Due in large part to aggressive renewable energy goals and the push for decarbonization, the solar industry is booming in New York State. Over the past few years, Thew Associates has served as the land surveying consultant for numerous community and utility scale solar developments throughout New York, Massachusetts and Vermont. As with most land development projects, topographic, utility, and boundary retracement surveying and mapping are essential components for the development of a solar project. The following are few items solar developers should consider when procuring professional surveying and mapping services.
Some solar developers look to their environmental permitting and/or site/civil consultant to procure the surveying and mapping for a project. While it may seem convenient to have the design professional subcontract with a professional land surveyor, there are strategic advantages for the developer to retain control of the professional land surveyor.
- Decreased Project Costs: Procuring the surveyor directly eliminates the mark-up (frequently 10%) the design professionals typically include cost for utilizing a subconsultant and management costs to cover the time necessary to manage the surveying subconsultant.
- More efficient project management: Frequently, the Solar Developer is dealing with real estate issues such as parcel acquisition, creation of lease parcels, subdivisions, access and utility easements, commitments for title insurance. These items typically are legal matters that design professionals do not handle on a routine basis. Therefore, the design professional simply acts as intermediary conveying information between the Developer and the Surveyor.
Topographic mapping is required to facilitate site/civil design. We are frequently asked if publicly available LiDAR can be utilized as a source for topographic information. Our answer is typically “it depends”. If a two-foot contour interval is sufficient for site/civil design, then yes, publicly available LiDAR may be suitable. However, our experience is that LiDAR with a point density of ≤ 2 points per square meter (ppsm) in wooded terrain is not sufficient to meet the accuracy requirements for two-foot contours. Public LiDAR data sets that have densities greater than 4 ppsm have proven to meet the accuracy standards for two-foot contours.
Public LiDAR data sets acquired prior to 2012, typically don’t meet the accuracy standards, especially in wooded or brushy areas.
Ground truthing and check shots are required to confirm the accuracy of public LiDAR data.
In some instances, the civil/site engineer requires topography with a one-foot contour interval for storm water and access road design, whereby ground surveys can be conducted to collect the required topographic information.
Every Developer and Design Professional should be aware that accurate breaklines and planimetric information (e.g. buildings and structures, headwalls, railroads, paved and unpaved roads, utilities, signs, etc.) cannot be extracted from LiDAR due to the density of the data set.
Depending on the size of the project and the land cover (i.e. woodlands, abandoned agricultural lands, or active agricultural lands), Thew Associates recommends acquiring topographic information suitable for 50 scale (1” = 50’) topographic mapping with a one-foot contour interval utilizing conventional surveying techniques (i.e. ground survey), UAV-mounted LiDAR and aerial photography, or manned aircraft LiDAR and aerial photography.
Ground surveys may be more economical to conduct if a site is relatively small (i.e. less than 30 acres) and is open agricultural lands, while UAV LiDAR data and aerial photography acquisition is most economical for open or wooded sites ranging from 10 to 800 acres. Acquisition of LiDAR and aerial photography from a manned aircraft is typically more economical for larger projects ranging from 300 to several thousand acres. The disadvantage of utilizing a manned aircraft is that data must be collected during periods of “leaf-off” without snow cover. UAV LiDAR can be acquired in “leaf-on” conditions because of the greater point density due to the low altitude and slow speeds the UAV’s operate at.
Watch for our next topics regarding UAV LiDAR and ALTA/NSPS Land Title Surveys for Solar Developments.