Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 875 - VIRGINIA EROSION AND STORMWATER MANAGEMENT REGULATION › Part V - Criteria and Requirements for Regulated Land-Disturbing Activities › Article 4 - Water Quantity and Water Quality Technical Criteria for Grandfathered Projects and Time Limits of Applicability Projects › Section 9VAC25-875-690 - General

Current through Register Vol. 40, No. 24, July 15, 2024
A.
					 Determination of flooding and channel erosion impacts to receiving streams due
					 to land-disturbing activities shall be measured at each point of discharge from
					 the land disturbance and such determination shall include any runoff from the
					 balance of the watershed that also contributes to that point of
					 discharge.
B. The specified design
					 storms shall be defined as either a 24-hour storm using the rainfall
					 distribution recommended by the U.S. Department of Agriculture's Natural
					 Resources Conservation Service (NRCS) when using NRCS methods or as the storm
					 of critical duration that produces the greatest required storage volume at the
					 site when using a design method such as the Modified Rational Method.
C. For purposes of computing runoff, all
					 pervious lands in the site shall be assumed prior to development to be in good
					 condition (if the lands are pastures, lawns, or parks), with good cover (if the
					 lands are woods), or with conservation treatment (if the lands are cultivated);
					 regardless of conditions existing at the time of computation.
D. Construction of stormwater management
					 facilities or modifications to channels shall comply with all applicable laws,
					 regulations, and ordinances. Evidence of approval of all necessary permits
					 shall be presented.
E. Impounding
					 structures that are not covered by the Impounding Structure Regulations
					 (4VAC50-20) shall be engineered for structural integrity during the 100-year
					 storm event.
F. Predevelopment and
					 post-development runoff rates shall be verified by calculations that are
					 consistent with good engineering practices.
G. Outflows from a stormwater management
					 facility or stormwater conveyance system shall be discharged to an adequate
					 channel.
H. Proposed residential,
					 commercial, or industrial subdivisions shall apply these stormwater management
					 criteria to the land disturbance as a whole. Individual lots in new
					 subdivisions shall not be considered separate land-disturbing activities, but
					 rather the entire subdivision shall be considered a single land development
					 project. Hydrologic parameters shall reflect the ultimate land disturbance and
					 shall be used in all engineering calculations.
I. All stormwater management facilities shall
					 have an inspection and maintenance plan that identifies the owner and the
					 responsible party for carrying out the inspection and maintenance
					 plan.
J. Construction of stormwater
					 management impoundment structures within a Federal Emergency Management Agency
					 (FEMA) designated 100-year floodplain shall be avoided whenever possible. When
					 this is unavoidable, all stormwater management facility construction shall be
					 in compliance with all applicable regulations under the National Flood
					 Insurance Program ( 44 CFR Part 59 ).
K. Natural channel characteristics shall be
					 preserved to the maximum extent practicable.
L. Land-disturbing activities shall comply
					 with the ESCL or VESMA, as applicable, and attendant regulations.
M. Flood control and stormwater management
					 facilities that drain or treat water from multiple development projects or from
					 a significant portion of a watershed may be allowed in Resource Protection
					 Areas defined in the Chesapeake Bay Preservation Act provided such facilities
					 are allowed and constructed in accordance with the VESMA and this chapter, and
					 provided that (i) the local government has conclusively established that the
					 location of the facility within the Resource Protection Area is the optimum
					 location; (ii) the size of the facility is the minimum necessary to provide
					 necessary flood control, stormwater treatment, or both; (iii) the facility must
					 be consistent with a comprehensive stormwater management plan developed and
					 approved in accordance with
					 9VAC25-875-660 or with a stormwater
					 management plan that has been approved prior to July 1, 2012, by the
					 department, the Chesapeake Bay Local Assistance Board prior to its abolishment
					 on July 1, 2012, or the Board of Conservation and Recreation; (iv) all
					 applicable permits for construction in state or federal waters must be obtained
					 from the appropriate state and federal agencies; (v) approval must be received
					 from the local government prior to construction; and (vi) routine maintenance
					 is allowed to be performed on such facilities to ensure that they continue to
					 function as designed. It is not the intent of this subsection to allow a best
					 management practice that collects and treats runoff from only an individual lot
					 or some portion of the lot to be located within a Resource Protection
					 Area.
Statutory Authority: §
													62.1-44.15:28 of the Code of
						  Virginia; Chapters 68 and 758 of the 2016 Acts of
						  Assembly.