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HomeMy WebLinkAbout08.a. (Handout) KarpDear President Nejedly & Board Members: CCCSD is reconsidering the granting of exceptions to a Contractural Assessment District (CAD) proposed for upper El Toyonal and Alta Vista in Orinda. According to CCCSD, a CAD is a "program to provide financial assistance to small groups of homeowners with inadequate septic tank systems so that they may extend the public sewer system to serve their properties ". However, no such "inadequate septic tank systems" exist. The main purpose of this CAD is to extend CCCSD's facilities to promote development of vacant lots. Basically, the proponents of the CAD do not want to pay for the project so they are seeking exceptions to CCCSD's policies so the project will be built with debt to be paid in the future by others. Once built, the debt will be shifted to homeowners by future connections that have been projected by staff to occur. Unfortunately, staff has allowed this proposal to reach this point without requiring the CAD's proponents to produce a legitimate feasibility study and then a cost estimate for the project. The current project cost appears to be grossly underestimated. Similar projects have been proposed since 1970 and they were abandoned due to instabilities in the substandard El Toyonal and Alta Vista roadways, which, if possible, will be prohibitively expensive to remediate. Information concerning the instabilities in the project area are (attached) as follows: 1. Report "Dos Osos /Alta Vista Sewer Line Extension, CCCSD Job 4103 ", October 29, 1985. 2. Sections of "Maps of Landslide & Colluvial Deposits across Alta Vista and El Toyonal ". 3. Photographs of El Toyonal (the only arterial) between Camino del Cielo and Alta Vista. Most of the of homeowners in the neighborhood are against the project and are unlikely to connect in 20 years, just as was determined in 1970 and later. No exceptions should be granted. �111111i11!/!! ,OQROFESS/0 ft�, Yours truly,•• "'•• ' W • • ` � s No. 452 �oG ; Ren 12131113 ; V Lawrence B. Karp * :� ago 's 100 TRES MESAS, ORINDA CA 94563 (925) 254 -1222 fax: (92�, 5�.�`� -mail: lbk@ibkarp.com lnlr0 ` 3•a LAWRENCE B. KARP • CONSULTING GEOTECHNICAL ENGINEER ( FOUNDATIONS, WALLS, PILES UNDERPINNING. TIEBACKS DEEP RETAINED EXCAVATIONS SHORING 8 BULKHEADS CEQA, EARTHWORK 8 SLOPES CAISSONS, COFFERDAMS July 18, 2012 COASTAL 8 MARINE STRUCTURES SOIL MECHANICS, GEOLOGY GROUNDWATER HYDROLOGY CONCRETE TECHNOLOGY Board of Directors Central Contra Costa Sanitary District _ Ka r•A 5019 Imhoff Place Martinez, CA 94553 11'"' J(,Z3 Pp, Subject: Proposed CCCSD Assessment District El Toyonal - Alta Vista, Orinda Dear President Nejedly & Board Members: CCCSD is reconsidering the granting of exceptions to a Contractural Assessment District (CAD) proposed for upper El Toyonal and Alta Vista in Orinda. According to CCCSD, a CAD is a "program to provide financial assistance to small groups of homeowners with inadequate septic tank systems so that they may extend the public sewer system to serve their properties ". However, no such "inadequate septic tank systems" exist. The main purpose of this CAD is to extend CCCSD's facilities to promote development of vacant lots. Basically, the proponents of the CAD do not want to pay for the project so they are seeking exceptions to CCCSD's policies so the project will be built with debt to be paid in the future by others. Once built, the debt will be shifted to homeowners by future connections that have been projected by staff to occur. Unfortunately, staff has allowed this proposal to reach this point without requiring the CAD's proponents to produce a legitimate feasibility study and then a cost estimate for the project. The current project cost appears to be grossly underestimated. Similar projects have been proposed since 1970 and they were abandoned due to instabilities in the substandard El Toyonal and Alta Vista roadways, which, if possible, will be prohibitively expensive to remediate. Information concerning the instabilities in the project area are (attached) as follows: 1. Report "Dos Osos /Alta Vista Sewer Line Extension, CCCSD Job 4103 ", October 29, 1985. 2. Sections of "Maps of Landslide & Colluvial Deposits across Alta Vista and El Toyonal ". 3. Photographs of El Toyonal (the only arterial) between Camino del Cielo and Alta Vista. Most of the of homeowners in the neighborhood are against the project and are unlikely to connect in 20 years, just as was determined in 1970 and later. No exceptions should be granted. �111111i11!/!! ,OQROFESS/0 ft�, Yours truly,•• "'•• ' W • • ` � s No. 452 �oG ; Ren 12131113 ; V Lawrence B. Karp * :� ago 's 100 TRES MESAS, ORINDA CA 94563 (925) 254 -1222 fax: (92�, 5�.�`� -mail: lbk@ibkarp.com lnlr0 ` LAWRENCE B. KARP CONSULTING GEOTECHNICAL ENGINEER October 29, 1985 Central Contra Costa Sanitary District 5019 Imhoff Place Martinez, CA 94553 Attention: Jay S. McCoy Collection System Engineering & Services Division Manager Subject: Dos Osos /Alta Vista Sewer Line Extension CCCSD Job Igo. 4103 Dear Mr. McCoy: 0 FOUNDATIONS WALLS PILING TIEBACKS ANCHORS SHORING DEEP RETAINED EXCAVATIONS UNDERPINNING, CAISSONS. COFFERDAMS COASTAL 8 MARINE STRUCTURES GROUNDWATER HYDROLOGY SEA ICE PERMAFROST I write concerning slope stability in the area of subject sewer project. I are in receipt of the "Report- Geotechnical Investigation -El Toyonal Sewer Extension- Orinda, California" prepared by Gary Underdahl and Darwin Ayers, dated 10/2/85. On 9/16/85 I spoke with Mr. Myers and on 9/24 I spoke with Mr. Wnderdahl about the history of slope, road, and foundation failures along and near the proposed alignment. These discussions followed several meetings with CCCSD's Dennis Mall at which time the same history was reviewed. As you know, petitions, sigmed by most of the homeowners in the area of the proposed project., were submitted to the District in 1981. You will recall the meeting on 6/4/81 at District's offices on Springbrook Road; many holmeowners spoke concerning the instabilities in the area and urged the District to have an adequate investigation performed to supplement an EIR that was termed inadequate by the Orinda Association's Planning Committee. That meeting was before the building lasses and massive slope failures in the area subsequent to the 1981 -82 and 1982 -83 rains. Accordingly, I am surprised that the Underdahl acrd Myers report states "The purpose of this investigation was to provide info}rmafion on the depth to bedrock, and to provide recommendations pertaining to sewer alignment and sewer construction ". The report does not detail the history, and therefore the area's susceptibility to slope, road, and foundation failures. The one failure reference concerns the Morris home at 8 Alta Vista, and calls this storm damage. This home was actually abandoned due to progressive foundation failures and the inability of the septic tank system to function properly. I loomed at the property for Floyd Swenson in the 1960'x, and it was damaged then. Construction and use of the alignment as proposed presents unreasonable risks in terms of slope and roadway stability. I have been asked by several of the homeowners in the neighborhood to comment on the site and other conditions not addressed in the Underdahl and Myers report. 100 TRES MESAS ORINOA, CALIFORNIA 94563 (415) 254 -1222 Central Contra Costa Sanitary District, 29 October 1985; page 2 Most of the alignment is along E1 Toyonal, which is the neighborhood's (and my) only direct access and egress route to Orinda. The only other way 3 -s-- t-0- drive thr -ough Rerkeley and Oakland (Alameda County) . Every other route has been lost due to failure; the other end of El Toyonal suffered a deep seated rotational failure in 1982 and has not, even though it is supposed to be a County maintained road, been repaired. Cost estimates are $400,000 to $650,000 for restoration. Most of El Toyonal does not and cannot be improved to meet County width specifications, due to steepness and instability of adjacent slopes. The Uaderdahl and Moyers report was prepared after large sections of significant tension cracks in the El Toyonal asphaltic concrete section were covered over by the County. These crags appear every year in the outside half of the pavement, and are a clear indication of creep and instability. The alignment as proposed will cut through a 1982 failure wear 8ta 5 +87.95 (at Camino del Cielo); at this location, E1 Toyonal is supported by oak trees. There is a history of protracted litigation concerning access to Camino d"el Cielo. A proposal for a utility trench at this location should include a retaining structure. Other roadway failures that have occurred are near 8ta 3 +10.10 (inadequate shoulder support), Sta 8 +20.00 (loss of lateral support), and Sta 9477.81 (creep and subsidence). If this narfaw r-oad its impaired, children will be cut, off from school and the residents will be separated from the community. Alta Vista (private) read is cut into clay and pebble conglomerate and has failed or settled along the entire length of the alignment. In 1958 the roadway near Dos Osos dropped over a distance in excess of 100 feet, and has still not been repaired; the road failure (and the loss of two houses) was attributed to a percolating utility trench and reduction of lateral support. The road is now dead -ended at Dos Oros due to a 1981 failure. Camino del Monte, cut in pebble conglomerate, used to provide a link to Alta Vista but was lost several years ago and caftnot be repaired at any cost. Looking from 8ta 17 +54.24 one can see a sheer 90 foot drop in the pebble conglomerate of the western slope of Camino del Monte. One can also see. a PG &E gasline in the roadway failure scarp. The Underdahl and Myers report seems to focus on a postulation that if the sewer trench is cut into bedrock, slope stability will be ensured; that reasoning may be valid if the alignment is perpendicular to slope or in level terrain. At this project, the trench is proposed to be cut parallel to slope. Central Contra Costa Sanitary District 29 October 1985; page 3 By benching into bedrock as proposed, passive pressures supporting the roadway will be impaired. The alignment has been marked on the pavement by Schell & Martin, and in many cases, as indicated by cracking patterns over the years, the alignment will actually cut into the outer edge of the bedrock structures now barely supporting the roadway. Additionally, the trench backfill will either act as a subdrain (permitting seepage to enter under static head; resulting in reduction of the shear strength of the soil and the creation of a failure plane along the path between the trench and the slope below the roadway) or as a dam (permitting increased pore -water pressures uphill of the roadway). It will be virtually impossible to exactly duplicate the hydrological behavior of the natural material removed by backfilling. STRUCTURES In 1982 a house below 5ta 5 +87.95 on El Toyonal was disintegrated by a debris avalanche. Several foundation failures have damaged the house adjacent to Sta 7 +5$.9$ (244 Fl Toyonal). In 1964 foundation distress occurred in the house upslope from Sta 9 +12.29 on El Toyonal. In 1958 two houses on Alta Vista (belonging to Presnell and Hightower) were destroyed by a deep seated rotational failure which was attributed to a percolating utility trench and reducti ©n of lateral sspport. The previously mentioned house at 8 Alta Vista (Sta 15 +54.09) has suffered foundation instability for over 25 years. The property at 10 Alta Vista (Sta 16 +60.30) has been consistently damaged by soil movement. Pebble conglomerate is exposed in the uphill roadway cut and the retaining walls, squash court, and ether improvements downslope are beyond repair. Most of the houses have experienced soil movements due to their north slope locations and the insidious nature of the geology. The general vicinity of the proposed sewer project is particularily susceptible to slope failures mecause of the e *istenee of landslide: and dolliu-vial deposits, eNpansive soil, fortaetioft bedding, and adverse hydrology. Geologic maps (Brabb, 1976 & Dibblee, 1980) indicate that the area is underlain by the Orinda Fopmation (Tertiary/Lower 'Pliocene age; 1 -13 million years old), an unstable series of poorly cemented nonmarine sedimentary annd volcanic rocks, specifically weakly consolidated pebble conglomerates, sandsitones, claystones, and siltstones. In the project area, the interfingering of the weak pebble conglomerate and the elaystoRq has proven to be the most worrisome situation. At the interface of these two components of the Orinda Formation, weathering creates a discontinuity that increases the potential for landslidimg. Central. Co r" Costa Sanitary Di 29 October 1-"5; pacre Rainstorm elevated pore -water pressures in combination with adversely oriented joint surfaces, and the disturbance caused by construction and structures, are the principal causes of slope and foundation failures in the area. The conglomerates bleed, and the plastic clays and silts swell and become weaker in a saturated state as compared to unsaturated, drier conditions. Foundation support capacities decrease with reduced shear strength, and the potential for slope instabilities correspondingly increases. Creep, the gradual movement of plastic soils downslope upon cyclic wetting and drying, is another characteristic of the clays and silts. 1. The Underdahl and Myers report fails to adequately address roadway and slope instability. The premise that construction of the sewer trench should include the removal of bedrock supporting the roadway is questioned. 2. The report is superficial in discussing historical instability, the effects of trenching in the Orinda Formation, and the north slope exposures. 3. The report does not discuss mitigating measures to compensate for the compromise in roadway and slope stability, such as retaining structures, anchors, or other improvements. 4. There is a neighborhood concern that if and when a roadway failure occurs there will noit be funds available to repair, and the residents will be curt off from Contra Costa County. The newly incorporated City of Grinda does not have funds to repair El Toyonal, and the County has left the other ,end of El Toyonal in a mailed condition fon years. There is rmo commitment that the CCCSD 4nd /or the project Sponsor will repair the roadways and structures if a f ailukre occurs. 5. There is no mention in the report of the obvious alternative route for the sewer alignment; from La Encinal (CCCSO Project Igo. 3254) and up El Rincon to El Toyonal, argd up the draw to Alta Vista. This route would not be parallel to slope and would be mtIch more suitable. The distance is almost the same, and construction would not interfere with traffic. 6. There is no indication that the authors of the report, from which the project is to be designed and constructed, possess adequate professional liability insurance in the event their work product (investigation and recommendations) are in error, and a failure occurs. i w ,J No: 25389 Lawrence B. Karp / E_ CIVIV OF CAU Ventral Contra Costa Sanitary District, 29 October 1985: page 5 1. Brabb, Earl E., 1976 "Preliminary Geologic Map of Contra Costa County" (assembled from unpublished geologic maps by Ross Wagner, University of California, Berkeley, and Howard S. Sonneman & John R. Switzer, Jr., Exxon Corporation) unpublished map at 1:62,500 scale, distributed by the Contra Costa County Public Works Department,, Martinez, #T -651, 2 sheets. 2. Borchardt, Glenn A., 1977 "Clay Mineralogy and Slope Stability ", California Division of Mines and Geology - Special Report #133. 3. Central Contra Costa Sanitary District "New Proceedures for Design of Sewers in Hillside and Creek Areas", memorandum dated September 20, 1984. 4. Central Contra Costa Sanitary District, 1976 "Standard Specifications for Design and Construction" 5. Dibblee Jr., Thomas W., 1980 "Preliminary Geologic Map of the Briones Talley Quadrangle, Alameda and Contra Costa Counties, California ", U, S. Geological Survey -Open File Report #0 -539. 6. Ham, C. K., 1952 "Geology of Las Trampas Ridge, Berkeley Hills, California, California Division of Mines- Special Report #22, 26 p. 7. Karp, Lawrence B, "Proposed Development -Alta Vista between Camino del Monte and Dos Osos, ©rinds, Contra Costa County" letter - report dated July 3, 1979 prepared for Dieter M. Scholz, Orinda. 8. Keefer, David K. & Johnson, Arvid M., 1983 "Earth Flows: Morphology, Mobilization, and Movement ", T. S, Geological Survey - Professional Paper #1264, 56 p. (with plates in pocket). 9. Marliave, Burton N., "Slide Conditions Along E1 Toyonal ", letter - report dated November 10, 1962 prepared for Mr. Victor W. Sauer, Director of Public Works, Contra Costa County. 10. Myers, Darwin, "Dos Osos /Alta Vista Sewer Line Extension...." letter- report dated Mardi 9, 1981 prepared for Mir. Malcolm Sproul of Larry Seeman Associates, Inc. 11. National Research Council and U. S. Geological Survey, 1982 "Debris Flows, Landslides, and Floods in the San Francisco Bay Region January 1982 ", Overview and Summary o-€ a Conference field at Stanford University August 23 -26, 1982, 83 p., National P�cademy Press, Washington D.C. 1984. Central Contra Costa Sanitary District, 29 October 1985; page 6 12. Nilsen, T. H., 1973a "Preliminary Photointerpretation Map of Landslide and Other Surficial Deposits of the Concord 15-minute quadrangle and the Oakland West, Richmond, and part of the San Quentin 7.5- minute quandrangles, Contra Costa and Alameda Counties, Calif.," U. S. Geological Survey #MF -493, 2 sheets. 13. Nilsen, Tor (with parts of several quadrangles by Bartow, J. A., Frizzell Jr., V. A., and Sims, J. D.) 1973b, "Preliminary Photo - interpretation Maps of Landslide and Other Su}rficial Deposits of 56 7 -1/2 minute Quadrangles in the Southeastern San Francisco Bay Region, Alameda, Corbtra.Costa, and Sancta Clara Counties, Calif.," U. S. Geological Survey Open -File Report #75 -277, (Briones Valley Quadrangle) 1 sheet. 14. Nilsen, T. H. & Turner, B. L., 1975 "Influence of Rainfall and Ancient Landslide Deposits on Recent Landslides (1950 -71) in Urban Areas of Contra Costa County, Calif., V. S. Geological Survey- Bulletin #1386, 18 p. (with plates in pocket). 15. Radbrwch, D. H., and Weiler, L. M., 1963 "Preliminary Report of Landslides in a Part of the Orinda Formation, Contra Costa County, California "; U. S. Geological Survey -Open File Regent #63 -112, 35 p. 16. Schell & M4rtin, Inc., 1985, Job No. 418 -85, Sewer Improvement Plans prepared for Cortelyow & Cole, Lafayette. cc: City of Orinda 26 Orinda Way Orinda, CA 94563 Attention: Thomas C. Sinclair City Manager Gary Underdahl Darwin Myers 0 MAPS of LANDSLIDE & COLLUVIAL DEPOSITS in proposed CCCSD ASSESSMENT DISTRICT across private ALTA VISTA public EL TOYONAL roadways, ORINDA, Contra Costa County California rn CD co N O O FIGURE 1. POTENTIAL EL TOYONAL CAD SEWERS N: \ENVRSEC \Position Papers \Leavitt\2012\5- 17 -12 \PP Consider CAD Pol Excptns for Potential El Tononal CAD Final 5- 17- 12.doc Central Contra Costa Sanitary District [May 2012]; schematic map of proposed assessment riictrirt Orinds Califomia Scale 1 " =325' (Scale 1:4.320 (1 "360')1. 1 sheet. A-OJia" u — uaaaaaa is, et. al. nrio A * OPPOSES SEWER EXTENSION NO OPINION YET ON SEWER ? EXTENSION Page 5 cif 5 Cn co CD �— y 1 �t sj '�►s �` ' �. - .� '' �"� may. �;�::�.��'..• � ",fl -� �•y ^ ♦ �� , •: � .� /'. �• ..•�•y.+•�- f_ --ter .r••� ` ♦ } t ��, - .�,,,� -�' s» " R:. M• �••_— IZ '44' U. S. Geological Survey, 1959 (Photorevised 1968); "Briones Quadrangle ", 7%z Minute Series, Map (Topographic), Scale 1:24,000 (1"= 2,000'), 1 sheet [detail scaled V=360'to match CCCSD Map, May 2012] c� .A 0 0 4 M1 { 1 • , r - • e ' �� - *. + ,rs w t 1 6P f 4%e E b E 1• % t Y� Nilsen, Tor H., 1975; "Preliminary Photointerpretation Map of Landslide and Other Surficial Deposits of the Briones Valley 7'/2 Minute Quadrangle, Contra Costa County, California ", Open -File Map 75- 277 -8, U. S. Geological Survey, Department of the Interior, Scale 1:24,000 N "= 2.000'1. 1 sheet (detail scaled 1 " =360' to matrh c Y CT) Man Mnv xO V71 r �11 1P +Flp ti >R r yk r i it AR.O A %a 5968 14AGNET'17 N..ATIi )ECIrNATION AT CENTER Of ShE'E' C yt. $dN t RANG' SC[OI� /�ttfAf��+J, t rvY� �$Q9 1-5W SCALC 1:244 V � 0 : r' ow 13M mm 40w -00 FtEr � _ _ t 16lsOMe'fA CONTOUR INTERVAL 10 FEET DATUM IS MEAN SEA LEVEL -HIS MAP LOMPUCS WITH .? NAL MAP ACCiRACY 3TANDARUS FOR SALE BY U S GEOLOGICAL SURVEY DENVER COLORADO 80218 OR WASHINGTON. D -C 2 A FOLDER LESCRIBING TOKnGRAFRH!C MAF"i AND SYM0OLS IS AVAILABLE ON REQUEST rOINTERPRETATION MAP OF LANDSLIDE AND VALLEY 7 V2.' QUADRANGLE, CONTRA COSTA 1-4 1 by Sheet 5of10 Tor H. Nilson OTHE AND 'F u tit 4 JF 717 r4%, Ar Ik 41� :tN a "N lkv- elk jl�l IMN VID 40 , A*� —,PAP , NS ma W w CD 0 �-n 0 Rogers/Pacific - -1994; "Photointepretive Landslide Features Map ", orthocontour topography prepared for the City of Orinda, Scale 1" = 300', Sheet N9 [detail scaled 1" =360' to match CCCSD Map, May 2012] I IWW I-NI 4r Nk fA v; y �ki " AL Ap ;ta4y; f_t A 9eR' V. '+ ;� of ��_�.�� � '�;:�.�°;_,� ,• ` .1 -174 ¢OV Al C cr d� ;^ N.C. OFF OwN f f 4 F XX XX X extend into bedrock and may be co.ncident wr+h structural discontinuities suct- as: faults, oints, bead rg panes, etc. S :de mass `s port'a� y disrupted, however, large blocks of bedrock remain inioc'; rate of movement generally s ow. Original ggeomorphic features may be subdues or poorly def'ned .n o der ,ondslides. EARTH FLOW - ANDSLIDE: one of depletion; generally not shown on map i translated slide mass Characterized by shallow to moderately deep movement a ong discrete curviplanar slip surfaces; failure surface confined to sail and deeply weathered bedrock; rate of movement very slow to rapid; internal structure of translated slide mass is extensively disrupted. DEBRIS FLOW LANDSLIDE: Osource area 1 runout area Characterized by shallow, downslope movement of soil and bedrock debris; failure surface confined to soil profile or along soil— bedrock interface; internal structure of slide mass is completely disrupted. is very rapid; debris often stored within ephemeral channe's. ANCIENT OR INDISTINCT LANDSLIDE DEPOSIT: Source area absent, deeply eroded, disturbed or indistinguishable on aerial photographs; includes large deposits of landslide debris in canyons and swaies. NOTES Landslide features and surficia soil deposit information is based upon reconnaissance —level Interpretation of sfereopalr aerial photography token in 1928, 1946, 1950, 1957, 1969, 1978, 1984, and 1990. Boundaries of the landslide features were delineofbd on orfhophoio iopographic sheets taken ;n 1991, and prepared at an original scale of 1 Inch aqua's 300 feet (1.3600) with a contour Interval of 5 feet.Dota were not verified in the held and are not suitable in of themselves for evaluation of landslide or soil — related hazards for individual sites. Site specific evaluations of landslide features or associated soil deposits should take precedence over reconna'ssance —level studies, but such evaluations should only be made by licensed geotechnical engineers (G.E.) and engireering geologtsts (C.E.G.) with substantive experience in the Or'.ndo area. Sheet 10 of 10 1 , ....................... 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A- N A N T -O' N •1 ra't !F y,� =1� t•�"r�. 4'e 1 °•.Eureka "Pk3:. ,t® . '� 1 ;' •t' ( V NOD-PERALTA) \ '�: '' 0 a .• 1) 'r d!q1 �� @ l r al 1 Qf" -.. _._«..` 1 �•,` pl� , UttltE St71 ► 4 1 ✓' p .�,�,,.- - (�.. t r : Q \0 1` �.�pt .�;at �'r 1 . (-' l' °� �''1 f!� >tr, \ \ \��•� l �t x'11 `�• v�' �ns� uRin ;; A I �-p A K L.A_ NI.D. i, .`- : f lit; s✓ .t1. f\ �.j BM 09\; (- -?.,' ' O�•.i ••i'~� �>11t.��Ubl :a:'Q,ti;J- - . '�' f':,� •:i�'+ y�r� /J / +�V 6, j, \��, l�. •VV ' -� f/ ®,�yc T t , ,0�, °• , °.y • l�J �� ;:'zF �. �e 7 %it,�t�;. f Y <.��' Ilp I ��J 37 °52'30" ` 1 •s6) 11 500000 FEET ,568 �vs Arr. ro CALIF. 24 i2'30" t74 1224:151 AN Mapped, edited, and published by the--Geological Survey 1 Control by USGS and USUG5 1 00 J rE 000 �e• Topography from aerial photographs by photogrammetric methods * Mp >3 .,'� Aerial photographs taken 1958. Field check 1959 R FIGURE 3 0 PHOTOGRAPHS taken July 18, 2012 of EL TOYONAL at Third - Points between Camino del Cielo & Alta Vista El Toyonal is the only thoroughfare to and from the neighborhoods west of Orinda Village to the town. Construction of the necessary road improvements associated with the proposed sewer project will block access from Orinda to the neighborhoods. Along the proposed sewer route, El Toyonal is a narrow substandard public roadway improved to its present condition in the 1920s. El Toyonal was created by steep sidehill cutting and filling resulting in the outside of the lower edge being an almost a vertical drop to La Encinal or El Rincon. A sewer trench anywhere in the roadway will destabilize the hillside by bifurcating the roadway's support and groundwater will either infiltrate the trench or be blocked by the trench facility. To achieve stability with the necessary trench, a sewer project would have to include upgrading the roadway to current standards which would require removal of and replacement of sections of the roadway and the construction of major retaining walls. The necessary roadway improvements have not been engineered and the expense of the project has not been properly estimated. l f C L :lam _, ����•ti; - �`•r . _ T � ry "' mac' _ y'� � c . � 1 /' r a� :• � ` "�_. •'i � ? `fly„• \������66`.r>'>' j T > r