Sunday, April 30, 2017


Florida Power and Light has been working on proposing a new transmission line that runs through Manatee and Sarasota counties. After roughly 1,200 proposal drafts, they have come up with a transmission line that suits certain criteria. I used Geographic Information Software (GIS) to determine whether these criteria are met. The benefit of using GIS is that it provides a spatial representation so we can visualize the effect of the transmission line; it also allows us to analyze criteria separately or together and quantify certain criteria so that we can accurately determine whether the risk and impact is too great.

I’ve provided a cartographic model in the Powerpoint Link to depict the thought process and work-flow that went into the analysis of this particular project. This is usually the first step in analyzing a project of this magnitude, especially when it has a major effect on nearby attributes and populations.

So we were asked to analyze the data based on the proposed transmission line to determine whether the placement is feasible and affordable. We looked, specifically, at the imposition of environmentally sensitive lands (wetlands and conservation lands), the range of homes within 400 feet, schools and daycares within 400 feet, and the overall length and cost of constructing the transmission line.

The first feature I analyzed was the wetlands and conservation lands that would be impacted by constructing the proposed transmission line. Our goal was to define and quantify the imposition on environmentally sensitive lands. These lands were owned by a variety of people – some lands are public, while others are privately owned. After completing a series of GIS analyses using ArcMap, I determined that the acreage of wetlands affected was relatively high at about 13,000 acres, but that the percentage of wetlands affected was only 4.05%, which is pretty low. The total dry land affected was almost 96%, but that is to be expected with a project this size. Overall wetlands impacted was much higher, but that includes wetlands and uplands. This was not much of a surprise.

The next feature I analyzed was the range of homes impacted. I wanted to quantify the homes within the proximity of the transmission line. I created a 400 foot zone around the proposed line to determine how many homes were within the proposed line and how many were within 400 feet of the transmission line. I digitized the homes using parcel data for both counties, and we determined that there were about 58 homes that would be impacted. While this seems high, only 14 fell within the proposed line and 44 were within 400 feet of the line.

I then analyzed the schools and daycares within proximity of the proposed transmission line. Using data retrieved from the Florida Geographic Data Library, I defined and quantified these schools and daycares. Surprisingly, I found that absolutely no schools fell within the proposed line or within the 400 foot zone we had created around the line. 

I wanted to know just how long this transmission line is, so I used GIS to determine the length. Using the centerline and data type conversions, I calculated the length of the line and found it to be just over 25 miles long.Of course, the next step was to determine the overall cost of the proposed transmission line. I used a formula that is commonly used on projects like this to determine that, depending on what types of materials and number of circuits, the cost ranged from $1,100,000 to $1,800,000 per mile. This means that a transmission line 25 miles long, such as the one proposed, could cost anywhere from $55,000,000 to $80,000,000 in total. While this seems unreasonably costly, there are a lot of materials that factor into that cost. Cost is often based on certain variables, including, but not limited to engineering, materials, labor, topography, land use type, right-of-way acquisition, and environmental permitting fees.

Based on my analyses, there are very few, if any, limiting factors. The impact on wetlands is relatively low, so Objective 1 was met. There are few homes in a proximity of 400 feet of the proposed line; that means Objective 2 was met. No schools fall within close proximity of the proposed line, so Objective 3 is also met. This looks really good so far. The length and cost of the line are feasible. Although the cost seems high, the variables that are included in cost are logical and necessary, so the cost is not unreasonable. For these reasons, I think the proposed transmission line can be built with few or no issues based on the analyses conducted by our team.

I've provided a link to my PowerPoint and transcription below. 

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