Two‐Day Stormwater Management Design Review Course, October 29 & 31, 2019 NJ DEP Division of Water Quality 1 Mounding Analysis EXAMPLES Groundwater Changi Wu/Lisa Schaefer NJDEP Division of Water Quality SWMDR Training Day 2 October 31, 2019 Introduction • Demonstrate simple analysis • Demonstrate stretching the time interval • Demonstrate applicability to drainage pipes • Demonstrate calculating impacts to nearby structures Presentation Goals 2
13
Embed
Groundwater Mounding Analysis Examples...Mounding Analysis EXAMPLES Groundwater Changi Wu/Lisa Schaefer NJDEP Division of Water Quality SWMDR Training Day 2 October 31, 2019 Introduction
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Changi Wu/Lisa SchaeferNJDEP Division of Water Quality
SWMDR Training Day 2October 31, 2019
Introduction
• Demonstrate simple analysis• Demonstrate stretching the time interval• Demonstrate applicability to drainage pipes• Demonstrate calculating impacts to nearby
1. No adverse hydraulic impact to groundwater2. Adverse hydraulic impact to groundwater and
adjustment of infiltration period3. Underground perforated pipe4. Drywell
3
Scenarios:
No adverse hydraulic impact to groundwater scenario
• A major development located in the coastal plain proposes an infiltration basin, whose bottom footprint measures 50 ft by 50 ft, to infiltrate 5,000 cf of runoff generated by the Water Quality Design Storm (WQDS). o The maximum depth of ponding water is designed to be
2 ft o Soil testing was performed in accordance with Appendix Eo The soil testing report shows that the Seasonal High Water
Table (SHWT) is 7.5 ft below the 6 in thick bottom sand layer of the basin
o The tested soil permeability rate of the most restrictive soil horizon below the basin is 4 in/hr
Adverse hydraulic impact to groundwater and adjustment of drain time scenario
• A major development located in the coastal plain proposes an infiltration basin, whose bottom footprint measures 88 ft by 88 ft, to infiltrate 15,000 cf of runoff generated by the 2-year design storm. o The maximum depth of ponding water is designed to be
2 ft
o Soil testing was performed in accordance with Appendix E
o The soil testing report shows that SHWT is 7.5 ft below the 6-in thick bottom sand layer of the basin
o The tested soil permeability rate of the most restrictive soil horizon below the basin is 4 in/hr
9
Adverse hydraulic impact to groundwater and adjustment of drain time scenarioStep #1: Calculate the duration of infiltration period
Adverse hydraulic impact to groundwater and adjustment of drain time scenarioA Comparison of Mounding Effects Caused by Different Recharge Rates
15
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
0 20 40 60 80 100 120 140
---- R = 2.0 in/hr @ 11.62 hrs; ̶̶̶̶̶ ̶̶̶̶̶ ̶̶̶̶̶ R = 1.0 in/hr @ 23.24 hrs
.
SHWT (7.5 ft below sand layer)
Infiltration Basin
Sand Layer
Underground perforated pipe scenario
• A site is located in the coastal plain. A 500 LF, 36-inch diameter underground perforated pipe is proposed to store and infiltrate 12,000 cf of runoff. o The proposed duration of infiltration period is 24 hro The building has a basement floor located just above the
groundwater table. The center of the underground pipe is 20 ft away from the building
o Soil testing was performed in accordance with Appendix Eo The soil testing report shows that Seasonal High Water
Table (SHWT) is 2 feet below the pipeo The tested soil permeability rate of the most restrictive soil
• A site is located outside the coastal plain. A 7 ft high by 5 ft diameter drywell is proposed to store and infiltrate 137.4 cf of roof runoff from a single-family home for the Water Quality Design Storm.o The proposed duration of infiltration period is 42 hr o The house has a basement floor located just above the
groundwater table. The center of the drywell is 10 ft away from the house.
o Soil testing was performed in accordance with Appendix Eo The soil testing report shows that Seasonal High Water
Table (SHWT) is 2 ft below the bottom of the drywello The tested soil permeability rate of the most restrictive soil
Bureau of Nonpoint Pollution ControlDivision of Water Quality401 East State StreetPO Box 420, Mail Code 401-2BTrenton, NJ 08625-420Tel: 609-633-7021www.njstormwater.org