2021-08-27_REVISION - M2019028

• Permit No: M2019028
• IBM Index Class Name: REVISION
• Doc Date: 8/27/2021
• Doc Name: Adequacy Review Response
• From: J&T Consulting. Inc.
• To: DRMS
• Type & Sequence: TR1
• Email Name: PSH
• Media Type: D
• Archive: No

J-2 Contracting Co.—DPG Pit— Technical Revision No. 1 Adequacy Review Response
File No. M-2019-028
-5-
Geotech Review
The Division of Reclamation, Mining, and Safety (Division/DRMS) staff reviewed the geotechnical
stability analysis included with the technical revision by Civil Resources, LLC dated February 2, 2021.
The following list describes the information used by the Division as presented in the technical revision
to evaluate slope stability for the site.
• The stability analysis addresses the stability of the reclaimed 3HAV reservoir slopes and the
temporary 2H:1V silt pond slopes.
• The stability analysis does not address the stability of the man-made structures within 200 feet
of the affected land boundary.
• The reservoirs will be dry mined with the installation of slurry walls and dewatering.
• The silt ponds will be dry mined by dewatering.
• A maximum horizontal acceleration of 0.07g was utilized for the seismic loading.
• The slurry wall was modeled 25 feet from the mining limit.
• The strength properties for overburden (sandy clay), sand and gravel, claystone bedrock and
the slurry wall were based on field testing data and/or engineering judgement.
• The Applicant used the following soil parameters for the anticipated soil types;
o Overburden — 114 pcf, 28 degree friction angle, 50 psf cohesion
o Alluvial Material— 129 pcf, 35 degree friction angle, 0 psf cohesion
o Claystone Bedrock (Residual)— 110 pcf, 18 degree friction angle, 50 psf cohesion
o Claystone Bedrock (Peak) — 126 pcf, 26 degree friction angle, 100 psf cohesion
o Soil-Bentonite Slurry Wall— 112 pcf, 0 degree friction angle, 0 psf cohesion
• No laboratory strength tests were performed on soils.
• No borehole data was submitted by the Operator with the technical revision.
In accordance with Table 1 — Recommended Factors of Safety for Slope Stability Analysis for
Operations and Reclamation within Section 30.4 of the Policies of the Mined Land Reclamation Board
effective May 16, 2018, the Division will require the Applicant to comply with the factor of safety of 1.5
(static and rapid drawdown) and 1.3 (seismic) for critical structures and a factor of safety (FOS) of 1.3
(static and rapid drawdown) and 1.15 (seismic) for non-critical structures since the Applicant utilized
generalized strength measurements in the analysis.
The following information is required by the Division to complete the stability analysis review.
12. On page 2 of the report, the Operator states two (2) sections were evaluated at the tallest
highwall in each mine cell based on the section provided by Al (Aggregate Industries). The
3HAV analysis utilized 90 feet as the maximum depth of the reservoirs. The maximum depth for
the reservoirs in the approved permit application is 114 feet. See Item #16 in the adequacy
response letter for the original application dated August 26, 2019. Please explain this
discrepancy and provide a map indicating the location of the two sections.
Response: The Division can disregard the geotechnical stability analysis done by Civil
Resources. The original stability analysis done by J&T Consulting remains valid for all
mining areas as they have been proposed in Technical Revision Request 1 with the
exception of Cases 3 and 4. Case 3 is the silt pond slope in the proposed Phase 3 area.
Case 4 is the silt pond slope in the Phase 1 area.
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