Rhode Island Code of Regulations › Title 250 - Department of Environmental Management › Chapter 150 - Water Resources › Subchapter 10 - Wastewater And Storm Water › Part 8 - Stormwater Management, Design and Installation Rules › Section 250-RICR-150-10-8.8 - Minimum Standard 2: Groundwater Recharge

Current through June 14, 2024
A. Stormwater
				  must be recharged within the same subwatershed to maintain baseflow at
				  pre-development recharge levels to the maximum extent practicable in accordance
				  with the requirements described in §§
										8.8(D) through
				  (H) of this Part. Applicants may be required
				  to provide a water budget analysis for proposed groundwater dewatering.
				  Recharge volume is determined as a function of annual pre-development recharge
				  for site-specific soils or surficial materials, average annual rainfall volume,
				  and amount of impervious cover on a site. Recharge must occur in a manner that
				  protects groundwater quality.
B.
				  Stormwater runoff from a LUHPPL is not allowed to infiltrate into groundwater.
				  The stormwater recharge requirement may be specifically waived if an applicant
				  can demonstrate a physical limitation that would make implementation
				  impracticable or where unusual geological or soil features may exist such as
				  significant clay deposits or ledge, where recharge does not currently occur;
				  fill soils; or areas of documented slope failure.
C. Maintaining pre-development groundwater
				  recharge conditions may also be used to reduce the volume requirements dictated
				  by other sizing criteria (water quality, channel protection, and overbank flood
				  control) and the overall size and cost of stormwater treatment
				  practices.
D. The recharge
				  criterion (Rev) requires that the following volume of stormwater be recharged
				  based on the amount of impervious area. The groundwater recharge requirement
				  may be waived or reduced by applying the LID Stormwater Credit outlined in
				  §
										8.18
				  of this Part. Recharge requirements are based on hydrologic soil group (HSG) as
				  follows:
Rev = (1 inch) (F) (I)/12
Where:
Rev = groundwater recharge volume (acre feet)
F = recharge factor, see table below in §
											8.8(F) of
					 this Part
I = impervious area (acres)
E. Recharge Factors Based on Hydrologic Soil
				  Group (HSG)
HSG
Recharge Factor (F)
A
0.60
B
0.35
C
0.25
D
0.10
F.
				  The recharge volume is considered as part of the total water quality volume
				  that must be provided at a site and must be achieved by disconnection of
				  impervious areas (see §
										8.18 of this Part), a
				  structural practice that infiltrates stormwater into the underlying soils or
				  substratum, or a combination of the two.
G. Roof runoff may be infiltrated without
				  pretreatment unless the roof is deemed to have a higher potential pollution
				  load pursuant to §
										8.14(C) of
				  this Part. Recharged roof runoff can be subtracted from WQv but not from larger
				  storm calculations, unless applicant verifies that the drywells are sized for
				  the 100-year, 24-hour Type III storm event.