HomeMy WebLinkAboutCT 2019-0006; 2690 ROOSEVELT; PRELIMINARY DRAINAGE STUDY; 2020-01-31,-,
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PRELIMINARY
DRAINAGE STUDY
FOR
2690 Roosevelt Street
APN: 203-102-15
PREPARED BY:
SOWARDS AND BROWN ENGINEERING, INC.
CONSULTING ENGINEERS
~ity of Carls ad
MAR 02. 2020
Planning Divis n •
2187 NEWCASTLE AVENUE, STE 103, CARDIFF, CA 92007
(760) 436-8500
• 18-007
1/31/20
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2690 ROOSEVELT STREET
DRAINAGE STUDY FOR:
THE SOUTHWESTERLY HALF OF LOT 40, EXCEPTING THEREFROM THE
NORTHWESTERLY 10.60 FEET OF THE SOUTHWESTERLY 120.00 FEET
THEREOF OF SEASIDE LANDS, IN THE CITY OF CARLSBAD, COUNTY OF SAN
DIEGO, STATE OF CALIFORNIA, ACCORDING TO MAP THEREOF NO. 1722,
FILED IN THE OFFICE OF COUNTY RECORDER OF SAN DIEGO COUNTY JULY
28, 1921.
APN: 299-173-16
CRITERIA:
1. USE THE CURRENT COUNTY OF SAN DIEGO HYDROLOGY MANUAL
"RATIONAL METHOD" .
2. DESIGN FOR A 100-YEAR FREQUENCY STORM USING THE COUNTY
OF SAN DIEGO 6 HOUR AND 24 HOUR PRECIPITATION ISOPLUVIALS,
AND THE INTENSITY-DURATION FORMULA. SEE ATTACHED
3. RUNOFF COEFFICIENT FACTORS HAVE BEEN WEIGHTED BASED ON
THE INDIVIDUAL "C" FACTORS FOR DIFFERENT SURF ACES (I.E.
CONCRETE=0.90), AND THE AREAS OF THE INDIVIDUAL SURF ACES.
4. RUNOFF COEFFICIENT FOR PERVIOUS SURF ACES (LANDSCAPING
AND PERVIOUS PAVERS) BASED ON SITE SOILS REPORT (SEE
ATTACHED EXCERPT) AS TYPE "D" AND TABLE 3-1. IT SHOULD BE
NOTED THAT THE REGION IS DEPICTED AS TYPE "B" BASED ON
USDA WEB SOIL SURVEY WEBSITE. SEE ATTACHED
5. TIMES OF CONCENTRATION (TC) ARE DETERMINED FROM THE
URBAN OVERLAND NATURAL WATERSHED FLOW FORMULAS.
6. REFER TO THE ATTACHED DRAINAGE MAPS FOR BASIN AREAS AND
LOCATIONS.
Sowards & Brown Engineering, Inc.
2187 Newcastle Avenue, Cardiff By The Sea, CA 92024
phone: 760-436-8500
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SITE SPECIFIC:
1. THE PROJECT SITE IS A 0.44 ACRE LOT LOCATED ON THE EASTERLY
SIDE OF SEA VEIW A VENUE. TPIE SITE HAS AN EXISTING SINGLE
FAMILY RESIDENCE CONVERTED TO A DOCTOR'S OFFICE. THERE IS
A VACANT LOT TO THE NORTH, A SINGLE FAMILY RESIDENCE TO
THE EAST, AND A MULTI-UNIT COMPLEX TO THE SOUTH. ACCESS TO
THE SITE IS FROM ROOSEVELT STREET TO THE WEST. THERE IS
ESTABLISHED GROUNDCOVER AND TREES COVERING THE SITE.
2. THIS PROJECT PROPOSES TO REMOVE THE EXISTING RESIDENCE AND
REPLACE IT WITH THREE MULTI-UNIT CONDOMINIUMS. A
PERMEABLE MOTOR COURT FROM ROOSEVELT STREET WILL
PROVIDE ACCESS TO THE CONDOMINIUMS. PERMEABLE
WALKWAYS AND PATIOS ARE PROPOSED TO THE NORTH, EAST AND
SOUTH OF THE CONDOMINIUMS. FIVE BIOFILTRATION BASINS WILL
COLLECT THE RUNOFF FROM THE ROOFS FOR WATER QUALITY
TREATMENT AND PEAK FLOW MITIGATION. THE SITE IS
HYDROMODIFICATION EXEMPT.
3. RUNOFF FROM A PORTION OF THE SITE IS COLLECTED AND
COMINGLED IN THE CURB AND GUTTER ALONG ROOSEVELT STREET.
RUNOFF FROM MOST OF THE SITE AND ALL FIVE BIOFIL TRA TION
BASINS WILL BE COLLECTED IN A PUMP VAULT WHICH WILL BE
USED FOR ADDITIONAL PEAK FLOW MITIGATION. A CURB INLET IN
FRONT OF THE SITE WILL BE RELOCATED NORTHERLY; A PORTION
OF THE SITE DRAINS INTO THIS INLET WHILE THE BALANCE DRAINS
INTO A SECOND INLET UP THE STREET. BOTH INLETS ARE
CONNECTED TO A STORM DRAIN PIPE IN ROOSEVELT STREET.
4. THERE IS APPRECIABLE RUN-ON FROM THE SITE TO THE SOUTH, AND
A SIGNIFICANT PORTION OF THE EXISTING SITE DRAINS TO THE
VACANT LOT TO THE NORTH. THE RUNOFF TO THE VACANT LOT
WILL BE SIGNIFICANTLY REDUCED BY THIS PROJECT. AN EXISTING
WALL TO THE EAST PREVENTS RUNOFF FROM MIXING WITH THE LOT
TO THE EAST. WEEPHOLES WILL BE INCLUDED IN THE PROPOSED
WALL ALONG THE SOUTHERLY AN DEASTERL Y PROPERTY LINES TO
ALLOW RUN-ON FROM THE ADJACENT SITES.
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PRE-DEVELOPMENT HYDROLOGY
BASIN A: AREA= 8,909 SF = 0.20 AC 3,750 SF IMPERVIOUS
BASED ON TABLE 3-1 C=0.35 FOR SOIL TYPE 'D'
C=0.90 FOR IMPERVIOUS SURF ACES
CA= [3,750(0.90) + 5,-159(0.35)] I 8,909 = 0.58
DUE TO INITIAL RUNOFF FROM ADJACENT SITE ROOF, FLOW IS
IMMEDIATELY CONCENTRATED AND OVERLAND FLOW IS NOT
APPLICABLE.
Tt FOR 217', USE NATURAL WATERSHED FORMULA
L = 217' = 0.041 MILE ~E = 47.0 -41.5 = 5.5'
Tt = (1 l.9L3/ ~E)°-385 X 60 = (11.9(0.041)3/5.5)°-385 X 60 = 2.0 MIN
Tc= 2.0 MIN< 5 MIN MINIMUM THEREFORE Tc= 5.0 MIN
1100 = 7.44P6Tc-·645 = 7.44(2.5)5.0-·645 = 6.59 IN/HR
Q100 =CIA= 0.58(6.59)0.20 = 0.76 CFS
FLOW IS OVER VEGETATED SLOPE TO ROOSEVELT STREET, THEN
NORTHERLY IN EXISTING FLOWLINE TO AN INLET AT THE FRONT OF THE
PROPERTY.
BASIN B: AREA= 3,257 SF= 0.08 AC 2,115 SF IMPERVIOUS
CB= [2,115(0.90) + 1,142(0.35)] I 3,257 = 0.71
BY INSPECTION, Ti< 5 MIN THEREFORE Tc= 5.0 MIN, 1100 = 6.59 IN/HR
Q100 = 0.71(6.59)0.08 = 0.37 CFS
FLOW IS TO ROOSEVELT STREET, THEN NORTHERLY IN AN EXISTING
FLOWLINE. A PORTION FLOWS INTO AN INLET AT THE FRONT OF THE
PROPERTY.
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BASIN C: AREA= 11,640 SF= 0.27 AC 1,262 SF IMPERVIOUS
Cc= [1,262(0.90) + 10,378(0.35)] I 11,640 = 0.41
Ti FOR THE FIRST 90', USE OVERLAND FLOW (S = 3.9%)
Ti= l.8(1.1-C)D112/S 113 = l.8(1.1-0.32)(90)112/3.9113 = 8.5 MIN
T1 FOR THE REMAINING 66', USE NATURAL WATERSHED FORMULA
L = 66' = 0.013 MILE ~E=43.7-42.6= 1.1'
T1 = (1 l.9L3/ ~E)0.385 x 60 = (11.9(0.013)3/1.1)°.385 x 60 = 1.0 MIN
Tc= Ti+ Tt = 8.5 + 1.0 = 9.5 MIN
l100 = 7.44P6Tc-·645 = 7.44(2.5)9.5-·645 = 4.35 IN/HR
Q100 =CIA= 0.41(4.35)0.27 = 0.48 CFS
FLOW IS OVER VEGETATED SLOPE NORTHWESTERLY TO NEIGHBORING
VACANT LOT, THEN WESTERLY TO ROOSEVELT STREET, THEN
NORTHERLY IN AN EXISTING FLOWLINE.
PRE-DEVELOPMENT FLOOD ROUTING
JUNCTION A: BASINS A+B+C
PIPE TRANSIT TIMES ARE NEGLIGIBLE AND WILL BE IGNORED
QA= Qs = 0.76 + 0.37 + (5.0/9.5)0.48 = 1.38 CFS*
Qc = (4.35/6.59)0.76 + (4.35/6.59)0.37 + 0.48 = 1.23 CFS
Q1A = 1.3 8 CFS T1A = 5.0 MIN l1A = 6.59 IN/HR
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POST-DEVELOPMENT HYDROLOGY
BASIN 1: AREA= 9,522 SF= 0.22 AC 3,400 SF IMPERVIOUS
C1 = [3,400(0.90) + 6,122(0.35)] / 9,522 = 0.55
BY INSPECTION, Ti< 5 MIN THEREFORE Tc= 5.0 MIN, l100 = 6.59 IN/HR
Q100 =CIA= 0.55(6.59)0.22 = 0.80 CFS
FLOW IS OVER VEGETATED SURFACE TO INLETS, THEN PIPED TOA VAULT
THEN PUMPED TO AN INLET AT THE FRONT OF THE PROPERTY.
BASIN 2: AREA= 2,828 SF= 0.07 AC
C2 = [2,764(0.9) + 64(0.35)] I 2,828 = 0.89
2,764 SF IMPERVIOUS
BY INSPECTION, Ti< 5 MIN THEREFORE Tc= 5.0 MIN, l100 = 6.59 IN/HR
Q100 = 0.89(6.59)0.07 = 0.41 CFS
FLOW IS ROUTED TO A BIOFILTRATION BASIN FOR TREATMENT AND PEAK
FLOW MITIGATION. OUTPUT FROM THE BASIN IS PIPED TO A VAULT THEN
PUMPED TO AN INLET AT THE FRONT OF THE PROPERTY.
BASIN 3: AREA= 2,803 SF= 0.06 AC
C4 = [2,798(0.9) + 5(0.35)] I 2,828 = 0.90
2,798 SF IMPERVIOUS
BY INSPECTION, Ti < 5 MIN THEREFORE Tc= 5.0 MIN, l100 = 6.59 IN/HR
Q100 = 0.90(6.59)0.06 = 0.36 CFS
FLOW IS ROUTED TO A BIOFILTRA TION BASIN FOR TREATMENT AND PEAK
FLOW MITIGATION. OUTPUT FROM THE BASIN IS PIPED TO AV AULT THEN
PUMPED TO AN INLET AT THE FRONT OF THE PROPERTY.
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BASIN 4: AREA= 2,721 SF= 0.06 AC
C4 = [2,660(0.9) + 61(0.35)] I 2,828 = 0.89
2,660 SF IMPERVIOUS
BY INSPECTION, Ti< 5 MIN THEREFORE Tc= 5.0 MIN, 1100 = 6.59 IN/HR
Q100 = 0.89(6.59)0.06 = 0.35 CFS
FLOW IS ROUTED TO A BIOFILTRATION BASIN FOR TREATMENT AND PEAK
FLOW MITIGATION. OUTPUT FROM THE BASIN IS PIPED TO AV AULT THEN
PUMPED TO AN INLET AT THE FRONT OF THE PROPERTY.
BASIN 5: AREA= 2,777 SF= 0.06 AC
C5 = [2,708(0.9) + 69(0.35)] I 2,828 = 0.89
2,708 SF IMPERVIOUS
BY INSPECTION, Ti< 5 MIN THEREFORE Tc= 5.0 MIN, 1100 = 6.59 IN/HR
Q100 = 0.89(6.59)0.06 = 0.35 CFS
FLOW IS ROUTED TO A BIOFILTRA TION BASIN FOR TREATMENT AND PEAK
FLOW MITIGATION. OUTPUT FROM THE BASIN IS PIPED TO AV AULT THEN
PUMPED TO AN INLET AT THE FRONT OF THE PROPERTY.
BASIN 6: AREA= 1,145 SF= 0.03 AC 1,145 SF IMPERVIOUS
BY INSPECTION, Ti< 5 MIN THEREFORE Tc= 5.0 MIN, 1100 = 6.59 IN/HR
Q100 = 0.90(6.59)0.03 = 0.18 CFS
FLOW IS ROUTED TO A BIOFILTRA TION BASIN FOR TREATMENT AND PEAK
FLOW MITIGATION. OUTPUT FROM THE BASIN IS PIPED TO A VAULT THEN
PUMPED TO AN INLET AT THE FRONT OF THE PROPERTY.
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BASIN 7: AREA= 2,010 SF= 0.05 AC 408 SF IMPERVIOUS
C7 = [408(0.90) + 1,602(0.35)] I 2,010 = 0.46
BY INSPECTION, Ti< 5 MIN THEREFORE Tc= 5.0 MIN, 1100 = 6.59 IN/HR
Q100 = 0.46(6.59)0.05 = 0.15 CFS
FLOW IS TO ROOSEVELT STREET, THEN NORTHERLY IN AN EXISTING
FLOWLINE. A PORTION FLOWS INTO AN INLET AT THE FRONT OF THE
PROPERTY.
POST-DEVELOPMENT FLOOD ROUTING
JUNCTION 1: BASINS 1 + 2+ 3+4+5+6
PIPE TRANSIT TIMES ARE NEGLIGIBLE AND WILL BE IGNORED
Q = 0.77 + 0.41 + 0.36 + 0.35 + 0.35 + 0.18 = 2.45 CFS
Qn = 2.45 CFS Tn = 5.0 MIN In = 6.59 IN/HR
JUNCTION 2: JUNCTION 1 + BASIN 7 Tn = T 1
PIPE TRANSIT TIMES ARE NEGLIGIBLE AND WILL BE IGNORED
Q = 2.45 + 0.15 = 2.60 CFS
Q12 =2.60 CFS Tn =5.0MIN In = 6.59 IN/HR
PRE vs POST-DEVELOPMENT IMPERVIOUS AREA
PRE DEVELOPMENT: BASIN AREA (SF)
A 3,750
I B 2,115
C 1,262
7,127 SF IMPERVIOUS
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POST DEVELOPMENT: BASIN AREA(SF)
1 3,400
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2 2,764
3 2,798
4 2,660
'"' 5 2,708
6 1,145
7 408
15,883 SF IMPERVIOUS
THERE IS AN INCREASE IN IMPERVIOUS AREA.
PRE vs POST-DEVELOPMENT HYDROLOGY
,_-....,· PRE DEVELOPMENT: BASIN FLOW (CFS) Tc (MIN) 1100
A 0.76 5.0 6.59
B 0.37 5.0 6.59
'--C 0.48 9.5 4.35
JUNCTION A 1.38 CFS 5.0 6.59
POST DEVELOPMENT: BASIN FLOW (CFS) Tc (MIN) 1100
/---.. .... 1 0.80 5.0 6.59
2 0.41 5.0 6.59
3 0.36 5.0 6.59
4 0.35 5.0 6.59
5 0.35 5.0 6.59
6 0.18 5.0 6.59
7 0.15 5.0 6.59
.. I JUNCTION 1 ., 2.60 CFS 5.0 6.59
' ,. THERE IS AN 88% INCREASE IN TOTAL FLOW FROM THE SITE. THE
INCREASE IN FLOW IS OFFSET BY THE USE OF FIVE BIOFILTRATION BASINS
I AND A PUMP VAULT SIZED FOR PEAK FLOW MITIGATION.
FLOW ONTO THE ADJACENT VACANT LOT HAS BEEN SUBSTANTIALLY
REDUCED.
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BIOFILTRA TION BASIN SIZING FOR PEAK MITIGATION
THE INCREASE IN FLOW NEEDS TO BE RETAINED ONSITE. DRAINAGE FROM
THE ROOFS OF THE PROPOSED 4 BUILDINGS IS PIPED TO 4 BIO FILTRATION
BASINS. THESE BASINS WILL BE USED TO RETAIN THE INCREASED FLOW.
PRE DEVELOPMENT SUMMARY: (JUNCTION A)
Tc= 5.0 MIN
p6 = 2.5"
TOTAL AREA= 0.55 ACRES
SITE C =[ 0.58(0.20) + 0.71(0.08) + 0.41(0.27)]/0.55 = 0.52
PEAK DISCHARGE= 1.38 CFS
POST DEVELOPMENT SUMMARY: (JUNCTION 2)
Tc= 5.0 MIN
p6 = 2.5"
TOTAL AREA= 0.55 ACRES
SITE C = 0.72
= [ 0.55(0.22)+0.89(0.07)+0.9(0.06)+0.89(0.06)+0.89(0.06)+0.9(0.03)+0.46(0.05)]/0. 55
PEAK DISCHARGE= 2.60 CFS
STORAGE VOLUME CALCULATIONS:
PER THE FOLLOWING UNIT HYDROGRAPH, 559 CF OF WATER NEEDS TO BE
RETAINED ONSITE. THE STORAGE WILL BE SPLIT BETWEEN THE 4
BIOFILTRATION BASINS BASED ON THE INDIVIDUAL BASIN AREAS, WITH
ALL BASINS HAVING AN EFFECTIVE DEPTH OF 1.67'
AREA %TOTAL STORAGE VOLUME
BASIN 1: 89 SF 22% 148 CF
BASIN 2: 50 SF 13% 83 CF
BASIN 3: 82 SF 21% 137 CF
BASIN 4: 86 SF 22% 143 CF
BASIN 5: 89 SF 22% 148 CF
396 SF 100% 659 CF > 559 CF
o,oo
(CFS)
2.8
2.4
2.0
1.6
1.2
0.8
0.4
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RATIONAL METHOD HYDROGRAPH for ROOSEVELT
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50 100 150
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l.....-_,, ..... --
O,oo PK= 2.60 CFS
_L--" POST on -LOPMENT
PRE 0
POST-1
1,
O,ooPK = 1.38 CFS
, i---PRE O "-VELOPMENT
Vsm?A<l" = 0.466 IN 2 x 50 ~IN/IN X 60 SEC
REO'D
I Vsn !?AGE= 559 CF
REC'D
L
1--1--,.\.
VF LOr-MEN T ff rVROG RAPH
GRAPH ~fltfLOPMENT HYDRO
VMIN X 0. 4 CFS/IN
200 TIM[ (MIN) 250 300 350 400
COPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
RUN DATE 1/31/2020
HYDROGRAPH FILE NAME Text1 p (Zf O [VL of f1 EA,17
TIME OF CONCENTRATION 5 MIN.
6 HOUR RAINFALL 2.5 INCHES
BASIN AREA 5.5 ACRES
1 RUNOFF COEFFICIENT 0.52
PEAK DISCHARGE 13.8 CFS
TIME (MIN) = 0
,TIME (MIN) = 5
TIME (MIN)= 10
TIME (MIN)= 15
'TIME (MIN)= 20
iTIME (MIN)= 25
TIME (MIN)= 30
TIME (MIN)= 35
TIME (MIN)= 40
TIME (MIN)= 45
'TIME (MIN)= 50
TIME (MIN) = 55
TIME (MIN)= 60
TIME (MIN)= 65
TIME (MIN)= 70
TIME (MIN)= 75
.. TIME (MIN)= 80
TIME (MIN)= 85
TIME (MIN)= 90
'TIME (MIN)= 95
TIME (MIN)= 100
. ,, TIME (MIN)= 105
fflME (MIN)= 110
, TIME (MIN)= 115
·,r TIME (MIN)= 120
. TIME (MIN)= 125
• 'TIME (MIN)= 130
TIME (MIN)= 135
TIME (MIN)= 140
TIME (MIN)= 145
.TIME (MIN)= 150
TIME (MIN) = 155
TIME (MIN)= 160
TIME (MIN)= 165
, TIME (MIN)= 170
TIME (MIN)= 175
I TIME (MIN)= 180
TIME (MIN)= 185
TIME (MIN)= 190
TIME (MIN)= 195
TIME (MIN) = 200
TIME (MIN)= 205
TIME (MIN)= 210
,--... TIME (MIN)= 215
TIME (MIN)= 220
TIME (MIN) = 225
TIME (MIN)= 230
TIME (MIN)= 235
TIME (MIN) = 240
TIME (MIN)= 245
TIME (MIN)= 250
TIME (MIN)= 255
• TIME (MIN)= 260
TIME (MIN)= 265
TIME (MIN)= 270
TIME (MIN)= 275
TIME (MIN)= 280
TIME (MIN) = 285
TIME (MIN) = 290
. TIME (MIN) = 295
TIME (MIN)= 300
TIME (MIN)= 305
I flME (MIN)= 310
, flME (MIN)= 315
TIME (MIN)= 320
TIME (MIN) = 325
rlME (MIN)= 330
rlME (MIN)= 335
rlME (MIN)= 340
TIME (MIN)= 345
TIME (MIN)= 350
rIME (MIN)= 355
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = DA
DISCHARGE (CFS) = 0.4
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS)= 0.5
DISCHARGE (CFS)= 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS)= 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS)= 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS)= 1
DISCHARGE (CFS)= 1
DISCHARGE (CFS) = 1. 1
DISCHARGE (CFS) = 1. 1
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS) = 1.4
DISCHARGE (CFS) = 1.5
DISCHARGE (CFS)= 1.7
DISCHARGE (CFS) = 1.8
DISCHARGE (CFS) = 2.2
DISCHARGE (CFS)= 2.5
DISCHARGE (CFS)= 3.7
DISCHARGE (CFS) = 10.3
DISCHARGE (CFS)= 13.8
DISCHARGE (CFS) = 3
DISCHARGE (CFS) = 2
DISCHARGE (CFS)= 1.6
DISCHARGE (CFS) = 1.3
DISCHARGE (CFS) = 1. 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.6
DISCHARGE (CFS) = 0.6
O1:SCHARGE (CF.S) = 0.6
DISCHARGE (CFS)= -0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.5
DISCHARGE (CFS) = 0.4
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TIME (MIN)= 365 DISCHARGE (CFS) = 0
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)11f~OII~ /if/){lO~RfiPH /Hl()f/h.y. P1VtfJ[ PIJlflA/Uif. if,<rl-V~f gy/6.
COPYRIGHT 1992, 2001 RICK ENGINEERING COMPANY
1 WN DATE 1/31/2020
-rlYDROGRAPH FILE NAME Text1
TIME OF CONCENTRATION 5 MIN.
i HOUR RAINFALL 2.5 INCHES
3ASIN AREA 5.5 ACRES
.~UNOFF COEFFICIENT 0.72
PEAK DISCHARGE 26 CFS
rlME (MIN)= 0
rlME (MIN)= 5
TIME (MIN)= 10
, TIME (MIN)= 15
rJME (MIN)::: 20
rJME (MIN)= 25
TIME (MIN)= 30
TIME (MIN)= 35
rlME (MIN)= 40
flME (MIN)= 45
rlME (MIN) = 50
TIME (MIN)= 55
TIME (MIN) = 60
rJME (MIN) = 65
rJME (MIN)= 70
TIME (MIN)= 75
,TIME (MIN)= 80
!
, rJME (MIN) = 85
rJME (MIN)= 90
flME (MIN)= 95
TIME (MIN)= 100
· -TIME (MIN)= 105
rlME (MIN)= 110
1 __ rJME(MIN)= 115
-TIME (MIN)= 120
TIME (MIN)= 125
flME (MIN)= 130
rJME (MIN)= 135
rlME (MIN)= 140
TIME (MIN)= 145
rlME (MIN)= 150
rlME (MIN) = 155
rlME (MIN)= 160
TIME (MIN)= 165
TIME (MIN)= 170
rlME (MIN)= 175
flME (MIN)= 180
rlME(MIN)= 185
TIME (MIN)= 190
•ilME (MIN)= 195
rlME (MIN)= 200
rlME (MIN)= 205
TIME (MIN)= 210
TIME (MIN)= 215
flME (MIN) = 220
flME (MIN)= 225
flME (MIN) = 230
TIME (MIN)= 235
rJME (MIN)= 240
rlME (MIN) = 245
• rlME (MIN) = 250
TIME (MIN) = 255
TIME (MIN) = 260
rlME (MIN) = 265
rlME (MIN) = 270
TIME (MIN) = 275
. TIME (MIN)= 280
rlME (MIN) = 285
flME (MIN)= 290
rlME (MIN) = 295
TIME (MIN) = 300
TIME (MIN)= 305
rlME (MIN)= 310
' rlME (MIN)= 315
TIME (MIN)= 320
TIME (MIN)= 325
rlME (MIN) = 330
rlME (MIN)= 335
rlME (MIN)= 340
TIME (MIN)= 345
--TIME (MIN)= 350
'rlME (MIN)= 355
DISCHARGE (CFS) = 0
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS) = 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 0.9
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS) = 1.1
DISCHARGE (CFS)= 1.1
DISCHARGE (CFS) = 1.2
DISCHARGE (CFS)= 1.2
DISCHARGE (CFS)= 1.3
DISCHARGE (CFS)= 1.4
DISCHARGE (CFS) = 1.5
DISCHARGE (CFS)= 1.5
DISCHARGE (CFS) = 1.7
DISCHARGE (CFS) = 1.7
DISCHARGE (CFS) = 1.9
DISCHARGE (CFS) = 2
DISCHARGE (CFS) = 2.3
DISCHARGE (CFS) = 2.5
DISCHARGE (CFS) = 3.1
DISCHARGE (CFS)= 3.5
DISCHARGE (CFS)= 5.2
DISCHARGE (CFS)= 7.4
DISCHARGE (CFS) = 26
DISCHARGE (CFS)= 4.1
DISCHARGE (CFS) = 2.8
DISCHARGE (CFS)= 2.2
DISCHARGE (CFS)= 1.8
DISCHARGE (CFS)= 1.6
DISCHARGE (CFS) = 1.4
DISCHARGE (CFS) = 1.3
DISCHARGE (CFS)= 1.2
DISCHARGE (CFS)= 1.1
DISCHARGE (CFS) : 1
DISCHARGE (CFS) = 1
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS)= 0.9
DISCHARGE (CFS): 0.8
DISCHARGE (CFS) = 0.B
DISCHARGE (CFS) = 0.8
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS)= 0.7
DISCHARGE (CFS) = 0.6
DISCHARGE (CFS) = 0.6
TIME (MIN)= 365 DISCHARGE (CFS) = 0
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GEOTECHNICAL INVESTIGATION
2690 ROOSEVELT STREET
CARLSBAD, CALIFORNIA
PREPARED FOR
~TCHELLDEVELOPMENTCOMPANY
DEL MAR, CALIFORNIA
APRIL 8, 2019
PROJECT NO. G2245-52-01
APPENDIXC
STORM WATER MANAGEMENT INVESTIGATION
We understand storm water management devices will be used in accordance with the 2016 City of
Carlsbad BMP Design Manual. If not properly constructed, there is a potential for distress to
improvements and properties located hydrologically down gradient or adjacent to these devices.
Factors such as the amount of water to be detained, its residence time, and soil permeability have an
important effect on seepage transmission and the potential adverse impacts that may occur if the storm
water management features are not properly designed and constructed. We have not performed a
hydrogeological study at the site. If infiltration of storm water runoff occurs, downstream properties
may be subjected to seeps, springs, slope instability, raised groundwater, movement of foundations
and slabs, or other undesirable impacts as a result of water infiltration.
Hydrologic Soil Group
The United States Department of Agriculture (USDA), Natural Resources Conservation Services,
possesses general information regarding the existing soil conditions for areas within the United States.
The USDA website also provides the Hydrologic Soil Group. Table C-1 presents the descriptions of
the hydrologic soil groups. If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first
letter is for drained areas and the second is for undrained areas. In addition, the USDA website also
provides an estimated saturated hydraulic conductivity for the existing soil.
TABLE C-1
HYDROLOGIC SOIL GROUP DEFINITIONS
Soil Group Soil Group Definition
Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These
A consist mainly of deep, well drained to excessively drained sands or gravelly sands. These
soils have a high rate of water transmission.
Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of
B moderately deep or deep, moderately well drained or well drained soils that have moderately
fine texture to moderately coarse texture. These soils have a moderate rate of water
transmission.
Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils
C having a layer that impedes the downward movement of water or soils of moderately fine
texture or fine texture. These soils have a slow rate of water transmission.
Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These
D consist chiefly of clays that have a high shrink-swell potential, soils that have a high-water
table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow
over nearly impervious material. These soils have a very slow rate of water transmission.
Project No. G2245-52-0l -C-1 -April 8, 2019
' I ' , __
The property is underlain by man-made fill and should be classified as Soil Group D. Table C-2
presents the information from the USDA website for the subject property.
TABLE C-2
USDA WEB SOIL SURVEY -HYDROLOGIC SOIL GROUP
Approximate ksAT of Most
Map Unit Hydro logic Limiting Map Unit Name Symbol Percentage Soil Group Layer of Property (inches/hour)
Marina loamy coarse sand, 2 to 9 percent slopes MIC JOO B 0.57-1.98
In-Situ Testing
The degree of soil compaction or in-situ density has a significant impact on soil permeability and
infiltration. Based on our experience and other studies we performed, an increase in compaction
results/ in-place density results in a general decrease in soil permeability.
Based on discussions with the local regulatory agencies, the infiltration categories include full
infiltration, partial infiltration and no infiltration. Table C-3 presents the definitions of the potential
infiltration categories.
Infiltration Category
Full Infiltration
Partial Infiltration
No Infiltration (Infeasible)
TABLE C-3
INFILTRATION CATEGORIES
Field Infiltration Rate, I
(Inches/Hour)
I> 1.0
0.IO < I ::S 1.0
I< 0.IO
Factored Infiltration Rate, I
(Inches/Hour)
I> 0.5
0.05 < I ::S 0.5
I< 0.05
The infiltration rate, percolation rates and saturated hydraulic conductivity are different and have
different meanings. Percolation rates tend to overestimate infiltration rates and saturated hydraulic
conductivities by a factor of IO or more. Table C-4 describes the differences in the definitions.
Project No. G2245-52-0l -C-2 -April 8, 20 I 9
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TABLE C-4
SOIL PERMEABILITY DEFINITIONS
Term Definition
The observation of the flow of water through a material into the ground
Infiltration Rate downward into a given soil structure under long term conditions. This is
a function of layering of soil, density, pore space, discontinuities and
initial moisture content.
The observation of the flow of water through a material into the ground
Percolation Rate downward and laterally into a given soil structure under long term
conditions. This is a function of layering of soil, density, pore space,
discontinuities and initial moisture content.
The volume of water that will move in a porous medium under a
Saturated Hydraulic hydraulic gradient through a unit area. This is a function of density,
Conductivity (ksAT, Permeability) structure, stratification, fines content and discontinuities. It is also a
function of the properties of the liquid as well as of the porous medium.
The degree of soil compaction or in-situ density has a significant impact on soil permeability and
infiltration. Based on our experience and other studies we performed, an increase in compaction
results in a decrease in soil permeability.
We performed 2 Aardvark Permeameter tests at locations shown on the attached Geologic Map,
Figure 2. The test borings were 4½ inches in diameter. The results of the tests provide parameters
regarding the saturated hydraulic conductivity and infiltration characteristics of on-site soil and
geologic units. Table C-5 presents the results of the estimated field saturated hydraulic conductivity
and estimated infiltration rates obtained from the Aardvark Permeameter tests. The field sheets are
also attached herein. We did not use a factor of safety applied to the test results on the worksheet
values. The designer of storm water devices should apply an appropriate factor of safety. Soil
infiltration rates from in-situ tests can vary significantly from one location to another due to the
heterogeneous characteristics inherent to most soil. Based on a discussion in the County of Riverside
Design Handbook for Low Impact Development Best Management Practices, the infiltration rate
should be considered equal to the saturated hydraulic conductivity rate.
TABLE C-5
FIELD PERMEAMETER INFILTRATION TEST RESULTS
Test Test Depth Geologic Field-Saturated C.4-1 Worksheet
Infiltration Rate, ksat Infiltration Rate1, ksa1 Location (feet, below grade) Unit (inch/hour) (inch/hour)
P-1 2 Qop 0.008 0.004
P-2 2 Qop 0.183 0.092
Average: 0.096 0.048
1 Using a factor of safety of 2.
Project No. G2245-52-0l -C-3 -April 8, 2019
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The test results indicate the approximate infiltration rates range from approximately 0.008 to 0.183
inches per hour (0.004 to 0.092 inches per hour with an applied factor of safety of 2). The average
infiltration rate with an applied factor of safety of 2 is 0.048 inches per hour. Full and partial
infiltration should be considered infeasible at the site because the average infiltration rate is less than
0.05 inches per hour.
Groundwater Elevations
We encountered perched groundwater during our investigation at depths ranging from
approximately 7½ to 11 ½ feet below the existing ground surface (approximate elevations ranging
from approximately 32½ to 37½ feet MSL). Therefore, infiltration is considered infeasible at the
site.
New or Existing Utilities
Utilities are present on the existing property and within the existing adjacent Roosevelt Street. Full or
partial infiltration should not be allowed in the areas of the utilities to help prevent potential
damage/distress to improvements. Mitigation measures to prevent water from infiltrating the utilities
consist of setbacks, installing cutoff walls around the utilities and installing subdrains and/or installing
liners.
Existing and Planned Structures
Existing structures exist to the north and south and east of the site. Water should not be allowed to
infiltrate in areas where it could affect the existing and neighboring properties and existing and
adjacent structures, improvements and roadways. Mitigation for existing structures consist of not
allowing water infiltration within a 1: 1 plane from existing foundations and extending the infiltration
areas at least 10 feet below the existing foundations and into formational materials.
Slopes and Other Geologic Hazards
There are no slopes present or geologic hazards at the site that would preclude infiltration at the site.
Storm Water Evaluation Narrative
The site is underlain by approximately 1 to 3 feet of undocumented fill across the site. In our
experience, fill does not possess infiltration rates appropriate with infiltration. Therefore, infiltration is
considered infeasible within the undocumented fill.
The formational Old Paralic Deposits underlies the undocumented as shallow as 1 to 3 feet deep and
extending to approximately 14 to 19 feet below existing grade. We performed 2 infiltration tests
within the Old Paralic Deposits and the results indicate an infiltration rate of less than 0.05 inches
Project No. G2245-52-0 I -C-4-April 8, 2019
per hour. Infiltration should not be allowed in soils that possess an infiltration rate less than 0.05
inches per hour; therefore, partial and full should be considered infeasible within the Old Paralic
Deposits.
The Santiago Formation exists below the Old Paralic Deposits. We did not perform infiltration testing
within the Santiago Formation due to the depth of the formation. It would be unreasonable and costly
to install storm water devices at depths exceeding approximately 15 feet at the site.
We encountered perched groundwater during our investigation at depths ranging from approximately
7½ and 11 ½ feet below the existing ground surface. We expect the bottom of planned storm water
infiltration devices will extend to depths of 2 feet or greater below the existing ground surface at the
site, therefore, we expect the bottom of the any planned storm water devices will be within 10 feet of
groundwater. Therefore, infiltration is considered infeasible at the site.
Therefore, due to the characteristics of the onsite soils and the depth of the groundwater relative to the
bottom of planned storm water devices, infiltration should be considered infeasible and any planned
storm water device should be lined.
Storm Water Management Devices
Liners and subdrains should be incorporated into the design and construction of the planned storm
water devices. The liners should be installed on the sides and bottoms of the planned basins and should
be impermeable ( e.g. High-density polyethylene, HOPE, with a thickness of about 40 mil or
equivalent Polyvinyl Chloride, PVC) to prevent water migration. The subdrains should be perforated
within the liner area, installed at the base and above the liner, be at least 3 inches in diameter and
consist of Schedule 40 PVC pipe. The subdrains outside of the liner should consist of solid pipe. The
penetration of the liners at the subdrains should be properly waterproofed. The subdrains should be
connected to a proper outlet. The devices should also be installed in accordance with the
manufacturer's recommendations.
Storm Water Standard Worksheets
The SWS requests the geotechnical engineer complete the Categorization of Infiltration Feasibility
Condition (Worksheet C.4-1 or 1-8) worksheet information to help evaluate the potential for
infiltration on the property. The attached Worksheet 1-8 presents the completed information for the
submittal process.
The regional storm water standards also have a worksheet (Worksheet D.5-1 or Form 1-9) that helps
the project civil engineer estimate the factor of safety based on several factors. Table C-5 describes the
suitability assessment input parameters related to the geotechnical engineering aspects for the factor of
safety determination.
Project No. G2245-52-0I -C-5 -April 8, 2019
33" 9'43"N
Hydr Soil o Cc rea,
Map Scale: 1:2,070 ifpnrta'.l on A landscape (11" x BS') sheet.
N ----====--------========Metets 120 18:l 0 9'.J
A ----=====---------========Feet 400 em
Ed;Je tics: UTM ZOne llN WGS84
0 100 200
Map projection: \Neb Mercator Comer aiordinates: WGS84
Web Soil Survey USDA Natural Resources
:iiiiiii Conservation Service National Cooperative Soil Survey
nia
3/11/2019
Page 1 of 4
33" 9'53"N
~
Hyar 0 I.,( rea,
MAP LEGEND
Area of Interest (AOI) D Area of Interest (AOI)
Soils
Soil Rating Polygons
A
AID
B
BID
0 C
LJ CID
D D
O Not rated or not available
Soil Rating Lines
,,..; A
.,,,., AID
,,..; B
,,..; B/D
C
,,..; CID
D
.. , Not rated or not available
Soll Rating Points
A
■ B
■ BID
Natural Resources
Conservation Service
C
CID
■ D
□ Nol rated or not available
Water Features --Streams and Canals
Transportation
+++ Rails
,,,.., Interstate Highways
-.-US Routes
Major Roads
Local Roads
Background
• Aerial Photography
Web Soil Survey
National Cooperative Soil Survey
MAP INFORMATION
The soil surveys that comprise your AOI were mapped at
1:24,000,
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required .
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 13, Sep 12, 2018
Soil map units are labeled (as space allows) for map scales
1 :50,000 or larger.
Date(s) aerial images were photographed: Nov 3, 2014-Nov
22,2014
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
3/11 /2019
Page 2 of4
Hydrologic Soil Group-San Diego County Area, California
Hydrologic Soil Group
Map unit symbol I Map unit name Rating I Acres in AOI Percent of AOI
1MIC B I 22.2
sand, 2 to 9 percent
slopes _[
1 Marina loamy coarse
[Totals for Area of Interest ---i---~·2 1 ---------
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (AID, BID, and CID). The groups are defined as follows:
Group A Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroug hly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (AID, BID , or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
m.. Natural Resources
.iii Conservation Service
Web Soil Survey
National Cooperative Soil Survey
100.0%
--
100.0%
--
3/11/2019
Page 3 of 4
Hydrologic Soil Group-San Diego County Area, California
r -,
\ :
L -
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Natural. Resources
Conservation Service
Web Soil Survey
National Coppeiative Soil Survey
3/11/2019
Page4of4
San Diego County Hydrology Manual
Date: June 2003
Table 3-1
Section:
Page:
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use
NRCS Elements
Undnturbed Natural Terrain (Natural)
Low Density Residential (LDR)
Low Density Residential (LDR)
LowDensity Residential (LDR)
Medium Density Residential (MDR)
Medlum Density Residential (MDR)
Medlm:n Density Residential (MDR)
Medium Density Residential (¥OR)
Higb Density Residential (HDR)
Higli Density Residential (HDR)
Commercial/Industrial (N. Com)
Commercial/Industrial (G. Com)
Commercial/Industrial (O.P. Com)
Conunercial/Industrial (Limited I.)
Coll1lllercial/lndustdal General I.
Coun Elements
Permanent Open Space
Residential, 1.0 DU/A or less
Residential, 2.0 DU/A or less
Residential, 2.9 DU/A or less
Residential, 4.3 DU/A or less
Residential, 7.3 DU/ A or less
Residential, 10.9 DU/A or less
Residential, 14.5 DU/A or less
Residential, 24.0 DU/ A or less
Residential, 43.0 DU/A or less
Neighborhood Commercial
General Commercial
Office Professional/Commercial
Limited Industrial
General Industrial
%IMPER.
O*
10
20
25
30
40
45
50
'65
80
80
85
90
90
95
Runoff Coefficient "C"
Soil Type
A B
0.20 0.25
0.27 0.32
0.34 0.38
0.38 0.41
0.41 0.45
0.48 0.51
O.S2 0.54
0.55 0,58
0.66 0.67
0.76 0.77
0.76 0.77
• 0.80 0.80
0.83 0.84
0.83 0.84
0.87 0.87
C
0.30
0.36
0.42
0.45
0.48
0.54
0.57
o.~o
0.69
0.78
0.78
0.81
0.84
0.84
0.87
3
6of26
D
0.35
OAl
0.46
0.49
0.52
0.57
0.60
0.63
0.71
0.79
0.79
0.82
0.85
0.85
0.87
*The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff
coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever ( e.g., the area
is located in Cleveland National Forest).
DU)A = dwelling units per acre
NR.CS = National Resources Conservation Service
3-6
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County of San Diego
Hydrology Manual
Rainfall Isopluvials
100 Year Rainfall Event -6 Hours
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3 Miles
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Rainfall lsopluvials
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Intensity-Duration Design Chart -Template
Directions for Application:
(1) From precipitation maps determine 6 hr and 24 hr amounts
for the selected frequency. These maps are included in the
County Hydrology Manual (10, 50, and 100 yr maps included
in the Design and Procedure Manual).
(2) Adjust 6 hr precipitation (if necessary) so that it Is within
the range of 45% to 65% of the 24 hr precipitation (not
applicaple to Desert).
(3) Plot 6 hr precipitation on the right side of the chart .
(4) Draw a line through the point parallel to the plotted lines.
(5) This line is the intensity-duration curve for the location
being analyzed.
Application Form:
(a) Selected frequency / DO year
(b) P6 = 2 ·> in., p24 = 4, S ,;6 = ~ 6 %(2)
24
(c) Adjusted p6(2l = 2 • 5"" In.
(d) tx = >. O min.
(e) I= 6 -~q in./hr.
Note: This chart replaces the Intensity-Duration-Frequency
curves used since 1965.
P6 1 1.5 2 2.5 3 3.5 • 4 • 4.5 5 • 5.5 : 6
Duration 1 I I I I , I • I ' I • I • I • I I
5 2.63 ~3.95 ( 5.27 . 6.59 _7.90 9.22 t 10.?4 11.86 13.17. 14.49
1
. 15.~1
7 2.12 3.18 • 4.24 5.30 6.36 7.42 8.48 9.54 10.60 11.66 12.72 I ' • • ' • 10 1,68 2.5313.37 4.21 5.05 15.90 6.74 7.58 8.42 9.27 10.11 • 1 ~·-···-t'--··~•~· --·-•---· .. -· 15 1.30 1.95 2.59 3.24 3.8914.54 5.19 5.84 I 6.49 7.13 7.78
20 • 1 .Oif ' 1 .62 , 2.15 ).69 : ~:23: 3,7! j _4.3_1~~ ; 5.3_9.: 5.9~ I 6.4·6
25 o.93 . 1.40 11.~1 . 2.33 r2,ao1 3.21 3.73 . 4.20 . 4.67 . s .13
1
s.so
30 0.83 1.24 1.66 2.07 2.49 2.90 3.32 3.73 4.15 • 4.56 4.98
4Q 0:69 : 1 .03 '. 1.38 : 1.72 : 2.07: 2.41 , 2.76 ; 3.10 I 3.45 : 3.79 4.13
50 0.60 0.90 1.19 1.49 1.79 2.09 2.39 2.69 I 2.98 3.28 ' 3.58
so o.53 ·o.so·1.os ·1.33 ·1.s9·1.8si 2.12 • 2.39 : 2.ss i 2.92 ' 3.18
go o.41 :o.s(o.82 . 1.0( 1.23) 1.43 ' 1.~3 : 1.84 2.04 '. 2.25 • 2.4~
120 0.34 0.51 0.68 0.85 1.02 1.19 1.36 1.53 1. 70 1.87 1 2.04
1~0 ..Q,?9 0.44!0.59 ;o.73:o._8al1.03 · 1.10 : 1.32 1 1.41 : 1.62 qs
180 0.26 :0,39 10.52 1 0.65 . 0.78 l 0.91 :. 1.04 1.18 ! 1.31 . 1.44 .I 1.57
240 0.22 .0.33 0.43 10.54 0.65 0.76 0.87 0.98 1,08 1.19 1 1.30 ·aoo 0:,9 : 0.28: 0.38 ! O.< 0.56 ' 0.66 : 0.75 : 0.85 , 0.94 : 1.03 f I ~1_3
360 0.17 0.25 0,33 0.42 0,5010,58 0,67 l 0.75 I 0,84 0,92 1 1.00
FIGURE
3-1
San Diego County Hydrology Manual
Date: June 2003
S<;Ction:
Page:
3
12of26
Note that the Initial Time of Concentration should be reflective of the general land-use at the
upstream. end of a drainage basin. A single lot with an area of two or less acres does not have
a significant effect where the drainage basin area is 20 to 600 acres.
Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in
hydrology studies. Initial Ti values based on average C values for the Land Use Element are
also included. These values can be used in planning and design applications as described
below. Exceptions may be approved by the "Regulating Agency" when submitted with a
detailed study.
Element*
Natural
LDR
LDR
LDR
MDR
MDR
MDR
MDR
HDR
HDR
N.Com
G.Com
O.P./Com
Limited I.
General I.
Table3-2
MAXIMUM OVERLAND FLOW LENGTH (LM)
& INITIAL TIME OF CONCENTRATION (Ti)
DU/ .5% 1% 2% 3% 5%
Acre LM Ti LM Ti. LM Ti LM Ti LM L
50 13.2 70 12.5 85 10.9 100 10.3 100 8.7
1 50 12.2 70 11.5 85 10.0 100 9.5 100 8.0
2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4
2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0
4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7
7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0
10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7
14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4
24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3
43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4
50 5.3 60 4.5 75 4.0 85 3.8 95 3.4
50 4.7 60 4.1 75 3.6 85 3.4 90 2.9
50 4.2 60 3.7 70 3.1 80 2.9 90 2.6
50 4.2 60 3.7 70 3.1 80 2.9 90 2.6
50 3.7 60 3.2 70 2.7 80 2.6 90 2.3
*See Table 3-1 for more de4liled description
3-12
10%
LM Ti
100 6.9
100 6.4
100 5.8
100 5.6
100 5.3
100 4.8
100 4.5
100 4.3
100 3.5
100 2.7
100 2.7
100 2.4
100 2.2
100 2.2
100 1.9
I
I
.6.E
Feet
5000
4000
Tc
Tc
L
.6.E
=
=
=
=
EQUATION
(1~~3)0.385
Time of concentration (hours)
Watercourse Distance (miles)
Change in elevation along
effective slope line (See Figure 3-S)(feet)
3000
2000
1000
0
0
0
o,
soo' ' 400 '
300
200
100
30
20
10
5
'~ ,~..,,,.
~-6>
' ' ' ' ' '
.::CURCI::: California Division of Highways (1941) and Kirpich {1940)
' '
L Miles Feet
'1
' 3000
0.5 '
2000
1800
1600
300
200
L
'
Nomograph for [)etermination of
' '
Tc
Hours Minutes
' ' '
Tc
100
90
80
70
50
40
30
20
18
16
14
12
10
9
a
7
6
5
4
3
Time of Concentration (Tel or Trc;wel Time (Tt) for Natural wat~rsheds
FIGURE
3-4
jjj w LL
z
w (.)
! -en 0 w en 0:: ::,
0 (.)
0:: w ~ ~
·-
2.50% slope----..
2.0 -+-----l-'-111
' ' -
1001--__,1....,·.5,:_-_+-1--_ -_ -_ --fi~"111""~~_,..-1,__._
0
EX.A.MPLE:
Given: Watercourse Distance (D) = 70 Feet
Slope (s) =1.3%
Runoff Coefficient (C) = 0.41
Overland Flow Time (T) = 9,5 Minutes
. SOURCE: Airport Drainage, Federal Aviation Administration, 1965
·-
T= 1.8(1.1-C)VD
3Vs
20
:-
en ~ z
~
~ w :E i==
~ g
LL
0 z ~ a:: UJ ~
FIGURE
Rational Formula .. Overland Time of Flow Nomograph 3.3