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Home My WebLink AboutGEOTECHNICAL INVESTIGATION - 00-00035 - US Cellular - Tower & Building Remodelf Ke -rel no I" 0 . Mr. Joseph Head United States Cellular Corp 7600 NE 41st Street. Suite 325 Vancouver, Washington 98662 Dear Mr. Head: Project No. 121-.209.G rilf Nil I Re; Geotechnicall Investigation, Proposed Rexburg Cellular Communications Tower Site, 117 forth 2nd East, Rexburg (Madison County), Idaho (# G84382) INTRODUCTION In accordance with the request of Mr. David Monselle of Land Acquisition, inc. and that of Mr. .Joseph Head of United States C el I u 1 a r,. we have completed oar Geotechnical I nvestigation for the above subject communications tower project. Our work was performed in general conformance with our formal proposal to Mr. Joe Head dated September 29, 2000. Wriften authorization of our services was provided by Mr, Joseph Head through a Purchase Order No. 45003D44490 dated October 25, 200Q. We understand that present plans are to construct a neve communications tower and possible equipment shelter at the site. The tower reportedly will consist of an approximate 8a -feet tali self- support, steed many -pale tower structure while the equipment shelter is anticipated to be constructed within an existing metal mini -storage building. The scope of work for this invesfig ati on included the d d1fl ng of one (1) exploratory Desi boring at the proposed tower location on October 24, 2000 (see Site Vicinity Mai, Figure Na. 1). The test bodng was drilled utilizing true mounted, sofid-flight, hollow -stem., auger and/or mud -rotary dn"lling equipment. The results of our investigation, including design and construction recommendations for the project, are summarized within this report - SITE CONDMONS The subject tower site is located to the gest of North 2nd East and south of North 2nd North at 117 North 2nd East in the city of Rexburg in, Madison County, Idaho see Site Vicinity Map, ..Figure No. 1}. The subject tower area is generally improved and consists of an existing mini- -storage facility. Topographically,. the subject site is characterized as relatively flat -lying terrain and is estimated at about Elevation 4,855 feet. SurfaGe vegetation at the tower s-ite is generally void due to the presence of surface improvernentso I I y f Ke -rel no I" 0 . Mr. Joseph Head United States Cellular Corp 7600 NE 41st Street. Suite 325 Vancouver, Washington 98662 Dear Mr. Head: Project No. 121-.209.G rilf Nil I Re; Geotechnicall Investigation, Proposed Rexburg Cellular Communications Tower Site, 117 forth 2nd East, Rexburg (Madison County), Idaho (# G84382) INTRODUCTION In accordance with the request of Mr. David Monselle of Land Acquisition, inc. and that of Mr. .Joseph Head of United States C el I u 1 a r,. we have completed oar Geotechnical I nvestigation for the above subject communications tower project. Our work was performed in general conformance with our formal proposal to Mr. Joe Head dated September 29, 2000. Wriften authorization of our services was provided by Mr, Joseph Head through a Purchase Order No. 45003D44490 dated October 25, 200Q. We understand that present plans are to construct a neve communications tower and possible equipment shelter at the site. The tower reportedly will consist of an approximate 8a -feet tali self- support, steed many -pale tower structure while the equipment shelter is anticipated to be constructed within an existing metal mini -storage building. The scope of work for this invesfig ati on included the d d1fl ng of one (1) exploratory Desi boring at the proposed tower location on October 24, 2000 (see Site Vicinity Mai, Figure Na. 1). The test bodng was drilled utilizing true mounted, sofid-flight, hollow -stem., auger and/or mud -rotary dn"lling equipment. The results of our investigation, including design and construction recommendations for the project, are summarized within this report - SITE CONDMONS The subject tower site is located to the gest of North 2nd East and south of North 2nd North at 117 North 2nd East in the city of Rexburg in, Madison County, Idaho see Site Vicinity Map, ..Figure No. 1}. The subject tower area is generally improved and consists of an existing mini- -storage facility. Topographically,. the subject site is characterized as relatively flat -lying terrain and is estimated at about Elevation 4,855 feet. SurfaGe vegetation at the tower s-ite is generally void due to the presence of surface improvernentso I M Project No. 121.209.G 1 Page No. 2 The subsurface soil conditions at the site consist of alluvial soil deposits of Pliocene and MbI?TTnT t 7117 IrI51111, ihiii i iii iii illiyiii loll miif ill f1i Ii ni ii iiRliil it iR upper unit of loose to medium dense, silty fins to medium said to a depth of about 6.o feet 7 " beneath existing site grades. Ikese si'liyIo Pine medium San� 501"I tAAll �A?8 6to characterized by relatively low to moderate strength and wmpressibility. These upper sandy soil materials were inturn undedain by medium dense to dense, silty, sander gravel is gravers sand with occasivnal cobbles to the maximum depth explored of about 26-.5 feet beneath existing site grades. These medium dense to dense, silty, sandy gravel to gravells said with occasiflnal cobbles soil materials ars fest charactedzed by relatively moderate to high strength and tow compressibility. Ground wafer was also encountered within the exploratory boring at the time of drilling at a depth of about 14 feet. However, topsoil materials were generally not encountered at the she due to the presence of the existing surface improvements. All sails encountered at the site were classified in accordance w�t� the llnified Soil Cfassifc�tion Sys#em �USCS} which is vu�l��ed o� Figure Na. 3. CONCLUSIONS AND RECOMMENDATIONS Based on the results of our field exploration, the tower site was found to be generally undeda�n by alluvial sail bedrock deposits of Pliocene and Miocene age. These subsurface and/or bedrock matenals were generally found to be loose to medium dense, silty, fine to medium sand within the upper f deet followed by medium dense to dense, silty, sandy grave! to gravelly sand with occasional cobbles to the maximum depth explored of 26.5 feet beneath existing site grades. As noted above, ground water was also encountered at the time of our feed exploration work at a depth of about 14 feet and is expected to be a factor during construction. In this regard, we are of the opinion that the site is suitable for the planned s#eek mina -poke tower stn.icture and equipment shelter provided that the following recommendations are incorporated into the design and construction of the project. In general,. we are of the opinion that support of the tower structure could best be provided by means of a direct bury or drilled concrete pier footing den'ving frictional resistance and end bearing support on the underfying medium dense to dense silty, sandy gravel to gravelly sand subsurface soil materials. However, die to the relatively dean nature of the underlying silty said and/or sandy gravel subsurface svil deposits, deep and/or drilled shaft excavations for the tower foundations are expected to encounter at least minor to moderate caving andlor soughing conditions especially below ground wader elevations. As such, casing and/or sharing of deep or open drilled shat excavations is generally recommended within the silky sand anular sandy gravel subsurface soil deposits. The fallowing sail strength parameters may be used for foundation design purposes: Medium brown to gray -brown, silty, fine to medium SAND with occasional graved (SM); Allowable vertical bearing pressure.- Allowable lateral bearing pressure: Soil unit weight (moist): Angle of internal ffiction: Cohesion: Coefficient of friction: Passive earth pressure; Adhesion of concrefe to sail (ultimate): 3,000 psf 200 psf 110 PGf 32 degrees 100 psf 0.35 zso per 1,00Q psf RFi)MAssociATF-soND & A ?[Olga f�o.ill .T09.G Page No. 3 Gray -brown, silty, sandy GRAVEL to gravelly SAND with occasional cobbles (GM/SM): Allowable vertical beadag pressure: Ilowa le laleral Leanlng pressure: Soil'unit weight (moist): Angle of inte mal frictiond. Cohesion: Coefficient of fdction* Passive earth pressure: Adhesion of concrete to soil (UjtfMrate)I 7,000 psf 38U Pi 125 pcf 38 degrees 100 psf 0.4D 300 psf 1,5 00 psf Nage: The above recommended allowable vertical beadng pressures are intended for dead Toads and sustained lige loads andmay be increased by one-third for the total of all loads including Aort-term wind or seismic loads. Foundations For conventional (lightly loaded) shallow foundations with no more than 12 to 18 'Inches of embedment, such as those required for an equipment shelter slab and/or pad, we recommend that an allowable contact beadng pressure on the order of 2,0D0 psf be used for design were foundations are supported by the native, medium dense., silty, fine to medium sand subsurface soil materials. However, Oft may be desirable to place an approximate 6 -inch layer of compacted grave! below a surface supported cast in-place concrete slab. Additionally, should the equipment shelter be founded above the dower foundation backfill ma#edals, it is recommended that the tower foundation backfill materials be compacted to the requirements of structural fill. A coefficient of ffiction between the silty sand subgrade and footing elements of x.35 "is recommended. Seftlements of foundations.,- for beth the tower and equipment shelter,, designed and constructed in accordance with the above recommendations are expected to be fess than 1/2 -inch. Site Prenaratio,n and Excavations Site preparation �s anticipated to consist generally of the stripping and removal of the surficiai n pavement materials which are believed to be about 2 to 3 inches in depth. Where structural fill$ are required, we recommend that stnuctural fills be compacted to at feast 92 percent of the � ASTM D -I 557 test procedures. Additionally; the on -sits silty sand and sandy gravel subgrade soil materials are considered suitable for use/re-use as structural til materials provided they are free of rock fragments in excess of about 6 inches and at or year to optimum moisture content at the time of compaction. In general, temporary excavations should remain fairly sable at rear vertical inclinations to depths of about four (4) feet. Excavations between the depth of four (4) feed and ten (10) feel should be backcut to inclinations of about 1 to 1 (horizontal to vertical) or flatter. However, where excavations exceed abut five (5) feel and where workers will be present within the bottom of the excavation, we recommend a minimum temporary excavation inclination of at least I to 1 (horizontal to vertical). As an alternative, the excavation may be propedy braced and/or shored to provide for worker safety. However, the bracing and/or shoring of the excavation should be the responsibility of the excavation contractor. Additionally, as noted above, deep excavations such as those required for drilled concrete piers should be cased to prevent caring andlor sloughing during constructionof tie piers. However, dewatering of the open dulled shaft excavation is not recommended dere to the potential for bottom heave. a } RF-.DMOND & ASSOCIATES 9 Project No. t21. Rags No. 4 CLOSURE 209.G The services peiformed by the Geotechnidal Engineer for this project have been conduced with that level of Gaye and skill ordinadly exercised by members of the profession currently practicing in this area under similar budget and time restraints. No warranty, ether expressed or implied, is -- made. We will be pleased to provide such additional assistance or information as you may require in the balance of the design phase o€this project and to aid in construction control or solution of unforeseen conditions which may an e daring the construction period. Sincerely, IN ��}NAL FN 1 �r, Daniel M. Redmond, P. E. i��0 President/Principal Engineer ILL $$70 � sj, C cc: Mr. Dave Monselle Land Acquisitions, Inc. RTINp,E 1 1 1 i REDMOND & ASSOCIATF., S 1 REXBURG QUADRANGLE IDAHO—MADIS-ON CO. 7.5 MINUTE SERIES (TOPOGRAPHIC) SCALE 1-24 000 -.000 0 two 2DOU" 3- 4000 5001- 600C 7000 FEET KILOMEFTER' CONTOUR INTERVAL 5 FEET NATIONAL GEODETIC VERTICAL DATUM OF 1929 Project No. 1 2 1.209. G SITE VICINITY MAP PROPOSED, REXBURG CELL SITE Figure NG. 1 PRIMARY DIVISIONS srn►�eUa� SECONDARY DIVISIONS GRAVELS CLEAN��r Well graded gravels, gravel -$arid mixtures, little or no Q _ GRAVELS fines U011 TfiN 0Q4 ([[)1 TrM111. U11910 Qlff of ulffif 11,nq M111U190 11111 J w '� % F11�1 � � P no fines. U) FRACTION ISG�iAVEL GIVE 5ifiy gravels, gravel -sand --sitz mixtures, non -plastic fines_ Li� z � LARGER THAN WITH � LL u: N0. 4 SIEVE FINES C Clayey gravels, gravel-sand -clay rnixtures, plastic fines. LL 0 z j,.-� SANDS CLEAN SANDS Sw Well graded sands, gravelly sans_ l�tile or no fines. Q � �' MORE THAN HALF (LESS THAN � 5 °� FINES) SP Pwrly graded sands or gravelly sands, little or no fines. cc� < DF COARSE Uj FRACTION IS 0: V)SANpS SM Silty sands, sand -sift mixtures, non-plasticine5U- SMALLER THAN WITH � NO. 4 SIVE FiN4ES $C Clayey sands, sand -clay mixtures. �iasts� f- ines. LU �L inorganic slits and very dine sands. rack flour, ssity_ or J � � � Sf�TS AND CLAYS c�ayey ffn�e sar��5 or clayey. silts witF� slight ptasticiry. o J -- �] � -J, w LIQUID LIMIT IS C L Inor�anic Clays of !aw to medium ptasticrty, gravelly � c ays, sandy clays, silty clays. lean days. < "'' LESS THAN 5096 d 2 OL Organic sills and organic S1f:y clays Of iDw piBStfCkty. W � _ --i " SILTS AND CLA`t'S �H lnorg�nse sill5, micaceous wdiats�ma�eous €ine sandy or <silty soils,'elastic sites. C) Uj LIQUID LIMIT 15 CH Inorganic clays of high plasticity. fit Clays. LU C, � Z UL s GREATER THAN 50%OH Organic ct�ys of medsum to #sigh pl�siieity, organs,,:., sElts. HIGHLY ORGANIC SOILS Pi Feat and other highly organic soils - DEFINITION' OF TERMS L1. S. STANDARD SERIES SIEVE CLEAR SQUARE STEVE OPFNNGS ZQt] 40 10 4 3%4" 3" 12" SAND GRAVEL SILTS AND CLAYS COBBLES BOULDERzD SINE MI-DiLM CO -ARSE FINE DA RS SANDS,,GRAVELS AND NON-PLAST'IC SILTS BLOWS.IFOOV VERY LOOSE , i L 6 4 —10 MEDtUM DENSE 10 - 30 DENSE 3 50 VERY CENSE OVER 50 GRAIN SIZES CLAYS AND BLASTIC SILTS STRENGTH BLOWS./FOOT VERY SOFA �: SOFT 1 _ 1. 2 r T! 1 1 ' 9 STI FF 1 a 8 1 V EERY STIFF4 16 32 HARD OVER RELATIVE DENSITY CONSISTENCY }Number of blows of 140 pound hammer failing 30 inches to drive a 2 inch ❑.D. C1-3/8 inch 1.0.3 split spoon CAS7M D-1586). �lkiconfined compressive strength in tonsrsq. #t. as determined by laboratory testing or approximated by the standard penetration cert CAS7M ❑- 1585), packet penetrometer, torvane, or visual observation. KEY TO EXPLC}RATaDRY BORING LOGS Unified Soil Classification System CD-2487) REDM�ND � �UCL�41`ES PROPOSED RF�H�URG CELL SI`�*E Rexburg, Idaho P. 0. Bax 30I545 9 PoRnAism, DR 97294 FRQ,JECT NO. DATA Figure 3 121.w209.mG opt, 2 s, 2000 i t 100 90 so 70 z O 6Q� z so 30 0 UNIFIED SOIL CLASSIFICATION SYSTEM! (ASTM o 42-2-72) U. S. STANDARD SIEVE 5iZE5 100 50 I.IV U.Z P A RT1C.LE 5.11 Z IN NilMETE R 0 10 A JD 0 40 LU So. z 60 70 FKIEY UNIF[EID Ri f N C . �. Ev. SEEP Ha (#eek SOT PINI SAMP� � � I�� s� } feet'. SYMBOL rn 1 6.0 SM um browngray-brown,silty. fine mum SAND GM/SM Gray-brownr i t y r an GRAVM tc 1 01 gravelly P.O. Box 301545 . PoRTuviD, OR 972,94 GRADATION TEST BATA PR0PC3SED R.�S`.TRG C=t. 52'1TP- RPxl)l1Y'g ? Z da"lfl PROJECT NO. DATE FtGL}Re :1:2:1 .209.G opt. 2-6, 2000 Nino go x 100 Ii 1 1 TABLE A Field Resistivity fest Results N -S Direction Spacing (ft) Resistivity (ohm -feet) 2.0 62 5.0 58 10.0 48 15.0 30 20.0 27 40.0 20 E -W Direction Spacing (ft) Resistivity (ohm -feet) 2.0 63 5.0 60 10.0 53 15.0 38 201.0 30 40.0 23 Resisfivitv (ohm -meter' r! 85 175 145 90 80 60 ResistiVitv Bohm -meter' 190 180 160 115 90 70