WPC  2"B Z`XArial ItalicArialArial BoldHP LaserJet 4 PlusIIHPLA4PLU.PRS2xCQ\'sZX#|9ND,C2xjAG;X1mC9,  Xm2PG;XP/qC:,cXq2pPG;X2n T|TOO "4^DDV6OOYAOAADDAwDADn6wD66w6RwDwwwuR?ROAnOOODOOOOOOuOAwCCCCCCCCwwwwwwA6AAA6AAgww6A6[6RRRwwwwTDDwuuu6RwDwwDu414WddddddddddddddddddddddddddddddddddddddddNTT~PYVPTO33PPPPTTyuu3OuO"uu~uu"m+^99Ipp.DDNt9D99pppppppppp99tttp̅}9ep}}999\p.ppepp9pp..e.ppppDe9peeeeE5EtD9sZDDD9DDDDDDpD|9pppppȰepppp99999999pppppppppepp|pepppppeeee|pppppppppppp9.999.99Xeep.p:p.pDp.pxppppȼDDDeeee}L}9}9ppppppe}e}e}epp.pDe}9ee|pp8dp,(,WddddddddddddddddddddddddddddddddddddddddNHxxHlpD|pppppLJpDHpD,,DDpDDxppxHxxHsdd,DdD"dxdldtxxd"m+^:D`pp8DDLt8D88ppppppppppDDttt|Đ|8p|||D8Dtp8p|p|pD||88p8||||LpD|pppdL8LtD8ttDDD8DDDDDDpD|8pppppȰppppp88888888|||||||||pp|||p||ppppppppppp||||||||88888888ppp|8|L|8|`|8|||||ȼLLLpppp|`|D|D||||||p|d|d|d||8|Lp|Dpp||:dp,0,WddddddddddddddddddddddddddddddddddddddddNHxxHppD|pppppLHpDPpD88ddpDDxppxHxxHs||8ddD"dxxldtxxd2  P #Xp2PQ XP#e  yxdddy Jicarilla Dulce|'`v(#5Conceptual Design   IV. GEOTECHNICAL/EMBANKMENT DESIGN CRITERIA  R A.` ` Development of Conceptual Improvements(#` XX` ` Several geotechnical improvements were studied in the feasibility design report, but not recommended for further study in this report. They include: (1) construct a replacement roller compacted concrete (RCC) dam at present location, (2) relocate a RCC dam upstream, (3) relocate a RCC dam downstream, (4) chemical grouting as a foundation treatment, (5) compaction grouting as a foundation treatment, (6) stone columns as a foundation treatment, (7) grout rock foundation to reduce seepage, (8) install sheet pile cutoff wall, and (9) install slurry trench cutoff wall.(#` ` ` The RCC dam was not pursued in this report because of its high cost as compared to a zoned embankment dam and because of the possibility of greater foundation settlement. Chemical grouting or compaction grouting as a foundation treatment was not pursued because of cost. The stone column foundation treatment was not pursued because it would have a negative impact on the seepage. A sheet pile cutoff wall was not considered due to cost.(#` ` ` The following improvements were considered essential for one or more of the conceptual design alternatives. The purpose of each improvement follows.(#`  R" ` ` * 9ddddKdd@ddddKdd@9Massive stone overtopping protection Protects the dam against breaching when the dam is overtopped.(#  R-& ` ` * Roller compacted concrete protection Protects the dam against breaching when the dam is overtopped.(# (,))Ԍ R ` ` * Remove and replace foundation Helps control foundation seepage and prevent liquefaction.(#  R X` ` * Partial removal & replacement of foundation with dynamic compaction Helps control foundation seepage and prevent liquefaction.(#   R B.` ` General Criteria(#` ` ` Various geotechnical criteria were used during the development of the conceptual design alternatives for Dulce Lake Dam. It was determined that each alternative for conceptual design must include the removal and replacement of the existing embankment primarily due to the need to densify or stabilize the foundation. The following list shows the general geotechnical criteria and assumptions applied to the conceptual design alternatives that will be outlined and discussed later in this report:(#`  R- ` ` * The water table elevations are such that foundation excavation and replacement will require dewatering. (#  RD ` ` * Explorations E1 and E4 were drilled to bedrock with E1 finding a fine to medium grained sandstone at 27 feet below the crest of the dam and E4 finding highly weathered shale consisting of mudstones and claystones at approximately 85 feet below the dam crest. Explorations E2 and E3 were drilled 84 and 45 feet respectively without drilling into bedrock. Exploration E6 reached rock at approximately 88 feet below the dam crest. Explorations E8 and E9 reached rock at approximately elevations 6947 and 6967, respectively. Additional investigations will be completed before final design is initiated.(# (,))Ԍ R C.` ` Material Properties(#` XX` ` The alluvial foundation materials are a mix of silty sands, silty clayey sands, clayey sands, lean clays, and some fat clays. The liquefaction potential of the noncohesive soils is considered to be high. Therefore, the foundation materials must be treated by one of the geotechnical improvements listed earlier. The entire alluvial material can be removed and recompacted. Alternatively, a combination of partial removal in conjunction with dynamic compaction of deeper materials can be performed. Both of these improvements will allow for construction control of the foundation materials to reduce seepage and liquefaction potential. (#` XX` ` The embankment will be a zoned embankment with a central impervious core and random fill on each side of the central core. The impervious core will be 10 feet wide and extend into the foundation the total depth of excavation to create a seepage barrier. If roller compacted concrete (RCC) is used for overtopping protection on the downstream face then a two foot thick select sand layer will be placed between the RCC and the embankment to act as both a transition zone and a drain. If massive stone fill is used for overtopping protection then two to three transition zones will be placed between the stone and the embankment. On the upstream face, a 2 foot layer of riprap along with a six inch gravel bedding will be placed.(#`  R D.` ` Static Stability(#` XX` ` Based on the existing dam section and concern for protecting upstream highway and hay meadows from backwater inundation, the maximum height of the dam was chosen to be 30 feet and the crest width was chosen to be 20 feet. Final height may be modified slightly, 2 to 4 feet, in the final design process to accommodate roadway transition.(#` (,))ԌXX` ` The upstream and downstream slopes were chosen to be 3h to 1v and 2.5h to 1v, respectively. Given the maximum height of the dam and the assumption of engineered soil properties, these slopes are stable for both the High Level Steady State (HLSS) and the rapid drawdown loading conditions. The actual computations for the static stability will be included in final design. The factor of safety for the HLSS loading condition should be a minimum of 1.5. The factor of safety for the rapid drawdown loading condition should be a minimum of 1.3.(#`  RE XE.X` ` Dynamic Stability(#` XX` ` The Deficiency Verification Analysis (DVA) analyzed the liquefaction potential of the existing embankment and foundation materials during a Maximum Credible Earthquake (MCE) from three possible sources: Transition Zone, Rio Grande Rift, and Random earthquake. A MCE is the largest reasonably conceivable earthquake that appears possible along a recognized fault or within a geographically defined tectonic province under the presently known or presumed tectonic framework (USCOLD, 1985). The DVA found that a Transition Zone MCE could cause liquefaction in the existing embankment and alluvial foundation materials and was considered as the design earthquake.(#` XX` ` The conceptual design alternatives discussed in this report contain geotechnical improvements where the entire foundation materials are removed and replaced or part of the foundation materials are removed along with dynamic compaction. The design intent is that both the foundation materials and the embankment materials will be improved to limits where no liquefaction potential will exist for any of the conceptual design alternatives. Construction plans should require Standard Penetration Testing (SPT) for verification of the design intent.(#` X(#(,))Ԍ` ` Post earthquake stability analyses will be made in the final design using estimated embankment and improved foundation material strengths. The analyses will be psuedostatic in nature with the failure modes representing post liquefaction conditions. Search techniques using UTEXAS3 along with engineering judgement will be used to find the critical failure surfaces in the embankment and the foundation. A factor of safety of 1.2 will be maintained for the postliquefaction case.(#`  R F.` ` Seepage/Piping(#` XX` ` The conceptual design alternatives must consider protection against uplift pressure, internal erosion, and phreatic surface location. For the existing embankment and foundation the velocity of the seepage is not considered significant enough to be an imminent threat to piping. Since all of the geotechnical improvements will act to increase the length of the seepage path, the potential for piping and volume of seepage will become even less for the new embankment and foundation. There is some perennial inflow to this reservoir. Consequently, loss of pool elevation caused by seepage is insignificant and therefore a complete cutoff is not recommended. The adequacy of seepage control will be verified in final design.(#` XX` ` The existing piezometers will have to be replaced due to the removal and replacement of the embankment. The existing monitoring system should also be reinstalled and reoriented for spillway discharge alerts.(#`