APPENDIX E

Tree Counts

June

State Route 56 Danger Trees (Map 1 of 3) State Route 56 Danger Trees (Map 2 of 3) State Route 56 Danger Trees (Map 3 of 3)

 

Draft for Discussion

MEMO

To: Dean Long From: Rich Futyma Date: June 21, 2007 Re: Counting trees to be cleared within the 64-foot-wide right-of-way and danger trees along the Tri-Lakes transmission line route through state forest preserve lands

 

Last week, on June 13th through 15th, Will Buetow and I conducted counts of trees that would be cleared on state forest preserve lands if the transmission line were to be installed along NYS Route 56. This included the task of identifying danger trees, i.e., trees standing outside of the transmission line right-of-way that are tall enough to be capable of falling onto the transmission line.

Tree Clearing in Transmission Line Right-of-Way

To locate the bounds of the area to be cleared of trees (i.e., the 64-foot-wide right-of-way, 32 ft on either side of the transmission line centerline), we used a Trimble GeoXm® GPS receiver, which had been pre-programmed with a map of the proposed transmission line. This map also included the boundaries of the NYSDOT right-of-way, the centerline of the transmission line, and locations of poles. The pole locations had also been staked out by surveyors, which helped us confirm the accuracy of the locations indicated by the GPS receiver. Because we wanted to distinguish between clearing that would take place within the NYSDOT right-of-way and clearing outside that right-of-way (but still within the 64-foot-wide powerline r.o.w.), we used flagging tape (pink with black stripes) to mark the boundary of the DOT right-of-way. Then, starting at one pole site and walking toward the next, we counted the number of trees within the DOT right-of-way that had a diameter at breast height (dhb) of 3 inches or greater. After reaching the pole site at the end of the segment being counted, we walked back to the starting point, counting trees •3 inches dbh standing in the clearing zone but outside the DOT right-of-way, while using the GPS receiver to keep us within the transmission line r.o.w.

To start, each transmission line route segment that we counted comprised two inter-pole spans (e.g., from pole 182 to 184). Later, we also counted some single-span segments. We found that it took approximately 30 to 45 minutes to count all of the trees in two inter-pole spans. During our three days on the site, we were able to count all of the trees in 22 of the 40 inter-pole spans lying within the forest preserve. Although the census of trees in the clearing zone goes quickly, we were not able to count all 40 spans due to the length of time it took to identify and measure danger trees (see below).

Table 1 lists the number of trees within each route segment counted. Each “Plot” in Table 1 comprises one or two inter-pole spans, and is either inside or outside the DOT right-of-way. Within the 22 inter-pole segments of the route that we counted, there was a total of 1,305 trees having diameters of 3 inches or greater, or an average of 59 trees per segment. Applying this number to all 40 segments yields an estimate of 2,360 trees to be cut.

Alternatively, we can look at each inter-pole segment where tree counts were not taken, and assign it to one of the several plant communities found in this area, as determined during field studies in the spring of 2006. An estimate of the tree count in that segment is derived by finding counted segments in the same plant community and determining the average number of trees in those segments. Doing so yields an estimate of 1,239 trees in the uncounted segments. Adding that to the total for the counted segments produces a total of 2,544 trees having diameters of three inches or greater.

Danger Trees

The way that we identified and recorded the danger trees is as follows. We used the GPS receiver to locate the outer edge of the area within which complete clearing would take place (the 64-foot-wide r.o.w.). We then looked for trees in the adjacent forest that might be tall enough to be danger trees. To confirm that a tree was indeed tall enough to reach the center of the transmission line right-of-way if it were to fall, one of us would stand approximately on the line between proposed transmission line pole locations, and sight the candidate trees with an inclinometer. If the angle between the horizontal and line of site to the top of the tree exceeded 45°, it was classified as a danger tree. The species of each danger tree was identified and its location was recorded using the GPS receiver. After its position was recorded, each danger tree was marked with blue chalk dust on the side of its trunk facing away from the road.

Also, a measurement of the height of each tree was made using an Opti-Logic® laser rangefinder/hypsometer. To make a height measurement using this device, it is necessary to first sight the trunk of the tree to get a horizontal distance, then sight the top of its canopy, and its base, both of which measure angles. When doing this in the forest, it can be difficult to determine the exact spot to sight for the canopy top due to intervening branches of other trees. Therefore, the tree height measurements are only approximate, and it may not be unusual for them to be off by 10 feet or more.

We found that it took approximately one hour to locate and measure all the danger trees adjacent to one inter-pole span. In the first two days of our work, we located the danger trees from pole 182 south to the point where the transmission line crosses to the west side of Route 56, just before pole 190. This is approximately 8 inter-pole segments, or about 20% of the route through the forest preserve. Due to the length of time required to take these measurements, we decided not to continue taking them on the third day.

Table 2 lists the danger trees that were found in that segment between poles 182 and 190, including their height and species. Maps 1, 2, and 3 show the locations of the danger trees in relation to the transmission line and 64-foot-wide zone to be cleared of all trees. There were 201 danger trees found in this area, or an average of 25 danger trees adjacent to each inter-pole span.

Using these counts to estimate the total number of danger trees along the entire route within the forest preserve yields a total of about 1,005 danger trees. I believe that this is an under-estimate of the number of danger trees that we would identify using the method. A large portion of the route that was not evaluated for danger trees has areas where hillsides rise steeply above the proposed location of the transmission line. In these areas, most of which are covered with plantations of tall white pines and red pines, a large number of trees would rise above the 45° sighting line for identifying danger trees. In many cases, such trees may be too short to reach the transmission line right-of-way if they were to fall over, but they are intercepted by the 45° line due to the rise of the hillside. Therefore, completion of an accurate inventory of danger trees may require a method that takes topography into account.

Completion of the Work

As discussed above, the measurements we collected allows us to estimate the number of trees that would need to be cleared in order to construct the transmission line through the forest preserve. It appears that between 2,400 and 2,600 trees with diameters of 3 inches or greater would have to be cleared in the 64-foot-wide right-of-way. If an exact count of these trees is required, it should be possible to complete those counts in one full day of work.

The completion of danger tree identification will take longer, approximately 4 days of effort for two people. It appears likely that more than 1,000 danger trees would be identified if we were to continue using the technique described here.

Table 1. Numbers of Trees 3 inches in Diameter or Greater

 

Plot 1

Plot 2

Plot 3

Plot 4

Plot 5

Plot 6

Plot 7

Plot 8

Pole interval

182-184

182-184

184-186

186-188

186-188

188-Rt56

188-Rt56

Rt56-192

Located Inside DOT r.o.w. (Y/N)

Y

N

N

Y

N

Y

N

Y

Abies balsamea

 

 

 

 

2

 

26

13

Acer rubrum

6

10

5

2

12

 

15

 

Acer saccharum

13

36

52

2

60

 

7

 

Betula alleghaniensis

 

2

2

 

3

 

 

 

Betula papyrifera

 

 

 

 

 

 

 

 

Betula populifolia

 

 

 

 

 

 

 

1

Fagus grandifolia

3

16

23

1

13

 

2

 

Larix laricina

 

 

 

 

 

 

 

10

Ostrya virginiana

 

1

2

1

5

 

 

 

Picea mariana

 

 

 

 

 

 

 

 

Picea rubens

 

2

2

 

 

 

 

4

Pinus resinosa

 

 

 

 

 

 

 

 

Pinus strobus

 

 

 

2

2

1

14

11

Populus balsamifera

 

 

 

 

 

 

 

 

Populus grandidentata

 

 

 

 

 

 

6

 

Populus tremuloides

 

 

 

 

 

 

 

 

Prunus serotina

3

3

4

 

15

 

4

3

Totals

25

70

90

8

112

1

74

42

Community Type‡

BMF

BMF

BMF

BMF

BMF

FWP

FWP

FWP

‡Community Type: BMF = beech-maple forest, FWP = balsam fir-white pine forest, RPP = red pine plantation, TFS = tamarack-fir swamp, WPP = white pine plantation.

Table 1 (continued).

 

Plot 9

Plot 10

Plot 11

Plot 12

Plot 13

Plot 14

Plot 15

Plot 16

Pole interval

Rt56-192

199-200

201-202

202-203

204-205

206-207

208-210

208-210

Located Inside DOT r.o.w. (Y/N)

N

N

N

N

N

Y

Y

N

Abies balsamea

30

26

38

13

3

8

4

47

Acer rubrum

1

3

 

17

11

12

 

2

Acer saccharum