Stormwater Management

facebooktwittermail
Print Friendly, PDF & Email

Redevelopment of Innsbrook to a vibrant, mixed-use community for the benefit of all stakeholders is predicated on three integral components: (1) Urban Mixed-Use (“UMU”) designation on the Henrico County Comprehensive Plan, (2) Urban Development Area (“UDA”) designation by the Board of Supervisors and (3) acceptance by Henrico County of the Innsbrook Comprehensive Stormwater Plan that incorporates the first two elements and allows them to be achieved.  Close coordination is essential to making these advanced planning objectives a reality.

Click Here For Comprehensive
Stromwater management Report PDF

Stormwater Management: Concern for the long term rights of all Innsbrook property owners to the lake system as a communal BMP caused the IOA to commission an Innsbrook Comprehensive Stormwater Management Plan.  This plan was submitted to Henrico County and accepted by them.  The result was to grandfather the development rights of all Innsbrook property owners and to prevent those outside Innsbrook but still in the drainage basin from utilizing our lake system for their own development plans.  The Executive Summary from this report is outlined below.

In order to ensure the rights of each Innsbrook property owner to use their allocated share of the lake system as a BMP for future development, a master worksheet has been created showing the impervious surface area for each property owner as a percentage of their total land area and their allocated percentage under the Stormwater Management Plan.  If a property owner wishes to change the impervious surface area on their property, whether as a result of new development or otherwise, engineered plans are to be submitted to the ARC showing the current ratio of impervious surface area and the proposed level of impervious surface area.  In all instances, such plans will only be approved if the proposed ratio is equal to or less than the allocated ratio.

In this manner, the ARC is able to ensure that all property owners are treated equally and their property rights are preserved over time.  To the extent a property owner is willing to sell a portion of their rights to the lake BMP, such transfer will be noted on the worksheet as a permanent transfer along with a suitable recorded document to that effect.  To determine the extent of your rights under the Stormwater Management Plan, please contact Brian Menditto (804-747-7800) for additional details.

Stormwater Quantity: Burgess & Niple performed an analysis of the five Innsbrook lakes (the “Lakes”) to determine the stormwater runoff that can be expected to be discharged from the Innsbrook development.  It has been determined that the existing drainage area will generate a peak discharge of 218(+/-) cfs over the spillway of Lake No.  5 from a 1-year, 24-hour storm event.  Furthermore, a 2-year storm has a peak discharge of 368(+/-) cfs, a 10-year storm has a peak discharge of 381(+/-) cfs, a 50-year storm has a peak discharge of 505(+/-) cfs and a 100-year storm has a peak discharge of 533(+/-) cfs.  The downstream discharge channel, Rooty Branch, has been able to accommodate all of these storm events in the past with no noticeable indication of capacity problems or erosion issues.  Rooty Branch is adequate to handle any design storm event that may be anticipated.

Stormwater Quality: The five Innsbrook lakes are fed by 840(+/-) acres within Innsbrook, plus 51(+/-) acres of offsite commercial development and 71(+/-) acres of offsite residential development.  The total drainage area to the Lakes is 962(+/-) acres.  The five Lakes currently remove, under DCR requirements and regulations, a total of 490(+/-) pounds of phosphorous per year from 962(+/-) acres that drain to the Lakes.  The land within the Innsbrook Boundary, including 43(+/-) acres that are part of Innsbrook, but do not drain to the Lakes, are utilizing the credit for this phosphorus removal.

The proposed Innsbrook redevelopment area contains 630(+/-) acres, and currently has 290(+/-) acres of impervious surface (46%), based on GIS calculations of the existing buildings, parking areas, roadways, and sidewalks.  The redevelopment of the 630(+/-) acres could be developed with up to 422(+/-) impervious acres (67%), excluding 37(+/-) acres of lakes.  Under existing zoning conditions of Innsbrook, up to an impervious cover of 62% is allowable.  Therefore, it can be concluded that the Innsbrook Redevelopment Area can be redeveloped to 67% impervious surface area within the capacity of the existing lake system, and using the 0.45 lbs/ac./yr phosphorous removal standard.  It will require additional water quality measures if development above the level of 422(+/-) impervious acres were to be approved through rezoning.  Those additional water quality measures will be governed by applicable statute using both UDA and DCR criteria.

Innsbrook Architectural Review Committee: The development rights existing at Innsbrook will be allocated to all property owners at Innsbrook through the Architectural Review Committee (“ARC”).  The ARC will track the development density and impervious surface area as part of its normal approval process in order to assure equitable allocation among all property owners.

Off-Site Redevelopment: Any redevelopment within the Innsbrook drainage area but not subject to the covenants of the Innsbrook Owners Association will have no right to use the Innsbrook lake system or other stormwater control measures to satisfy any redevelopment requirements, or additional requirements that may emanate from the proposed stormwater regulations.  Any and all such redevelopment will be required to meet DCR and Henrico stormwater criteria as a stand-alone project.

Stormwater Regulations: The following stormwater regulations and guidelines were followed in the analysis and shall apply to the Innsbrook Redevelopment:

  • Henrico County Erosion and Sediment Control (ESC) Program (Chapter 10, Article II of the County Code), required by Erosion and Sediment Control Law (Section 10.1-560 et seq.  of the State Code), and compliance with the minimum standards of the Erosion and Sediment Control Regulations (VR 625-02-00); Virginia Erosion and Sediment Control Handbook (VESCH, 3rd Edition, 1992)
  • The Chesapeake Bay Preservation Act (Section 10.1-2100 et seq.  of the State Code) and the Chesapeake Bay Preservation Area Designation and Management Regulations (9VAC10-20 et seq.)
  • The Virginia Sormwater Management Law (Section 10.1-603 et seq.  of the State Code) and the Virginia Stormwater Management Regulations (4VAC3-20 et seq.)
  • The National Pollutant Discharge Elimination System (NPDES) and Virginia Pollutant Discharge Elimination System (VPDES) developed under the authority of Section 402(p) of the Clean Water Act.