attachments c city of larkspur storm drain master …
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City of Larkspur - Request for Proposals – Storm Drain Master Plan October 1, 2018
Attachment C
ATTACHMENTS C
CITY OF LARKSPUR STORM DRAIN MASTER PLAN 1988,
LARKSPUR CREEK CHANNEL STUDY 1989 AND
GREENBRAE STORM DRAINAGE STUDY 1987
STORM
REENBR~E
DRaINaGE STUDY
PROJECT NO. ECR71~
Pr-epnr-ecl bu
COUNTY OF MRR!N
DEPRRTMEN~T OF PUBLIC WORKS
Julg 1987
TRBLE OF CONTENTS
SITE I]ESCEIPTION ................. 1
UICINITY I'IRP ................... 2
SCOPE OF ORR INROE STUDY ............. 3
ORT~ COLLECTI ON ................. ~ 1
HYDROLOBY/HYDRRUL I CS .............. S
RECOMMENDAT IONS ................. B
Rt-eo R ................... 8
Arco B . . ................. 9
Rroa C ................... 10
The purpose, oF this studw wes to collect data on the existing
storm drain culverts in the public rights oF wow end
easements within the studw oreo, perform h~drologu end
hUdroulic calculations, end recommend improvements, os
needed, For these Facilities. These recommendations opplw to
the entire drainage swstem (both Larkspur and Countw oF Matin
portions) located between Sir Francis Drake Boulevard end the
northerlu top oF the watershed. The Follo~ing is o detailed
explanation oF the methods and criteria used For each oF
these tasks.
D~T~ COLLECTION
1! o~ the cuZverts or drainage ~acllittes were numbered and
shown on o topographic map entitled "GR££NBR~£ DRaINaGE
STUDY, CULUERT LOC~TION M~P" on Eile with the Countw o~
Narin, Department o~ Public Uorks. The'culverts or drainage
ocl~lties within oreo NAN and O portion o~ the culverts or
drainage ~acllities within oreo NBN were ~leld located.
In~ormotion o~ the remainder o~ the culverts or drainage
acllities within oreo NBN end Oil O~ the culverts or
drainage ~ociiities within area NCN woe obtained ~rom
previous ln~ormation on ~lie in the ~arin Countu Deportment
o~ Public WorkS. The exact dote and the dote collection
method used to obtain the previous in~ormotion is unknown.
Where ~leid located, the size o~ each culvert was measured.
The slope o~ each culvert was assumed to match the slope o~
the ground above it. The length o~ the culvert was scaled
rom o-topographic map.
HYDROLOBY/HYDRRULI~S
fl hwdrologu, mop end hudrologu/hudrauXic co~cu~otions for this
etudw ore on fiXe in the Herin Countw Deportment of Public
Works. The studw oreo mos divided into three main droinooe
areas end each of tl~ese areas mere further subdivided into
smo~ler ormos to calculate the flom In each culvert, The
Rotiono! flethod mos used to calculate storm meter runoff, end
the storm meter quantities from these calculation hove been
entered into the data sheets for each culvert. These dote
sheets are on file. in the rlorin Countw Deportment of Public
Works.
A ten-wear design storm mos used to calculate storm water
quantities for areas less than ~0 acres, and a tmentu-f~ve
wear design storm mas used to calculate quantities for
culvert drainage areas containing ~0 acres or more.
ecommendations For the replacement oF storm drain
within each oF the three main drainage areas ore shown on the
Following sheets. ?he dashed lines indicate where the
exlstino storm drain pipes ore adequate to handle the design
Flou. The solid lines .show where the existing storm
pipe diameters £number In parenthesis) are inadequate end the
diameter oF the pipe required to corfu the design Flow.
existino and replacement pipes ore rein~orced concrete pipes,
unless otheruise noted on plan.
The maJoritw oF the pipes to. be replaced ore located within
the rood right oF woU and normal construction techniques con
be used. However, within oreo 'B', the pipes to be replaced
between Los Certes end Sir Francis Drake Boulevard ore
located within drainage easements where residences are
located-within close proximitg. Specie! construction
techniques could be required to prevent damage to the
ex~st~ng dwellings. ~ more econom~co! approach might be to
divert some oF this drainage into o ne~ drainage s~stem that
would extend the Lo Cuesta drainage pipe et Los Certes
southerl~ to Sir Francis Drake Boulevard end .then wes~erlg