Geotechnical and Soils: desk report

The rule

Code computed the rating from the assessor's inputs:

impact_likely=yes -> 2

Set by the rule

Decision

Released with flags

The engine's reasons

• Agencies not in the register or the evidence: OPSB

Evidence state

VERIFIED · field study or agency determination

The assessor's comments

Abandoned Elsby No. 2 underground mine lies beneath approximately 165 acres of the East Block; borings hit voids and two mine-subsidence sinkholes are on Parcel 10. Geotechnical consultant rates further sinkhole probability high over shallow workings. Two plugged wells on site; seismic hazard is low.

Worst case

If what is pending at the cut-off went badly, the same rule gives a higher rating.

• Present: yes

  Field geotechnical work documents mine-subsidence sinkholes on Parcel 10 (C-e98a4f0f1c) and voids in borings B-17 and B-19 (C-e538cf508c). ODNR records show the abandoned Elsby No. 2 Mine (C-d9db0a1832, C-caad69ed74). Two plugged wells (C-2a9ce2a49f, C-a3cebd779c), a landslide scar (C-2b0121cadd) and hydric soils (C-440f326a24) are also documented. The title absence statement (C-9dcc852809) covers severed mineral estates only. Seismic hazard is low (C-560f40e113), so faults are not an issue. Blasting not expected (C-fd52f76b29) is not a hazard absence.

  Cites C-e98a4f0f1c, C-e538cf508c, C-d9db0a1832, C-caad69ed74, C-2a9ce2a49f, C-a3cebd779c, C-2b0121cadd, C-440f326a24, C-9dcc852809, C-560f40e113, C-fd52f76b29

• Extent: peripheral

  The undermined area is approximately 165 acres of the East Block (C-d106c90db2), about 21% of 780 buildable acres, so it is localized to the east. Wells are point features (C-2a9ce2a49f) and the landslide scar is small (C-2b0121cadd). Core is arguable given the 20 to 25 MW at stake (C-6a69538071), but the hazard does not underlie most of the site; a mine-void investigation would settle it.

  Cites C-d106c90db2, C-2a9ce2a49f, C-2b0121cadd, C-6a69538071

• Avoidable: partly

  The substation, BESS yard and inverters must not be built over the undermined area (C-f29a379025). Excluding it removes about 165 of 240 fenced East Block acres, roughly 20 to 25 MW (C-6a69538071). Northfold intends to keep it out of the layout (C-44efda80b8). Grouting is the alternative but costs several million dollars and takes 4 to 8 months (C-1efb994b8f). Wells can be set back (C-28570f896a).

  Cites C-f29a379025, C-6a69538071, C-44efda80b8, C-1efb994b8f, C-28570f896a

• Pathway: standard

  The route is engineering investigation and setbacks. OPSB pre-application summary calls for a geotechnical report on the East Block mine (C-eaec90390e). ODNR mine comments are typically made certificate conditions (C-03c910d4d1). No separate individual mine-subsidence approval is documented.

  Cites C-eaec90390e, C-03c910d4d1

• Impact likely: yes

  Layout exclusion or grouting of shallow workings is likely (C-6a69538071, C-1efb994b8f). Sinkhole probability is high over shallow workings (C-5c5e675182). Plugged wells need 100-foot structure setbacks and operator setbacks from the pad (C-28570f896a).

  Cites C-6a69538071, C-1efb994b8f, C-5c5e675182, C-28570f896a

Supporting statements (21)

Each claim the row cites: the statement in the assessor's words, then the quote the engine found on the page.

1. C-03c910d4d1

   ODNR comments on wildlife, wetlands and mines are typically made conditions of the certificate.

   ODNR comments on wildlife, wetlands and mines are typically made conditions of the certificate.

   OPSB Pre-Application Conference Summary - Tamsin Ridge Solar and Storage Project · DR-0026 · Page 2 · 2023-03-28

   Source agency_determination · Claim type agency_position · Polarity neutral · Confidence high · Quote check exact, 100 of 100

   Cited by EC-01 · Filed under AQ-01, EC-01, EN-02, PE-02

   See it on page 2, claim C-03c910d4d1

2. C-1efb994b8f

   Grouting of shallow workings typically costs several million dollars and takes 4 to 8 months; option (b) still leaves residual risk.

   Grouting of shallow workings typically costs several million dollars for an area of this size and takes 4 to 8 months.

   Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 3 · 2023-05-15

   Source consultant_memo · Claim type cost · Polarity presence · Confidence high · Quote check exact, 100 of 100

   See it on page 3, claim C-1efb994b8f

3. C-28570f896a

   Structures should be kept at least 100 feet from plugged wells and follow the operator's setbacks from the pad and flowlines.

   Keep structures at least 100 feet from plugged wells, and follow the operator's setbacks from the pad and its flowlines.

   Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

   Source consultant_memo · Claim type recommendation · Polarity neutral · Confidence high · Quote check exact, 100 of 100

   Cited by EN-01 · Filed under EN-01, EN-02

   See it on page 1, claim C-28570f896a

4. C-2a9ce2a49f

   Two plugged and abandoned oil and gas wells (Parcels 4 and 10) and an active horizontal Utica well pad adjoining Parcel 5 were located.

   Two plugged and abandoned oil and gas wells (Parcels 4 and 10) and an active horizontal Utica well pad adjoining Parcel 5 were located.

   Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

   Source field_study · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

   See it on page 1, claim C-2a9ce2a49f

5. C-2b0121cadd

   One small landslide scar was seen on Parcel 12.

   one small landslide scar was seen on Parcel 12.

   Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

   Source field_study · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

   See it on page 1, claim C-2b0121cadd

6. C-324cdd0ed0

   Sinkhole-type subsidence is most likely where cover is under about 100 feet, which applies over the whole undermined area; this is the main geotechnical constraint.

   This is the main geotechnical constraint on the Project.

   Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

   Source consultant_memo · Claim type study_finding · Polarity presence · Confidence high · Quote check exact, 100 of 100

   See it on page 1, claim C-324cdd0ed0

7. C-440f326a24

   Hydric soil indicators were present in all five delineated wetlands.

   Hydric soil indicators (depleted matrix, redox dark surface) were present in all five wetlands.

   Wetland and Stream Delineation Report - Tamsin Ridge Solar and Storage Project · DR-0013 · Page 2 · 2023-05-22

   Source field_study · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

   Filed under AQ-01, EN-02

   See it on page 2, claim C-440f326a24

8. C-44efda80b8

   Northfold will keep the undermined area out of the layout unless the mine investigation shows it is safe.

   Keep the undermined area out of the layout unless the mine investigation shows it is safe.

   Summary of the County Public Meeting under ORC 303.61 - Tamsin Ridge · DR-0023 · Page 1 · 2023-05-12

   Source developer_document · Claim type recommendation · Polarity presence · Confidence high · Quote check exact, 100 of 100

   See it on page 1, claim C-44efda80b8

9. C-560f40e113

   Seismic site class C; seismic hazard is low.

   Seismic site class C; seismic hazard is low.

   Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

   Source consultant_memo · Claim type absence · Polarity absence · Confidence high · Quote check exact, 100 of 100

   Cited by EN-08 · Filed under EN-02, EN-08

   See it on page 1, claim C-560f40e113

10. C-5c5e675182

    Graywacke considers the probability of further sinkholes over the operating life to be high over the shallow workings; the mine map is incomplete and true limit may reach further west.

    Graywacke considers the probability of further sinkholes over the operating life of the Project to be high over the shallow workings.

    Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 2 · 2023-05-15

    Source consultant_memo · Claim type study_finding · Polarity presence · Confidence high · Quote check exact, 100 of 100

    See it on page 2, claim C-5c5e675182

11. C-6a69538071

    Excluding the undermined area removes about 165 of 240 fenced East Block acres, roughly 20 to 25 MW of capacity.

    about 165 acres of the 240 fenced acres in the East Block, or roughly 20 to 25 MW of the Project's capacity

    Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 3 · 2023-05-15

    Source consultant_memo · Claim type recommendation · Polarity neutral · Confidence high · Quote check exact, 100 of 100

    Filed under EN-02, PE-04

    See it on page 3, claim C-6a69538071

12. C-9dcc852809

    No severed mineral estate other than coal (Parcel 9) and oil and gas (Parcels 2 and 5) was found.

    No mineral estate other than coal (Parcel 9) and oil and gas (Parcels 2 and 5) was found severed.

    Commitment for Title Insurance No. ATA-23-0418 (Parcels 2, 5 and 9) · DR-0006 · Page 3 · 2023-04-18

    Source public_record · Claim type absence · Polarity absence · Confidence high · Quote check exact, 100 of 100

    Cited by PE-05 · Filed under EN-02, PE-05

    See it on page 3, claim C-9dcc852809

13. C-a3cebd779c

    Two plugged and abandoned oil and gas wells are within the project area, and an active horizontal Utica well pad adjoins it.

    two plugged and abandoned oil and gas wells within the project area and an active horizontal Utica well pad adjoining it.

    ODNR Environmental Review - Tamsin Ridge Solar and Storage Project (ODNR 23-0477) · DR-0011 · Page 1 · 2023-05-02

    Source agency_determination · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

    Cited by EN-01 · Filed under EN-01, EN-02

    See it on page 1, claim C-a3cebd779c

14. C-caad69ed74

    Mine subsidence is possible over abandoned underground workings.

    Mine subsidence is possible over abandoned underground workings.

    ODNR Environmental Review - Tamsin Ridge Solar and Storage Project (ODNR 23-0477) · DR-0011 · Page 1 · 2023-05-02

    Source agency_determination · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

    See it on page 1, claim C-caad69ed74

15. C-d106c90db2

    ODNR maps show the abandoned Elsby No. 2 underground coal mine beneath approximately 165 acres of the East Block (Parcels 9, 10 and 12).

    beneath approximately 165 acres of the East Block (Parcels 9, 10 and 12)

    Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

    Source consultant_memo · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

    Cited by EG-01 · Filed under EG-01, EN-02

    See it on page 1, claim C-d106c90db2

16. C-d9db0a1832

    Records show abandoned underground Elsby No. 2 Mine beneath the eastern part of the project area, plus pre-1977 reclaimed surface mining.

    Division records show abandoned underground coal mining, the Elsby No. 2 Mine in the Upper Freeport (No. 7) coal, beneath the eastern part of the project area

    ODNR Environmental Review - Tamsin Ridge Solar and Storage Project (ODNR 23-0477) · DR-0011 · Page 1 · 2023-05-02

    Source agency_determination · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

    Cited by EN-01 · Filed under EN-01, EN-02

    See it on page 1, claim C-d9db0a1832

17. C-e538cf508c

    Borings B-17 and B-19 dropped through voids and collapsed rubble at 61 and 74 feet.

    Borings B-17 and B-19 dropped through voids and collapsed rubble at 61 and 74 feet.

    Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

    Source field_study · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

    See it on page 1, claim C-e538cf508c

18. C-e98a4f0f1c

    Two closed depressions on Parcel 10 are mine subsidence features (sinkholes).

    Two closed depressions, 12 and 20 feet across, on Parcel 10 are mine subsidence features (sinkholes).

    Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 1 · 2023-05-15

    Source field_study · Claim type presence · Polarity presence · Confidence medium · Quote check exact, 100 of 100

    See it on page 1, claim C-e98a4f0f1c

19. C-eaec90390e

    A geotechnical report must address an abandoned underground mine in the East Block.

    A geotechnical report addressing the abandoned underground mine in the East Block.

    OPSB Pre-Application Conference Summary - Tamsin Ridge Solar and Storage Project · DR-0026 · Page 1 · 2023-03-28

    Source agency_determination · Claim type presence · Polarity presence · Confidence high · Quote check exact, 100 of 100

    Filed under EN-01, EN-02

    See it on page 1, claim C-eaec90390e

20. C-f29a379025

    The substation, BESS yard and inverters must not be built over the undermined area.

    The substation, the BESS yard and the inverters must not be built over the undermined area.

    Preliminary Geotechnical Engineering Report - Tamsin Ridge Solar and Storage Project · DR-0018 · Page 2 · 2023-05-15

    Source consultant_memo · Claim type constraint · Polarity presence · Confidence high · Quote check exact, 100 of 100

    Cited by EG-04 · Filed under EG-04, EN-02

    See it on page 2, claim C-f29a379025

21. C-fd52f76b29

    Blasting is not expected.

    Blasting is not expected;

    Noise Assessment - Tamsin Ridge Solar and Storage Project · DR-0016 · Page 3 · 2023-07-10

    Source consultant_memo · Claim type absence · Polarity absence · Confidence high · Quote check exact, 100 of 100

    Cited by CO-03 · Filed under CO-03, EN-02

    See it on page 3, claim C-fd52f76b29

• Keep the undermined area out of the layout, with no substation, BESS or inverters over it; commission a mine-void investigation to confirm its limits.
• Survey, fence and set back plugged wells; coordinate pad setbacks with the operator and ODNR.
• Compare grouting cost against capacity loss.

Agencies