REP29999 - Laserfiche WebLink

Home Browse Search

I _~ .e INSPECTION OF EXCESS SPOIL, FILL First Quarter 2004 Certification Fill Area No. 9 Date: March 30, 2004 . GENERAL DESCRIPTION OR REFERENCE TO SITE PLAN: The CTL Thompson report dated April 27, 2001, "Stability Analysis and Geo-technical Recommendations Lorencito Surface Mine Phase 1" addresses the general requirements as also cited in Sections 4.09.1 to 4.09.2 of [he Colorado Mined Land Reclamation Board for Coal Mining. ACTT VITY DURING INSPECTION: Removal of Topsoil and Organic Matter Placement of Under-drains [nsfallafion of Surface Drainage System _Construction of Fill X Placement of Topsoil X Seeding SEDIMENT CONTROL Sediment pond construction has been completed in accordance with plans submitted to and approved by the DMG and as-constructed survey/drawings certified by Registered Land Surveyor and Registered Professional Engineer. All surface run-off from the fill areas is directed to this sediment control facility known as pond 7No evidence of significant erosion was observed. SITE PREPARATION As indicated by previous inspection reports, organic materials such as brush and trees were removed from the proposed fill area followed by topsail removal prior to fill placement. Design criteria did not require keyway cuts for steeper valleys with minimal soil cover (fill #9). DRAINAGE SYSTEM (UNDERDRAINS) Drain sizes are specified by CDMG regulations for fills which can be classified as Valley Fills. Fill area #9 is not a valley fill. CTL Thompson recommended a minimum 6' x t2' triangular sec[ion(area = 64 SF) for this size fill. As indicated by previous inspection reports, as constructed drainages generally were more trapezoidal with a [op width of 12', bottom width of 8', and average height of 8' (m ca = 80 SF). Sandstone recovered from durable "channel" sandstone deposits encountered during the mining process were used in drain construction. Mirafi 160 fabric was used in lieu of filter material. FILL PLACEMENT CDMG regulations require that spoil be "placed in horizontal lifts in a controlled manner, concurrently compacted as necessary to ensure mass stability". Maximum IiR thicknesses are not specified. As indicated by previous inspection reports, lifts were placed in accordance with plans specified by the CTL "fhompson report. Spoil material was transported to the fill area using a combination of trucks and dozers. Left thicknesses of up to 50 feet were placed within the area removed from the till face by more than 50 fee[. Fill placement terminated by second quarter 2002.