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Home My WebLink AboutCT 2022-0001; HOPE APARTMENTS; STRUCTURAL ENGINEERING DEPARTMENT SUBMITTAL; 2024-05-23 VCA STRUCTURAL 1845 W. Orangewood Ave., Suite 200 Orange, CA 92868 STRUCTURAL ENGINEERING DEPARTMENT SUBMITTAL FOR: HOPE APARTAMENTS 945 & 955 Grand Ave. Carlsbad, CA 92008 2nd Submittal SUBMITTED TO: City of Carlsbad, California May 23, 2024 Job No – 10-12063 These calculations are reproduced here only for submittal to the governing building authority to assist in obtaining a building permit. Any reproduction or distribution is expressly forbidden. Any calculation without a cover sheet, wet stamp, and signature are unauthorized and cannot be used for any purpose. Computations involving scientific principles only serve as a guide for the experienced engineer and to assist in making engineering decisions. The final design is reflected solely in the construction documents. VCA STRUCTURAL 1845 W. Orangewood Ave., Suite 200 Orange, CA 92868 STRUCTURAL ENGINEERING DEPARTMENT SUBMITTAL FOR: HOPE APARTAMENTS 945 & 955 Grand Ave. Carlsbad, CA 92008 2nd Submittal SUBMITTED TO: City of Carlsbad, California May 23, 2024 Job No – 10-12063 These calculations are reproduced here only for submittal to the governing building authority to assist in obtaining a building permit. Any reproduction or distribution is expressly forbidden. Any calculation without a cover sheet, wet stamp, and signature are unauthorized and cannot be used for any purpose. Computations involving scientific principles only serve as a guide for the experienced engineer and to assist in making engineering decisions. The final design is reflected solely in the construction documents. VCA Structural 1845 West Orangewood Ave., Suite 200 Orange, CA 92868 TABLE OF CONTENTS DESCRIPTION PAGES LANDSCAPE Terrace Retaining Wall Design 01-06 “L” Shape Retaining Wall Design 06-12 Soil Report Excerpts 13-17 --I r♦:U 1 Structural 1 2.0'-6.0' 4" TYPICAL DETAIL - TERRACED WALL NOT TO SCALE 2 Site wall H = 7ft SOILS DESIGN PARAMETER RETAINED SOIL OTHER LOADINGS Soil Unit Wt 120 pcf Retained Soil Ht, H2 =6.5 ft Unif. Surcharge, po =0 psf Conc Unit Wt 150 pcf Ground Water Ht, Hw =0 ft Lateral @ Stem, p =0 psf EFP active 40 pcf Total Wall Ht, H1 =7.03 ft Ht to Load Bot Hp =0 ft EFP Passive 300 pcf Length,Lp =0 ft EFP Under Water 0 pcf SEISMIC Adjacent Ftg Type None Increment, E/1.4 =12.85 psf Load,P =0 plf Distribution Type Inverted Triangle Distance to Wall, Xp =4 ft Depth to Ftg, Hf =7.03 ft WALL GEOMETRY STORY CLEAR HEIGHT FOUND DESIGN PARAMETERS Lvl 4 :Podium h 4 =0.01 ft Allow Brg Pressure 4500 psf Lvl 3 :Street h 3 =0.01 ft Increase by Width 200 psf Lvl 2 :Garage 1 h2 =0.01 ft Increase by Depth 300 psf Lvl 1 :Garage 2 h1 =7 ft Max Allow Brg Pressure 6500 psf WALL DESIGN Garage 2 10 in. thick Vertical Load @ Stem Stress Increase =1.33 Wall Thickness 8 in Trib Area (ft)DL (psf) LL (psf) Load Material CMU Slab 0 125 0 0 plf CMU Strength 2000 psi Superimpose Load 0 0 0 0 plf Reinf Fs 32000 psi Cover ρunif Wall Weight 7 100 700 plf Reinf @ EarthSide (-)5 @ 16 2 0.002 Load from above 0 plf Reinf @ ToeSide (+)4 @ 16 1.5 0.002 Total Load (lbs)700 plf Ma-t =0.0 lbs-ft M-Allow_t =3917.6 lbs-ft OK Added Reinf Total Reinf Ratio, ρ Ma+ =0.0 lbs-ft Critical Section No Rebar Spacing Provided ρmin Check M+Allow=2833.9 lbs-ft OK Top 0 16 0.002513448 0.0013 OK Ma-b =-3007.2 lbs-ft Mid 0 14 0.001608607 0.0013 OK M-Allow_b =3917.6 lbs-ft OK Bot 0 10 0.002513448 0.0013 OK va =17.5 psi Hor Reinf EF 4 16 0.003066406 0.0025 OK v_allow. =69.45805007 psi OK fa/Fa + fb/Fb=0.9 OK Footing Design CONCRETE Soil Bearing Check Footing Thickness, t 14 in P (lbs)d (ft) M (lbs-ft) Footing Width, B 48 in Stem 700 -1.333333333 -933.3333 Heel Width, L 4 in Footing 700 0 0 f'c 3000 psi Soil @ Heel 260 -1.833333333 -476.6667 Reinf Fy 60000 psi Cover Ma @ Stem 3007.1721 Reinf @ Bottom 5 @ 16 3 Total 1660 1597.1721 Mu 4.3 K-ft OK Allow Bearing 4900 psf fMn 10.8 K-ft q1 0 psf OK Vuh 15.3 psi OK q2 1066.308879 psf OK fVn 80.8 psi Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls3 I I I Site wall H = 7ft Va_t 0 # Ma- 0 Mallow 3918 #-ft DCR 0.00 Ma+0 #-ft Mallow 2834 #-ft DCR 0.00 DCR 0.77 Mallow 3918 #-ft Ma- -3007 Va_b -1116 # 0 plf Wall Restraint FIX t = 1.16667 OTHER LOADINGS SOILS LOADINGS L=0.0 MOMENT DIAGRAM SHEAR DIAGRAM q1 B= 4.0 q2 0 1066 0 10 20 30 40 50 60 70 80 90 100 -6,000 -4,000 -2,000 0 2,000 M_TOTAL_FACTORED M_TOTAL_ASD 0 10 20 30 40 50 60 70 80 90 100 -2000 -1000 0 1000 SHEAR_FACTORED SHEAR_ASD 0 10 20 30 40 50 60 70 80 90 100 -300 -200 -100 0 100 1-SOIL EFP 0 10 20 30 40 50 60 70 80 90 100 -100 0 100 3- SURCH… 0 1000 2000 3000 4000 5000 6000 0 50 100 SOIL BRG PRESSURE H2 Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls4 Site wall H = 5ft SOILS DESIGN PARAMETER RETAINED SOIL OTHER LOADINGS Soil Unit Wt 120 pcf Retained Soil Ht, H2 =4.5 ft Unif. Surcharge, po =0 psf Conc Unit Wt 150 pcf Ground Water Ht, Hw =0 ft Lateral @ Stem, p =0 psf EFP active 40 pcf Total Wall Ht, H1 =5.03 ft Ht to Load Bot Hp =0 ft EFP Passive 300 pcf Length,Lp =0 ft EFP Under Water 0 pcf SEISMIC Adjacent Ftg Type None Increment, E/1.4 =12.85 psf Load,P =0 plf Distribution Type Inverted Triangle Distance to Wall, Xp =4 ft Depth to Ftg, Hf =5 ft WALL GEOMETRY STORY CLEAR HEIGHT FOUND DESIGN PARAMETERS Lvl 4 :Podium h 4 =0.01 ft Allow Brg Pressure 4500 psf Lvl 3 :Street h 3 =0.01 ft Increase by Width 200 psf Lvl 2 :Garage 1 h2 =0.01 ft Increase by Depth 300 psf Lvl 1 :Garage 2 h1 =5 ft Max Allow Brg Pressure 6500 psf WALL DESIGN Garage 2 10 in. thick Vertical Load @ Stem Stress Increase =1.33 Wall Thickness 8 in Trib Area (ft)DL (psf) LL (psf) Load Material CMU Slab 0 125 0 0 plf CMU Strength 2000 psi Superimpose Load 0 0 0 0 plf Reinf Fs 32000 psi Cover ρunif Wall Weight 5 100 500 plf Reinf @ EarthSide (-)4 @ 16 2 0.002 Load from above 0 plf Reinf @ ToeSide (+)4 @ 16 1.5 0.002 Total Load (lbs)500 plf Ma-t =0.0 lbs-ft M-Allow_t =2584.3 lbs-ft OK Added Reinf Total Reinf Ratio, ρ Ma+ =0.0 lbs-ft Critical Section No Rebar Spacing Provided ρmin Check M+Allow=2833.9 lbs-ft OK Top 0 16 0.001608607 0.0013 OK Ma-b =-997.8 lbs-ft Mid 0 14 0.001608607 0.0013 OK M-Allow_b =2584.3 lbs-ft OK Bot 0 10 0.001608607 0.0013 OK va =8.3 psi Hor Reinf EF 4 16 0.003066406 0.0025 OK v_allow. =68.73127412 psi OK fa/Fa + fb/Fb=0.4 OK Footing Design CONCRETE Soil Bearing Check Footing Thickness, t 12 in P (lbs)d (ft) M (lbs-ft) Footing Width, B 48 in Stem 500 -1.333333333 -666.6667 Heel Width, L 4 in Footing 600 0 0 f'c 3000 psi Soil @ Heel 180 -1.833333333 -330 Reinf Fy 60000 psi Cover Ma @ Stem 997.82507 Reinf @ Bottom 4 @ 16 3 Total 1280 1.1584066 Mu 1.5 K-ft OK Allow Bearing 4900 psf fMn 5.7 K-ft q1 319.5655975 psf OK Vuh 9.2 psi OK q2 320.4344025 psf OK fVn 80.0 psi Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls5 I I I Site wall H = 5ft Va_t 0 # Ma- 0 Mallow 2584 #-ft DCR 0.00 Ma+0 #-ft Mallow 2834 #-ft DCR 0.00 DCR 0.39 Mallow 2584 #-ft Ma- -998 Va_b -535 # 0 plf Wall Restraint FIX t = 1 OTHER LOADINGS SOILS LOADINGS L=0.0 MOMENT DIAGRAM SHEAR DIAGRAM q1 B= 4.0 q2 320 320 0 10 20 30 40 50 60 70 80 90 100 -2,000 -1,500 -1,000 -500 0 500 M_TOTAL_FACTORED M_TOTAL_ASD 0 10 20 30 40 50 60 70 80 90 100 -1000 -500 0 500 SHEAR_FACTORED SHEAR_ASD 0 10 20 30 40 50 60 70 80 90 100 -200 -150 -100 -50 0 50 1-SOIL EFP 0 10 20 30 40 50 60 70 80 90 100 -100 -50 0 50 3- SURCH… 0 1000 2000 3000 4000 5000 6000 0 50 100 SOIL BRG PRESSURE H2 Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls6 7 8 L shape ret wall H = 7ft SOILS DESIGN PARAMETER RETAINED SOIL OTHER LOADINGS Soil Unit Wt 120 pcf Retained Soil Ht, H2 =6.5 ft Unif. Surcharge, po =0 psf Conc Unit Wt 150 pcf Ground Water Ht, Hw =0 ft Lateral @ Stem, p =0 psf EFP active 40 pcf Total Wall Ht, H1 =7.03 ft Ht to Load Bot Hp =0 ft EFP Passive 300 pcf Length,Lp =0 ft EFP Under Water 0 pcf SEISMIC Adjacent Ftg Type None Increment, E/1.4 =12.85 psf Load,P =0 plf Distribution Type Inverted Triangle Distance to Wall, Xp =4 ft Depth to Ftg, Hf =7.03 ft WALL GEOMETRY STORY CLEAR HEIGHT FOUND DESIGN PARAMETERS Lvl 4 :Podium h 4 =0.01 ft Allow Brg Pressure 4500 psf Lvl 3 :Street h 3 =0.01 ft Increase by Width 200 psf Lvl 2 :Garage 1 h2 =0.01 ft Increase by Depth 300 psf Lvl 1 :Garage 2 h1 =7 ft Max Allow Brg Pressure 6500 psf WALL DESIGN Garage 2 10 in. thick Vertical Load @ Stem Stress Increase =1.33 Wall Thickness 8 in Trib Area (ft)DL (psf) LL (psf) Load Material CMU Slab 0 125 0 0 plf CMU Strength 2000 psi Superimpose Load 0 0 0 0 plf Reinf Fs 32000 psi Cover ρunif Wall Weight 7 100 700 plf Reinf @ EarthSide (-)5 @ 16 2 0.002 Load from above 0 plf Reinf @ ToeSide (+)4 @ 16 1.5 0.002 Total Load (lbs)700 plf Ma-t =0.0 lbs-ft M-Allow_t =3917.6 lbs-ft OK Added Reinf Total Reinf Ratio, ρ Ma+ =0.0 lbs-ft Critical Section No Rebar Spacing Provided ρmin Check M+Allow=2833.9 lbs-ft OK Top 0 16 0.002513448 0.0013 OK Ma-b =-3007.2 lbs-ft Mid 0 14 0.001608607 0.0013 OK M-Allow_b =3917.6 lbs-ft OK Bot 0 10 0.002513448 0.0013 OK va =17.5 psi Hor Reinf EF 4 16 0.003066406 0.0025 OK v_allow. =69.45805007 psi OK fa/Fa + fb/Fb=0.9 OK Footing Design CONCRETE Soil Bearing Check Footing Thickness, t 14 in P (lbs)d (ft) M (lbs-ft) Footing Width, B 54 in Stem 700 -1.916666667 -1341.667 Heel Width, L 0 in Footing 787.5 0 0 f'c 3000 psi Soil @ Heel 0 -2.25 0 Reinf Fy 60000 psi Cover Ma @ Stem 3007.1721 Reinf @ Bottom 5 @ 16 3 Total 1487.5 1665.5055 Mu 6.5 K-ft OK Allow Bearing 4900 psf fMn 10.8 K-ft q1 0 psf OK Vuh 11.9 psi OK q2 877.3229947 psf OK fVn 80.8 psi Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls9 I I I L shape ret wall H = 7ft Va_t 0 # Ma- 0 Mallow 3918 #-ft DCR 0.00 Ma+0 #-ft Mallow 2834 #-ft DCR 0.00 DCR 0.77 Mallow 3918 #-ft Ma- -3007 Va_b -1116 # 0 plf Wall Restraint FIX t = 1.16667 OTHER LOADINGS SOILS LOADINGS L=0.0 MOMENT DIAGRAM SHEAR DIAGRAM q1 B= 4.5 q2 0 877 0 10 20 30 40 50 60 70 80 90 100 -6,000 -4,000 -2,000 0 2,000 M_TOTAL_FACTORED M_TOTAL_ASD 0 10 20 30 40 50 60 70 80 90 100 -2000 -1000 0 1000 SHEAR_FACTORED SHEAR_ASD 0 10 20 30 40 50 60 70 80 90 100 -300 -200 -100 0 100 1-SOIL EFP 0 10 20 30 40 50 60 70 80 90 100 -100 0 100 3- SURCH… 0 1000 2000 3000 4000 5000 6000 0 50 100 SOIL BRG PRESSURE H2 Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls10 L shape ret wall H = 5ft SOILS DESIGN PARAMETER RETAINED SOIL OTHER LOADINGS Soil Unit Wt 120 pcf Retained Soil Ht, H2 =4.5 ft Unif. Surcharge, po =0 psf Conc Unit Wt 150 pcf Ground Water Ht, Hw =0 ft Lateral @ Stem, p =0 psf EFP active 40 pcf Total Wall Ht, H1 =5.03 ft Ht to Load Bot Hp =0 ft EFP Passive 300 pcf Length,Lp =0 ft EFP Under Water 0 pcf SEISMIC Adjacent Ftg Type None Increment, E/1.4 =12.85 psf Load,P =0 plf Distribution Type Inverted Triangle Distance to Wall, Xp =4 ft Depth to Ftg, Hf =5.03 ft WALL GEOMETRY STORY CLEAR HEIGHT FOUND DESIGN PARAMETERS Lvl 4 :Podium h 4 =0.01 ft Allow Brg Pressure 4500 psf Lvl 3 :Street h 3 =0.01 ft Increase by Width 200 psf Lvl 2 :Garage 1 h2 =0.01 ft Increase by Depth 300 psf Lvl 1 :Garage 2 h1 =5 ft Max Allow Brg Pressure 6500 psf WALL DESIGN Garage 2 10 in. thick Vertical Load @ Stem Stress Increase =1.33 Wall Thickness 8 in Trib Area (ft)DL (psf) LL (psf) Load Material CMU Slab 0 125 0 0 plf CMU Strength 2000 psi Superimpose Load 0 0 0 0 plf Reinf Fs 32000 psi Cover ρunif Wall Weight 5 100 500 plf Reinf @ EarthSide (-)4 @ 16 2 0.002 Load from above 0 plf Reinf @ ToeSide (+)4 @ 16 1.5 0.002 Total Load (lbs)500 plf Ma-t =0.0 lbs-ft M-Allow_t =2584.3 lbs-ft OK Added Reinf Total Reinf Ratio, ρ Ma+ =0.0 lbs-ft Critical Section No Rebar Spacing Provided ρmin Check M+Allow=2833.9 lbs-ft OK Top 0 16 0.001608607 0.0013 OK Ma-b =-997.8 lbs-ft Mid 0 14 0.001608607 0.0013 OK M-Allow_b =2584.3 lbs-ft OK Bot 0 10 0.001608607 0.0013 OK va =8.3 psi Hor Reinf EF 4 16 0.003066406 0.0025 OK v_allow. =68.73127412 psi OK fa/Fa + fb/Fb=0.4 OK Footing Design CONCRETE Soil Bearing Check Footing Thickness, t 12 in P (lbs)d (ft) M (lbs-ft) Footing Width, B 44 in Stem 500 -1.5 -750 Heel Width, L 0 in Footing 550 0 0 f'c 3000 psi Soil @ Heel 0 -1.833333333 0 Reinf Fy 60000 psi Cover Ma @ Stem 997.82507 Reinf @ Bottom 4 @ 16 3 Total 1050 247.82507 Mu 1.6 K-ft OK Allow Bearing 4700 psf fMn 5.7 K-ft q1 175.7640169 psf OK Vuh 8.6 psi OK q2 396.9632558 psf OK fVn 80.0 psi Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls11 I I I L shape ret wall H = 5ft Va_t 0 # Ma- 0 Mallow 2584 #-ft DCR 0.00 Ma+0 #-ft Mallow 2834 #-ft DCR 0.00 DCR 0.39 Mallow 2584 #-ft Ma- -998 Va_b -535 # 0 plf Wall Restraint FIX t = 1 OTHER LOADINGS SOILS LOADINGS L=0.0 MOMENT DIAGRAM SHEAR DIAGRAM q1 B= 3.7 q2 176 397 0 10 20 30 40 50 60 70 80 90 100 -2,000 -1,500 -1,000 -500 0 500 M_TOTAL_FACTORED M_TOTAL_ASD 0 10 20 30 40 50 60 70 80 90 100 -1000 -500 0 500 SHEAR_FACTORED SHEAR_ASD 0 10 20 30 40 50 60 70 80 90 100 -200 -150 -100 -50 0 50 1-SOIL EFP 0 10 20 30 40 50 60 70 80 90 100 -100 -50 0 50 3- SURCH… 0 1000 2000 3000 4000 5000 6000 0 50 100 SOIL BRG PRESSURE H2 Z:\2023\10-12063 - AO - Hope Ave Apartments (Carlsbad)\Engineering\Calcs\Excel\10-12063 - Hope Avenue - Site Walls12 13 SUPPLEMENTAL GEOTECHNICAL RECOMMENDATION LETTER October 23, 2023 Wermers Companies Project No. 3780-SD Proposed Hope Apartments, Carlsbad, California 92008 Page 2 foot of passive resistance for foundations should be neglected unless confined by pavement or slab. A coefficient of friction of 0.33 may be utilized between concrete slabs and subgrade soils without a moisture barrier, and 0.20 for slabs underlain by moisture barrier. A modulus of subgrade reaction (k-value) of 250 pounds per cubic inch (pci) may be considered for design. The design of mat foundations should incorporate the vertical modulus of subgrade reaction. This value is a unit value for a 1-foot square footing and should be reduced in accordance with the following equation when used with the design of larger foundations. This assumes that the bearing soil will consist of dense old paralic deposits or Santiago Formation bedrock. Where: KS = unit subgrade modulus KR = reduced subgrade modulus B = foundation width (feet) 5.4 RETAINING WALL DESIGN AND CONSTRUCTION General Design Criteria Preliminary grading plans are not yet available. Retaining wall foundations embedded a minimum of 18 inches into engineered fill or dense formational materials should be designed using an allowable bearing capacity of 4,500 pounds per square foot (psf) may be used for design of continuous and perimeter footings that meet the depth and width requirements in the table above. This value may be increased by 300 pounds per square foot for each additional 12 inches in depth and 200 pounds per square foot for each additional 12 inches in width to a maximum value of 6,500 psf. Additionally, an increase of one-third may be applied when considering short- term live loads (e.g., seismic and wind loads). Passive pressure may be computed as an equivalent fluid having a density of 300 psf per foot of depth, to a maximum earth pressure of 4,500 psf for footings founded on engineered fill. A coefficient of friction between soil and concrete of 0.33 may be used with dead load forces. Passive pressure and frictional resistance can be combined without reduction. An equivalent fluid pressure approach may be used to compute the horizontal active pressure against the wall. The appropriate fluid unit weights are given in the table below for specific slope gradients of retained materials. 14 K = K [B+ 1]2 R s 2B 5.4.1 GEOTEK SUPPLEMENTAL GEOTECHNICAL RECOMMENDATION LETTER October 23, 2023 Wermers Companies Project No. 3780-SD Proposed Hope Apartments, Carlsbad, California 92008 Page 3 Surface Slope of Retained Materials (H:V) Equivalent Fluid Pressure (PCF) Select Backfill* Level 40 2:1 65 *Select backfill should consist of approved materials with an EI<20 and should be provided throughout the active zone. The above equivalent fluid weights do not include other superimposed loading conditions such as expansive soil, vehicular traffic, structures, seismic conditions, or adverse geologic conditions. 5.4.2 Restrained Retaining Walls Any retaining wall that will be restrained prior to placing backfill should be designed for at-rest soil conditions using an equivalent fluid pressure of 65 pcf (select backfill), plus any applicable surcharge loading. 5.4.3 Seismic Earth Pressures on Retaining Walls As required by the 2019 CBC, walls with a retained height greater than six feet are required to include an incremental seismic earth pressure in the wall design. Based upon review, walls with retained heights of up to approximately 15 feet are planned at the site. The lateral pressure on retaining walls due to earthquake motions (dynamic lateral force) should be calculated as PA = 3/8H2kh where PA = dynamic lateral force (pounds-per-foot)  = unit weight = 127-pounds-per-cubic-foot H = height of wall (feet) kh = seismic coefficient = 0.187 The dynamic lateral force may also be expressed as 18-pounds-per-cubic-foot EFP. The dynamic lateral force is in addition to the static force and should be applied as an inverted triangular distribution, with the resultant applied at a height of 2/3H above the base of the wall. The dynamic lateral force need not be applied to retaining walls 6-feet or less in height. Restrained retaining walls may be designed for at-rest loading condition or the active and seismic loading condition combined. Typically, it appears the design of the restrained at-rest condition for retaining wall loading may be adequate for the seismic design of the retaining walls. However, 15 GEOTEK SUPPLEMENTAL GEOTECHNICAL RECOMMENDATION LETTER October 23, 2023 Wermers Companies Project No. 3780-SD Proposed Hope Apartments, Carlsbad, California 92008 Page 4 the active earth pressure combined with the seismic design load should be reviewed and also considered in the design of the retaining walls. 5.4.4 Hydrostatic Conditions Retaining walls experiencing hydrostatic conditions free to rotate (cantilevered walls) should be designed for an active pressure of 80-pounds-per-cubic-foot equivalent fluid pressure (EFP). Retaining walls experiencing hydrostatic conditions restrained from movement at the top should be designed for an at-rest pressure of 90-pounds-per-cubic-foot EFP. 5.4.5 Wall Backfill and Drainage Wall backfill should include a minimum one (1) foot wide section of ¾ to 1-inch clean crushed rock (or approved equivalent). The rock should be placed immediately adjacent to the back of wall and extend up from the backdrain to within approximately 12 inches of finish grade. The upper 12 inches should consist of compacted onsite materials. If the walls are designed using the “select” backfill design parameters, then the “select” materials shall be placed within the active zone as defined by a 1:1 (H:V) projection from the back of the retaining wall footing up to the retained surface behind the wall. Presence of other materials might necessitate revision to the parameters provided and modification of wall designs. The backfill materials should be placed in lifts no greater than 8-inches in thickness and compacted to a minimum of 90% of the maximum dry density as determined in accordance with ASTM Test Method D 1557. Proper surface drainage needs to be provided and maintained. Water should not be allowed to pond behind retaining walls. Waterproofing of site walls should be performed where moisture migration through the wall is undesirable. Retaining walls should be provided with an adequate pipe and gravel back drain system to reduce the potential for hydrostatic pressures to develop. A 4-inch diameter perforated collector pipe (Schedule 40 PVC, or approved equivalent) in a minimum of one (1) cubic foot per lineal foot of 3/8 to one (1) inch clean crushed rock or equivalent, wrapped in filter fabric should be placed near the bottom of the backfill and be directed (via a solid outlet pipe) to an appropriate disposal area. As an alternative to the drain, rock and fabric, a pre-manufactured wall drainage product (example: Mira Drain 6000 or approved equivalent) may be used behind the retaining wall. The wall drainage product should extend from the base of the wall to within two (2) feet of the ground surface. The subdrain should be placed in direct contact with the wall drainage product. 16 GEOTEK SUPPLEMENTAL GEOTECHNICAL RECOMMENDATION LETTER October 23, 2023 Wermers Companies Project No. 3780-SD Proposed Hope Apartments, Carlsbad, California 92008 Page 5 Drain outlets should be maintained over the life of the project and should not be obstructed or plugged by adjacent improvements. CLOSURE Since GeoTek’s recommendations are based on the site conditions observed and encountered, and laboratory testing, GeoTek’s conclusions and recommendations are professional opinions that are limited to the extent of the available data. Observations during construction are important to allow for any change in recommendations found to be warranted. These opinions have been derived in accordance with current standards of practice and no warranty is expressed or implied. Standards of practice are subject to change with time. Should you have any questions after reviewing this supplementary letter, please feel free to contact our office at your convenience. Respectfully submitted, GeoTek, Inc. Christopher D. Livesey CEG, 2733 Exp. 05/31/23 Vice President Edwin R. Cunningham RCE 81687, Exp. 03/31/24 Project Engineer 17 GEOTEK