HomeMy WebLinkAboutMINUTES - 03181986 - 1.15 THE BOARD OF SUPERVISORS OF CONTRA COSTA COUNTY, CALIFORNIA
Adopted this Order on March 18, 1986 by the following vote:
AYES: Supervisors Fanden, Schroder, McPeak, Torlakson and Powers
NOES: None
ABSENT: None
ABSTAIN: None
SUBJECT: Initiating proceeding to )
form a geologic hazard ) RESOLUTION NO. 86/ 139
abatement district ) (Pub. Res. C. Section .26558)
Blackhawk area )
The Board of Supervisors of Contra Costa County RESOLVES that:
Pursuant to the provisions of Division 17 (Section 26500 et seq. ) of the
Public Resources Code a petition has been filed with the Clerk of this Board for
the formation of a geologic hazard abatement district ("GHAD") in the Blackhawk
area. This petition complies with the provisions of Pub. Res. Code Section
26552 and has attached to it a legal description of the boundaries of the pro-
posed GHAD (Exhibit A) , a map showing the boundaries of the proposed GHAD
(Exhibit B) and a plan of control (Exhibit C) .
The Director of Community Development and Clerk of the Board. have reviewed
the petition and determined that it is substantially in the form described in
Pub. Res. C. Sections 26550.5 and 26552 and verified that the signatures affixed
to the petition represent owners of not less than 10 percent of the real
property to be included within the proposed GHAD. Further, the Clerk has
accepted the petition because the signatures thereon were secured within 120
days of the date on which the first signature on the petition was affixed and
said petition was submitted to the Clerk within 30 days after the last signature
was affixed.
This Board hereby Resolves, Finds, Certifies and Orders as follows:
1. This resolution is made pursuant to the provisions of Division 17
(Pub. Res. C. Section 26550 et seq. ) .
2. It has been presented with and reviewed the plan of control and has
determined that the health, safety, and welfare requires formation of the GHAD.
3. A public hearing on the filed petition, above determination and
proposed GHAD shall be held on April 22, 1986, 2:30 p.m. , in the chambers of
this Board, 651 Pine Street, Martinez.
4. Notice of said hearing shall be mailed pursuant to the provisions of
Pub. Res. Code Sections 26557, 26561 and 26562.
1 hereby certify that Ihls Is a trwa arW cone,!crzy of
cc• Clerk - Au 1 e n e Joseph an action taken and ontar3d on 319 trfnat-j of the
hoard of Supervisora an the date shorn.
County Administrator
Harvey Bragdon, Community. Development ATTESTED:
Si 1 vano Marchesi , County Counsel PHIL BATCHELOR,Clerk of the Board
Dan Curtin, Blackhawk Corporation of Supervisors and CountyAdministratot
Milt Kubicek, Public Works Flood Control
By Deputy
5:geohazrd.r
' PETITION FOR FORMATION OF
GEOLOGIC HAZARD ABATEMENT DISTRICT
PURSUANT TO DIVISION 17 (commencing with Section 26500)
OF THE PUBLIC RESOURCES CODE
OF THE STATE OF CALIFORNIA �ED
NOV 1985
TO: The Clerk of the Board of Supervisors
of Contra Costa County ►MQeATCKLOR
CLERK HOARD Of SU►ERY501S
RA COST CO.
The undersigned owners of land within the boundaries of
the district proposed in this petition hereby request that
the Board of Supervisors initiate proceedings to form a
Geologic Hazard Abatement District pursuant to the provi-
sions of, Division 17 of the Public Resources Code , Sections
26500 et seq.
(a) This petition is made pursuant to Division 17
of the Public Resources Code with particular reference to
Sections 26550. 5, 26552 and 26553 of said Code.
(b) Opposite the signature of each of the peti-
tioners is an indication of the lot, tract and map number or
other legal description sufficient to identify the signature
of the petitioner as that of an owner of land within the
territory proposed to be included within the proposed
district.
(c) Opposite the signature of each petitioner is
an indication of the date on which said petitioner ' s signa-
ture was affixed to this petition.
(d) The following documents are attached to this
petition and are incorporated herein by this reference as if
set forth in full in the petition:
156-8411 -1-
r
1. As Exhibit A, a legal description of the
boundaries of the territory proposed to be included within
the proposed district;
2. As Exhibit B, a map of the boundaries of
the territory to be included within the proposed district;
and
3. As Exhibit C, a plan of control prepared
by an engineering geologist certificated pursuant to Section
7822 of the Business and Professions Code which describes
the actual or threatened landslides, land subsidance, soil
erosion and other natural or unnatural movements of land or
earth and the plan for their prevention, mitigation, abate-
ment and control thereof.
Dated: /,d BLACKHAWK CORPORATION,
a Delaware co r n
Map Numbers of Property B (�
Owned: 5746 Daniel Van Voorhis,
5747 President
5748
5749
156-8411 -2- -
EXHIBIT A
BEING A PORTION OF SECTIONS 14, 22, 23. 24, 25 AND 36, TONN,r+HIP 1
SOUTH, RANGE I NEST, MOUNT DIABLO BASE AND MERIDIAN AND A PORTION OF
!:CTIONS 19, 20., 2l?, 30.- 31 AND 32, TOWNSHIP 1 SOUTH, RANGE 1 EAST,
Mi.JNT DIABLO BASE AND MERIDIAN, DESCRIBED AS FOLLOWS:
BEGINNING AT A POINT ON THE EASTERN BOUNDARY OF THE DIARLO COM-
KJNITY. SERVICES DISTRICT, SAID POI`4T BEING AN THE CENTER. OF THE PARCEL
OF LAND DESCRIBED IN THE DEED TO THE ATHENIAN SHCOOL, RECORDED OCTO ER
S', 1964, IN BOOK 4719, OF OFFICIAL RECORDS, FACE 211; THENCE LEAVING
InE EASTERN POUNDAR}' OF SAID SERVICES DISTRICT AND ALONG THE SOUTHERN
AV3 EASTERN L 114ES OF' SAID ATHENIAN SCHOOL PARCEL (4719 O. R. 211 ) AS
FC.LLONS: SOUTH W52 '59" EAST, 288. 40 FEET; SOUTH 54*13'44" EHST, 28E�
FEET; SOUTH 3v C18"44" EAST, 2"75 FEET; NORTH 79*11 '42" EAST, 885. 9S FEET..-
NORTH
EET.NORTH 2,90-12. 'J'2" EAST, 495. 62 FEET: AND NORTH I8 28 IB EAST, 1,422. 89
F.'-:ET TO THE MOST SOUTHERN CORNER OF THE PARCEL OF LAND DESCRIBED IN TrE
LSP ED TO THE ATHENIAN SCHOOL, RECORDED NOVEMBER 22, 1968, IN BOOK 5756,
OF OFFICIAL RECORD::, PAGE 433: THENCE NORTH 4500549" EAST, ALONG THE
EASTERN LINE ,OF SAID ATHENIAN SHCOOL PAPCEI t 57_0 O. P. 433>.. 1 .003. 57
FEET TO THE MOST EASTERN CORNER OF SAID ATHENIAN SHCOOL PAFI:EL i.'56
O.R. 433,x, SAID P0I14T BEING AN ANGLE POINT ON THE SOUTHERN FOUNDAP't' OF
THE LAND KNOWN AS THE BLACf:HANK CORPORATION DEDICATION TO MOUNT DIkR-10
TATE PARR'; THENCE SOUTH S7`08'44" EAST, ALONG SAID SOUTHERN BOUNDARY,
7:0 FEET, TO AN ANGLE POINT THEREIN;, THENCE CONTINUING ALONG SAID -SOUTH-
ERN BOUNDARY, AS FOLLOWS: SOUTH 76'00S"44" EAST, .400 FEET; SOUTH 6P"08 '44„
EAST. 1 ,600- FEET; SOUTH 10051 '16" 14EST. 600 FEET: SOUTH 00*51 '1 t. " WEST,
!,00 FEET; NORTH 69*08 '44" EAST, 500 FEET; SOUTH 31p!?8'44" EAST, 7.70 FEET;
N":FTH 71*51 ''16" EAST. 950 FEET. THENCE CONTINUING ALONG SAID SCK►TrrEPN
FOUNDAiRY AS FOLLONS: S,-•,,TH 08 '44" EAST: 300 FEt i ; :SOUTH, 1 . 503. 48
FEET; SOUTH S-90 EAST, 531 . C1- FEET.; SOUTH 1 v NEST: 94. 3E FEET; SOUTH oL:'o
EAST, 581 . 79 FEET; EAST, 1 .277. 801 FEET; NORTH, 550 FEET TO THE SOUTHERN ,
LINE OF THE PARCEL OF LAND DESCRIBED IN THE DEED TO SLACKHAMK CORPORA-
TI 11N, RECORDED .DUNE 8, 157.+, IN BOOK 6911-55, OFFICIAL. RECORDS, PAGE 841,
C►E�:_:R1EEC1 AS THE "NORTH 200 ACRES OF THE EAST-HALF OF SAID SECTION Ey
1NENCE CONTINUING ALONG SAID SOUTHERN EOUNDARY AS FOLL0146: EASTERLY,
PL ONG THE SOUTHERN LINE OF SAID NORTH 'f200 ACRES t 6 9r 5 O. R. 841 . 2, 000
FEET, THENCE SOUTH, LEAUING SAID EXTENSION 1 .000 FEET; EAST, 00 FEET;
SuUTH, $50 FEET; SOUTH 45"14EST, I,2501 FEET; SOUTH, 2001 FEET; EAST, 1 , 50. 0
FL ET; NORTH 450 EAST, 1 .- 500 FEET; SOUTH 45o EAST, 1 ,051 . 08, FEET TO A
POINT ON THE EASTERN LINE OF THE PACIFIC GAS AND ELECTRIC COMIPANY''S
EPSEr;ENT AS SAID EA :EMENT IS DESCRIBED IN THE DEED RECORDED OCTOBER
1959, IN 600k* 34,901, OF OFFICIAL RECORDS, PAGE 144: SOUTH 14039'09" NEST,
ALONG THE EASTERN LII4E OF SAID EASEMEhl, 1, 14.3. 44 FEET; SOUTH 42047'57"
Ew-.T, LEAQING THE EASTERN LINE OF :.AID Ei;'_:EMENT. 961 . 60 FEET; NORTH
4#-,'`12 '03" EAST, 5501 FEET; NORTH 42'°47'57" NEST, 9012. 23 FEET; NORTH
6".50 '28" EAST, 1 , 021 FEET. EAST, 0`60 FEET; THENCE CONTINUING 0_0,14G SAID
SOUTHERN EOLINDARY AS FOLLOWS; NORTH, 101 CI FEET; EAST, 800 FEET; SOUTH
67°40 '17" EAST, 90t:. 09 FEET: SOUTH, 400 FEET; SOUTH 43°47 '3'" EAST,
FEET; SOUTH, 1 .450 FEET: SOUTH 43020 '0 " NEST, 1,21 ;. 74 FEET:
Sf._JTH, 551_1 FEET; SOUTH C?°`� '15" EAST, 556. 36 FEET; NORT*H 36*00 ' 11 " Ek.'---"TP
1 ,.216. 34 FEET; !JEST, 2501 FEET; NORTH, 34' FEET; NORTH 44*3.1 '39" EAST,
341 . 54 FEET; EAST, 4*' FEET; THENCE NJRTH 42'49'50" E4 T, 9S9. 915 FEET;
THENCE SOUTH 66`22 '00" EAST: 813. 20 FEET; THENCE SOUTH 27°229 ':x" !JEST,
1 . 1-14. 79 FEET; SOUTH 622 *30 '28" EAST, l-'00 FEET; SOUTH 27*29'33" WEST,
4::0. 01 FEET; SOUTH 6_2`30 '23" REST... 200 FEET; SOUTH 27`29'32" WEST, 739. 27
FL"-.'T; SOUTH 55' 28 ' 16" EAST, 57'3. 69 FEET: NORTH 45+°33'011 " EAST, 1 , �zp5
FEET, NORTH 41* 04 '54" WEST, 517. 401 FEET: NORTH 28018'3 " EAST, 485 FEET;
SOUTH 89'17'30" EAST, 521 . 40 FEET; THENCE SOUTH 00"42'30" NEST, LEAVING;
-2-
;�:�ID SOUTHERN BOUNDARY ter THE LAND TO BE DEDICATED TO [HE MOUNT DI:-E'LO
9 i::1 TE PARK, 5,027. 25 FEET; THENCE SOUTH 00'36'17- NEST, 1,282.22 FEET TO
R POINT ON THE NORTHERLY RIGHT OF MAY LINE OF CAMINO TASSAJARA; THENCE
a'_STERLY ALONG A NON—TANGENT CURVE CONCAVE TO THE SOUTH, THE CENTER OF
NHI CH BEARS SOUTH 06°32'16" WEST, HAUI NG A RADIUS OF 2,050.21 FEET,
1 HROUGH A CENTRAL ANGLE OF 05°13'17", HAUI NG AN ARC LENGTH OF 186. f4
Ft CT; THENCE NORTH 884'41 '01 " (JEST, 920. 24 FEET; THENCE SOUTH 69022 '23"
WI ST, 149. 71 FEET.; TkENCE NESTERL Y ALONG A NON–TANGENT CURVE CONCAVE
TV THE SOUTH, THE CENTER OF NHICH BEHRS SOUTH 02043'00" EAST, HAVING
A RADIUS OF 2, 050. 21 FEET, THROUGH A CENTRAL ANGLE OF 161"50 '31 ", HRU:�►G
AM ARC LENGTH OF 357. 96 FEET; THENCE SOUTH ;6°26'29" WEST; fHEN:'E
14 S TERL Y ALONG A TA JGENT CURVE CONCAVE TO THE NORTH. HAUNG A R0401LIS
OF 1,950.21 FEET, THROUGH A CENTRAL At4GLE OF 17°29'?3", HAVING AN AFC
LENGTH OF 595. 40 FEET; THENCE LEA('IgG THE SAID NORTHERLY RIGHT OF WAY
I INE OF CANINE► T4,5SAJAR4, NORTH 0E.°48'15" FAST, 1,5118. 59 FEET; THENCE
NORTH 89°28 ' 18" NEST, 1 ,285. 61 FEET; THENCE 14ORTH 010 35'38 e EAST,
1 -325. 98 FEET; THENCE NORTH 86-'53'38" !JEST, 1 ,286. 61 FEET; THENCE
N :RTH fi;°1 , '1C+" 1JE'_='T, 48. 41 FEET; THENCE NORTH 00°:5'02- EAST, 1, 111 .0i
FELT, THENCE NORTH 64*03'36" NEST, 488. 05 FEET; THENCE NORTH fig°33'44"
!JEST, 2,205. 16 FEET; THENCE SOUTH 14039 '09" WEST, 786. 59 FEET; THENCE
tiOP.TH 8S°3 i '30 WEST, 2,47t S. 13 FEET; THENCE SOUTH 00'5 '31 " WEST,
1 .916. 16 FEET; THENCE SOUTH 88042'22" WEST, 1, 125. 59 FEET; THENCE
Si?:JTH 000 53'31 " WEST, 1413. 73 FEET TO A POINT ON THE NORTHERLY RIGHT
OF WAY LINE OF "CAMINO TASSAJARA; THENCE NORTH 61014 '17" k'EST, 1,531 . ;'1
FLIT;' THENCE LEAVING NORTHERLY RIGHT OF WAY LINE OF CAMINO TASSAJARA,
NORTH 00036'48 EAST, 1, 145.9: FEET; THENCE NORTH 00"20-30" EAST,
•681 .95 FEET; THENCE NORTH 22025'27" EAST, 631.21 FEET; THENCE NORTH–
E:;STERL Y ALONG A TANGENT CURUE CONCN►JE TO THE WEST, HAUI NG A RNDI US 0=
1100. 80 FEET, THROUGH A CENTRAL ANGLE OF 86'16'00", AN ARC LENGTH OF
3 ' 12 FEET; THENCE NORTH 16'09 '27- EAST, 126. 88 FEET; THENCE NORTH–
, _Q
ALONG A TPNGEn , CURVE CONCA;!E TO THE EgS:1, PAVING A PPIOI LIS OF
.E1E10. 00 FEET. THROUGH A CENTRAL ANGLE OF 4N ARC' LENGTH OF
410. 15 FEET; THE14C:E NORTH 27"54 '27" EPST. 4S-5. 72 FEET; THENCE NORTHERLY,
ALI ONG A TANGENT CURVE CONCAVE TO THE WEST, HAVING A RAnI US OF 5Cicl. oo
FLET. THROUGH A CENTRAL ANGLE OF 34°131 ,15 AN ARC LENGTH OF 301 . 25
FLET; THENCE NORTH 06'36 '48" NEST. 104. 22 FEET; THENCE NORTHERLY ALONG
A TANGENT CURVE CONCPQE TO THE EAST, HAVING A RALIIU; OF 1, 000. 00 Fr-ET,
)HROUGH A CENTRAL ANI..-LE OF E1*25 '00", AN ARC LENGTH OF J73. 79 FEET;
Tt;INCE NORTH 14445: 112" EAST, 34. 95 FEET; THENCE SOUTH S9*24 ' " IJES-T,
41 . 93 FEET; THENCE SOUTH 69'24 '30" WEST, 2110. 48 FEET; THENCE SOUTH
F.C"`E4 '19" WEST. 1290. 35 FEET; THENCE NORTH 00'26'21 " EAST, !'63;'. 94
FEET; THENCE NORTH 00*15'56." EAST; 763. FEET; THENCE NORTH 05'943'58"
EAST, 60. 74 FEET; THENCE NORTH 1` 21 '17" !JEST, 1153. CIO FEET; THENCE
NORTH 7142-Q "-;3" !JEST, 60. 77 FEET.; NORTH 6901P12" NEST, 400. 02 FEET;
P;LNCE NORTH 70011 '2S" WEST, 69. 53 FEET: THENCE NORTH 70011 '57" !JEST,
y�.... 66 FEET; THENCE NORTH 70'011 '4" !:'EST, 726. 85 FEET; THENCE NORTH
'.4°58 '43" WEST, 958. 37 FEET: THENCE NORTH 59'008 '27" WEST, 555. 70 FEET;
THENCE NORTH 5&-14 '10- " WEST, 682. 11 FEET; THENCE NORTH 89054 '5911 WEST,
70 FEET; THENCE NORTH 007'012 '5,3" EAST: 166. 82 FEET TO THE POINT OF
Ff INNING.
CONTAINING 2, 716 AC RES, MORE OR LESS.
..d.
EXHIBIT B
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EXHIBIT C
PLAN OF CONTROL
1. , Description of Geologic Hazard . The proposed
district (described by the map and legal description
attached' hereto as Exhibits A and B) largely encompasses the
Orinda Formation which is composed of soft claystone and
sandstone, and is prone to new landslides and reactivation
of pre-existing landslide areas. Geotechnical studies for
the various residential subdivisions within the proposed
district located a large number of existing and possible
landslide areas. These studies employed field recon-
naissance, air photo interpretation and subsurface test
borings. The majority of possible landslide areas are
within the open areas of the proposed district which are to
remain undeveloped in perpetuity.
The open areas of the proposed district contain a series
of aligned natural ridges with scattered oak trees on the
flanks. The side slopes are indented with natural ravines
or swales which are filled with thickened colluvium (rock
fragments and soil transported by gravity) . The colluvium is
an accumulation from past mass movements and active
landslides are concentrated within these natural ravines.
Typically, rapid debris flows, orvalanches, can only
4boKf /e/°
occur on slopes steeper than twenty-five (25) degrees or
about two (2) horizontal to one (1) vertical. The typical
434-8502 -1-
slopes within the proposed district are less steep than
those subject to avalanches and are therefore not usually
subject to such rapid debris flows.
Past land movements identified within the proposed
district , are typically either deeper slides in the soil and
weathered bedrock or shallow mud flows (mudslides) in the
upper adobe (clay) soils near the surface. About one-half
of all recent slides reported in the past four years were
within open areas. The other recent slides were in areas of
residential and/or golf course excavations or were induced
by homeowner backyard enlargements at the base of the
hillside's.
2. Plan for Prevention, Mitigation, Abatement or
Control.' The proposed district will retain geologic and
engineering consultants to identify known and potential
slides within the proposed district. Identification -
techniques may include field mapping, infra-red and other
aerial photographs, slope stability analysis, logging
borings and trenches , laboratory soils testing and
continuous monitoring of surface, subsurface and
ground-water conditions. Computer programs may be utilized
to calculate volume and driving force of slides.
Earth movements within the proposed district may be
monitored by the following techniques, among others:
434-8502 -2-
{ document offering geotechnical guidelines which will be
subject to revisions and modifications, as new data or
investigations warrant.
Date Richard J. rioctor , Consultant
California Engineering
Geologist #134
327 Fairview Avenue
Arcadia, California 91006
SAG:rd-Q:6
EXC
434-8502 -4-