GENERAL48922

• Permit No: C1980001
• IBM Index Class Name: General Documents
• Doc Date: 10/29/1981
• Doc Name: Proposed Decision and Findings of Compliance
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

-17-
The West Ridge and Centel Ridye ponds were chcckc•d and found to provide adcn uate
detention times, storage nn!1 spillNaq ca pa ci ti cs. furthermore, NPDES discharge
data at the outlet of both ponds indicates that the outflow is meetiny effluent
limitations (Appendix 3.6A, Volume 9 of the permit application). The Moffat and
Tipple area ponds, however, demonstrate detention times that are well below the
twenty-four' hours recommended by the Colorado Mined Land Reclamation~Division for
achieving effluent limitations. The applicant does not subscribe to the State
detention time guideline and cannot at this time generate data that proves the
proposed ponds will meet effluent limits. Since the hloffat area ponds will not
be constructed until 1984, the applicant proposed to resubmit pond designs no
•~ Iater than six months before pond construction begins. A summary of alternatives
for the hloffat area ponds is given on p. 4.5-142 of the permit application. The
ponds will be designed to meet the effluent !imitations in effect at the time of
the proposed operation in the hloffat area (sec stipulation below). Zn addition,
concerns were raised over the location of the F?offat area sediment ponds. Seven
of the ponds are located on a slope of approximately ,':l adjacent to the East
bank of Trout Creek. The ponds will be excavated into colluvium and probable
bedrock, as shown on the geologic cross-sac tons. The primary spillways of
the ponds will be laid through colluvium, and colluvium ~.'i11 be saturated
around the ponds when thou begin to fill. Additionallu, colluvium material
upslope of the pond may become primed to slump into the pond and become a
severe maintenance problem. Because this concern has not adequately been
addressed, the Division will require additional information prior to construction
of the ponds. (See stipulation below). Finally, two additional design problems
were identified.with the hloffat area ponds. For convenience, the Division has
decided that all design problems for the Moffat area ponds can be handled as
one stipulation. Since the ponds will not be needed for several years the
issues can be resolved beforehand. Despite the design problems identified
the Division finds that the sediment control susr~•m for the Moffat area can be
feasibly constructed and reclaimed. The following stipulation is needed to
address the specific design problems noted above:
4. THE APPLICANT hfUST RES UBFIIT TO ,9LRD T11E DESZGJJS FOR THE MOFFAT AREA
SEDI hfENT PONAS AT LEAST SIX MONTIIS PRIOR TO CONSTR UCTIOPI, AND RELIEVE
APPROVAL FOR THE PROPOSED DGS IGh' BEFORE COh1.MENCING CONSTRUCTION OF THE
PONDS OP, i•?INING IN TIIE h10FFAT AREA. T1fESE DE.S IG,\'S ['JILL REFLECT CURREPJT
REGULATORl' DESIGi! CP.I'IERIA AfJD 1PP.20VaL C'Z LL QE COiJTIJJGEiJT ON IJJFOR-
IdATION DEJ^ONSTRATI!dG TIIAT TIDE PON D$ ODTPL,p[J WILL !IEF.T EFFLUENT LIi•iI T.r TIOi:S.
4a. PITTS UB RG A.ND h1IlJhJ,i 3' CUiiL COh1P:711Y iS DIREC'T'ED :"n pREp,1RE r1ND SUQi•!IT,
FOR APPROVAL Bl' TlfE DI VIS ZO!/, GEOTFCflNIC:7L :1.VD .S'TABILZTY AJJA Lk'SES OF
TJIE PROPOSED h10FFAT AREA SEDL4Eh1T i'ON U.S. TifESE ANALYSES SHOULD INCLUDE
•C07JSIDEILITION OF BOTH BEDROCK (BEDDING PLANE Ah'D JOIPJTZNG) A:JD
S URFICIAL (ROTATIONAL) h1ATE RIAL FA ZLURE SCENARIOS, EFFECTS OF GROUND-
WATER AND FONDED .S lJRFACE [/ATER UPON FOivD SLOPE STABILITY, THE POTENTIAL
FOR CUT SLOPE FAILURES ADOVE TIIE E:{CA VA TED PGN DS, T;JJD THE STABILITY
OF THE FINAL REC7~17hIED CONFIGURATION. (STATIC SLOPF. SAFETY FACTORS OF
1. 3 h1UST BE ATTAIhJED FOR RECLAIMED CONFIG(JR•1TION5) . REPRESENTATIVE'
"WORST CASE" ANAL}"S ES ARE ACCEPTAQLE, IF GEOTECIfNI Cr1L ANALYSES SIIO[/
THAT THE POND SITUATIOPlS PURPO P.TED TO EE REP@ES ENTED P.RE AifA LOGO US.
THE RESULTS OF THF..SE ANAL}'S'GS MUST BC APPROVED QS' T!!E DI L'IS ION PRIOR
TO THE COMFIENCEMENT OF CONSTRUCTION OF AiJ 3' OF TIIE I~l0IFr1T AREA POhl DS.
4b. THE APPLICANT hfUST CONSTRUCT DIVERS IOh' DITCII 1 IN THE b10FFAT AREA TO
ENSURE THAT FLOW FROM Tf1E DITCf! GOES NOT OUTLET INTO POND 8. THE
APPLICANT h7UST ALSO PROVIDE EROSIOfJ CONTROL A1' T11E DITCH OUTLET TO