Ministry Monitoring of Contaminants and Stormwater Runoff from GE into Little Lake

We present a map titled “Ministry Monitoring of Contaminants and Stormwater Runoff from GE into Little Lake” to  help the general public appreciate the past, present, and potential future impacts of the General Electric in Peterborough, ON.

The map depicts two major classes of objects:

1. Devices that monitor contaminants of concern on GE’s properties and in nearby neighbourhoods.
2. Stormwater infrastructure that carries rainwater runoff from GE’s properties into Little Lake.

Primary sources

Monitoring devices

• Director’s Order No. 1-228916698 (Ministry of the Environment, Conservation and Parks, issued March 6, 2024), especially:
  • Table 1 — Groundwater Monitoring & Sampling Program.
  • Table 2 — Soil Vapour Monitoring & Sampling Program.
  • Table 3 — Storm Sewer Monitoring & Sampling Program.
• Environmental Compliance Approval No. 8032-BEJNAK (Ministry of the Environment, Conservation and Parks, issued September 30, 2019), especially:
  • Table 1 — Effluent Objectives at Outfall manholes MH.R1 and MH.R41.
  • Table 2 — Effluent Monitoring at Outfall manholes MH.RI and MH.R41 and at the Lake Outfall manhole MH 135683.
• Environmental Compliance Approval No. 7896-9HDRYN (Ministry of the Environment, Conservation and Parks, issued March 24, 2013; last amended September 14, 2017).
• Permit to Take Water No. 6551-BCWQSV (Ministry of the Environment, Conservation and Parks, issued June 7, 2019).
• Slug Discharge Permit (City of Peterborough, issued May 12, 2004).
• 2024 Groundwater Extraction and Treatment System Monitoring Report, GEPR Peterborough (AECOM, February 2025).
• 2024 PCB Monitoring Report for Stormwater and Groundwater, GEPR Peterborough (AECOM, February 2025).
• 2024 Soil Vapour Monitoring Report, GEPR Peterborough (AECOM, February 2025).

Stormwater Infrastructure

3.2 Contaminants of concern

• PCBs (polychlorinated biphenyls, as Aroclors) — in groundwater (Facility and Monaghan Rd well sets), in storm-sewer sediment and stormwater (Table 3), and in the stormwater effluent (ECA 8032).
• Chlorinated VOCs — specifically 1,1-DCE; trans-1,2-DCE; cis-1,2-DCE; TCE (trichloroethylene); and VC (vinyl chloride) — in groundwater (RAP/SSRA well set), soil vapour, and the GETS.
• PAHs (polycyclic aromatic hydrocarbons) — in the stormwater effluent (ECA 8032, Table 2).
• Supporting analytes: TOC (sediment) and TSS (stormwater) in the storm-sewer program; MNA parameters (five-yearly) in groundwater. (“RAP/SSRA” = Remedial Action Plan / Site-Specific Risk Assessment.)

3.3 Device classes and their regulatory association

The stormwater sampling points break down (per DO Table 3) into Facility Outfalls (e.g., MHR1, MHR35, MHR41, the CBR-series, C.STM.MH, CBMHR113), Monaghan Rd Outfalls (CBMHR130, CBR137, and CBR140/142 — the latter two noted as not connected to the City system), five City of Peterborough storm manholes (135686, 135683, 136551, 166902, 135703 — the last sampled six times per year), and the Little Lake receiving-water point (LL-15). A sixth City manhole, 135704, appears in the ECA 8032 conveyance description (the manholes the effluent discharges downstream of to Little Lake) but is not a Director’s-Order Table 3 sampling point; it is shown for context without a sampling program.

3.4 Geolocation and precision

Each device’s coordinates come from one of four sources, and the pop-up states which, so a reader can weigh positional confidence:

The Little Lake sampling point LL-15 is a manually placed receiving-water point; on the map it is positioned on the extension of the pipe centre-line running into outfall 139977, ~15 m beyond it into the lake (its documented separation from the discharge point), rather than on the shoreline.

3.5 Underlying datasets

Beyond the City GIS TopoJSON layers (§1), three JSON datasets carry the Ministry and runoff data:

• well_coordinates.json (45 Ministry devices): id, lat, lon, location, type (monitoring_well / extraction_well / soil_vapour_probe / treatment_system), categories (PCB_Facility, PCB_Monaghan, VOC_RAP_SSRA, MNA, Extraction, Soil_Vapour), source, precision_m.
• stormwater_monitoring.json (24 points): id, lat, lon, category (Facility Outfall / Monaghan Rd Outfall / City of Peterborough / Little Lake), type, frequency, source, precision_m, notes.
• ge_runoff_collectors.json: for each GE receptor, the source side(s) it drains (the “Receives rainwater runoff from …” detail shown in orange on receptor pop-ups).

3.6 How the pop-ups are assembled

Every pop-up is built from the same five modules, so each device is described consistently and only the applicable modules appear:

1. Module 1 — identity: ID, Type, Coordinates, Precision.
2. Module 2 — physical characteristics (type-specific): for pipes, subtype / diameter / connection (FROM→TO) / up-&-down elevations / slope; for manholes and catchbasins, rim / invert elevations; for extraction wells, the permitted pumping rate.
3. Module 3 — ownership: Owner (Peterborough or GE) and installation year.
4. Module 4 — monitoring programs: one tagged block per regulatory program the device belongs to, each stating Authority × Program × Contaminants (e.g., Director’s Order 1-228916698 · Storm Sewer Monitoring & Sampling (Table 3) · PCB; or ECA 8032-BEJNAK · Effluent Monitoring (Table 2) · PCB, PAH). Devices in more than one program show stacked blocks.
5. Module 5 — runoff source (receptors only): an orange line naming the GE Site 1 / Site 2 area whose runoff the object receives.

4. References (academic)

Digital terrain / DEM hydrology — flow routing and catchment delineation

• O’Callaghan, J. F., & Mark, D. M. (1984). The extraction of drainage networks from digital elevation data. Computer Vision, Graphics, and Image Processing, 28(3), 323–344. — D8 flow direction.
• Jenson, S. K., & Domingue, J. O. (1988). Extracting topographic structure from digital elevation data for geographic information system analysis. Photogrammetric Engineering & Remote Sensing, 54(11), 1593–1600. — flow direction, accumulation, and watershed delineation from DEMs.
• Planchon, O., & Darboux, F. (2002). A fast, simple and versatile algorithm to fill the depressions of digital elevation models. Catena, 46(2–3), 159–176. — depression filling.
• Tarboton, D. G. (1997). A new method for the determination of flow directions and upslope areas in grid digital elevation models. Water Resources Research, 33(2), 309–319. — D-infinity (noted alternative; D8 was used here for transparency).
• Wilson, J. P., & Gallant, J. C. (Eds.). (2000). Terrain Analysis: Principles and Applications. New York: Wiley. (ISBN 978-0-471-32188-0). — standard synthesis of terrain-analysis methods.

Application to urban stormwater drainage

• Gironás, J., Niemann, J. D., Roesner, L. A., Rodriguez, F., & Andrieu, H. (2010). Evaluation of methods for representing urban terrain in storm-water modeling. Journal of Hydrologic Engineering, 15(1), 1–14. — DEM/terrain-based delineation of the areas draining to urban storm inlets.

Airborne-LiDAR bare-earth DEMs and the effect of resolution

• Meng, X., Currit, N., & Zhao, K. (2010). Ground filtering algorithms for airborne LiDAR data: A review of critical issues. Remote Sensing, 2(3), 833–860. — generating a bare-earth DTM from LiDAR.
• Vaze, J., Teng, J., & Spencer, G. (2010). Impact of DEM accuracy and resolution on topographic indices. Environmental Modelling & Software, 25(10), 1086–1098. — why high-resolution (LiDAR) DEMs improve terrain-derived flow/hydrologic indices.

5. Primary data sources and companion records

Primary data sources (to cite on the public product):

• City of Peterborough municipal GIS — storm-sewer asset layers (pipes, manholes, inlets, discharge points, culverts, open drains, oil/grit separators).
• Ontario provincial LiDAR-derived 0.5 m bare-earth Digital Terrain Model (Land Information Ontario / Ontario GeoHub), UTM Zone 17N (EPSG:26917).
• MECP regulatory instruments: Director’s Order No. 1-228916698 (2024-03-06) and its Monitoring Program Summary (Tables 1–3); ECA 8032-BEJNAK (2019-09-30); ECA 7896-9HDRYN; PTTW 6551-BCWQSV.
• AECOM 2024 PCB Monitoring Report (Appendix K) and the 2014 CRA drawing “Figure 1 — Storm Sewer Monitoring Locations,” reconciled in GE_StormSewer_Reconciled_Inventory.xlsx.

Companion method records (in the project):

• Runoff_Classification_Criteria_Statement_of_Record.md — the full terrain method and its revisions.
• Runoff_Classification_Criteria_Addendum_2026-09-09.md — the adopted capture criterion and the 68-receptor result.
• GE_Map_Simplification_Deletion_Log.md — every feature removed/restored (what, mechanism, when, why), the connectivity findings, and the Jackson Creek analysis.
• GE_Stormwater_Map_Summary.md — capstone summary of method and final state.
• ge_stage2_orange_ids.json (the 68 receptor IDs); ge_source_polygons.json (Site 1 / Site 2 boundaries); ge_dtm_0p5m_utm17n.tiff (the DTM).

Objectivity note: this document states the data sources, methods, criteria, and regulatory facts on which the map rests, so that a third party can examine and reproduce them. It does not argue a position; any advocacy use is the map owner’s.