Plan
APPLICATION TO THE OHIO POWER SITING BOARD FOR A
CERTIFICATE OF ENVIRONMENTAL COMPATIBILITY AND PUBLIC NEED FOR THE
SOLAR GRAZING CENTER
Case No. 24-0801-EL -BGN
Preliminary Grading Analysis
To: Doug Herling, Grange Solar, LLC
From:
www.woodplc.com
Venancio Mendez, Wood Group USA, Inc.
Date: 30 September 2024
Project: Grange Solar Grazing Center
Wood Reference: 261653
1. Introduction
On behalf of Grange Solar, LLC (the Client), Wood has conducted a Preliminary Grading and Drainage Analysis for the Grange Solar Grazing Center site (Project Site), which spans approximately 4,000 acres in Logan County, Ohio.
The proposed project involves a utility-scale 500 MWac solar photovoltaic (PV) facility.
The Project Site comprises multiple solar fields connected by a mix of private easements and public roads. It is situated adjacent to the municipalities of Russell’s Point and Lakeview, and is intersected by major public roads, including U.S. Route 33, State Road 274, and State Road 235, approximately 0.75 miles south of the Indian Lake.
The site consists primarily of grassland, wooded rangeland, cropland, and internal windrows and isolated woodlots, approximately 13 acres of which are proposed for removal. In addition, two small tributaries, the Jordan Creek and the Calico Creek, drain southward from the site’s area into the Great Miami River. Streams and Wetlands crossings were minimized and avoided where possible to limit any impact to local wildlife and water resources. Moreover, there is presence of areas designated as FEMA regulatory Floodway and FEMA Zone AE 100-Year Flood areas, adjacent to the project, as per initial desktop research. No land disturbance or development is planned within the regulated FEMA floodways. The terrain is relatively flat, with no significant topographic relief, and with a maximum negative slope of -1%, as well as an average elevation of approximately 991 feet above mean sea level (amsl).
Please refer to enclosed attachment for the Preliminary Grading plan.
2. Assumptions, Setbacks and Calculation
Wood has conducted a site grading and drainage analysis for the proposed project. This analysis outlines the total amount of cut and fill cubic yards, as well as, total disturbed acreage expected at the site, along with the total impervious area.
Assumptions for Analysis
a) Minimum Pile Reveal:
Wood established a minimum pile reveal of 5.7 feet, which corresponds to a minimum module ground clearance of 2-feet gap for operations and maintenance purposes. To minimize extensive grading, we have considered maintaining an additional 2-foot range above the minimum pile reveal to accommodate terrain undulations and maintaining racking installation tolerances.
b) Racking Type:
To adopt a conservative approach, we have utilized standard racking instead of terrain-following racking. This choice reflects a worst-case scenario, providing a realistic yet conservative estimate of the expected earthwork. Should terrain-following racking be implemented, we anticipate a reduced quantity of cut and fill and acreage of disturbance.
c) FEMA Zone AE 100-Year Flood Area:
For the FEMA Zone AE 100-Year flood areas, we have considered the installation of racking in locations where flooding depths do not exceed 4 feet. No land disturbance is planned within the regulated FEMA floodways.
d) Sediment Basin Calculation:
• Pond Volume: 134 cubic yards per acre-drained
• Pond Depth: 5FT
• Factor-of-Safety (FoS): 1.5
Setbacks
Setbacks and buffers proposed to comply with OPSB code regulation.
• 670 feet from Bald Eagle Nest
• 300 feet from dwellings
• 50 feet from active water wells
• 120 feet from streams or wetlands
• 50 feet from non-participating property lines
• 150 feet from public roads
Calculation
a) Sediment Basin Sizing
To determine the location and volume of the sediment basins, the standard sediment basin sizing criteria per the Ohio EPA standards for stormwater management as well as the NPDES Construction General Permit was utilized. This conservative approach states that the “sediment settling pond shall be sized to provide a minimum volume of 134 cubic yards per acre of drainage area” (67 yd3/acre for sediment storage and an additional 67 yd3/acre for the dewatering volume). Wood has assumed a 5ft deep pond and 1ft of freeboard. To account for the additional earthwork associated with building these sediment basins (berms, spillways, benches, etc) Wood has applied an additional safety factor of 1.5 for earthwork calculations. Please note that these values are preliminary and will be subject to final verification in the post-development hydrology study. Once the postdevelopment study is completed, Wood or a third-party engineer will be able to determine final volume of sedimentation ponds that will be considered permanent. At a very high level, we can estimate that a majority of the proposed ponds in this analysis are temporary and are to be removed and returned back to existing conditions once construction is finalized.
b) Total Disturbed Area Calculation:
As defined by the OPSB (Ohio Power Sitting Board) “Grading includes earth-moving activities incidental to building roads, equipment pads, substation, and laydown yards, installing buried electric lines, excavating stormwater basins, performing soil removal activities, soil filling activities, and cut-and-fill activities.
Grading does not include routine ground disturbance incidental to installing piles, drain tile, fences, poles for electric lines, vegetation, landscaping, and temporary erosion and sediment controls, performing soil sampling, geotechnical investigations, archaeological investigations, disking topsoil to promote the growth of vegetation, and raking, smoothing ruts, or otherwise creating a smooth and safe work surface”
To align with this definition, Wood has calculated the “Total Disturbed Area”, also known by the OPSB as “Maximum Graded Acreage Expectation” by summing the acreage requiring grading for the PV layout and the acreage of impervious areas, which include:
a. Roads
b. Temporary Laydown Yards
c. PV Substation and SCADA pads
d. Inverters
e. Sedimentation Ponds
f. Electrical Trenching
3. Results
A summary of all grading and disturbance calculation can be observed in Table 01 and Table 02 below.
Table 01: Total Earthwork Net Balance
Table 02: Total Site’s Disturbance
4. Conclusion
The preliminary calculations for the grading and drainage analysis, sediment basin sizing, and total disturbed area have been conducted in order to abide with the OPSB guidelines, as well as, the Ohio EPA standards and the NPDES Construction General Permit. These initial findings provide a high level understanding of the project’s scope and requirements in terms of total expected cut/fill volumes and disturbance acreage. However, it is crucial to emphasize that these values are subject to further verification during the detailed design of the final PV layout, racking technology utilized, a geotechnical study, a post-development hydrology study, as well as an electrical trenching. Wood appreciates the opportunity to work on this project and thanks you for your trust and collaboration. We look forward to continuing our partnership and delivery of high-quality outcomes. If you have any questions about the analysis results or would like to request any additional information, please don’t hesitate to contact me by telephone at (346) 772-5139 or by email venancio.mendez@woodplc.com.
Sincerely,
Venancio Mendez Levy
Senior Renewable Energy Consultant
5. References
https://codes.ohio.gov/ohio-administrative-code/4906
https://epa.ohio.gov/divisions-and-offices/surface-water/guides-manuals/rainwater-and-landdevelopment
NOTES
1.TOTALDISTURBEDAREAIS16,385,530SFOR376.16ACRES. 2.TOTALIMPERVIOUSAREAFORPROJECTCALCULATEDAT3,513,785SF(80.67ACRES). 3.STORMWATERFEATURESPROPOSEDINTHISDRAWINGCONSISTOFTEMPORARYSEDIMENTBASINS ANDASSOCIATEDBMP'sBASEDOFFPRELIMINARYRUNOFFCALCULATIONS.THESEBMP'sSHALLNOTBE CONSIDEREDASTHEFINALPERMANENTSTORMWATERMANAGEMENTFEATURES.FINALBMPAND PROPOSEDSTORMWATERPONDVOLUMESSHOULDBECONFIRMEDWITHPOSTDEVELOPMENT HYDROLOGYMODEL.HYDROLOGYMODELNOTPROVIDEDFORPRODUCTIONOFTHISDESIGN.
