HomeMy WebLinkAboutCT 2018-0006; LAGUNA DRIVE SUBDIVISION; RESPONSE TO REVIEW COMMENTS OF GEOTECHNICAL REPORTS; 2020-01-14COAST GEOTECHNICAL
RECORD COpy
CONSULTING ENGINEERING GEOLOGISTS
January 14,2020 W.O. P-686218
RECEIVED
Brett Farrow
Brett Farrow' Architect JUL 69 ZC
125 Mozart Avenue LAND DEVELOPMENT
Cardiff, CA 92007 ENGIN2ENG
Subject: RESPONSE TO REVIEW COMMENTS OF GEOTECHNICAL REPORTS
Laguna Drive Subdivision
570-580 Laguna Drive
Carlsbad, California
References: Please' see Page 4
Dear City of Carlsbad:
In response to the geotechnical review conducted by NV5, West Inc. (NVS) for the referenced
Preliminary Geotechnical Investigation Report, we have addressed the comments and provided the
additional information as requested.
Response' to Comment 1:
Apparently an unsigned reportwith a rnissing,page was utilized-for review. We suspect this was an
initial emailed report. A complete bound and signed report is included in, this, response.
Response to Comment 2:
The slope stability calculations have been reassessed and recalculated based on the most recent
topographic map'. Comparing the updated slope stability analysis t, the original submission, the
slopes are identical in gradient and dimensions (approximately 32.5 degrees from horizontal).
P.O. BOX 230163 ENCINITAS, CALIFORNIA 92023
(858) 7558622
Coast Geotechnical January 14,2020
W.O. P-686218
Page 2 of 4
Furthermore, a more accurate location of the soil profiles for Qop and Tsa have been implemented
in the updated analysis. This more precise contact calculated a more favorable factor of safety, with
a minimum of 1.565 for the static condition and 1.129 for the pseudo-static (seismic) condition.
Comment 2 also highlighted that the project geotechnical report on page 14 stated that the existing
rear bkif descends at a gradient of 11/4 to 1. However, the ieferenced report stated "the rear bluff
descends at a gradient approaching 11/4 to 1." Due to the uneven topography of the rear bluff, the
steepest sections (i.e. from 20 to 25 feet vertical elevations) approach 1 1/4 to 1. Even though the
overall slope from toe to base is approximately 33 degrees from horizontal, the maximum descent
of the slope approached 11/4 to 1. These topographic variances have also been implemented in the
slope stability analysis.
Cross Section A-A" has been updated to reflect the accurate descent of the slope and includes the
topographic variances. The originally submitted Cross Section A-A" appeared to have undergone
distortion upon printing, reflecting the steeper slope variant as commented by NV5. However,
contrary to what NV5 commented, this steeper slope variant was NOT used in the stability
calculations. As stated above, the slope stability calculations reflect the true gradient of the slope
according to the topographic map, in both the original submission and the updated analyses.
Response to Comment 3:
Section 4.3 Infiltration Testing in the report included the results of our preliminary infiltration testing
utilizing a Double Ring Infiltrometer. Infiltration data was presented on Figure 7 and graphically
depicted on Figure 8 in the Preliminary Geotechnical Investigation Report. The preliminary data was
utilized by the project civil engineer.
Categorization of Infiltration Feasibility Condition (Form 1-8) was performed jointly by the civil
engineer and geotechnical engineer. A copy of the report "Geotechnical Review Categorization of
Infiltration Feasibility Condition (Form 1-8)", dated July 2, 2018, is included in this report.
CoaSt Geotechnical January 14, 2020
W.O. P-686218
Page 3 Of 4
If you have any questions. regarding this report, please do not hesitate to contact our office.
.Reference to .6& Job NO. P-686218 will help expedite a response to your inqui±y.
Respectfully submitted,
COAST GEOTECHNICAL
Kevin McFarland
Project Geologist
Mark Burwell, C.E.O. Vithaya Singhanet, P.E.
,Engineering Geologist Geotechnical Engineer
Enclosures: Cross Section is-A"
Slope Stability Analysis Static
Slope Stability Analysis Pseudo-Static
Geotechnical Review Categorization of Infiltration Feasibility Condition (Form 1-8)
January 14, 2020
W.O. P-686218
Page 4 of 4
Coast Geotechnical
REFERENCES
PRELIMINARY GEOTECHNICAL INVESTIGATION
Proposed 12 Residential Structures
570-5801aguna Drive
Carlsbad, CA 92008
Prepared by Coast Geotechnical
Dated April 4,2018
GRADING PLAN REVIEW
Proposed 12 Residential Structures
570-580 Laguna Drive
Carlsbad, CA 9008
Prepared by Coast Geotechnical
Dated August 6, 2018
SECOND GRADING PLAN REVIEW
Proposed 12 Residential Structures
570-580 Laguna Drive
Carlsbad, CA 92008
Prepared by Coast. Geotechnical
Dated January 14, 2019
REVIEW OF GEOTECHNICAL REPORTS
Laguna Drive Subdivision
570-580 Laguna Drive
Carlsbad, California
prepared, byNV5
Dated December 9, 2019
ENCLOSURES
C:\STEDWIN\FARROW1.OUT Page 1
*** GSTh33L7 **
** GSTABL7 by Garry H. Gregory, P.E. **
** Version 1.0, January 1996; Version 1.14, Sept 1999 **
--Slope Stability Analysis--
Simplified Jan6u, Modified Bishop
or Spencers Method of Slices
(Based on STABL6-1986, by Purdue University)
Run Date: 1/13/2020
Time of Run: 2:46PM
Run B: km
Input Data Filename C:FARROW1.
Output Filename: C:FARROW1.OUT
Unit System: English
Plotted Output Filename: C:.FARROW1.PLT
PROBLEM DESCRIPTION Farrow P-686218 STATIC
BOUNDARY COORDINATES
9 Top Boundaries
9 Total Boundaries
Boundary X-Left Y-Left X-Right Y-Right Soil Type
No. (ft) (ft) (ft) (ft) Below Bnd
1 0.00 5.00 5.00 5.00 2
2 5.00 5.00 11.00 10.00 2
3 11.00 10.00 27.00 20.00 2
4 27.00 20.00 31.00 24.00 2
5 31.00 24.00 40.00 30.00 1
6 40.00 30.00 57.00 40.00 1
7 57.00 40.00 70.00 42.00 1
8 70.00 42.00 100.00 42.00 1
9 100.00 42.00 182.00 42.00 1
ISOTROPIC SOIL PARAMETERS
2 Type(s) of Soil
Soil Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pcf) (pcf) (psf) (deg) Param. (psf) No.
1 116.0 122.0 70.0 29.0 0.00 0.0 0
2 120.0 128.0 350.0 34.0 0.00 0.0 0
A Critical Failure Surface Searching Method, Using A Random
Technique For Generating Circular Surfaces, Has Been Specified.
1250 Trial Surfaces Have Been Generated.
25 Surfaces Initiate From Each Of 50 Points Equally Spaced
Along The Ground Surface Between X = 20.00(ft)
and X = 45.00(ft)
Each Surface Terminates Between X = 70.00(ft)
and X = 110.00(ft)
Unless Further Limitations Were Imposed, The Minimum Elevation
At Which A Surface Extends Is Y = 0.00(ft)
5.00(ft) Line Segments Define Each Trial Failure Surface.
Following Are Displayed The Ten Most Critical Of The Trial
Failure Surfaces Examined. They Are Ordered - Most Critical
First.
* * Safety Factors Are Calculated By The Modified Bishop Method * *
Failure Surface Specified By 13 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 23.06 17.54
2 28.05 17.94
3 32.99 18.70
4 37.86 19.82
5 42.63 21.30
6 47.29 23.13
7 51.79 25.30
8 56.13 27.79
9 60.27 30.60
10 64.19 33.70
11 67.87 37.09
12 71.29 40.73
13 72.31 42.00
Circle Center At X = 20.2 ; Y.- 85..3 and Radius, •67.8
1.565 ***
Individual data on the 17 slices
C:\STEDWIN\FARROW1.OUT Page 2
Water Water Tie Tie Earthquake
Force Force Force Force Force Surcharge
Slice Width Weight Top Bot Norm Tan Hor Ver Load
No. (ft) (ibs) (ibs) (ibs) (ibs) (ibs) (ibs) (ibs) (lbs)
1 3.9 507.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0
2 1.0 330.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0
3 3.0 1545.5 0.0 0.0 0.0 0.0 0.0 04 0.0
4 2.0 1410.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0
5 4.9 4345.0 0.0 0.0 0.0 0.0 0.0 0.0 00
6 2.1 2267.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0
7 2.6 .3019.7 0.0 0.0 0.0 0.0. 0.0 0.0 0.0
8 4.7 5776.1 0.0 0.6 0.0 0.0 0.0 0.0 0.0
9 4.5 5956.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0
10 4.3 5865.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0
11 0.9 1178.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0
12 3.3 4077.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0
13 .3.9 3935.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0
14 3.7 2559.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0
15 2.1 893.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0
16 1.3 292.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0
17 1.0 75.4. 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Failure Surface Specified By 13 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 21.53 16.58
2 26.51 17.05
3 31.44 17.85
4 36.31 18.98
5 41.10 20.44
6 45.77 :22.22
7 50.31 24.31
8 54.70 26.70
9 58.92 29.39
10 62.95 32.35
11 66.76 35.58
12 70.35 39.06
13 73.00 42.00
Circle Center At X = 17.1 ; Y = 90.4 and Radius,. 73.9
1.569 ***
Failure Surface Specified By 14 Coordinate Points
Point K-Surf Y-Surf
No. (ft) (ft)
1 20.00 15.63
2 24.9.7 16.16
3 29.90 17.00
4 34.77 18.15
5 .39.55 19.59
6 44.24 21.33
7 48.81 23.36
8 53.25 25.66
9 57.54 28.24
10 61.65 31.07
11 65.59 34.16
12 69.32 37.48 13 72.84 41.03
14 73.69 42.00
Circle Center At X = 13.9 ; Y = 95.8 and Radius, 80.4
1.573
Failure Surface Specified By 12 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 27.14 20.14
2 31.99 21.36
3 36.79 22.79
4 41.52 24.41
5 46.17 2622
6 .50.75 28.24
7 55.24 30.44
8 59.63 32.82
9 63.92 35.39
C':\STEDWIN\FPiRROWl.OUT Page 3
10 68.10 38.14
11 72.16 41.06
12 73.36 42.00
Circle Center At X = 0.6 ; Y = 136.1 and Radius, 119.0
1.588 4*4
Failure Surface Specified By 12. Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 26.63 19.77
2 31.3 19.70
3 36.61 20.14
4 41.52 21.08
5 46.31 22.52
6 50.93 24.44
7 55.32 26.83
8 59.4.5 29.64
9 63.27 32.87
10 66.74 36.47
11 69.83 40.41
12 70.83 42.00
Circle Center At. X = 29.9 ; Y 68.4 and Radius, 48.7
*4* 1.595
Failure Surface Specified By 13 Coordinate Point
Point X-Surf Y-Surf
No: (ft) (ft)
1 22.04 16.90
2 26.83 18.34
3 3156 19.95
4 36.24 21.73
5 40.84 23.68
6 45.38 25.78
7 49.83 .28.05
8 54.20 30.48-
9 58.48. 33.07
10 62.67 35.80
11 66.75 38.68
12 70.73 41.71
13 71.09 42.00
Circle Center At X = -15.8 ; Y = 151.3 and Radius, 139.6
**. 1.596
Failure Surface. Specified By 11 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 28.67 21.67
2 33:67 21.81
3 38.63 22.42
4 43.52 23.50
5 48.27 25.05
6 52.85 27.05
7 57.23 29.47
8 61.35 32.30
9 65.18 35.52
10 68.68 39.08
11 71.05 42.00
Circle Center At X = 29.8 ; Y = 73.8 and Radius, 52.2
*** 1.599 **
Failure Surface Specified By 13 Coordinate Points
Point •X-Surf Y-Surf
No. (ft) (ft)
1 22;04 16.90
2 .27.04 16.92
3 32.02 17.36
4 36.95 18.20
5 41.79 19.45
6 46.52 21.09
7 51.09 23.12
B 55.48 25.51
9 59.65 28.2.6
10 63.59 31.34
11 67.26 34.74
C:\STEDWIN\FARROW1.OUT Page 4
12 70.64 38.43
13 73.40 42.00.
Circle Center At X 24.3 ; Y = 77.5 and Radius, 60.7
1.602 **
Failure Surface Specified By 14 Coordinate Points
Point X-Sürf Y-Surf.
No. (ft) (ft)
1 20.51 15.94
2 25.
*
50 15.. 68
3 30.50 15.87
4 35.46 16.54
5 40.33 17.66
6 45.08 19.22
.7 49.66 21.23
8 54.03 23.65
9 58.16 26.46
10 62.02 29.65
11 65.55 33.19
12 68.75 37.03
13 71.57 41.16
14 72.04 42.00
Circle Center At X 25.9 ; Y = 69.3 and Radius, 53.6
1.613 *•**
Failure Surface Specified By 12 Coordinate Points
Point X-Surf Y-Surf
No. (ft) .(ft)
1 24.08 18.18
2 28:87 19.61
3 33.61 21:20
38.30 .22.94
5 42.93 24.83
6 47.50 26.86
7 52.00 29.04
8 56.43 31.36
9 60.78 33.82
10 65.06 .3.6.41
11 69.25 .39.14
12 73.34 42.00
Circle Center At X = -18:7 ; Y = 169.5 and Radius, 157.3
1.613
C:\STEDWIN\FARROW1.OUT Page 1
** GSThBL7 **
** GSTABL7 by Garry H. Gregory, P.E. **
** Version 1.0, January 1996; Version 1.14, Sept 1999
--Slope Stability Analysis--
Simplified Janbu, Modified Bishop
or Spencers Method of Slices
(Based on STABL6-1986, by Purdue University)
Run Date: 1/13/2020
Time of Run: 2:43PM
Run By: km
Input Data Filename: C:FARROW1.
Output Filename: C:FARROW1.OUT
Unit System: English
Plotted Output Filename: C:FARROW1.PLT
PROBLEM DESCRIPTION Farrow P-686218 PSEUDO-STATIC
BOUNDARY COORDINATES
9 Top Boundaries
9 Total Boundaries
Boundary X-Left Y-Left X-Right Y-Right Soil Type
No. (ft) (ft) (ft) (ft) Below Bnd
I 0.00 5.00 5.00 5.00 2
2 5.00 5.00 11.00 10.00 2
3 11.00 10.00 27.00 20.00 2
4 27.00 20.00 31.00 24.00 2
5 31.00 24.00 40.00 30.00 1
6 40.00 30.00 57.00 40.00 1
7 57.00 40.00 70.00 42.00 1
8 70.00 42.00 100.00 42.0.0 1
9 100.00 42.00 182.00 42.00 1
ISOTROPIC SOIL PARAMETERS
2 Type(s) of Soil
Soil Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pcf) (pcf) (psf) (deg) Param. (psf) No.
1 116.0 122.0 70.0 29.0 0.00 0.0 0
2 120.0 128.0 350.0 34.0 0.00 0.0 0
A Horizontal Earthquake Loading Coefficient
Of0.160 Has Been Assigned
A Vertical Earthquake Loading Coefficient
Of0.000 Has Been Assigned
Cavitation Pressure - 0.0(psf)
A Critical Failurd Surface Searching Method, Using A Random
Technique For Generating Circular Surfaces, Has Been Specified.
1250 Trial Surfaces Have Been Generated.
25 Surfaces Initiate From Each Of 50 Points Equally Spaced
Along The Ground Surface Between X = 20.00(ft)
and X = 45.00(ft)
Each Surface Terminates Between X = 70.00(ft)
and X = 110.00(ft)
Unless Further Limitations Were Imposed, The Minimum Elevation
At Which A Surface Extends Is Y = O.00(ft)
5.00(ft) Line Segments Define Each Trial Failure Surface.
Following Are Displayed The Ten Most Critical Of The Trial
Failure Surfaces Examined. They Are Ordered - Most Critical
First.
* * Safety Factors Are Calculated By The Modified Bishop Method * *
Failure Surface Specified By 12 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 27.14 20.14
2 31.99 21.36
3 36.79 22.79
4 41.52 24.41
5 46.17 26.22
6 50.75 28.24
7 55.24 30.44
8 59.63 32.82
9 63.92 35.39
10 68.10 38.14
11 72.16 41.06
C:\STEDWIN\FARROW1.OUT Page 2
1.2 73.36 42.00
Circle Center At X = 0.6 ; Y = 136.1 and Radius, 119.0
1.129 ***
Individual data on the 15 slices
Water Water Tie Tie Earthquake
Force Force Force Force Force Surcharge
Slice Width Weight Top Bot Norm Tan Nor Ver Load
No. (ft) (iba) (iba) (ibs) (iba) (iba) (iba) (ibs) (iba)
3.9 667.9 0.0 0.0 0.0 0.0 106.9 0.0 0.0
2 1.0 355.9 0.0 0.0 0.0 0.0 56.9 0.0 0.0
3 4.8 2327.1 0.0 0.0 0.0 0.0 372.3 0.0 0.0.
4 3.2 2085.1 0.0 0.0 0.0 0.0 333.6 0.0 0.0
5 1.5 1107.4 0.0 0.0 0.0 0.0 177.2 0.0 0.0
6 4.7 3753.0 0.0 0.0 0.0 0.0 600.5 0.0 0.0
7 4.6 4114.1 0.0 0.0 0.0 0.0 658.3 .0.0 0.0
8 4.5 4326.9 0.0 0.0 0.0 0.0 692.3 0.0. 0.0
9 1.8. 1748.6 0.0 0.0 0.0 0.0 279.8 0.0 0.0
10 2.6 2473.2 0.0 0.0 0.0 0.0 395.7 0.0 0.0
11 4.3 3297.6 0.0 0.0 0.0 0.0 527.6 0.0 0.0
12 4.2 2239.8 0.0 0.0 0.0 0.0 358.4 0.0 0.0
13 1.9 667.8 0.0 0.0 0.0 0.0 106.8 0.0 0.0
14 2.2 431.3 0.0 0.0 0.0 0.0 69.0 0.0 0.0
15 1.2 65.7 0.0 0.0 0.0 .0.0 10.5 .0.0 0.0
Failure Surface Specified By 13 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 23.06 17.54
2 28.05 17.94
3 32.99 18.70
4 37.86 19.82
5 42.63 21.30
6 47.29 23.13
7. 51.79 25.30
8 56.13 2.79
9 60.27 30.60
10 64.19 33.70
11 67.87 37.09
12 71.29 40.73
13 72.31 42.00
Circle Center At X = 20.2 ; Y = 85.3 and Radius, 67.8
1.138
Failure Surface Specified By 13 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 21.53 16.58
2 26.51 17.05
3 31.44 17.85
4 36.31 18.98
5 41.10 20.44
6 45.77 22.22
7 50.31 24.31
8 54.70 26.70
9 58.92 29.39
lb 62.95 32.35
11 66.76 35.58
12 70.35 39.06
13 73.00 42.00
Circle Center At X = 17.1 ; Y = 90.4 and Radius, 73.9
1.141 ***
Failure Surface Specified By 14 Coordinate Point
Point X-Surf Y-Surf
No. (ft) (ft)
1 20.00 15.63
2 24.97 16.16
3 29.90 17.00
4 34.77 18.15
5 39.55 19.59
6 44.24 21.33
7 48.81 23.36
8 53.25 25.66
C:\STEDWIN\FARROW1.OUT Page .3
9 57.54 28.24
10 61.65 31.07
11 65.59 34.16
12 69.32 37.48
13 72.84 41.03
14 73.69 42.00
Circle Center At X = 13.9 ; Y = 95.8
1.143 ***
Failure Surface Specified By 12 Coordinate
Point X-Surf Y-Surf
No. (ft) (ft)
1 26.63 19.77
2 31.46 21.06
3 .36.25 22.51
4 40.98 24.14
5 45.65 25.92
6 50.25 27.87
7 54.79 29.97
8 59.25 32.24
9 63.62 34.65
10 67.91 37.22
11 72.11 39.94
12 75.07 42.00
Circle Center At X = -7.8 ; Y 158.6
1.146
Failure Surface Specified By 11 Coordinate
'Point X-Surf Y-Surf
No. (ft) (ft)
1 28.67 21.67'
2 33.67 21.81
3 38.63 22.42
4 43.52 23.50
5 48.27 25.05
6 52.85 27.05
7 57.23 29.47
8 61.35 32.30
9 65.18 35.52
10 68.68 39.08
11 71.05 42.00
Circle Center At X = 29.8 ; .Y 73.8
1.149
Failure Surface Specified By 11 Coordinate
POint X-Surf 'Y-Surf
No. (ft) (ft)
1 29.18 22.18
2 34.03 23.42
3 38.82 24.86
4 43.54 26.49
5 48.20 28.31
6. 52.78 30.33
7 57.26' 32.53
8 61.66 34.92
9 65.95 37.48
10 70.13 40.22
11 72.61 42.00
Circle Center At K 1.7 ; Y = 140.1
1.152 **
Failure Surface Specified By 14 Coordinate
Point X-Surf Y-Surf
No. (ft) (ft)
1 22.04 16.90
2 26.94 17.90
3 31.79 19.10
4 36.59 20.1
5 41.33 22.11
6 45.99 23.92
7 50.57 25.93
8 55.06 28.12
9 59.46 30.51
1.0 63.74 33.08
and Radius, 80.4
Points
and Radius, 143.0
Points
and, Radius, 52.2
Points
and Radius., 121.1
Points
C:\STEDNIN\FARROW1.OUT Page 4
11 67.92 35.83
12 71.98 38.75
13 75.91 41.84,
14 76.09 42.00
Circle Center At X = 1.0 ; I = 132.9 and Radius, 117.9
1.153 ***
Failure Surface Specified By 12 Coordinate Points
Point X-Surf Y-Surf
No (ft) (ft)
1 24.08 18.18
2 28.87 19.61
3 3361 21.20
4 38.30 22.94
5 42.93 24.83
6 47.50 26.86
7 52.00 29.04
8 56.43 31.36,
9 60.7.8 33.82
10 65.06 36.41
11 69.25 39.14
12 .73.34 42.00
Circle Center At X = -18.1 ; Y 169.5 and Radius, 157.3
*** .1.156.
Failure Surface Specified By 12 Coordinate Points
Point X-Surf I-Surf
No. (ft) (ft)
1. 26.63 19.77
2 31.63 19.70
3 36.61 20.14
4 41.52 21.08
.5 46.31 22.52
6 50.93 24.44
7. 55.32 26.83
8 5945 29.64
9 63.27 32.87
10 66.74: 36.47
11. 6,9.83 40.41
12 70.83 42.00
Circle Center At X = 29.9 ; I = 68.4 and RadiUs, 48.7
1.161 ***
COAST GEOTECHNICAL
CONSULTING ENGINEERS AND GEOLOGISTS
July 2, 2018
Brett Farrow
Brett Farrow Architect
125 Mozart Avenue
Cardiff, CA 92007
Subject:. GEOTECHNICALREVIEW CATEGORIZATION OF INFILTRATION
FEASIBILITY CONDITION (FORM 1-8)
Proposed 12 Residential Structures
570-580 Laguna Drive
Carlsbad, California
Reference: PRELIMINARY GEOTECHNICAL INVESTIGATION
Proposed 12 Residential Structures
570-580 Laguna Drive
Carlsbad, California
Prepared by Coast Geotechnical
Dated April 4, 2018
Dear Mr. Farrow:
We have reviewed the above subject Infiltration Feasibility Form 1-8 and agree with the findings.
If you have any questions, please do not hesitate to contact us at (858) 755-8622.
Sincerely, A' COAST GEQTECHNI' s' 1'
Mark L4EG\* ELERING
Enginering Geologist
Enclosure: Infiltration Feasibility Form 1-8
P.O. BOX 230163 * ENCNITAS, CALIFORNIA 92023
(858) 755-8622
Appendix I: Forms and Checklists
- Categorization of Infiltration fW1t Form 1-8
I1't1fl[.1.
Part! - Full Infiltration Feasibility Screening Criteria
Would infiltration of the full design volume be feasible from a physical perspective without any undesirable
consequences that cannot be reasonably mitigated?
Criteria Screening Question Yes No
Is the estimated reliable infiltration rate below proposed
facility locations greater than 0.5 inches per hour? The response
I to this Screening Question shall be based on a comprehensive X
evaluation of the factors presented in Appendix C.2 and Appendix
D.
Provide basis:
An infiltration rate of 2.48 inches per hour (without a safety factor) was established on
site utilizing a double ring infiltrometer.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
Can infiltration greater than 0.5 inches per hour be allowed
without increasing ask of geotechnical hazards (slope stability,
2 groundwater mounding, utilities, or other factors) that cannot X
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.2.
Provide basis:
Provided potentially adverse impacts on bluff slope stability, perched water conditions,
foundations, improvements, and utilities are adequately mitigated to an acceptable level as
recommended in the Preliminary Geotechnical Report.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
1-3 February 2016
Appendix I: Forms and Checklists
Form 1-8 Page 2 of 4
Criteri I
Screening Question Yes No a
Can infiltration greater than 0.5 inches per hour be allowed
without increasing risk of groundwater contamination (shallow x water table, storm water pollutants or other factors) that cannot
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.3.
Provide basis:
From a review of historical aerials across the project site and a review of the State of
California's Geotracker database there does not appear to be known pollutants within the
general vicinity of the project that would create the potential hazard of pollutant transport.
See Attachment 5 of the project WQMP for aerial photographs and Geotracker map of the
area.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
Can infiltration greater than 0.5 inches per hour be allowed
without causing potential water balance issues such as change
of seasonality of ephemeral streams or increased discharge of
contaminated groundwater to surface waters? The response to
this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
Provide basis:
No ephemeral streams exist within the project site.
See response to number 3 regarding groundwater, as stated, no known contamination exists
within the project vicinity that additional groundwater from the project would have the
potential to cause pollutant migration.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
If all answers to rows 1 - 4 are "Yes" a full infiltration design is potentially feasible.
Part 1 The feasibility screening category is Full Infiltration Yes, Full
Result
*
. If any answer from row 1.4 s "No".infiltration may be possible to some extent but i Infiltration.
would not generally be feasible or desirable to achieve a "full infiltration" design.
Proceed to Part 2
'To be completed using gathered site information and best professional judgment considering the definition of MEP in
the MS4 Permit. Additional testing and/or studies may be required by the City to substantiate findings.
1-4 February 2016
Appendix I: Forms and Checklists
Part 2— Patial Infiltration vs. No Infiltration Feasibility Screening Criteria
Would infiltration of water in any appreciable amount be physically feasible without any negative
consequences that cannot be reasonably mitigated?
Criteria Screening Question Yes No
Do soil and geologic conditions allow for infiltration in any
appreciable rate or volume? The response to this Screening
Question shall be based on a comprehensive evaluation of the
factors presented in Appendix C.2 and Appendix D.
Provide basis:
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates.
Can Infiltration in any appreciable quantity be allowed
without increasing risk of geotechnical hazards (slope
6 stability, groundwater mounding, utilities, or other factors)
that cannot be mitigated to an acceptable level? The response
to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.2.
Provide basis:
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates.
1-5 February 2016
Appendix I: Forms and Checklists
Criteria
II
Screening Question Yes No
Can Infiltration in any appreciable quantity be allowed
without posing significant risk for groundwater related
concerns (shallow water table, storm water pollutants or other
factors)? The response to this Screening Question shall be. based
on a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis:
Summarize findings of studies; provide reference tostudies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability and why it was not feasible to mitigate low infiltration. rates.
Can infiltration be allowed without violating downstream
8 water rights? The Eesponse to this Screening Question shall be
based on a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis:
Summarize endings of studies; provide reference to studies, calculations, maps, data Sources, etc. Provide narrative
discussion of study/data source applicability and why it was not .feasible to mitigate low infiltration rates.
If all answers from row 5-8 are yes then partial infiltration design is potentially feasible.
Part 2 The feasibility screening category is Partial Infiltration.
Result* If any answer from row 5-8 is no, then infiltration of any volume is considered to be
infeasible within the drainage area. The feasibility screening category is No Infiltration.
To be completed using gathered site information and best professional judgment considering the definition of MEl' in
the MS4 Permit. Additional testing and/or studies may be required by the City to substantiate findings.
1-6 February 2016