PWS - KGYX Blockage Mitigation - Tree Survey.docx

PERFORMANCE WORK STATEMENT (PWS)

PROJECT: KGYX Radar Vegetation Management – Phase 1: Survey & Inventory WEATHER FORECAST OFFICE (WFO) LOCATION: 1 Weather Ln, Gray, ME 04039

RADAR COORDINATES: 43.891313° N, 70.256497° W

1. BACKGROUND

The National Weather Service (NWS) operates the WSR-88D Weather Radar (KGYX) in Gray, Maine. Radar beam blockage caused by surrounding vegetation is degrading data quality. The NWS is currently conducting a survey to determine the most cost-effective long-term solution: removing the vegetation and/or raising the radar tower. To make this decision, the NWS requires a high-precision "Tree Inventory" that maps the vegetation against both the current tower height and a potential future tower height.

2. OBJECTIVES

The Contractor shall provide a comprehensive geospatial inventory of all vegetation that obstructs—or threatens to obstruct—the radar's operational airspace. The primary objective is to generate a "Decision Matrix Dataset" that allows the Government to filter vegetation based on:

Vertical Threat: Will it block the current tower? Does it block the current tower? Will it block a future (+50 ft) tower?

Horizontal Ownership: Is it on State land (easy access) or Private land (complex access)?

3. SCOPE

The Contractor shall provide all labor, equipment, and technical expertise to conduct a non-destructive site survey within a 1200-foot radius of the radar tower.

· In Scope: Acquisition of high-density aerial LiDAR data and imagery to generate a geospatial model of vegetation canopy height.

· Out of Scope: Physical tagging of trees, species identification, or collecting Diameter at Breast Height (DBH) data. This is strictly a data collection effort.

4. PERFORMANCE REQUIREMENTS

4.1. Survey Boundaries (Horizontal Zones)

The Contractor shall survey vegetation within a maximum fixed radius of 1200 feet from the radar tower center point (43.891313, -70.256497). Within this 1200-foot operational circle, the Contractor shall attribute every inventoried tree to one of two "Stakeholder Zones" based on Land Ownership.

· ZONE A (Government Controlled): Any land within the 1200-foot radius that is owned by the State of Maine or the land owner currently leasing to the Federal Government, October Corporation.

· Operational Intent: This zone represents land where the NWS has existing or simplified access rights.

· ZONE B (Private/Other): Any land within the 1200-foot radius that does not meet the criteria for Zone A (e.g., private residential lots, commercial property).

· Operational Intent: This zone represents land requiring complex individual landowner negotiations for future access.

4.1.1. Boundary Identification (Cadastral Awareness)

The Contractor acknowledges that the boundary between Zone A and Zone B is an irregular shape of property lines.

· Requirement: The Contractor must possess sufficient Cadastral Surveying capability to accurately identify these property boundaries in the field.

· Methodology: The Contractor shall utilize available municipal tax maps, GIS parcel data, and existing physical monuments (pins/blazes) to ensure that vegetation is attributed to the correct legal landowner.

· Liability: The Contractor is responsible for ensuring that no physical tagging or marking occurs on Zone B (Private) property without obtaining written approval with a signature from the landowner..

4.2. Vertical Classification Standards (The "Matrix")

The NWS defines the survey based on Mean Sea Level (MSL) elevation, not tree height above ground level.

· Vertical Datum: All data must be referenced to NAVD 88.

· Inventory Threshold: The Contractor shall inventory ONLY vegetation with a calculated Tip Elevation (Ztip) greater than or equal to 448.0 Feet MSL (approx. 10 ft buffer below the critical plane).

Operational Definition

Critical Blockage. Obstruction persists even if the radar tower is raised 50 ft.

Conditional Blockage. Obstructs the current tower, but would be cleared if the tower is raised.

Growth Buffer. Future threat (5-10 years) to the current tower.

The Contractor shall classify each inventoried tree into one of three "Threat Tiers" based on its Tip Elevation (Ztip):

4.3. Verification of Reference Plane

· Benchmark: The "Current Top Plate" elevation is estimated at 458.2 ft MSL.

· Requirement: Prior to beginning the full survey, the Contractor shall measure the elevation of the radar tower's steel top plate (pedestal base) to verify this benchmark. If the field measurement differs by more than +/- 1.0 foot, the Contractor must contact the Contracting Officer's Representative (COR) for calibration.

4.4. LiDAR Data Specifications & Metrics

The Contractor shall provide a classified point cloud and derived surfaces meeting the following standards:

Point Density: Minimum of 8 points per square meter (ppsm) to ensure detection of individual tree crowns.

Vertical Accuracy: Root Mean Square Error (RMSE) of ≤10 cm to ensure precise "Tier" classification.

Classification: The point cloud shall be classified into standard ASPRS categories:

· Class 2: Ground

· Class 3, 4, 5: Low/Medium/High Vegetation

· Class 6: Buildings/Structures (if applicable) Canopy Height Model (CHM): A derived raster dataset representing the absolute height of vegetation above ground level.

5. Deliverables The Contractor shall provide the following deliverables:

RED: Vegetation ≥ 508.0 ft MSL (Tier 1) ORANGE: Vegetation 458.2 – 508.0 ft MSL (Tier 2) YELLOW: Vegetation 448.0 – 458.2 ft MSL (Tier 3)

6. GOVERNMENT FURNISHED INFORMATION (GFI)

· Site Access to 1 Weather Ln, Gray, ME.

· Contact information for the NWS Technical Point of Contact (TPOC) for coordination with State and Private landowners.

· Historical Site Survey (2016) – Provided for reference only; Contractor must verify current conditions.

7. Period of Performance

The Contractor shall complete all data acquisition and submit final deliverables within 90 Days of contract award.