UPDATED 4/1/2019: This version of VTrans road segment data represents an update from the initial dataset delivered as part of the VTrans_TS4_LoadFactors_20180919.gdb data deliverable from 9/19/2018 from Stone Environmental to VTrans and the VTDEC. The updated version includes an additional of approximately 3.2 miles of VTrans road not included in the initial dataset. This updated VTrans road segments dataset was used to calculate the total area of VTrans owned paved roads within the TS4 for the development of coefficient of loading rates, as outlined in the April 1, 2019 memo from Stone Environmental to VTrans and VTDEC.

This version of the VTrans road segment data was developed using a combination of data sources and manual editing. First, MATS roads data from VTrans was obtained. These data were used as a basis to determine VTrans maintained roads. All roads within the Lake Champlain Basin were extracted for purposes of Phosphorus Control Planning under the LCB TS4 permit.

The MATS road segments were intersected with soil polygons and then split into ~100m (or less) segments. The "LineID_Fnl" attribute is the unique identifier for each road segment.

Each road segment was assigned hydrologic connectivity based on the following criteria with the first being the most hydrologically connected and with the last being the least hydrologically connected:

1) Intersecting NHD Stream, Pond, or VSWI Wetland (attribute: HydroBisect_Criteria)

2) Within 100 ft of NHD Stream, Pond, or VSWI Wetland (attribute: HydroParallel_Criteria)

3) Within River Corridor (attribute: HydroRiverCorr_Criteria)

4) Intersecting Additional Intermittent Streams (used LiDAR-based Enhanced Hydro Network) (attribute: HydroBisectLidar3_Criteria)

5) Within 100 ft of Additional Intermittent Streams (used LiDAR-based Enhanced Hydro Network) (attribute: HydroParallelLidar3_Criteria)

6) Within 50 ft of Piped Stormwater Infrastructure that is Connected to Outfalls within 500 ft of NHD or VSWI (attribute: HydroStorm_Criteria)

7) Within 50 ft of a culvert in teh Small Culvert Inventory (SCI) (attribute: HydroSCI_Criteria_50ft)

If none of the above, the segment is considered NOT hydrologically connected. An attribute was added to provide an overall 'hydrologic connectivity ranking' called 'HydroConnectCriteria' which assigns the highest connectivity class to the road segment, when multiple criteria are met (of the seven criteria outlined above). Another attribute called ‘HydroConnectClass’ was included to indicate the general level of hydrologic connectivity (High, Moderate, Low).

Additional analyses were conducted to determine the potential for localized erosion with results added to the line segment, based on the following criteria:

1) Downslope & Steep ROW & Road Runoff (attribute: LE1_DownslpSteepRdRunoff)

1.a) Downslope = “Yes” (Meets 2 of the following criteria)

1.a.i) If the nearest road segment has a higher average elevation

1.a.ii) If the nearest road segment has a higher maximum elevation

1.a.iii) If the there is ‘runoff’ or flow accumulation from the road

1.b) Steep Slope in ROW (Meets either of the following criteria)

1.b.i) Ave Slope in adjacent ROW > 15% and Max Slope > 40%

1.b.ii) Ave Slope in adjacent ROW > 20% and Max Slope > 25%

1.c) Road Runoff

1.c.i) Max flow accumulation of > 5 road segment pixels (45 m2)

2) Potential Culvert Erosion (based on SCI - yes if any of the following) (attribute: LE2_CulvertErosion)

2.a) Culvert condition = Light, Moderate or Severe erosion

2.b) Culvert type = Concrete

2.c) Separation = Minor, Moderate or Major OR Proj_End = Yes

2.d) Sink Hole = Minor, Moderate, or Major

2.e) Connected to DI or Elbow (Elbows (Yes); then Both In_Treat = DI and Drain_Type = Slope)

3) Presence of Curb Board (Guardrail Dataset) (attribute: LE3_CurbBoard)

4) Evidence of Ditch (upslope along road) (attribute: LE4_PotentialDitch)

4.a) Downslope = “No” (Does NOT meet at least 2 of the following criteria)

4.a.i) If the nearest road segment has a higher average elevation

4.a.ii) If the nearest road segment has a higher maximum elevation

4.a.ii) If the there is ‘runoff’ or flow accumulation from the road

4.b) Road Runoff

4.b.i) Max flow accumulation of > 10 road segment pixels (90 m2)

Lastly, road slope was calculated based on LiDAR (attribute: Line_Slope_Mean). An attribute was added to indicate whether the slope fell above or below 10% (attribute: SlopeClass).