HomeMy WebLinkAboutPE 2.10.13; BRISTOL COVE; SILTATION STUDY; 1987-07-14P.E. 2.10.13
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BRISTOL COVE SILTATION STUDY
FOR BRISTOL COVE PROPERtY OWNERS ASSOCIATION
July 14, 1987
Prepared by Alton L. Ruden, RCE 10163
2733 Mesa Drive
Oceanside, CA 92054
Phone: 757-3112
1
I. INTRODUCTION
This short report on the problem of siltation and
various ways of dealing with it, is pre~ared in response to
a letter·da~ed March.20, J987, from Bristol Cove Property
Owners' Association. My primary assignment was to evaluate
the long term prospects and.how to deal with.them in the
future. A secondary assignment w~s conveyed to me in
conversations with Mr. DeThom~s and Pat Tuomi, and 1s to
.measure and discuss the silt already 1n the c~annel.
To understand and acquaint myself with the problem and
its history, I have reviewed previous reports on the subject
_by Bement~Dainwood-Sturgeon, civil Eniineers~ 1978; E. F.
C~ok, Civil Engineer; Wendell Gayman, Geologist; and an
undated, unsigned report fto~ your files (probab(y a City
staff report). f have also reviewed .the original .Bristol
Cove (Shelter.Cove) Plans 134-9, 1963, 8 sheets, the Bristol
Cove Reconstruction plans by.Moffatt & Nichol-, Ci~il
Engineers (152~3, .1966, 12 sheets), and.the plans. for
Pannonia subdivision on· the hilltop east of Bristol Cove. I
have al~o reviewed .your.files ind those of Scott Williams,
~ttorney for your as~ociation. I .have .also.eonsulted:with
Mr. Nat~.DeThomas, Mr.· Graham.Finch, Mr. iefferdink, Mr. Vic
.Arndt and Mr. Pat .Tuomi, and various City of Carlsbad
employees. I have als~ ta;ked.extensively with .various
p•ople in the dredging industry.
2.
II. THE PROBLEM
The drainage basin,. which drains by gravity to the
receiving water inlet of Agua Hediohda Lagoon known as·
Bristol Cove, .is approximately 450 acres, and ~ill gene~ate_
a runoff .peak flow of ~bout 540 cubic ft./second. The basin
extends roughly from the Cove northward to a point north of
Basswood Avenue, and from Highland Avenue eastward to
S k y 1 i n e. D r i ye • The area south of Tamarack. Avenue is mostly
developed with housing and a sto~m drainage.system, with the
notable exception of Pannonia Subdivision ~hie~ ¥ill be
discussed later hereiri. The .a~ea north of Tamarack is about
50% develope~ and.there are many large parcels with one
house and 2 to 10 acres of fi~ld or orchard. There is a
storm drainage trunk line .which follows th~ intermittent
James Drive, and is partly underground pipe and.partly paved ·
Ch an ne l. rA-c.n>Ati..,.. /flo.s11. 'r'
' 11N lJN1t11fR.ov~p
This basin is comprised of highly erodible so CA~"f"H 1:-IJ ~JWNIU..
~CIFIClfl.1. I" Fit.4/ft j
described in .. more d·etail in .the previous .reports r CH'iESrNur 7o
-rilm111tAt. I( • . .. above •. During mode.rate. and heavy rainstorms the s~ __________ __)
has produced large volumes .of silt which, carried by storm
runoff_and picking up more and more load along the way, has
.been a severe problem to the boat.docking .and .channel a~eas
of Bristol Cove, .especially at the north end whete most.of
th• storm runoff ~ith its silt load is discharged into ihe
lagoon.
3
III. PREVIOUS EFFORTS TO ALLEVIATE THE PROBLEM
The siltation problem, which actually had existed for
centuries, began almost as soon ~s the dredging of .the cove
and construction of the streets and utilities was completed
in 1964, .as Shelter Cove Subdivision, Map 5163. By .1966 the
north end of the Cove was silted up to the .extent it was-
virtually useless to.boats.except at high tide •. At.that
time Janss Corp., who took over from the original developer
and who still owned most of the lots, had Moffatt & Nichol,
Civil Engineers who specialize in marine structures, prepare
plans to "reconstruct'' the· re-named Bristol Cove .•. This. plan
was implemented shortly thereafter and provided for rock
slope p'rotection, re-dredging to -9 •. 0 M.S.L. datum, and 1n
an attempt to reduce siltation· 1n the Cove·, a diversion
structure was built and a 60". diversion pipe was 1·aid. along
the east bank at the top of the revetted slope. This 60"
pipe was laid.at a slope o~ .0046. The diversion structure
was designed to send.all flow into the diversion pipe.unless
the.flow exceeded .. the level of.the removable "stop logs".and
would flow.over into the.north end of the cove. The intent
of this structure·was to divert all of the siorm drain.flow
in t o the new 6 0 '.' p i p e ex c e p t f o r a . t r i c k 1 e . be tween .. the .· " s top
logs", unless .it were blocked or clogged. Un.fortunately,
.the diversi~n pipe plugged.up almost immediately and,
according t·o members of. your Association,. h_as. remained t,hat
way. Mr. Lefferdink recalls that .between.1967 and.1980 .. the
4
Janss Corp. cleaned out the pipe .several times, but it
always clogged again ai the first heavy storm. The
diversion pipe, .although laid at a grade which, absent tidal
•ction, would be self-cleaning with heavy flows, has •n
"effective grade" of zero at high tide (6.6 MLLW or more),
and at low tide. (+0.6 MLLW or less) would flow as designed
(MLLW is 2.61 feet b~low Mean Sea Level). The Association
then modified .the .di~ersion structure to permit water to
flow into the north end of the Cove. The cause of the
clogging is unknown but. probably.was due to the effective
flat grade .at high tide,·• and heavy sand and .silt. load in the
flows produced by the very heavy storms 1n 1967·,
particularly in January of that year, when all of this
region endured gre•t damage by flood waters, .mud slid~s,
erosion, blocked streets and drains~ We know that this
watershed, even now, produces rurtoff with relatively large
sand particles .which could cause clogging in a pipe with
that flat ~lope, even though the ~lope at low tide is
ade~uate for light silt, clejn wat•r or.~ven sewage. Since
1967 your Association has.had a continuous problem.with
frequent dredging required to keep the Cove usable.
In 1981 th~ Association, using furtds .obtained by the
lawsuit settlement .from the City.and Janss .Corp.~ dredged
the entire channel, .removing about 22,000 C.Y~ This was
done by dragline and clam bucket with the drained. spoil
being hauled away by truck. A great deal of this heavy silt
and.sand came into the Cove from the dirt· channel between
5
the end of James Drive and Adams Street (verified by reports
referred.to above). The Shelter Cove Improvement District,
which had been in process since .1978, finally alleviated
that major source of silt .by constructing a storm dr~in from
James Drive to Adams Street.
January o~ 1983 was a month of very heavy rains and
runoff so that the channel, es·pecially the north end, was
~ilted up badly again. This was in spite of the efforts
described above, but there was.considerable construction
grading.underway during this period and. the City
·r•quirements for desilting runoff from construction sites
were not as strict th~n as thei ~re in 1987. The
Association obtained a loan fr6m S~A and dredged again 1n
1983 ~sin~ the same method as in 1981 •. Approximately 2b,OOO
C.Y. were removed (accordint to Mr. Lef.ferdink) at a cost of
$45,058. Without. any documentation, which I have been
unable to locate, I would question.this quantity .for the
amount. actuaily.expended. Dredging by .this .method.usually
costs from.$7. to.$10 pe~.cubic yard remo~ed from the site.
Possibly the contractor overestimated his net cubic yards.
Both in 1981 .. and 1983 there were several vacant lots
spaced along the.channel .with_owners willing ~o permit
dredge spoil.to drain. _Now in 1987, due to building
development, there are only 3 or 4 lots available,.not
enough to dredge the channel effectively from shore. . \ . Since
1983 the Association has removed small amounts of .silt (500
6
to 1,000 C.Y.) periodically, .where drain and access lots
were available, and when money was available. The most
recent ~uch removal was in June 1987 when about 500 C.Y. was
removed.by clam bucket and drained on the only 3 lots
available in the north end of the channel.
rv·. PROJECTION OF FUTURE SILTATION
In the past 3 years the City has tightened up
regulations and is much more diligent in enforcing them in
regard to desilting construction runoff from construction
sites. With due ~ecognition of your Association efforts,
the Pannonia Subdivision.developers were required to
construct temporary siltation basins during grading and
.construction, and when Units 4 and 5 are constructed, a
permanent siltation basin will be constructed at .the .south
end of the project, just above Marina Drive. The discharge
of the de~silted water will be underground along Marina
Drive into.the. main lagoon. I have inspected this project
and confirm that the temporary .basins are effective. The
small ~~ea.of ~annonia north of Hillside Drive, during.1986-
87, discharged silt laden water into the drainage system
which flows into the cove, but this .will be corrected.before
the winter of 1987-88 by paving and landscaping.
The source of.great amounts .of -silt prior to 1981, .the
"gorge'', between James Drive and.Adams Street, has.been
effectively treated by diversion of all.but on-site .natural
runoff and.by heavy growth of ice plant.in the bottom of the
7
gorge, which catches m6st of .the silt from on-site runoff.
When this area developes, your Associatio'n and its members
should be alert to see that effective de-silting is provided
because it is the· worst threat left for producti6n.of silt
into the Cove. Another matter of concern is .the ironic fact
that the main· storm drain do~n from James Drive has cured
the heavy gorge erosion, but opened the door for more silt
from further ~pstream to Oak Avenue. The area north of
Tamarack Avenue in this watershed is only about 50%
developed. The many farmed parcels, producing vegetables,
are plowed every year, sometimes more o~ten. Runoff fro-
these fields used to pond in the low areas between Valley
Street and th~ ridge east of Highland Avenue. This
effectively de-silted.the water before it overflowed and ran
south toward the Cove. With .the construction of pipes and
channels north .to Oak Avenue almost continuous now, '.this
agric~ltural runoff can no ~onger pond, but instead rushes
southward in the drainage system, often carrying a
considerable.amount of silt. This is another area to.which :
th~ Association_should be.alert when development occurs.
The City will enforce their regula·tions when they are aware
of violations, but citizen watchfulness and complaints are
effective in .this enforcement •
. The pr_oblem of past .. years'. overflows from. the City
water tank, carrying silt .down into the Cove will be
alleviated.with the 1987 paving of Hillside Drive in.the
Pannonia development.
,,. ,,
!
8
[iJ.t.h-t-h-e_a_f_o_r~e.me n ti one d imp_r_o_v_eme.n.t.s-,-I-be-1-i-e-v-e-t.he~=?
(;fI-r qua n t it i es a_n_d_t_he-p.i:.o_b~i~;-Cove w i l_l_b.e~g..r-~~~ , ,-....,-,.._,.....,,
-~:· The previous reports on the sil~-ation, listed
above, .have estimated that prior to.1983 the annual silt
deposit in the Cove was ·about 8,000 C.Y. With the changes
and additions to the basin infrastructure since, I estimate
that the predicted silt deposi·t.to.be abo_ut 2,000 C.Y.
an~rially, which will decreasa gradually in the years ahead.
There could still be a catastrophic storm or other unusual
single event which_ could cause a sudden· influx to exceed
that estimate. T~ere is not much ·more that can be done .to
further redute silt carried to the C~ve. There is also, of·
course, the matter of silt already in the Cove.which has not
been removed.
V. FUTURE ~ILT REMOVAL OPTIONS
It is my opinion that the 60'' diversion pipe 1s .too
un_dependable to count on for keeping the Cove free of .silt,
and.the cost of .cleaning it is.considerable. Cleaning would
need .to .be repeated.periodically •. It.will.never. function as
interid~d at high .tide, .and it seems that most severe· storms
peak at .high tide. Low flows will.drop silt load durint
.hiih tid~ (there are.two highs each day) .. and.low .. flow
v~lo~ities .are .too low. to .scour out the silt.even at low
.tide. I do not consider this option> by itself> viable, .at
least .until the basin is more fully developed and the silt
does not contain the coarse .grains it .now does.
,c~. )
l • :
J
9
Another option is a floatin·g pump, similar to that
ou~lined in the E. F. Cook report of September 19, 1981~
This is a valid.option but the cost now would probably be
double the estim,te of .$16,400 made by.Co6k. This option
provides for cleani.ng out the 60" pipe as a discharge line.
The dredge pump could only be operated at low tide for
reasons discussed above. This option.would not get rid of
the silt but it .would move fu~ure silt to .the main Lagoon
where eventually. it would block the .60" pipe with buildup in
the lagoon. Th•re is ~lso .the matter of storing the pump
float year round, either by kee~ing .it in the water or
lifting it .out after use. Liftin~ out and storing would'
require use of a truck mounted crane .each time. This option
could be explored further if the board is interested, but
that is not in the scope of this report.
Another op~ion is the acquisition of a small dredge and
keeping it for .future dredging •. This opti6n .is more full1
·discussed.in Section VI •
. Another option is to implem•nt an.on shore catchmeit
for the silt .coming down.the pipe along Park Drfve. One
form of this. option ,is described in the E~ F. Cook report
dated.~uly.14,.1981, which called for a sheet pile cylinder
.about 20.ft. deep and.30.28.diameter,.locat~d on the lot
· where the 60" drain.approathes the diversion structure.
This would.catch and store_effectively, 310 C.Y •. If it
overloads, of course, the flow would run ~irectly into .th~
,;
!
10
Cove as it does now. This option 1s much more attractive
now than when it.was made 10 1981, because siltation is
~reatly reduced since 1981. Its cost is probably 50% more
now than the $51,600 Cook estimated in 1981 and the silt
would still have to be removed by clam bucket from the·
storage cylinder. Removal from the cylinder, however, 1s
mu~h easier than from the waters of the Cove. I.would place
the _suggested baffle. initially, because I am sure ·tt .. will be
needed. This option would eliminate most of the silt from
reaching the Cove waters. The danger is that it might not
be emptied when needed, .so that if a storm occurs when the
storage cylinder is full, the silt.from the new flow goes
into the Co.ve. As siltation decreases in the years ahead,
·clamming out would be needed less and less. I .believe this
is a ve~y attractive op~ion because the cost is .about the
same as other options, and it keeps the silt out of the
Cove. I ~ecommend that thi~ option be updated.and studied
further. I·t is flexible, in that the catchment chamber can
be located in the edge of.the Cove at the discharge of the
66~' pipe or· it could take other shapes .depending on space
available. Map B attached shows possible locations for such
a chamber."
The final option is to contlnue to .dredge small
quantities whenever they can be reached by clam bucket from
existing vacant lots. This is .the least costly and bas· been
quite. effective since 1983 due to.the decreased .amount of
silt deposited. This method, however, cannot .be the long
11
term sol~tion because there are only 3 or 4 open lots left.
It is likely the owners of these lots will build in the
future, eliminating effective access and silt storage to
drain before trucking.
VI. EXISTING SILT IN THE CHANNEL
This section is .my response to the secondary assignment
referred to in Section I.· . I. survey_ed cross sections from a
boat (courtesy of Mr. DeThomas) on July 1, 1987. The
sections were taken at 40 ·ft. intervals in the north end of
the Cove, and at 80 ft. intervals further south, where the
~ilt is more uniform indepth. The sections .were plotted arid
from them I have calculated 14,500 cubic yards of silt in
the Cove above the original depth ~f .-9.0 M.s.·L.
There are only two ways to remove this existing silt.
One way is by lan~ base~ equipment, as you have done in the
past. The costs of doing this have baen about $7.00 per
C.Y., as in 1981 when there .were many vacarit parcels, to .the
mo.st tecent removal of 500 C.Y •. for about .$11,000, or. $22.
per C.Y. With the availability of only about 3 or 4 p•rcels
for draining and loading as.we have now, I believe it likely
.the cost of ·1and b~sed dredging.and .disposal .to.be in excess
of $15.00 per C.Y. and you.would have the.disruption of .the
landscaped frontage for a road as in.1981. The one time
cost, theref~re, will be a~ound $100,000 io remove the
existing silt. You would still need to select one of the
options iri Section V.i~ o~der to handle tuture silt.
12
The other way to remo~e the silt now in the Cove is by
floating dredge similar to the one SDG&E uses in the west
lagoon. I have talked to SDG&E officials about using their
dredge but it is now in south San Diego Bay, There has been
talk.by SDG&E and the City, reported in _newspaper articles,
of dredging the east lagoon, which could include Bristol
Cove, but it seems to be a few years away according to
SDG&E • This would be .the best and. cheapest way, but there
. is no time t~ble or anything definite as to when this may.·
happen. I assrime the present condition is intolerable and
cannot.wait a "few years".
I have talked to Mr. Ron Burleson.of RB & Assoc.,
Dredgers, and· he tells me he can bring 1.n an 8" dredge and
remove the 14,500 C.Y. for about $100,000. or $7.00 per C.Y.
if the discharge is within 2,500 ft. A large part of this,
perhaps 50%, is for mobilization and de-mobilization Qf the
dredge and piping. Jerry Rombotis. of Kamar Co. is'.willing
'.
to let. us use .his de-silt basin opposit~ :Neblina Dr •. if
.proper· insurance riders and.hold harmless.agreements .are
provided, and we clean out the pond at the.end. We would'
have to dip it out with a clam and dry it on his adjacent
.land,.and haul it away. A contractor I know of will do this
for about $5.00 per C.Y., for a total of $12.00 per C.Y. or
about $175,000. This method would not .destroy .the existing
Cove .frontage landscaping •. Future siltation would still
need tq be handled.
'(
13
Another way is to buy a new or used 8" dredge. New
ones.cost about $175,000 ind used ones around $100,000. The
company I talked to, KMM of Laplace, .La., quoted these
prices and will_·send us a videotape showing the dredge at
work, and its operation. They will train an operator if a
dredge wer~ purchased from them. This option would require
a caiital outlay, but would also be a solution to the future
siltation fo~ i few years, until the in(low of silt is
reduced enough t·o permit sale of the dredge, with the
proceeds paying for one of.the options in Section V. Note
the comparison of cost of one time dredging by a contractor,
.$100,000, to purchase of the used dredge, $100,000~. The
limited scope of this report does not permit more.research.
and ·detailing any of these .options, but give~ you an
overview of what ~ptions are available for removal of
existing silt and methods to handle future siltation.
VII. SUMMARY
The wateished basi.n contributi?g runof.f and silt is
shown on the .small scale .map at~ached .as "Map A". It shows
the location of the areas in the watershed which have .the
most potential for producing silt in the future. These are
the.areas which need to be.watched for.adequate de-silting
basins whendevelopment occurs. Attached "Map B" shows
major drains in.the area.and pot~ntial locations for a
siltation chamber. No engineering .has been done.for any of
these potential sites but, if .your Association is interested
.;
...,-r..
14
1n pursuing this option, it, or any of the other options
co·uld be examined in detail for cost and operating
characteristics.
I . be 1 i eve the am o u n t o f s i 1 t . now reach in g the C o·v e . i s
about ·2,000 C.Y. per year, a vast improvement. over 1983 and
before. With this reduction and continuing reduction~
predicted for future years, I believe a catchment chamber
w i t h. c a p a c i t y · o f 3 0 0 t o 5 0 0 C • Y • i's f e a s i b 1 e : f o r f u t ~re
siltation. It would r~quire from $50,000 to $100,000 in
capital.costs and would need an operating budget to clam it
out periodically.
I·am convinced a .floating dredge is the.best method of
removing the 14,500 C.Y. o{ existing silt in the Cove. The
methods of removing it involve diffirent scopes of.personal
tolerance, as well as requiring varying amounts of money.
These can.be better decided by.your board, wh(ch has better
knowledge .of th~ desires of owners, and.bet.ter knowledge.of
amount and sources of money available • If the board wish~s
. f~rther study of any one.or .more.of ~he options outlined
I
herei~, I would be happy to discuss it -ith you.
15
It has.been a pleasure researching and preparing this
report for your Association. I hope this meets your needs.
If you care to.do any of the suggested additional work, I
would be happy to discuss it with you.
Respectfully.Submitted,
Alton L. Ruden, RCE 10163
Registered Civil Engineer
·->
:a ::,
8Ri5TOL COVE S(LTATJON STUDY
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TABLE 11.--INTERPRETATIONS FOR LAND MANAGEMENT--Continued
Map
symbol
Soil
LfE Las Flores-Urban land complex, 9 to 30 percent slopes:
Las Flores--------------------------------------------
Urban land--------------------------------------------
LpB Las Posas fine sandy loam, 2 to 5 percent slopes----------
LpC Las Posas fine sandy loam, 5 to 9 percent ·slopes----------
LpC2 Las Posas fine sandy loam, 5 to 9 percent slopes,
eroded.
LpD2 Las Posas fine sandy loam, 9 to 15 percent slopes,
Elroded. '-'
LpE2 Las Posas fine sandy loam, 15 to 30 percent slopes,
eroded.
LrE Las Posas stony fine sandy loam, 9 to 30 percent
slopes.
LrE2 Las Posas stony fine sandy loam, 9 to 30 percent
LrG
LsE
LsF
slopes, eroded.
Las Posas stony fine sandy loam, 30 to 65 percent
slopes.
Linne clay loam, 9 to 30 percent slopes------------------
Linpe clay loam, 30 to 50 percent slopes-----------------
Lu LoaJ)1y alluvial land--------------------------------------
LvF3 Loamy alluvial land-Huerhuero complex, 9 to SO percent
slopes, severely eroded:
Loamy alluvial land----------------------------------
Huerhuero-------------------------------------------
Md Made land------------------------------------------------
CMrc-Marina-1-oamy-coars·e-s-and-;-2~t0-9 :2ercen t s I OJ!eS --- -------
CMrE-Ma:rtn-a-ro-arn):'.-c·o-ars-e-s·ana-;-9-i-o-30-~er·c·en:t-sT01:re·s ---- · ----
, MnA Mecca coarse sandy loam, 0 to 2 percent slopes-----------
MnB Mecc::ii. cbarse sandy loam, 2··to 5 percent slopes------·=----
MoA Mecca sandy loam, saline, 0 to 2 percent slopes----------
MpA2 Mecca fine sandy loam, 0 to 2 percent slopes, eroded-----
MrG Metamorphic rock land------------------------------------
MvA Mottsville loamy coarse sand, 0 to 2percent slopes------
MvC Mottsville loamy coarse sand, 2 to 9 percent slopes------
MvD Mottsville loamy coarse sand, 9 to 15 percent slopes-----
MxA Mottsville loamy coarse sand, wet, 0 to 2 percent
OhC
OhE
OhF
OkC
slopes.
Olivenhain cobbly loam, 2 to 9 percent slopes------------
Olivenhain cobbly loam, 9 to 30 percent slopes-----------
Olivenhain cobbly loam, 30 to SO percent slopes----------
Olivenhain-Urban land complex, 2 to 9 percent slopes:
Olivenhain-------------------------------------------
Urban land-------------------------------------------
OkE Olivenhain-Urban land complex, 9 to 30 percent slopes:
Pe A
PeC
PeC2
PeD2
Pf A
Olivenhain-------------------------------------------
Urban land-------------------------------------------
Placentia sandy loam, 0 to 2 percent slopes--------------
Placentia sandy loam, 2 to 9 percent slopes--------------
Placentia sandy loam, 5 to 9 percent slopes, eroded------
Placentia sandy loam, 9 to 15 percent slopes, .eroded-----
Placentia sandy loam, thick surface, 0 to 2 percent
slopes.
PfC Placentia sandy loam, thick surface, 2 to 9 percent
slopes.
Py Playas---------------------------------------------------
See footnotes at end of table.
36
Hydro-
logic
group
D
D
D
D
D
D
D
D
D
D
C
C
B
D
D
D
Erodibil i ty
Moderate 2----
Moderate 2----
Moderate 2----
Moderate 2----
Moderate 1---
Moderate 1---
Moderate 1---
Severe 1-----
Moderate 2---
Severe 1-----
Severe 16----
Severe 1-----
Severe 1-----
Limitatiens for
conversion
from brush to
grass·
Slight.
Slight.
Slight.
Slight.
Slight.
Moderate.
Moderate.
Moderate.
Moderate.
Moderate.
Slight.
Severe.
Severe.
A---s·evere-2-=='='='"' -s1Tglit . t
A -severe 2-----Sti'g~
B .. Severe 1_6,.. •. ..
B Severe 16
B Severe 16
B Severe 16
D Severe 1-----
A Severe 2-----
A Severe 2-----
A Severe 2-----
D Severe 2-----
D
D
D
D
D
D
D
D
D
D
D
D
D
D
Severe 16----
Severe 16----
Severe 1-----
Severe 9-----
Severe 9-----
Severe 9-----
Severe 9-----
Severe 16----
Severe 16----
Moderate 2
Severe.
Slight.
Slight.
Slight.
Slight.
4/
4/
4/ y
Slight.
Slight.
Moderate.
Slight.
Slight.
Slight.
Slight.
Slight.
Slight.
TABLE 11.--INTERPRETATIONS. FOR LAND MANAGEMENT--Continued
r Map·
symbol
Soil
f: CaD2 Calpine coarse sa.1:dy loam, 9 to 15 percent slopes, I · eroded. t · CbB Carlsbad gravelly loamy sand, 2 to S percent slopes------1 · CbC Carlsbad gravelly loamy sand, S to 9 percent slopes--'----
(CoD-CarlsbaCl wg~y-roamy-s-c:ma-;--9~to-rS--percent-sTop-es -----·1 c:-::::coE-ca-r·:rsoa-a-graverty-i-o-amy-s·ana;-i-s-to'-30-p-ercen:t-s·i-op·e·s ----
{ CcC K:arlsbad-Urban land complex, 2 to 9 _percent slopes-------
;, CcE ~arlsbad-Urban land complex, 9 to 30 percent slopes------
CeC tarrizo very 'gravelly sand, 0 to 9 percent slopes--.------
CfB ~hesterton fine sandy. loam, 2 to S percent slopes--------
CfC thesterton fine sandy loam, S to 9 percent slopes--------
CfD2 Chesterton fine sandy loam, 9 to 15 percent slopes,
'· ,.
\
i.
\ r
-~1._:.:1:
;.~ .
-i,.
.:I •.'
',
~ ~.·5: .. . -; .
;I
.. :1, : :
ltl
i
.. :·j~: -.
I.;
-\
I
eroded.
ceg<::-:'ahesterton=Urban-l·and-complex;-2-to-9-percent-s-lopes-:::-:-::,-
Cnesterton------------------------------------------
Urban land-------------------------------------------
ChA
ChB
CkA
ClD2
Chino fine sandy loam, 0 to 2 percent slopes-------------
Chino fine sandy loam, 2 to 5 percent slopes-------------
~hino silt loam, saline, 0 to 2 percent slopes-----------
Cieneba coarse sandy loam, S to 15 percent slopes,
eroded.
ClE2 Cieneba coarse sandy loam, 15 to 30 percent slopes,
~roded.
ClG2
CmE2.
CmrG
CnE2
CnG2
~ieneba coarse sandy loam, 30 to 65 percent slopes,
eroded.
tieneba rocky coarse sandy loam, ~9 to 30fpercent
'slopes,. eroded.
~ieneba very rocky coarse sandy loam, 30 to 75 percent
slopes.
Cieneba-Fallbrook rocky sandy loams, 9 to 30 percent
slopes, eroded: ·-·
Cieneba---------~---------------------· -------------
Fallbrook-------' -·----------------------------------
Cieneba-Fallbrook rocky sandy loams, 30 to 65 percent
~slopes, eroded:
~ Cieneba----------------------------------------------
Fallbrook--------------------------------------------
·co Clayey alluvial land-------------------------------------
Cr :oastal beaches---------------------·-------·-·----------
CsB Corralitos loamy sand, 0 to S percent slopes-------------
CCsC="orralTto~to=amy..=:s:an.a-.=,s-t-o-~1re·r·c"Emt-s·ro11e·s ---- ---------
CsD ~orralitos loamy sand, 9 to 15 percent slopes------------
CtE Crouch coarse sandy loam, S to 30 percent slopes---------
CtF ~rouch coarse sandy loam, 30 to SO percent slopes--------
CuE ~rouch rocky coarse sandy loam, 5 to 30 percent
slopes .
; -CuG K:iouch rocky coarse sandy loam, 30 to 70{ percent
slopes.
CvG trouch stony fine sandy loam, 30 to 75 percent
slopes.
Dae Diablo clay,
Diab lo clay,
Diablo clay,
Diablo clay,
Diablo clay,
DaD
DaE
DaE2
DaF
2 to 9 percent slopes-------------:-----------
9 to 15 percent slopes.,..---------------------
15 to 30 percent slopes-------:-----·----------
15 to 30 percent slopes, eroded-------------
30 .to so· percent slopes-------.------------:;-
See footnotes at end of table.
Hydro-Erodibility
logic
group
Limitations for
.conversion
from brush to
grass
B Moderate 2---Slight.-~
C Severe 2-----Slight.
C Severe 2-----Slight.
:=c==:-seve·re-2------s:l::_i]~
-c--severe-2-------su·gnt7
D
D
A
D
D
D
D
D
C
C
C
B
B
B
B
B
Severe
Severe
Severe
Severe
Severe
Severe
2
9-----
9-----
9-----
16----
16----
Moderate 2---
Severe 16----
Severe 16----
Severe 1-----
Severe 16----
Severe 1-----
Slight.
Slight.
Moderate.
Slight.
Slight.
Moderate.
Severe.
Severe.
Severe.
Severe.
Severe.
B Severe 16----Severe.
C Severe 16----·' Severe.
B Severe 1-----
C Severe 1-----
D Moderate 2---
A Severe 2
Severe.
Severe.
Slight.
A Severe 2-----Slight.
-A--Severe-2.::. __ ,b ... .J......i.s-hg~
A Severe 2-----Slight.
B Severe 16--:--Slight.
B Severe 1-----" Moderate.
B Severe 16--:.-Moderate.
B Severe 1-----Moderate.
B Severe 1-----Moderate.
D slight--_._ ----Slight. 1/
D Slight--------Slight. 1/
D ' Moderate-------Slight. 1/
D Moderate 1---. , Slight. 1/
D . Severe 1-----. · Moderate:-!I
3