STORMWATER MANAGEMENT REPORT FOR THE BORGATA OUTDOOR EVENT AREA POOL ADDITION

Transcription

1 STORMWATER MANAGEMENT REPORT FOR THE BORGATA OUTDOOR EVENT AREA POOL ADDITION City of Atlantic City, Atlantic County, New Jersey Prepared For: Marina District Development Company, LLC One Borgata Way Atlantic City, NJ Prepared By: PAULUS, SOKOLOWSKI AND SARTOR, LLC 1909 Route 70 East, Suite 307 Cherry Hill, New Jersey P/N December 23, 2015 Mark Herrmann, P.E. N.J. License # 48668

2 Stormwater Management Report Borgata Outdoor Event Area Pool Addition i TABLE OF CONTENTS 1.0 Introduction Stormwater Design Criteria Soil Conditions Stormwater Runoff Quantity Stormwater Runoff Quality Groundwater Recharge Nonstructural Stormwater Management Strategies Storm Sewer Design Conclusions... 3 Plan References: Application for Amended Preliminary and Final Site Plan Approval, Borgata Outdoor Event Area Pool Addition prepared by PS&S, dated December 23, 2015." P:\02265\0066\Reports\Civil\Storm_Report\_Borgata_OutdoorEvent_StormwaterReport.docx

3 Stormwater Management Report 1 Borgata Outdoor Event Area 1.0 INTRODUCTION The Applicant, Marina District Development Company, LLC (MDDC), is proposing to renovate the previously approved outdoor event area to eliminate a portion of the concert venue and replace it with an outdoor pool. Construction activities associated with the Project include removal of the decomposed granite area, a portion of the synthetic turf, and several of the structures. These will be replaced with a pool, concrete and IPE decks and landscaped areas. The site, known as Block 576; Lots 1.05, 1.07, 1.08, 1.10 and 1.12 on the City of Atlantic City Tax Map Sheet 94, is bound by the Borgata North Expansion to the south, Borgata surface parking lot and a vacant lot to the east, the Borgata employee garage to the north, and the Borgata self-park garage to the west. The intended purpose of this report is to demonstrate compliance with applicable stormwater management regulations as dictated by the City of Atlantic City code and N.J.A.C. 7: STORMWATER DESIGN CRITERIA The stormwater management design has been performed in accordance with the City of Atlantic City code and N.J.A.C. 7:8. According to N.J.A.C. 7:8 a Major Development is to meet the runoff quantity, runoff quality and groundwater recharge requirements. A Major Development is defined as a development which disturbs one or more acres of land or increases impervious coverage by one-quarter of an acre. The Outdoor Event Area project disturbs approximately 1.03 acres and therefore, meets the criteria for a Major Development. However, the impervious coverage has been decreased by 1,291 sf within the project area. Additional impervious area will be created by the installation of several curb islands in the adjacent parking lot. The project is, therefore, subject to the applicable stormwater management requirements of N.J.A.C 7:8. Stormwater management facilities have been designed to meet the requirements of the New Jersey Soil Erosion and Sediment Control Standards, the City of Atlantic City Code, N.J.A.C. 7:8, and the NJ BMP Manual. 3.0 SOIL CONDITIONS The hydrologic soil characteristics of the watershed were derived from the USDA Natural Resources Conservation Service Soil Survey. The site soils, as shown in Appendix B, are defined as Transquaking mucky peat. This soil type has the following characteristics. TrkAv Transquaking mucky peat, 0 to 1 percent slopes. This soil type is classified as Hydrologic Soil Group A/D. The water table has an upper limit of 0.0 feet and a lower limit of greater than 6 feet. This soil is subject to frequent but brief flooding and has a high surface runoff. The subject property, formerly the City of Atlantic City Municipal Landfill, has been capped and developed upon. The construction of the Borgata Hotel and Casino, as well as its supporting parking structures and surface lots, resulted in several feet of clean fill being placed above the landfill cap. Due to these conditions, a Hydrologic Soil Group of A was utilized for the stormwater conveyance sizing. 4.0 STORMWATER RUNOFF QUANTITY The runoff quantity regulations require one of the following measures to be met in order to address stormwater runoff quantity for a proposed development. 1. Demonstrate that the stormwater leaving the site for the 2, 10, and 100 year storm events does not exceed, at any point in time, the pre-construction runoff quantities for the same storm event. P:\02265\0066\Reports\Civil\Storm_Report\_Borgata_OutdoorEvent_StormwaterReport.docx

4 Stormwater Management Report 2 Borgata Outdoor Event Area 2. Demonstrate that there is no increase in the peak runoff rates for the 2, 10, and 100 year storm events and that the increased volume or change in timing of stormwater runoff will not increase flood damage at or downstream of the site. 3. Demonstrate that the peak runoff rates for the 2, 10, and 100 year storm events are 50, 75, and 80 percent of the pre-construction peak runoff rates respectively. 4. In tidal flood hazard areas, stormwater runoff quantity analysis shall only be applied if the increased volume of stormwater runoff could increase flood damages below the point of discharge. The proposed improvements ultimately discharge to the Clam Thorofare which is a tidal tributary to the Absecon Inlet. The Absecon Inlet then directly discharges to the Atlantic Ocean. As this area is both tidal and any increase in stormwater runoff would represent a minimal increase as compared to the Atlantic Ocean, runoff quantity analysis has not been performed. 5.0 STORMWATER RUNOFF QUALITY A land development that creates 0.25 acres or more of new or additional impervious surface must include stormwater management measures that reduce the average annual total suspended solids (TSS) load in the site s post-construction runoff by 80% for new impervious cover and 50% for existing impervious cover. The proposed improvements include the addition of pervious planter areas to the fully impervious site. These improvements account for a net decrease in impervious cover and as such, stormwater runoff quality measures have not been provided for the project. 6.0 GROUNDWATER RECHARGE Pursuant to N.J.A.C. 7:8-5.4 (a) 2 iii(1), stormwater shall not be recharged if the stormwater is from areas of high pollutant loading which includes areas where recharge would be inconsistent with a remedial action work plan or a NJDEP approved landfill closure plan. The subject property is located on the site of the former City of Atlantic City Municipal Landfill. Site remediation and landfill closure activities have been performed in accordance with a NJDEP approved Sanitary Landfill Disruption and Closure/Post Closure Cap Plan, therefore, groundwater recharge is not recommended or required for the development. 7.0 NONSTRUCTURAL STORMWATER MANAGEMENT STRATEGIES In accordance with N.J.A.C. 7:8-5.3, nonstructural stormwater management strategies have been incorporated to the maximum extent practical. Below is a summary of the nonstructural stormwater management strategies implemented in the design of the stormwater management system. 1. Protect areas that provide water quality benefits or areas particularly susceptible to erosion and sediment loss: As a closed landfill, the existing site features do not currently provide a water quality benefit for the site. A Soil Erosion and Sediment Control plan has been prepared to prevent erosion of the soils and control sediments onsite. 2. Minimize impervious surfaces and break up or disconnect the flow of runoff over impervious surfaces: The existing site is fully impervious and is part of the cover of the existing landfill. Due to site constraints the opportunity to disconnect impervious surfaces is very limited. However, the addition of planter areas allow for an increase in pervious areas as compared to the existing condition. The stormwater runoff for the proposed development is directly connected to the existing storm sewer conveyance system. 3. Maximize the protection of natural drainage features and vegetation: No natural drainage features or vegetation (excluding grass areas) exist on the project site. P:\02265\0066\Reports\Civil\Storm_Report\_Borgata_OutdoorEvent_StormwaterReport.docx

5 Stormwater Management Report 3 Borgata Outdoor Event Area 4. Minimize the decrease in the time of concentration from pre-construction to postconstruction: Due to the proximity to a tidal water body, the site is not required to meet the stormwater runoff quantity requirements of N.J.A.C 7:8-5.4, therefore an analysis for the pre-construction versus post-construction time of concentration is not required. 5. Minimize land disturbance including clearing and grading: The project site has been previously disturbed as part of the landfill closure process. The proposed development will not disturb any additional areas that have not been previously disturbed. 6. Minimize soil compaction: Due to the site being a former landfill, groundwater recharge is not required, therefore, a reduction in the soil compaction onsite for infiltration is not necessary. In addition, soil compaction measures are required in order to maintain the landfill cap. 7. Provide low-maintenance landscaping that encourages retention and planting of native vegetation and minimizes the use of lawns, fertilizers and pesticides: The proposed development is an Outdoor Pool Area, therefore higher quality landscaping materials have been used. While lawn areas are not proposed planter areas have been added throughout the site. 8. Provide vegetated open-channel conveyance systems discharging into and through stable vegetated areas: The site is bound by the Borgata Hotel Casino, parking garages and a parking lot. No open-channel conveyance exists on site, nor is there opportunity to create open-channel flow to the Clam Thorofare. 9. Provide other source controls to prevent or minimize the use or exposure of pollutants at the site in order to prevent or minimize the release of those pollutants into stormwater runoff: During the previous improvements to the site the an 80% TSS removal treatment device was installed to minimize the release of pollutant into the stormwater discharging from the project site. Soil erosion control measures have been provided in accordance with the Cape-Atlantic Soil Conservation District to control erosion and sediment throughout construction. 8.0 STORM SEWER DESIGN The Rational Method has been used for the storm inlet and pipe design. Bentley s StormCad version 8i has been utilized in the design. The pipes have been designed for the 25 year storm event with a minimum pipe size of 12 inches. The Manning s n value used for HDPE is A minimum slope of 0.5% has been used. 9.0 CONCLUSIONS This report has demonstrated that the proposed improvements meet the requirements of the City of Atlantic City as well as N.J.A.C. 7:8. Due to the location and previous land use on site, stormwater runoff quantity measures and groundwater recharge methods are not required. Due to the reduction in impervious cover water quality measures are also not required. P:\02265\0066\Reports\Civil\Storm_Report\_Borgata_OutdoorEvent_StormwaterReport.docx

6 74 26' 9'' W Hydrologic Soil Group Atlantic County, New Jersey (Borgata Hotel Casino Outdoor Event Center) 74 26' 0'' W 39 22' 53'' N ' 53'' N ' 45'' N ' 45'' N 74 26' 9'' W N Map Scale: 1:1,310 if printed on A portrait (8.5" x 11") sheet. Meters Feet Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS ' 0'' W Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/18/2014 Page 1 of 4

7 Hydrologic Soil Group Atlantic County, New Jersey (Borgata Hotel Casino Outdoor Event Center) MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Atlantic County, New Jersey Survey Area Data: Version 11, Sep 24, 2014 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: 26, 2011 Mar 19, 2011 Mar The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/18/2014 Page 2 of 4

8 Hydrologic Soil Group Atlantic County, New Jersey Borgata Hotel Casino Outdoor Event Center Hydrologic Soil Group Hydrologic Soil Group Summary by Map Unit Atlantic County, New Jersey (NJ001) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI TrkAv UdrB Transquaking mucky peat, 0 to 1 percent slopes, very frequently flooded Udorthents, refuse substratum, 0 to 8 percent slopes A/D % B % Totals for Area of Interest % Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/18/2014 Page 3 of 4

9 Hydrologic Soil Group Atlantic County, New Jersey Borgata Hotel Casino Outdoor Event Center Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 12/18/2014 Page 4 of 4

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14 REV. / ISSUE DATE DESCRIPTION PAULUS, SOKOLOWSKI AND SARTOR, LLC ROUTE 70 EAST SUITE 307 CHERRY HILL, NEW JERSEY PHONE: (856) PROJECT BORGATA OUTDOOR EVENT AREA POOL ADDITION BLOCK 576, LOTS 1.05, 1.07, 1.08, 1.10, & 1.12 ONE BORGATA WAY, ATLANTIC CITY, NJ SHEET TITLE INLET DRAINAGE AREA PLAN PROJ. NO.: DATE: DRAWN BY: CHECKED BY: SCALE: SHEET NO /23/2015 KDR MH 1" = 40' DA-1

15 STORM DRAINAGE COMPUTATION SHEET PROJECT NAME: Borgata Outdoor Event Area Pool Addition MUNICIPALITY: City of Atlantic City COUNTY: Atlantic County DATE: 12/23/2015 COMPUTED BY: KDR SHEET: 1 OF 1 STORM: 25 YR password: pipe INLET NUMBER DRAINAGE AREA ( C ) A x C LENGTH OF PIPE L FROM TO INCREMENT TOTAL C INCREMENT TOTAL OVERLAND COMPUTATION TABLE - STORM SEWER DESIGN FLOW TIME (TC) IN U/S PIPE CUM. TIME IN PIPE FEET ACRES ACRES ACRES ACRES MIN MIN MIN IN / HR C.F.S. IN. FT / FT C.F.S. F.P.S. F.P.S. A103 A HDPE A102 Ex.Area HDPE Ex.Area Ex.A Inlet HDPE RAINFALL INTENSITY I DISCHARGE Q=CIA DIA. SLOPE MATERIAL MANNING N VALUE PIPE FACTOR CAPACITY FLOWING FULL FLOWING FULL VELOCITY DESIGN FLOW U/S END INVERTS D/S END A101 Ex.A Inlet HDPE Ex.A Inlet Ex.MH HDPE