small scale infiltration basin. The combination of the two devices in series results in the removal of 90% of the suspended solids from the stormwater. The project also proposes one large scale infiltration basin which has filterra stormwater treatment devices before each inlet in a vehicle surface area. Filterra is approved as green technology for the removal of 80% of the suspended solids from stormwater Two porous pavement systems are proposed to provide a green technology solution for water quality quantity and recharge making all aspects of the stormwater system green technology. Water Quantity The stormwater system proposed has been designed to reduce the discharge from the site for the 2-, 10- and

ty and recharge making all aspects of the stormwater system green technology. Water Quantity The stormwater system proposed has been designed to reduce the discharge from the site for the 2-, 10- and 100-year storms as required by the stormwater regulations. Each of the drainage/detention areas has been designed to control stormwater to below its current discharge rate. The routing of the basins do not include exfiltration in the quantity analysis. The results of the stormwater analysis for existing and proposed discharge are provided in the tables below. Detailed Hydrocad output is also included in this report. Detention Basin 1 Area Tc Computations. The existing conditions of the drainage area that is routed to Basin 1 a forested area with very light underbrush due to deer over browsing. The path of the existing conditions Tc is shown on the Existing Conditions Drainage Area Map. The Tc is calculated in the Hydrocad program with the factors shown on the map and is as follows. 3 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com

The Basin 1 contributing area is 368392 sf of Woods in good condition. AA, i Fp The initial 100 LF is sheet flow with a slope of 5% in woods with light underbrus' The next segment is shallow concentrated flow 1260 If with a slope of 5.7% throtignawoudsvith ight underbrush. There is no discernable channel in the field along this path that would change the categorization of the flow type. Tc = 17.6 min. Total pre-development Tc= 32 min The proposed Tc for the area flowing to Detention 1 uses the following input Sheet flow 100 If @0.5% over grass Tc= 24 min Shallow concentrated flow 144 If over grass @ 6.9% Tc=0.6 min Shallow concentrated flow 642 If over pavement @ 2.6% Tc= 3.7 min Pipe flow 873 If of 18 inch pipe N= 0.13, To=1.9 min Total Tc = 30.2 min Un-detained Area associated with Basin 1. These are small area at the perimeter of the drainage area that have minimal distance to travel before exiting the area of analysis. The longest path is Sheet flow 70 If @ 8% over grass Tc=5.9 min Detention basin 1 collects water from the east side of the site that drains to the Canoe Brook. The existing conditions have been modeled with a coverage as woods is good condition as required by the standards with NOAA type D rainfall curves. The table below outlines the results of the routing for this area. Filterra Treatment devices have been added prior to each paved surface inlet providing approved green technology water quality treatment for the basin Large scale Infiltration basins are listed as green technology for quantity in Table 5-2. The basin has been routed without exfiltration for the quantity Without Exfiltrations EXISTING Permitted DETENTION | OVERLAND] TOTAL (CFS) (CFS) (CFS) (CFS) (CFS) 2YR 4.51 2.26 0 1.36 1.36 10 YR 11.02 7.71 75 2.97 3.72 100 YR 25.26 20.21 2.09 6.40 8.49 Water Quality Water Quality is attained with Filterra treatment devices which are approved as green technology for 80% suspended solids removal. Groundwater Recharge Because green technology has been provide for 80% suspended solid removal the groundwater recharge has been calculated and included in the recharge spreadsheet. 4 Detention Basin 2 Area Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com

The existing conditions of the drainage area that is routed to Basin 2 a forested ah \ifie? GS underbrush due to deer over browsing. The path of the existing conditions Tc isshol Existing Conditions Drainage Area Map. The Tc is calculated in the Hydrocad prégrertawitrrtHes -c factors shown on the map and is as follows. The Basin 2 contributing area is 465453 sf of Woods in good condition. The initial 100 LF is sheet flow with a slope of 0.5% in woods with light underbrush. Tc=14.4 min The next segment is shallow concentrated flow 1260 If with a slope of 5.7% through woods with light underbrush. There is no discernable channel in the field along this path that would change the categorization of the flow type. Tc = 17.6 min. Total pre-development Tc= 32 min Basin 2-1 Tc. Basin 2-1 collects runoff by overland flow from the area down hill of the dog park. The 17,946 sf area will be grass cover and the Tc was computed with the flowing factors Sheet flow 100 LF @6% Tc=6.1 Min Shallow concentrated flow 90 If @ 3.4% Tc=.5 min Total Tc = 6.6 min Basin 2-2 Tc. Basin 2-2 collects runoff from the parking area behind Building A. The area of 61,497 sf is mostly paved coverage with grass area outside and the Tc was computed with the following factors. Sheet Flow 60 LF @13 % grass cover Tc= 3min Shallow concentrated flow 120 If @ 4.5% Tc =.5 min, grass cover Pipe Flow 426 If of 12 inch pipe @ 3.5% N=0.01 Tc 1.1 min Total Tc = 4.6 min Basin 2-3 Tc. Basin 2-3 collect runoff from the area around the clubhouse and a portion of Kusik Drive. The Tc was computed with the following factors. Sheet Flow 100 LF @3% grass cover Tc= 8 min Shallow concentrated flow 60 If @ 3.3% Tc = .4 min, grass cover Shallow Concentrated Flow 72 LF@ 8% Tc =.2 min, Pavement Cover Pipe Flow 1326 If of 15 inch pipe @ 3% N=0.01 Tc 1.9 min Total Tc= 10.5 min Basin 2-4 Tc basin 2-4 collects runoff from behind Building C and the clubhouse parking lot. The Tc was computed with the following factors. Sheet Flow 100 LF @8% grass cover Tc= 5.4 min Shallow concentrated flow 120 If @ 2% Tc =.9 min, grass cover Pipe Flow 1692 If of 15 inch pipe @ 3.7% N=0.01 Tc 3.7 min Total Tc= 10 min 5 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com

BGO) Basin 2-5 Tc me Basin 2-5 collects runoff from the roof of building A. The Tc was computed with i . Sheet Flow 100 LF @ 1% on roof Te = 1 min Anderson Consutting Servioes LLC Pipe Flow 920 If of 12 inch pipe @ 4.1% N=0.01 Tc3 min Total Tc= 4.5 min Basin 2-6 Tc Basin 2-6 collects water from the roof and patio of building C. The Tc was computed with the following factors. Sheet Flow 100 If on roof s=1%, Tc= 1.5 min Shallow concentrated flow 40 LF @ 1% Te =.3 min Pipe flow 1622 LF s=3.7 % n= 0.01, 12 inch pipe tc= 4.8 min Total Tc = 6.6 min Un-detained Area associated with Basin 2. These are small areas at the perimeter of the drainage area that have minimal distance to travel before exiting the area of analysis. The longest path is Sheet flow 36 If @ 16% over grass Tc=4 min Detention basins 2-1 though 2-6 collects water from the east of drainage area 1 that drains to the Canoe Brook Tributary. The existing conditions have been modeled with a coverage as wood is good condition as required by the standards with NOAA type D rainfall curves. This area previously designed as one large scale infiltration basin has been redesigned to be 6 small scale infiltration basins with distinct drainage areas smaller than the 2.5-acre limit as required by the definition of a small scale infiltration basin. The table below outlines the results of the routing for this area without exfiltration. Small scale Infiltration basins are listed as green technology for quality, quantity and recharge in Table 5-2 EXISTING | Permitted | OL 2-1 2-2 2-3 2-4 2-5 2-6 TOTAL 2yr 5.69 2.85 91 0.4 11 15 11 19 18 1.69 10 yr_| 13.90 9.73 1.98 44 61 75 62 64 68 5.72 100 32.35 25.88 4.26 2.50 2.02 2.26 2.06 1.16 1.27 16.53 yr Water Quality Water quality in drainage area 2 is provided with a pre-treatment cascade separator prior to flowing into the small-scale infiltration basins. Table 5-1 lists small-scale infiltration basins as green technology for water quality, quantity, and groundwater recharge. Total removal from the separator and small scale infiltration basin is 90% 6 Anderson Consulting Services LLC 40 Miller Drive, Boonton, NJ 07005 973-975-0703 (O) 973-886-7336 (C) PAndersonpe@gmail.com