HomeMy WebLinkAbout02-22 Glare Study Assessment Report Memo
1602 Village Market Boulevard SE
Suite 330
Leesburg, VA 20175
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www.pennoni.com
January 31, 2022
ORIDN 21002
Oriden Power
106 Isabella Street, Suite 400
Pittsburgh, PA 15212
Attention: Ali Trunzo, Development Manager
RE: Glare Assessment Report
Redbud Run Photovoltaic Solar Array
Frederick County, Virginia
Dear Ms. Trunzo,
Pennoni is pleased to submit the enclosed Glare Assessment Report prepared for the Redbud Run
Photovoltaic Solar Array in Frederick County, Virginia to assess the potential for glare impacts to motorists
northbound on Woods Mill Road and east and west bound on Pine Road. The results of our study are
summarized as follows:
Project Background
The Redbud Run Solar project (the Project) is a proposed small utility-scale solar energy facility with a project
nameplate of up to 30 MWac. The Project is located on a tract of land containing approximately 263 acres of
pasture and timberland adjacent to Woods Mill Road (VA Route 660) and Pine Road (VA Route 661), of which
approximately 150 acres will be developed with solar panels and related facilities enclosed by security fencing.
Pennoni performed a Glare Assessment Report utilizing ForgeSolar’s Solar Glare Hazard Analysis Tool (SGHAT)
at the request of the Virginia Department of Transportation. This document assesses the results of the SGHAT
modeling along with the Project setting and proposed mitigation measures (e.g., vegetation screening) to
confirm that potential glare will not affect motorists on public roads adjacent to the Project.
Project Setting and Proposed Screening
The proposed Project contains favorable topography with existing vegetation that provides natural
concealment while minimizing the nature and extent of viewshed impacts. These attributes were key
contributors in assessing initial site feasibility. The Project is situated within a tract that is largely bordered by
well-established trees. Solar arrays will adhere to the setbacks as specified in the Frederick County ordinances,
with solar arrays no less than 60 feet from road rights-of-way. Setbacks have been increased voluntarily to
100 feet where possible in response to community feedback and to preserve mature trees along the site
boundaries. Additionally, streams and riparian corridors within the site include substantial areas of mature
woodlands, the preservation of which will screen significant portions of the solar arrays from surrounding
viewsheds. There are no locations or instances due to the road alignment and southern facing solar panels
where a motorist will be directly driving north or facing the primary orientation of the solar array.
Where existing vegetation does not exist or is otherwise insufficient, supplemental landscaping will be
planted. Such landscaping will consist of a double row of evergreen plantings six (6)-feet in height at time of
ORDIN 21002 January 31, 2022 Page 2
Oriden Power Redbud Run Glare Study
installation, with the row closest to the road interspersed with deciduous plantings to create a more natural
and aesthetically appealing visual screen. Coupled with the site’s favorable topography, the combination of
tree preservation and new landscape plantings will mitigate potential visual impacts at adjacent roads.
Pennoni understands that the proposed landscape screening will be included in the Project’s Concept Plan
submitted to Frederick County as part of the Conditional Use Permit application.
Modeling Analysis
The SGHAT modeling software utilized was developed in conjunction with Sandia Laboratories and is the most
widely accepted glare modeling tool on the market. Additional documentation and more detailed descriptions
about the fundamental workings of the SGHAT software can be found at ForgeSolar.com. SGHAT modeling is
subject to various assumptions and limitations as identified within the Assumptions section of the report. For
example, the model does not account for physical obstructions including buildings, tree cover and other
geographic obstructions, does not rigorously simulate detailed system geometry and assumes clear, sunny
skies year-round.
Any prominent features (vegetation, terrain, structures, screening etc.) blocking the view of the PV array from
the observer will also block potential glare from the PV array to the observer. In addition, shade across the
array from local site features, for example, a high tree line along the eastern or western perimeter of the site
may cast extensive shadows during the early morning and late afternoon sun-hours (when the sun angle is
lowest in the sky). The timing of this phenomenon happens to correspond significantly with the time periods
in the model that are predicted to have the highest potential for glare impacts.
The model ignores any row spaces or gaps in the actual array and treats the entire PV area as if it has the
potential to produce glare. The design of the array will further limit glare due to the inter-row spacing
configuration and the ability of one row to block the view of the row behind it from an observer.
Conclusion
Pennoni evaluated the results of the SGHAT modeling in the context of the model limitations and the Project
setting. Based on our review and analysis, Pennoni is of the professional opinion that the terrain
characteristics and existing mature vegetation combined with new landscape plantings can provide a
sufficient visual barrier between the solar arrays and the observation paths (Woods Mill Road and Pine Road)
to prevent potential glare impacts to motorists on public roads adjacent to the Project.
Should you require additional information please contact me at 703-840-4812.
Sincerely,
PENNONI ASSOCIATES INC.
Paul Noursi, PE
Senior Engineer
Enclosures
U:\Accounts\ORIDN\ORIDN21002 - Red Bud - VA\DOC PREP\GLARE STUDY\2022.01.31 ORIDN21002 Glare Study Opinion Letter.docx