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CC - Drainage Report
T H E tell r 00 LAND MEW GROUP Seasons at Meridian 2700 E. Overland Road Meridian, ID 83642 Storm Water Management & Engineered Drainage Report Engineer The Land Group, Inc. 462 East Shore Drive, Ste. 100 9s&0 STE Eagle, Idaho 83616 ��'�F, 10 Ph: 208.939.4041 , Prepared By: Riley Langan, El 09/28/2021 Reviewed By: James W. Gute, PE of J t71. September 281", 2021 � WP TLG Project No. 120124 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208,939.4041 thelandgroupinc.com Seasons at Meridian 2700 E. Overland Road, Meridian, ID 83642 Storm Water Management& Engineered Drainage Report Project Description The proposed construction is a multi-family apartment complex on a 15.875-Acre parcel located at 2700 E. Overland Road in Meridian, ID.The site consists of 10 multi-plex units, a clubhouse, maintenance room and complex pool area. Landscaping, paved drive isles and parking areas will be constructed throughout the site. All stormwater runoff will be infiltrated and treated on-site by seepage beds. Existing Condition Currently,the site is undeveloped and consists of cultivated farmland. Stormwater falling on the undeveloped area infiltrates in place.The general topography of the site is gradually sloping from northeast to southwest. All geotechnical considerations were investigated by Atlas Technical Consultants and detailed in the Geotechnical Report dated October 19th, 2020 (File No. B201400g). Referenced report is attached in Appendix C. For construction purposes, groundwater depth is estimated to remain greater than 15 feet below ground surface throughout the year. On-Site Proposed Condition The proposed site development includes 14 tributary drainage areas shown in Appendix A. Generally, collection, routing, and treatment of storm drainage from the project is as follows: 1. Roadways and parking areas sheet flow to catch-curbs where they are conveyed to curb inlets. 2. Rooftop gutters collect and convey drainage to a seepage bed. 3. Stormwater landing on landscaping areas shall infiltrate in place. 4. Drainage flows through the catch basins/gutters into a storm drain piping network, and sand & grease traps prior to being conveyed into seepage beds for final disposal via infiltration to the native soils underlying the project site. ACHD Proposed Condition The proposed right-of-way development includes 3 tributary drainage areas shown in Appendix A. Generally, collection, routing and treatment of storm drainage from the project is as follows: 1. Roadways slope to catch-curbs where they are conveyed to curb inlets. 2. Drainage flows through the catch basins into a storm drain piping network, and sand & grease traps prior to being conveyed into seepage beds for final disposal via infiltration to the native soils underlying the project site. Peak Rate of Discharge and Storage Volume Peak storm discharge and required storage volume was determined using the Rational Method, with a 100-year storm return period. An infiltration rate of 8 inches per hour was used to determine the percolation rate. Poorly graded gravel with sand sediments were experienced throughout the site and typically provide free-drainage into native subsoils. Drainage calculations are attached in Appendix B. r" = THE LAND 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 - thelandgroupine.com LE GROUP Seasons at Meridian 2700 E. Overland Road, Meridian, ID 83642 Storm Water Management & Engineered Drainage Report Appendix A Drainage Basin Map THE LAND 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 - thelandgroupine.com LE GROUP �� .. LAND AREA13 ' GROUP \ <> 50,027 sf AREA 14 36,161 sf ONSITE SUB-BASIN LEGEND: I UI\ I I AREA 1 AREA 8 PERVIOUS AREA=7,694-SF PERVIOUS AREA=4,546-SF IMPERVIOUS AREA=38,772-SF IMPERVIOUS AREA=11,645-SF \ AREA 12 .............. ... EE \ IMPERVIOUS AREA- 0 5 SF IMPERVIOUS AREA- 54 SF PERVIOUS AREA 20,072 SF PERVIOUS AREA 8,920 SF l \ AREA 3 AREA 10 \ I \ PERVIOUS AREA=12,190-SF PERVIOUS AREA=7,876-SF / ® IMPERVIOUS AREA=24,318-SF IMPERVIOUS AREA=58,168-SF 1 AREA AREA 11 PERVIOUS AREA=12,491-SF PERVIOUS AREA=15,940-SF I I — 74,180 sf I IMPERVIOUS AREA=38,637-SF IMPERVIOUS AREA=58,240-SF AREA 10 ,66,044 sf 1 I AREA AREA12 __ I I PERVIOUS AREA 8,142-SF PERVIOUS AREA 8,985-SF IMPERVIOUS AREA-35,790-SF IMPERVIOUS AREA-47,618-SF AREA 6 AREA 13 PERVIOUS AREA=2,438-SF PERVIOUS AREA=14,276-SF ( AREA 5 .. I ' IMPERVIOUS AREA=18,274-SF IMPERVIOUS AREA=35,752-SFMimi i _ 43,932 sf —4 AREA 9 I - AREA? AREA14 36, �' PERVIOUS AREA A 6,58 PERVIOUS AREA A 12,098-SF 374 sf I i - IMPERVIOUS AREA=48,130,130-SF IMPERVIOUS AREA=24,064-SF W J 1Cm Z AREA 8 ACHD SUB-BASIN LEGEND: \ 16,191 sf AREA A AREA B �J — IMPERVIOUS AREA- 6 SF IMPERVIOUS AREA- 6 SFad - - PERVIOUS AREA 1,625 SF PERVIOUS AREA 3,574 SF 12 37- 21 00- R/W R/W/ \ AREA 6 AREA 7 �' AREA C Q y -�- -20,712 sf sf PERVIOUS AREA=7,686-SF c /v R -----�— 54 715 IMPERVIOUS AREA=22,268-SF R/W , \ RAW l / W AREA A \ �- 14,002 sf \ I m 0.321 —� I W Q = 000 o0o yo00 AREA 1 AREA 4 Z R r I I Z I 46,467 sf I 51,128 sf Z N E \ , aye �00 CZ W oin 0 0 0 AREA B o \24,581 sf - 0 CO) N 10.564 ac AREA 2 ' 90,546 sfqki 36,508 sf Revisions 10 ............. I . ..................:.::::::::::::::::::: 41 narE a D J Zu — - —_;.---- ----,�--- —Zv ZVJ _ AREA C Project No.: 120124 29,953 sf Date of Issuance: 09/28/2021 " / 0.688 ac 0 150' 300' Storm Drainage Watershed Map Exhibit-Storm Drainage Watershed Map Horizontal Scale: 1" = 150' pp ■ Seasons at Meridian 2700 E. Overland Road, Meridian, ID 83642 Storm Water Management & Engineered Drainage Report Appendix B Storm Drainage Calculations THE LAND 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 - thelandgroupine.com LE GROUP 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 1 Prepared By:Riley Langan Impervious Area = 38,772 sf Date:09/28/2021 Pervious Area = 7,694 sf Project#: 120124 lArea = 46,466 sf lArea = 1.07 acres C Coefficient = 0.83 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 7.00 ft Inf Trench Length = 125.00 ft Inf Trench Depth = 9.00 ft Storage Volume of trench = 3150 cf Total Volume = 3,150 cf Infiltration Area = 875 sf Infiltration Rate = 583 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 2.74 1,644 97 1,547 15 900 2.62 2.31 2,077 146 1,931 20 1,200 2.28 2.01 2,410 194 2,216 30 1,800 1.82 1.60 2,886 292 2,594 40 2,400 1.37 1.21 2,896 389 2,508 50 3,000 1.17 1.03 3,092 486 2,606 60 3,600 1.15 1.01 3,647 583 3,064 120 7,200 0.66 0.58 4,186 1,167 3,019 180 10,800 0.48 0.42 4,567 1,750 2,817 360 21,600 0.30 0.26 5,708 3,500 2,208 720 43,200 0.19 0.17 7,230 7,000 230 1,440 86,400 0.12 0.11 9,133 14,000 -4,867 System Checks Maximum Runoff Developed = 3,064 cf Total Volume Provided = 3,150 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 3,064 cf Other Sources = 0 cf Percolation Volume = 3,064 cf Recovery Time = 5.3 hours System Summary: 7.00 ft wide x 9.00 ft deep x 125.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 2.74 cfs System OK(Excess Capacity) Velocity = 0.39 fps Number of Traps(in parallel) = 1 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 2 Prepared By:Riley Langan Impervious Area = 70,475 sf Date:09/28/2021 Pervious Area = 20,072 sf Project#: 120124 lArea = 90,547 sf lArea = 2.08 acres C Coefficient = 0.78 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 24.00 ft Inf Trench Length = 76.00 ft Inf Trench Depth = 8.00 ft Storage Volume of trench = 5837 cf Total Volume = 5,837 cf Infiltration Area = 1,824 sf Infiltration Rate = 1,216 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 5.07 3,040 203 2,837 15 900 2.62 4.27 3,842 304 3,538 20 1,200 2.28 3.71 4,457 405 4,052 30 1,800 1.82 2.97 5,337 608 4,729 40 2,400 1.37 2.23 5,357 811 4,546 50 3,000 1.17 1.91 5,718 1,013 4,705 60 3,600 1.15 1.87 6,745 1,216 5,529 120 7,200 0.66 1.08 7,742 2,432 5,310 180 10,800 0.48 0.78 8,445 3,648 4,797 360 21,600 0.30 0.49 10,557 7,296 3,261 720 43,200 0.19 0.31 13,372 14,592 -1,220 1,440 86,400 0.12 0.20 16,891 29,184 -12,293 System Checks Maximum Runoff Developed = 5,529 cf Total Volume Provided = 5,837 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 5,529 cf Other Sources = 0 cf Percolation Volume = 5,529 cf Recovery Time = 4.5 hours System Summary: 24.00 ft wide x 8.00 ft deep x 76.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 5.07 cfs Not OK(Insufficient Capacity) Velocity = 0.72 fps Number of Traps(in parallel) = 1 CD Seasons at Meridian SeepageBedSizing 120124.xlsx Drainage Calculations r/a ` Basin Developed Volume 4 Till;LAND GBUL'P,INC:. Seasons at Meridian - Area 3 Prepared By:Riley Langan Impervious Area = 24,318 sf Date:09/28/2021 Pervious Area = 12,190 sf Project#: 120124 lArea = 36,508 sf lArea = 0.84 acres C Coefficient = 0.70 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 70.00 ft Inf Trench Depth = 8.00 ft Storage Volume of trench = 2240 cf Total Volume = 2,240 cf Infiltration Area = 700 sf Infiltration Rate = 467 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A" IDF Curve, 100-yr Return Period) -1 Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 1.82 1,094 78 1,016 15 900 2.62 1.54 1,383 117 1,266 20 1,200 2.28 1.34 1,604 156 1,449 30 1,800 1.82 1.07 1,921 233 1,687 40 2,400 1.37 0.80 1,928 311 1,617 50 3,000 1.17 0.69 2,058 389 1,669 60 3,600 1.15 0.67 2,427 467 120 7,200 0.66 0.39 2,786 933 1,853 180 10,800 0.48 0.28 3,039 1,400 1,639 360 21,600 0.30 0.18 3,799 2,800 999 720 43,200 0.19 0.11 4,813 5,600 -787 1,440 86,400 0.12 F 0.07 6,079 11,200 -5,121 System Checks Maximum Runoff Developed = 1,961 cf Other Sources = cf Total Volume Provided = 2,240 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 1,961 cf Other Sources = 0 cf Percolation Volume = 1,961 cf Recovery Time - 4.2 hours System Summary: 10.00 ft wide x 8.00 ft deep x 70.00 ft long Sand &Grease Trap: lsoo-Gal 1000-Gal Trap Size 1500-Gal 9.71 sf Maximum Discharge = 1.82 cfs System OK(Excess Capacity) Velocity = 0.19 fps Number of Traps(in parallel) = 1 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 4 Prepared By:Riley Langan Impervious Area = 38,637 sf Date:09/28/2021 Pervious Area = 12,491 sf Project#: 120124 lArea = 51,128 sf lArea = 1.17 acres C Coefficient = 0.77 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 100.00 ft Inf Trench Depth = 8.00 ft Storage Volume of trench = 3200 cf Total Volume = 3,200 cf Infiltration Area = 1,000 sf Infiltration Rate = 667 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 2.80 1,679 111 1,568 15 900 2.62 2.36 2,122 167 1,955 20 1,200 2.28 2.05 2,462 222 2,240 30 1,800 1.82 1.64 2,948 333 2,615 40 2,400 1.37 1.23 2,959 444 2,515 50 3,000 1.17 1.05 3,159 556 2,603 60 3,600 1.15 1.03 3,726 667 120 7,200 0.66 0.59 4,277 1,333 2,943 180 10,800 0.48 0.43 4,666 2,000 2,666 360 21,600 0.30 0.27 5,832 4,000 1,832 720 43,200 0.19 0.17 7,387 8,000 -613 1,440 86,400 0.12 0.11 9,331 16,000 -6,669 System Checks Maximum Runoff Developed = 3,059 cf Total Volume Provided = 3,200 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 3,059 cf Other Sources = 0 cf Percolation Volume = 3,059 cf Recovery Time = 4.6 hours System Summary: 10.00 ft wide x 8.00 ft deep x 100.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 2.80 cfs System OK(Excess Capacity) Velocity = 0.40 fps Number of Traps(in parallel) = 1 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 5 Prepared By:Riley Langan Impervious Area = 35,790 sf Date:09/28/2021 Pervious Area = 8,142 sf Project#: 120124 lArea = 43,932 sf lArea = 1.01 acres C Coefficient = 0.81 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 110.00 ft Inf Trench Depth = 7.00 ft Storage Volume of trench = 3080 cf Total Volume = 3,080 cf Infiltration Area = 1,100 sf Infiltration Rate = 733 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 2.54 1,526 122 1,404 15 900 2.62 2.14 1,929 183 1,745 20 1,200 2.28 1.86 2,238 244 1,993 30 1,800 1.82 1.49 2,680 367 2,313 40 2,400 1.37 1.12 2,689 489 2,200 50 3,000 1.17 0.96 2,871 611 2,260 60 3,600 1.15 0.94 3,386 733 2,653 120 7,200 0.66 0.54 3,887 1,467 2,420 180 10,800 0.48 0.39 4,240 2,200 2,040 360 21,600 0.30 0.25 5,300 4,400 900 720 43,200 0.19 0.16 6,714 8,800 -2,086 1,440 86,400 0.12 0.10 8,480 17,600 -9,120 System Checks Maximum Runoff Developed = 2,653 cf Total Volume Provided = 3,080 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 2,653 cf Other Sources = 0 cf Percolation Volume = 2,653 cf Recovery Time = 3.6 hours System Summary: 10.00 ft wide x 7.00 ft deep x 110.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 2.54 cfs System OK(Excess Capacity) Velocity = 0.18 fps Number of Traps(in series) = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 6 Prepared By:Riley Langan Impervious Area = 18,274 sf Date:09/28/2021 Pervious Area = 2,438 sf Project#: 120124 lArea = 20,712 sf lArea = 0.48 acres C Coefficient = 0.86 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 50.00 ft Inf Trench Depth = 7.00 ft Storage Volume of trench = 1400 cf Total Volume = 1,400 cf Infiltration Area = 500 sf Infiltration Rate = 333 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 1.27 765 56 709 15 900 2.62 1.07 966 83 883 20 1,200 2.28 0.93 1,121 111 1,010 30 1,800 1.82 0.75 1,342 167 1,176 40 2,400 1.37 0.56 1,347 222 1,125 50 3,000 1.17 0.48 1,438 278 1,160 60 3,600 1.15 0.47 1,696 333 1,363 120 7,200 0.66 0.27 1,947 667 1,280 180 10,800 0.48 0.20 2,124 1,000 1,124 360 21,600 0.30 0.12 2,655 2,000 655 720 43,200 0.19 0.08 3,363 4,000 -637 1,440 86,400 0.12 0.05 4,248 8,000 -3,752 System Checks Maximum Runoff Developed = 1,363 cf Total Volume Provided = 1,400 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 1,363 cf Other Sources = 0 cf Percolation Volume = 1,363 cf Recovery Time = 4.1 hours System Summary: 10.00 ft wide x 7.00 ft deep x 50.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 1.27 cfs System OK(Excess Capacity) Velocity = 0.18 fps Number of Traps(in parallel) = 1 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 7 Prepared By:Riley Langan Impervious Area = 48,130 sf Date:09/28/2021 Pervious Area = 6,585 sf Project#: 120124 lArea = 54,715 sf lArea = 1.26 acres C Coefficient = 0.86 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 11.00 ft Inf Trench Length = 100.00 ft Inf Trench Depth = 9.00 ft Storage Volume of trench = 3960 cf Total Volume = 3,960 cf Infiltration Area = 1,100 sf Infiltration Rate = 733 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 3.36 2,015 122 1,893 15 900 2.62 2.83 2,546 183 2,363 20 1,200 2.28 2.46 2,955 244 2,710 30 1,800 1.82 1.97 3,538 367 3,171 40 2,400 1.37 1.48 3,551 489 3,062 50 3,000 1.17 1.26 3,790 611 3,179 60 3,600 1.15 1.24 4,471 733 ,737 120 7,200 0.66 0.71 5,132 1,467 3,665 180 10,800 0.48 0.52 5,598 2,200 3,398 360 21,600 0.30 0.32 6,998 4,400 2,598 720 43,200 0.19 0.21 8,864 8,800 64 1,440 86,400 0.12 0.13 11,196 17,600 -6,404 System Checks Maximum Runoff Developed = 3,737 cf Total Volume Provided = 3,960 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 3,737 cf Other Sources = 0 cf Percolation Volume = 3,737 cf Recovery Time = 5.1 hours System Summary: 11.00 ft wide x 9.00 ft deep x 100.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 3.36 cfs System OK(Excess Capacity) Velocity = 0.47 fps Number of Traps(in parallel) = 1 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 8 Prepared By:Riley Langan Impervious Area = 11,645 sf Date:09/28/2021 Pervious Area = 4,546 sf Project#: 120124 lArea = 16,191 sf lArea = 0.37 acres C Coefficient = 0.74 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 50.00 ft Inf Trench Depth = 4.50 ft Storage Volume of trench = 900 cf Total Volume = 900 cf Infiltration Area = 500 sf Infiltration Rate = 333 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 0.85 513 56 457 15 900 2.62 0.72 648 83 565 20 1,200 2.28 0.63 752 111 641 30 1,800 1.82 0.50 900 167 734 40 2,400 1.37 0.38 904 222 681 50 3,000 1.17 0.32 965 278 687 60 3,600 1.15 0.32 1,138 333 120 7,200 0.66 0.18 1,306 667 639 180 10,800 0.48 0.13 1,425 1,000 425 360 21,600 0.30 0.08 1,781 2,000 -219 720 43,200 0.19 0.05 2,256 4,000 -1,744 1,440 86,400 0.12 0.03 2,850 8,000 -5,150 System Checks Maximum Runoff Developed = 804 cf Total Volume Provided = 900 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 804 cf Other Sources = 0 cf Percolation Volume = 804 cf Recovery Time = 2.4 hours System Summary: 10.00 ft wide x 4.50 ft deep x 50.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 0.85 cfs System OK(Excess Capacity) Velocity = 0.06 fps Number of Traps = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 9 Prepared By:Riley Langan Impervious Area = 27,454 sf Date:09/28/2021 Pervious Area = 8,920 sf Project#: 120124 lArea = 36,374 sf lArea = 0.84 acres C Coefficient = 0.77 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 20.00 ft Inf Trench Length = 40.00 ft Inf Trench Depth = 7.00 ft Storage Volume of trench = 2240 cf Total Volume = 2,240 cf Infiltration Area = 800 sf Infiltration Rate = 533 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 1.99 1,194 89 1,105 15 900 2.62 1.68 1,508 133 1,375 20 1,200 2.28 1.46 1,750 178 1,572 30 1,800 1.82 1.16 2,096 267 1,829 40 2,400 1.37 0.88 2,103 356 1,748 50 3,000 1.17 0.75 2,245 444 1,801 60 3,600 1.15 0.74 2,648 533 2,115 120 7,200 0.66 0.42 3,040 1,067 1,973 180 10,800 0.48 0.31 3,316 1,600 1,716 360 21,600 0.30 0.19 4,145 3,200 945 720 43,200 0.19 0.12 5,251 6,400 -1,149 1,440 86,400 0.12 0.08 6,632 12,800 -6,168 System Checks Maximum Runoff Developed = 2,115 cf Total Volume Provided = 2,240 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 2,115 cf Other Sources = 0 cf Percolation Volume = 2,115 cf Recovery Time = 4.0 hours System Summary: 20.00 ft wide x 7.00 ft deep x 40.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 1.99 cfs System OK(Excess Capacity) Velocity = 0.14 fps Number of Traps = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 10 Prepared By:Riley Langan Impervious Area = 58,168 sf Date:09/28/2021 Pervious Area = 7,876 sf Project#: 120124 lArea = 66,044 sf lArea = 1.52 acres C Coefficient = 0.86 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 12.00 ft Inf Trench Length = 120.00 ft Inf Trench Depth = 8.00 ft Storage Volume of trench = 4608 cf Total Volume = 4,608 cf Infiltration Area = 1,440 sf Infiltration Rate = 960 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 4.06 2,435 160 2,275 15 900 2.62 3.42 3,077 240 2,837 20 1,200 2.28 2.97 3,570 320 3,250 30 1,800 1.82 2.37 4,274 480 3,794 40 2,400 1.37 1.79 4,290 640 3,650 50 3,000 1.17 1.53 4,580 800 3,780 60 3,600 1.15 1.50 5,402 960 120 7,200 0.66 0.86 6,200 1,920 4,280 180 10,800 0.48 0.63 6,764 2,880 3,884 360 21,600 0.30 0.39 8,455 5,760 2,695 720 43,200 0.19 0.25 10,709 11,520 -811 1,440 86,400 0.12 0.16 13,528 23,040 -9,512 System Checks Maximum Runoff Developed = 4,442 cf Total Volume Provided = 4,608 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 4,442 cf Other Sources = 0 cf Percolation Volume = 4,442 cf Recovery Time = 4.6 hours System Summary: 12.00 ft wide x 8.00 ft deep x 120.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 4.06 cfs System OK(Excess Capacity) Velocity = 0.29 fps Number of Traps = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 11 Prepared By:Riley Langan Impervious Area = 58,240 sf Date:09/28/2021 Pervious Area = 15,940 sf Project#: 120124 lArea = 74,180 sf lArea = 1.70 acres C Coefficient = 0.79 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 135.00 ft Inf Trench Depth = 9.00 ft Storage Volume of trench = 4860 cf Total Volume = 4,860 cf Infiltration Area = 1,350 sf Infiltration Rate = 900 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 4.18 2,507 150 2,357 15 900 2.62 3.52 3,168 225 2,943 20 1,200 2.28 3.06 3,675 300 3,375 30 1,800 1.82 2.44 4,401 450 3,951 40 2,400 1.37 1.84 4,417 600 3,817 50 3,000 1.17 1.57 4,715 750 3,965 60 3,600 1.15 1.54 5,561 900 120 7,200 0.66 0.89 6,384 1,800 4,584 180 10,800 0.48 0.64 6,964 2,700 4,264 360 21,600 0.30 0.40 8,705 5,400 3,305 720 43,200 0.19 0.26 11,026 10,800 226 1,440 86,400 0.12 0.16 13,928 21,600 -7,672 System Checks Maximum Runoff Developed = 4,661 cf Total Volume Provided = 4,860 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 4,661 cf Other Sources = 0 cf Percolation Volume = 4,661 cf Recovery Time = 5.2 hours System Summary: 10.00 ft wide x 9.00 ft deep x 135.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 4.18 cfs System OK(Excess Capacity) Velocity = 0.29 fps Number of Traps = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 12 Prepared By:Riley Langan Impervious Area = 47,618 sf Date:09/28/2021 Pervious Area = 8,985 sf Project#: 120124 lArea = 56,603 sf lArea = 1.30 acres C Coefficient = 0.83 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 115.00 ft Inf Trench Depth = 9.00 ft Storage Volume of trench = 4140 cf Total Volume = 4,140 cf Infiltration Area = 1,150 sf Infiltration Rate = 767 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 3.36 2,015 128 1,887 15 900 2.62 2.83 2,546 192 2,354 20 1,200 2.28 2.46 2,954 256 2,699 30 1,800 1.82 1.97 3,537 383 3,154 40 2,400 1.37 1.48 3,550 511 3,039 50 3,000 1.17 1.26 3,790 639 3,151 60 3,600 1.15 1.24 4,470 767 120 7,200 0.66 0.71 5,131 1,533 3,598 180 10,800 0.48 0.52 5,597 2,300 3,297 360 21,600 0.30 0.32 6,997 4,600 2,397 720 43,200 0.19 0.21 8,863 9,200 -337 1,440 86,400 0.12 0.13 11,195 18,400 -7,205 System Checks Maximum Runoff Developed = 3,704 cf Total Volume Provided = 4,140 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 3,704 cf Other Sources = 0 cf Percolation Volume = 3,704 cf Recovery Time = 4.8 hours System Summary: 10.00 ft wide x 9.00 ft deep x 115.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 3.36 cfs System OK(Excess Capacity) Velocity = 0.24 fps Number of Traps = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 13 Prepared By:Riley Langan Impervious Area = 35,752 sf Date:09/28/2021 Pervious Area = 14,276 sf Project#: 120124 lArea = 50,028 sf lArea = 1.15 acres C Coefficient = 0.74 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 95.00 ft Inf Trench Depth = 8.00 ft Storage Volume of trench = 3040 cf Total Volume = 3,040 cf Infiltration Area = 950 sf Infiltration Rate = 633 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 2.63 1,577 106 1,472 15 900 2.62 2.21 1,993 158 1,835 20 1,200 2.28 1.93 2,313 211 2,102 30 1,800 1.82 1.54 2,769 317 2,452 40 2,400 1.37 1.16 2,779 422 2,357 50 3,000 1.17 0.99 2,967 528 2,439 60 3,600 1.15 0.97 3,499 633 2,866 120 7,200 0.66 0.56 4,017 1,267 2,750 180 10,800 0.48 0.41 4,382 1,900 2,482 360 21,600 0.30 0.25 5,477 3,800 1,677 720 43,200 0.19 0.16 6,938 7,600 -662 1,440 86,400 0.12 0.10 8,764 15,200 -6,436 System Checks Maximum Runoff Developed = 2,866 cf Total Volume Provided = 3,040 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 2,866 cf Other Sources = 0 cf Percolation Volume = 2,866 cf Recovery Time = 4.5 hours System Summary: 10.00 ft wide x 8.00 ft deep x 95.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 2.63 cfs System OK(Excess Capacity) Velocity = 0.19 fps Number of Traps = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx 0K Drainage Calculations �� R Basin Developed Volume �M THE LAND GROUP,INC. Seasons at Meridian - Area 14 Prepared By:Riley Langan Impervious Area = 24,064 sf Date:09/28/2021 Pervious Area = 12,098 sf Project#: 120124 lArea = 36,162 sf lArea = 0.83 acres C Coefficient = 0.70 Drainage System Characteristics System Infiltration Rate = 8.00 in./hr Swale Top Area = - sf Swale Bottom Area = - sf Swale Depth = 0.00 ft Swale Volume = - cf Inf Trench Width = 10.00 ft Inf Trench Length = 100.00 ft Inf Trench Depth = 5.00 ft Storage Volume of trench = 2000 cf Total Volume = 2,000 cf Infiltration Area = 1,000 sf Infiltration Rate = 667 cf/hr Storage Volume Required (100-yr Storm) (based on Zone"A"IDF Curve, 100-yr Return Period) Intensity Time(min) Time(sec) (in/hr) Q dev.(cfs) V dev.(cf) V inf.(cf) Vs(cf) 10 600 3.11 1.80 1,083 111 972 15 900 2.62 1.52 1,368 167 1,202 20 1,200 2.28 1.32 1,588 222 1,366 30 1,800 1.82 1.06 1,901 333 1,568 40 2,400 1.37 0.80 1,908 444 1,464 50 3,000 1.17 0.68 2,037 556 1,482 60 3,600 1.15 0.67 2,403 667 120 7,200 0.66 0.38 2,758 1,333 1,425 180 10,800 0.48 0.28 3,009 2,000 1,009 360 21,600 0.30 0.17 3,761 4,000 -239 720 43,200 0.19 0.11 4,764 8,000 -3,236 1,440 86,400 0.12 0.07 6,017 16,000 -9,983 System Checks Maximum Runoff Developed = 1,736 cf Total Volume Provided = 2,000 cf System OK(Excess Capacity) System Recovery Maximum Runoff = 1,736 cf Other Sources = 0 cf Percolation Volume = 1,736 cf Recovery Time = 2.6 hours System Summary: 10.00 ft wide x 5.00 ft deep x 100.00 ft long Sand & Grease Trap: 1500-Gal 1000-Gal Trap Size 1000-Gal 7.08 sf Maximum Discharge = 1.80 cfs System OK(Excess Capacity) Velocity = 0.13 fps Number of Traps = 2 CD Seasons at Meridian SeepageBedSizing 120124.xlsx ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. rge Rate using th r post-developm Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seasons at Meridian 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) 3 Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 30 5 Area of Drainage Subbasin(SF or Acres) SF 12,376 1,625 Acres 0.32 6 Determine the Weighted Runoff Coefficient(C) 0.95 0.20 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.86 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 user Calculate min i0 Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"I 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in/hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) QPeak 0.72 Cfs Urban neighborhoods 0.50-0.70 Residential 10 Calculate total runoff vol(V)(for sizing primary storage) V 959 ft Single Family 0.35-0.50Multi-family 0.60-0.75 V=Ci(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Light areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 599 W Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,cemeteries 0. Playgrounds 0.20-0.0-0.35 5 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 095 Basin Foreba V 96 ft' . Y Concrete 0.95 Primary Treatment/StorageBasin V 863 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Gravel Volume Without Sediment Factor(See BMP 20 Tab) V 959 ft' Fields:Sandy soil Soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 0. Adapted from ASCE G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcs 120124.xlsm 9/28/2021,9:28 AM Version 10.5,November 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. rge Rate using th r post-developm Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seasons at Meridian,Facility 2 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 21,006 3,574 Acres 0.56 6 Determine the Weighted Runoff Coefficient(C) 0.95 0.20 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.84 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 user calculate min 10 Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"I 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qpeak 1.22 cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) 640 ft Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in fight areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 1,025 ft' Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cis Parks,Cemeteries 0.10-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Basin Foreba V 164 ft, Asphalt 0.95 Y Concrete 0.95 Primary Treatment/StorageBasin V 1,476 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Volume Without Sediment Factor(See BMP 20 Tab) V 1,640 ft, Gravel 0.75 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0. Steep:>6% 0.13 0.18 0.23 0. Adapted from ASCE G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcs 120124.xlsm 9/28/2021,9:28 AM Version 10.5,November 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. rge Rate using th r post-developm Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seasons at Meridian,Facility 3 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 22,268 7,686 Acres 0.69 6 Determine the Weighted Runoff Coefficient(C) 0.95 0.20 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.76 7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 user calculate min 10 Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"I 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i &.534 in hr Business Downtown areas 0.70-0.95 9 Calculate the Post-Development peak discharge(QPeak) Qpeak cfs Urban neighborhoods 0.50-0.70 Residential Single Family 0.35-0.50 10 Calculate total runoff vol(V)(for sizing primary storage) ft Multi-family 0.60-0.75 V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40 11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70 Industrial and Commercial Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in fight areas 0.80 Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 1,125 ft' Heavy areas 0.90 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cis Parks,Cemeteries 0.10-0.25 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Basin Foreba V 180 ft` Asphalt 0.95 Y Concrete 0.95 Primary Treatment/StorageBasin V 1,620 ft' Brick 0.95 Subsurface Storage Roofs 0.95 Volume Without Sediment Factor(See BMP 20 Tab) V 1,800 ft, Gravel 0.75 Fields:Sandy soil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 O. Average:2-6% 0.09 0.12 0.15 O. Steep:>6% 0.13 0.18 0.23 O. Adapted from ASCE G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcs 120124.xlsm 9/28/2021,9:28 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seasons at Meridian,Seepage Bed A 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.86 Link to: Lqv 5 Area A(Acres) 0.32 acres Q,v3 6 Approved discharge rate(if applicable) 0.00 cfs avrass 7 Is Seepage Bed in Common Lot? No V 1,198 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 10.0 ft 9 Set Total Design Depth of All Drain Rock D 3.3 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr 12 Size of WQ Perf Pipe(Pert 1800) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 3600),READ if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 20.0 Oft 15 Calculate Design Length L 0 60 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 60 ft 17 Variable Infiltration Window W SWW 10.0 ft 18 Time to Drain 2.7 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 60 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxV(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ftz 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcs 120124.xism 9/28/2021,9:28 AM Version 10.0,May 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seasons at Meridian,Seepage Bed B 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.84 Link to: qv Qv2�n 5 Area A(Acres) 0.56 acres a,v3 6 Approved discharge rate(if applicable) 0.00 cfs avrass 7 Is Seepage Bed in Common Lot? No V 2,050 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 10.0 ft 9 Set Total Design Depth of All Drain Rock D 7.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr 12 Size of WQ Perf Pipe(Pert 1800) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 3600),READ if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 34.8 Oft 15 Calculate Design Length L 0 60 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 60 ft 17 Variable Infiltration Window W SWW 10.0 ft 18 Time to Drain 4.6 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 60 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxV(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ftz 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcs 120124.xism 9/28/2021,9:28 AM Version 10.0,May 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seasons at Meridian,Seepage Bed C 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.76 Link to: Qv 5 Area A(Acres) 0.69 acres lqvl� 6 Approved discharge rate(if applicable) 0.00 cfs avrass 7 Is Seepage Bed in Common Lot? No V 2,250 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 6.0 ft 9 Set Total Design Depth of All Drain Rock D 10.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr 12 Size of WQ Perf Pipe(Pert 1800) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 3600),READ if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 28.2 Oft 15 Calculate Design Length L 0 80 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 80 ft 17 Variable Infiltration Window W SWW 6.0 ft 18 Time to Drain 6.3 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 80 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxV(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ftz 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcs 120124.xism 9/28/2021,9:28 AM Version 10.0,May 2018 ACHD Calculation Sheet for Sand/Grease Traps NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. User input in yellow cells. 1 Project Name Seasons at Meridian,S&G-A 2 Enter number of Sand/Grease Traps(25 max) 1 Number of Peak Flow Baffle Throat Velocity Is the Vault Size Spacing width Area(ftZ) 0.5 fps Velocity S/G Traps Q-cfs inch inch max. ok? 1000 G 1 0.715612 20 51 7.08 0.10 Reference for Throat widths(inch) ADS Boise Lar-ken WQU, Vault BMP 16 1000 G 48.0 50.5 n/a 1500 G 60.0 61.5 n/a WQU1000 n/a n/a 60 WQU1500 n/a n/a 60 G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcg/2Z020a:K19YH AM Version 10.0, May 2018 ACHD Calculation Sheet for Sand/Grease Traps NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. User input in yellow cells. 1 Project Name Seasons at Meridian,S&G-B 2 Enter number of Sand/Grease Traps(25 max) 1 Number of Peak Flow Baffle Throat Velocity Is the Vault Size Spacing width Area(ftZ) 0.5 fps Velocity S/G Traps Q-cfs inch inch max. ok? 1000 G 1 1.224286 20 51 7.08 0.17 Reference for Throat widths(inch) ADS Boise Lar-ken WQU, Vault BMP 16 1000 G 48.0 50.5 n/a 1500 G 60.0 61.5 n/a WQU1000 n/a n/a 60 WQU1500 n/a n/a 60 G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcg/2Z020a:�19YH AM Version 10.0, May 2018 ACHD Calculation Sheet for Sand/Grease Traps NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. User input in yellow cells. 1 Project Name Seasons at Meridian,S&G-C 2 Enter number of Sand/Grease Traps(25 max) 1 Number of Peak Flow Baffle Throat Velocity Is the Vault Size Spacing width Area(ftZ) 0.5 fps Velocity S/G Traps Q-cfs inch inch max. ok? 1000 G 1 1.344005 20 51 7.08 0.19 Reference for Throat widths(inch) ADS Boise Lar-ken WQU, Vault BMP 16 1000 G 48.0 50.5 n/a 1500 G 60.0 61.5 n/a WQU1000 n/a n/a 60 WQU1500 n/a n/a 60 G:\2020\120124\CAD\Calcs and Reports\Storm\SD Report Supporting Documents\Seasons at Meridian ACHD SD Calcg/2Z020a:K19YH AM Version 10.0, May 2018 Seasons at Meridian 2700 E. Overland Road, Meridian, ID 83642 Storm Water Management & Engineered Drainage Report Appendix C Geotechnical Report THE LAND 462 East Shore Drive, Suite 100, Eagle, Idaho 83616 208.939.4041 - thelandgroupine.com LE GROUP S r L f F_I�T'•� + 4 , . -5t w , r - _ GEOTECHNICAL INVESTIGATION PROPOSED MIXED-USE DEVELOPMENT 2700 East Overland Road Meridian, ID PREPARED FOR: Mr. Blake Morgan Morgan Holdings, LLC 2223 Avenida de la Playa, Suite 350 La Jolla, CA 92037 PREPARED BY: Atlas Technical Consultants, LLC October 19, 2020 2791 South Victory View Way Boise, ID 83709 B201400g EVE Z 2791 South Victory View Way (208)376-4748 1 oneatlas.com October 19, 2020 Atlas No. B201400g Mr. Blake Morgan Morgan Holdings, LLC 2223 Avenida de la Playa, Suite 350 La Jolla, CA 92037 Subject: Geotechnical Investigation Proposed Mixed-Use Development 2700 East Overland Road Meridian, ID Dear Mr. Morgan: In compliance with your instructions, Atlas has conducted a soils exploration and foundation evaluation for the above referenced development. Fieldwork for this investigation was conducted on October 5, 2020. Data have been analyzed to evaluate pertinent geotechnical conditions. Results of this investigation, together with our recommendations, are to be found in the following report. We have provided a PDF copy for your review and distribution. Often, questions arise concerning soil conditions because of design and construction details that occur on a project. Atlas would be pleased to continue our role as geotechnical engineers during project implementation. If you have any questions, please call us at (208) 376-4748. Respectfully submitted, SS\OSAL F� ,\CENSFD Q 14919 ' 10-19-20 Weston Jorgenson, GIT Monica Saculles, P T9TF of \oP��C-� Staff Geologist Senior GeotechnicaI SAO��'\<`' Page 1 �TrTG7T�1 CONTENTS 1. INTRODUCTION................................................................................................................. 1 1.1 Project Description ..................................................................................................... 1 1.2 Authorization .............................................................................................................. 1 1.3 Scope of Investigation................................................................................................ 1 2. SITE DESCRIPTION........................................................................................................... 2 2.1 Site Access ................................................................................................................ 2 2.2 Regional Geology....................................................................................................... 2 2.3 General Site Characteristics....................................................................................... 2 2.4 Regional Site Climatology and Geochemistry............................................................. 3 3. SEISMIC SITE EVALUATION ............................................................................................ 3 3.1 Geoseismic Setting .................................................................................................... 3 3.2 Seismic Design Parameter Values ............................................................................. 3 4. SOILS EXPLORATION....................................................................................................... 4 4.1 Exploration and Sampling Procedures........................................................................ 4 4.2 Laboratory Testing Program....................................................................................... 4 4.3 Soil and Sediment Profile........................................................................................... 5 4.4 Volatile Organic Scan................................................................................................. 5 5. SITE HYDROLOGY............................................................................................................ 5 5.1 Groundwater.............................................................................................................. 5 5.2 Soil Infiltration Rates .................................................................................................. 6 F- FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS............................ 6 6.1 Foundation Design Recommendations....................................................................... 7 6.2 Foundation Drain Recommendations ......................................................................... 8 6.3 Floor Slab-on-Grade................................................................................................... 8 7. PAVEMENT DISCUSSION AND RECOMMENDATIONS................................................... 9 7.1 Flexible Pavement Sections ....................................................................................... 9 7.2 Pavement Subgrade Preparation ..............................................................................10 7.3 Common Pavement Section Construction Issues......................................................10 8. CONSTRUCTION CONSIDERATIONS .............................................................................10 8.1 Earthwork..................................................................................................................10 8.2 Dry Weather..............................................................................................................11 8.3 Wet Weather.............................................................................................................11 8.4 Soft Subgrade Soils...................................................................................................11 8.5 Frozen Subgrade Soils..............................................................................................12 8.6 Structural Fill .............................................................................................................12 8.7 Backfill of Walls.........................................................................................................13 8.8 Excavations...............................................................................................................14 Atlas No. 13201400g Page I i Copyright©2020 Atlas Technical Consultants �M" ■ �TrTG7T-Zr-_. 8.9 Groundwater Control.................................................................................................14 9. GENERAL COMMENTS....................................................................................................15 10. REFERENCES.................................................................................................................16 TABLES Table 1 — Seismic Design Values................................................................................................4 Table2 — Groundwater Data.......................................................................................................6 Table 3 — Soil Bearing Capacity..................................................................................................7 Table 4 —AASHTO Flexible Pavement Specifications.................................................................9 APPENDICES Appendix I Warranty and Limiting Conditions Appendix II Vicinity Map Appendix III Site Map Appendix IV Geotechnical Investigation Test Pit Log Appendix V Geotechnical General Notes Appendix VI AASHTO Pavement Thickness Design Procedures Appendix VI Important Information About This Geotechnical Engineering Report Atlas No. 13201400g Page I ii Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 1. INTRODUCTION This report presents results of a geotechnical investigation and analysis in support of data utilized in design of structures as defined in the 2015 International Building Code (IBC). Information in support of groundwater and stormwater issues pertinent to the practice of Civil Engineering is included. Observations and recommendations relevant to the earthwork phase of the project are also presented. Revisions in plans or drawings for the proposed development from those enumerated in this report should be brought to the attention of the soils engineer to determine whether changes in the provided recommendations are required. Deviations from noted subsurface conditions, if encountered during construction, should also be brought to the attention of the soils engineer. 1.1 Project Description The proposed development is in the southern portion of the City of Meridian, Ada County, ID, and occupies a portion of the SW'/4SE'/4 of Section 17, Township 3 North, Range 1 East, Boise Meridian. This project will consist of construction of several 3-story, multi-family apartment structures and a series of retail structures to be developed on approximately 15.885 acres. Total settlements are limited to 1 inch. Loads of up to 4,000 pounds per lineal foot for wall footings, and column loads of up to 50,000 pounds were assumed for settlement calculations. Additionally, assumptions have been made for traffic loading of pavements. Retaining walls are not anticipated as part of the project. Atlas has not been informed of the proposed grading plan. 1.2 Authorization Authorization to perform this exploration and analysis was given in the form of a written authorization to proceed from Mr. Blake Morgan of Morgan Holdings, LLC to Elizabeth Brown of Atlas Technical Consultants (Atlas), on August 25, 2020. Said authorization is subject to terms, conditions, and limitations described in the Professional Services Contract entered into between Morgan Holdings, LLC and Atlas. Our scope of services for the proposed development has been provided in our proposal dated August 18, 2020 and repeated below. 1.3 Scope of Investigation The scope of this investigation included review of geologic literature and existing available geotechnical studies of the area, visual site reconnaissance of the immediate site, subsurface exploration of the site,field and laboratory testing of materials collected, and engineering analysis and evaluation of foundation materials. The scope of work did not include design recommendations specific to individual structures. Atlas No. B201400g Page11 Copyright©2020 Atlas Technical Consultants �TWPM M1`a�11 2. SITE DESCRIPTION 2.1 Site Access Access to the site may be gained via Interstate 84 to the Eagle Road exit. Proceed south on Eagle Road and immediately turn west on Overland Road. Travel west on Overland Road approximately 0.3 mile to the site, which is situated to the north of the roadway. The location is depicted on site map plates included in the Appendix. 2.2 Regional Geology The project site is located within the western Snake River Plain of southwestern Idaho and eastern Oregon. The plain is a northwest trending rift basin, about 45 miles wide and 200 miles long, that developed about 14 million years ago (Ma) and has since been occupied sporadically by large inland lakes. Geologic materials found within and along the plain's margins reflect volcanic and fluvial/lacustrine sedimentary processes that have led to an accumulation of approximately 1 to 2 km of interbedded volcanic and sedimentary deposits within the plain. Along the margins of the plain, streams that drained the highlands to the north and south provided coarse to fine-grained sediments eroded from granitic and volcanic rocks, respectively. About 2 million years ago the last of the lakes was drained and since that time fluvial erosion and deposition has dominated the evolution of the landscape. The project site is underlain by "Gravel of Sunrise Terrace" as mapped by Othberg and Stanford (1993). The Sunrise terrace is the third terrace above the modern Boise River in the eastern Boise Valley, composed of sandy pebble and cobble gravel, and is about 115 feet above river level. Quaternary faulting has probably truncated and tilted this terrace along with older surfaces. The surface of this deposit is mantled with 3-7 feet of loess containing a weakly to moderately developed duripan. Based on stratigraphic correlation the Sunrise terrace may be correlative with the Wilder terrace further to the west. 2.3 General Site Characteristics The site to be developed is approximately 15.885 acres in size. Currently, the site exists as an agricultural field. At the present time, vegetation on the site is limited to weeds and grasses along the north, east, and south property edges. The site is relatively flat and level. Regional drainage is north and west toward the Boise River. Stormwater drainage for the site is achieved by percolation through surficial soils. The site is situated so that it is unlikely that it will receive any drainage from off-site sources. Stormwater drainage collection and retention systems are not in place on the project site, but currently exist within the vicinity of the project site in the form of curbs, gutters, and drain inlets on Overland Road. Atlas No. B201400g Page12 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 2.4 Regional Site Climatology and Geochemistry According to the Western Regional Climate Center, the average precipitation for the Treasure Valley is on the order of 10 to 12 inches per year, with an annual snowfall of approximately 20 inches and a range from 3 to 49 inches. The monthly mean daily temperatures range from 21°F to 95°F, with daily extremes ranging from roughly -25°F to 111°F. Winds are generally from the northwest or southeast with an annual average wind speed of approximately 9 miles per hour (mph) and a maximum of 62 mph. Soils and sediments in the area are primarily derived from siliceous materials and exhibit low electro-chemical potential for corrosion of metals or concretes. Local aggregates are generally appropriate for Portland cement and lime cement mixtures. Surface water, groundwater, and soils in the region typically have pH levels ranging from 7.2 to 8.2. 3. SEISMIC SITE EVALUATION 3.1 Geoseismic Setting Soil on site are classed as Site Class D in accordance with Chapter 20 of the American Society of Civil Engineers (ASCE) publication ASCE/SEI 7-10. Structures constructed on this site should be designed per IBC requirements for such a seismic classification. Our investigation did not reveal hazards resulting from potential earthquake motions including: slope instability, liquefaction, and surface rupture caused by faulting or lateral spreading. Incidence and anticipated acceleration of seismic activity in the area is low. 3.2 Seismic Design Parameter Values The United States Geological Survey National Seismic Hazard Maps (2008), includes a peak ground acceleration map. The map for 2% probability of exceedance in 50 years in the Western United States in standard gravity (g) indicates that a peak ground acceleration of 0.180 is appropriate for the project site based on a Site Class D. The following section provides an assessment of the earthquake-induced earthquake loads for the site based on the Risk-Targeted Maximum Considered Earthquake (MCER). The MCER spectral response acceleration for short periods, SMs, and at 1-second period, SMI, are adjusted for site class effects as required by the 2015 IBC. Design spectral response acceleration parameters as presented in the 2015 IBC are defined as a 5% damped design spectral response acceleration at short periods, SDs, and at 1-second period, SDI. The USGS National Seismic Hazards Mapping Project includes a program that provides values for ground motion at a selected site based on the same data that were used to prepare the USGS ground motion maps. The maps were developed using attenuation relationships for soft rock sites; the source model, assumptions, and empirical relationships used in preparation of the maps are described in Petersen and others (1996). Atlas No. B201400g Page 13 Copyright©2020 Atlas Technical Consultants �TrTG7Tdr-W1 Table 1 - Seismic Design Values Seismic Design Parameter Design Value Site Class D "Stiff Soil' Ss 0.291 (g) S1 0.102 (g) Fa 1.567 Fv 2.392 SMs 0.456 SMi 0.244 Sos 0.304 Sol 0.163 4. SOILS EXPLORATION 1 Exploration and Sampling Procedures Field exploration conducted to determine engineering characteristics of subsurface materials included a reconnaissance of the project site and investigation by test pit. Test pit sites were located in the field by means of a Global Positioning System (GPS) device and are reportedly accurate to within fifteen feet. Upon completion of investigation, each test pit was backfilled with loose excavated materials. Re-excavation and compaction of these test pit areas are required prior to construction of overlying structures. In addition, samples were obtained from representative soil strata encountered. Samples obtained have been visually classified in the field by professional staff, identified according to test pit number and depth, placed in sealed containers, and transported to our laboratory for additional testing. Subsurface materials have been described in detail on logs provided in the Appendix. Results of field and laboratory tests are also presented in the Appendix. Atlas recommends that these logs not be used to estimate fill material quantities. 4.2 Laboratory Testing Program Along with our field investigation, a supplemental laboratory testing program was conducted to determine additional pertinent engineering characteristics of subsurface materials necessary in an analysis of anticipated behavior of the proposed structures. Laboratory tests were conducted in accordance with current applicable American Society for Testing and Materials (ASTM) specifications, and results of these tests are to be found in the Appendix. The laboratory testing program for this report included: Atterberg Limits Testing -ASTM D4318 and Grain Size Analysis -ASTM C117/C136. Atlas No. B201400g Page14 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 4.3 Soil and Sediment Profile The profile below represents a generalized interpretation for the project site. Note that on site soils strata, encountered between test pit locations, may vary from the individual soil profiles presented in the logs, which can be found in the Appendix. The materials encountered during exploration were quite typical for the geologic area mapped as Gravel of Sunrise Terrace. Lean clays encountered at ground surface across the site. These fine-grained soils were brown to light brown, dry to slightly moist, and ranged from medium stiff to very stiff. Below these surficial materials, various silt and sand mixtures were encountered. These soils were noted to be gray to tan to light brown, dry to slightly moist, very stiff to hard/loose to dense, and contained fine to coarse-grained sand. Fine to coarse gravel was also noted within these soils in test pit 3. Weak to moderate calcium carbonate cementation was noted throughout this soil horizon. At depth, poorly graded gravel with sand sediments were exposed. Poorly graded gravels were light brown to brown to gray, dry to slightly moist, and dense to very dense. Fine to coarse- grained sand, fine to coarse gravel, and 12-inch minus cobbles were noted throughout. Weak to strong calcium carbonate cementation was noted generally within the upper few feet of these gravels. Competency of test pit sidewalls varied little across the site. In general, fine grained soils remained stable while more granular sediments readily sloughed. However, moisture contents will also affect wall competency with saturated soils having a tendency to readily slough when under load and unsupported. 4.4 Volatile Organic Scan No environmental concerns were identified prior to commencement of the investigation. Therefore, soils obtained during on-site activities were not assessed for volatile organic compounds by portable photoionization detector. Samples obtained during our exploration activities exhibited no odors or discoloration typically associated with this type of contamination. No groundwater was encountered. 5. SITE HYDROLOGY Existing surface drainage conditions are defined in the General Site Characteristics section. Information provided in this section is limited to observations made at the time of the investigation. Either regional or local ordinances may require information beyond the scope of this report. 5.1 Groundwater During this field investigation, groundwater was not encountered in test pits advanced to a maximum depth of 16.2 feet bgs. Soil moistures in the test pits were generally dry to slightly moist throughout. In the vicinity of the project site, groundwater levels are controlled in large part by residential and commercial irrigation activity and leakage from nearby canals. Maximum groundwater elevations likely occur during the later portion of the irrigation season. Atlas No. B201400g Page 15 Copyright©2020 Atlas Technical Consultants -rr/�M" ■ Atlas has previously performed 7 geotechnical investigations within 0.50 mile of the project site. Information from these investigations has been provided in the table below. Table 2 — Groundwater Data Date Approximate Distance Direction from Site GroundwaterDepth from Site (mile) (feet .. July 2006 0.32 West Not Encountered to 13.7 August 2004 0.32 West Not Encountered to 15.0 October 2005 0.42 Southwest Not Encountered to 16.5 June 2017 0.20 Southwest Not Encountered to 15.2 June 2006 0.45 South Not Encountered to 12.4 February 2017 0.20 East Not Encountered to 15.7 December 2017 0.45 East 17.5 to 17.9 Based on evidence of this investigation and background knowledge of the area, Atlas estimates groundwater depths to remain greater than approximately 15 feet bgs throughout the year. 1.2 Soil Infiltration Rates Soil permeability, which is a measure of the ability of a soil to transmit a fluid, was not tested in the field. Given the absence of direct measurements, for this report an estimation of infiltration is presented using generally recognized values for each soil type and gradation. Of soils comprising the generalized soil profile for this study, lean clay soils generally offer little permeability, with typical hydraulic infiltration rates of less than 2 inches per hour. Sandy silt soils will commonly exhibit infiltration rates from 2 to 4 inches per hour and silty sand sediments usually display rates of 4 to 8 inches per hour. Poorly graded gravel sediments typically exhibit infiltration values in excess of 12 inches per hour. Varying degrees of calcium carbonate cementation were noted within many of the soils encountered. If present, cementation may reduce these values to near zero. It is recommended that infiltration facilities constructed on the site be extended into native non- cemented poorly graded gravel with sand sediments. Excavation depths ranging from 8.3 to greater than 12.4 feet bgs should be anticipated to expose these poorly graded gravel with sand sediments. Because of the high soil permeability, ASTM C33 filter sand, or equivalent, should be incorporated into design of infiltration facilities. An infiltration rate of 8 inches per hour should be used in design. Actual infiltration rates should be confirmed at the time of construction. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS Various foundation types have been considered for support of the proposed structures. Two requirements must be met in the design of foundations. First, the applied bearing stress must be less than the ultimate bearing capacity of foundation soils to maintain stability. Second, total and differential settlement must not exceed an amount that will produce an adverse behavior of the superstructure. Atlas No. B201400g Page 16 Copyright©2020 Atlas Technical Consultants �TWPM M1`a�11 Allowable settlement is usually exceeded before bearing capacity considerations become important; thus, allowable bearing pressure is normally controlled by settlement considerations. Considering subsurface conditions and the proposed construction, it is recommended that the structures be founded upon conventional spread footings and continuous wall footings. Total settlements should not exceed 1 inch if the following design and construction recommendations are observed. 6.1 Foundation Design Recommendations Based on data obtained from the site and test results from various laboratory tests performed, Atlas recommends the following guidelines for the net allowable soil bearing capacity: Table 3 — Soil Bearing Capacity FootingASTM D1557 Net Allowable Soil Subgrade CompactionCapacity Footings must bear on competent, undisturbed, 1,500 Ibs/ft2 native lean clay soils or compacted structural fill. Not Required for Native q , Existing organics and disturbed zone (plow depths) Soil A /3 increase is allowable must be completely removed from below foundation for short-term loading, elements.' An excavation depth of approximately 95% for Structural Fill which is defined by 1.0 foot bgs should be anticipated to expose proper seismic events or bearing soils.2 designed wind speeds. Footings must bear on competent, undisturbed, native cemented sandy silt or silty sand soils or Not Required for Native compacted structural fill. Existing lean clay soils Soil must be completely removed from below foundation 2,500 Ibs/ft2 elements.' Excavation depths ranging from roughly 95% for Structural Fill 1.3 to 2.1 feet bgs should be anticipated to expose proper bearing soils.2 'It will be required for Atlas personnel to verify the bearing soil suitability for each structure at the time of construction. 2Depending on the time of year construction takes place,the subgrade soils may be unstable because of high moisture contents. If unstable conditions are encountered,over-excavation and replacement with granular structural fill and/or use of geotextiles may be required. The following sliding frictional coefficient values should be used: 1) 0.35 for footings bearing on native lean clay or sandy silt/silty sand soils and 2)0.45 for footings bearing on granular structural fill. A passive lateral earth pressure of 349 pounds per square foot per foot(psf/ft) should be used for sandy silt/silty sand soils. For compacted sandy gravel fill, a passive lateral earth pressure of 496 psf/ft should be used. Footings should be proportioned to meet either the stated soil bearing capacity or the 2015 IBC minimum requirements. Total settlement should be limited to approximately 1 inch, and differential settlement should be limited to approximately '/2 inch. Objectionable soil types encountered at the bottom of footing excavations should be removed and replaced with structural fill. Atlas No. 13201400g Page 17 Copyright©2020 Atlas Technical Consultants �TWPM M1`a�11 Excessively loose or soft areas that are encountered in the footings subgrade will require over- excavation and backfilling with structural fill. To minimize the effects of slight differential movement that may occur because of variations in the character of supporting soils and seasonal moisture content, Atlas recommends continuous footings be suitably reinforced to make them as rigid as possible. For frost protection, the bottom of external footings should be 30 inches below finished grade. 6.2 Foundation Drain Recommendations Considering the presence of shallow cemented soils across the site, Atlas recommends that foundation drains be installed. The drains should be placed at the footing elevation, sloped at least 2 percent, and be directed to suitable discharge points at least 10 feet away from the structures. Discharge points should be protected to prevent erosion. 6.3 Floor Slab-on-Grade Plow zones with organic materials were encountered in portions of the site. Atlas recommends that the organic materials be removed. If plow zones remain after organic materials have been removed, the exposed subgrade must be compacted to at least 95 percent of the maximum dry density as determined by ASTM D1557. Atlas personnel must be present during excavation to identify these materials. Organic, loose, or obviously compressive materials must be removed prior to placement of concrete floors or floor-supporting fill. In addition, the remaining subgrade should be treated in accordance with guidelines presented in the Earthwork section. Areas of excessive yielding should be excavated and backfilled with structural fill. Fill used to increase the elevation of the floor slab should meet requirements detailed in the Structural Fill section. Fill materials must be compacted to a minimum 95 percent of the maximum dry density as determined by ASTM D1557. A free-draining granular mat should be provided below slabs-on-grade to provide drainage and a uniform and stable bearing surface. This should be a minimum of 4 inches in thickness and properly compacted. The mat should consist of a sand and gravel mixture, complying with Idaho Standards for Public Works Construction (ISPWC) specifications for %-inch (Type 1) crushed aggregate. The granular mat should be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D1557. A moisture-retarder should be placed beneath floor slabs to minimize potential ground moisture effects on moisture-sensitive floor coverings. The moisture-retarder should be at least 15-mil in thickness and have a permeance of less than 0.01 US perms as determined by ASTM E96. Placement of the moisture-retarder will require special consideration with regard to effects on the slab-on-grade and should adhere to recommendations outlined in the ACI 302.1 R and ASTM E1745 publications. Upon request, Atlas can provide further consultation regarding installation. Atlas No. B201400g Page 18 Copyright©2020 Atlas Technical Consultants �TrTG7T_�. '. PAVEMENT DISCUSSION AND RECOMMENDATIONS Atlas has made assumptions for traffic loading variables based on the character of the proposed construction. The Client shall review and understand these assumptions to make sure they reflect intended use and loading of pavements both now and in the future. Based on experience with soils in the region, a subgrade California Bearing Ratio (CBR) value of 4 has been assumed for near-surface clay soils on site. The following are minimum thickness requirements for assured pavement function. Depending on site conditions, additional work, e.g. soil preparation, may be required to support construction equipment. These have been listed within the Soft Subgrade Soils section. 7.1 Flexible Pavement Sections The American Association of State Highway and Transportation Officials (AASHTO) design method has been used to calculate the following pavement sections. Calculation sheets provided in the Appendix indicate the soils constant, traffic loading, traffic projections, and material constants used to calculate the pavement sections. Atlas recommends that materials used in the construction of asphaltic concrete pavements meet requirements of the ISPWC Standard Specification for Highway Construction. Construction of the pavement section should be in accordance with these specifications and should adhere to guidelines recommended in the section on Construction Considerations. Table 4—AASHTO Flexible Pavement Specifications Pavement Section Component JrDriveways • Parking Driveways and ModerateLight Duty Asphaltic Concrete 2.5 Inches 3.0 Inches Crushed Aggregate Base 4.0 Inches 4.0 Inches Structural Subbase 10.0 Inches 12.0 Inches Compacted Subgrade See Pavement Subgrade See Pavement Subgrade Preparation Section Preparation Section 'It will be required for Atlas personnel to verify subgrade competency at the time of construction. Asphaltic Concrete: Asphalt mix design shall meet the requirements of ISPWC, Section 810 Class III plant mix. Materials shall be placed in accordance with ISPWC Standard Specifications for Highway Construction. Aggregate Base: Material complying with ISPWC Standards for Crushed Aggregate Materials. Structural Subbase: Granular structural fill material complying with the requirements detailed in the Structural Fill section of this report except that the maximum material diameter is no more than 2/3 the component thickness. Gradation and suitability requirements shall be per ISPWC Section 801, Table 1. Atlas No. 13201400g Page 19 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 7.2 Pavement Subgrade Preparation Plow zones with organic materials were encountered across the site. Atlas recommends that the organic materials be removed. If plow zones remain after organic materials have been removed, the exposed subgrade must be compacted to at least 95 percent of the maximum dry density as determined by ASTM D698. Atlas personnel must be present during excavation to identify these materials. 7.3 Common Pavement Section Construction Issues The subgrade upon which above pavement sections are to be constructed must be properly stripped, inspected, and proof-rolled. Proof rolling of subgrade soils should be accomplished using a heavy rubber-tired, fully loaded, tandem-axle dump truck or equivalent. Verification of subgrade competence by Atlas personnel at the time of construction is required. Fill materials on the site must demonstrate the indicated compaction prior to placing material in support of the pavement section. Atlas anticipated that pavement areas will be subjected to moderate traffic. Subgrade clayey and silty soils near and above optimum moisture contents may pump during compaction. Pumping or soft areas must be removed and replaced with structural fill. Fill material and aggregates, in support of the pavement section must be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D698 for flexible pavements and by ASTM D1557 for rigid pavements. If a material placed as a pavement section component cannot be tested by usual compaction testing methods, then compaction of that material must be approved by observed proof rolling. Minor deflections from proof rolling for flexible pavements are allowable. Deflections from proof rolling of rigid pavement support courses should not be visually detectable. Atlas recommends that rigid concrete pavement be provided for heavy garbage receptacles. This will eliminate damage caused by the considerable loading transferred through the small steel wheels onto asphaltic concrete. Rigid concrete pavement should consist of Portland Cement Concrete Pavement (PCCP) generally adhering to ITD specifications for Urban Concrete. PCCP should be 6 inches thick on a 4-inch drainage fill course (see Floor Slab-on-Grade section), and should be reinforced with welded wire fabric. Control joints must be on 12-foot centers or less. CONSTRUCTION CONSIDERATIONS Recommendations in this report are based upon structural elements of the project being founded on competent, native lean clay, sandy silt, or silty sand soils, or compacted structural fill. Structural areas should be stripped to an elevation that exposes these soil types. arthwork Excessively organic soils, deleterious materials, or disturbed soils generally undergo high volume changes when subjected to loads, which is detrimental to subgrade behavior in the area of pavements, floor slabs, structural fills, and foundations. It is recommended that organic or disturbed soils, if encountered, be removed to depths of 1 foot (minimum), and wasted or stockpiled for later use. Atlas No. B201400g Page110 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 Stripping depths should be adjusted in the field to assure that the entire root zone or disturbed zone (plow depths) or topsoil are removed prior to placement and compaction of structural fill materials. Exact removal depths should be determined during grading operations by Atlas personnel, and should be based upon subgrade soil type, composition, and firmness or soil stability. If underground storage tanks, underground utilities, wells, or septic systems are discovered during construction activities, they must be decommissioned then removed or abandoned in accordance with governing Federal, State, and local agencies. Excavations developed as the result of such removal must be backfilled with structural fill materials as defined in the Structural Fill section. Atlas should oversee subgrade conditions (i.e., moisture content) as well as placement and compaction of new fill (if required) after native soils are excavated to design grade. Recommendations for structural fill presented in this report can be used to minimize volume changes and differential settlements that are detrimental to the behavior of footings, pavements, and floor slabs. Sufficient density tests should be performed to properly monitor compaction. For structural fill beneath building structures, one in-place density test per lift for every 5,000 square feet is recommended. In parking and driveway areas, this can be decreased to one test per lift for every 10,000 square feet. 8.2 Dry Weather If construction is to be conducted during dry seasonal conditions, many problems associated with soft soils may be avoided. However, some rutting of subgrade soils may be induced by shallow groundwater conditions related to springtime runoff or irrigation activities during late summer through early fall. Solutions to problems associated with soft subgrade soils are outlined in the Soft Subgrade Soils section. Problems may also arise because of lack of moisture in native and fill soils at time of placement. This will require the addition of water to achieve near-optimum moisture levels. Low-cohesion soils exposed in excavations may become friable, increasing chances of sloughing or caving. Measures to control excessive dust should be considered as part of the overall health and safety management plan. 8.3 Wet Weather If construction is to be conducted during wet seasonal conditions (commonly from mid-November through May), problems associated with soft soils must be considered as part of the construction plan. During this time of year, fine-grained soils such as silts and clays will become unstable with increased moisture content, and eventually deform or rut. Additionally, constant low temperatures reduce the possibility of drying soils to near optimum conditions. 8.4 Soft Subgrade Soils Shallow fine-grained subgrade soils that are high in moisture content should be expected to pump and rut under construction traffic. During periods of wet weather, construction may become very difficult if not impossible. The following recommendations and options have been included for dealing with soft subgrade conditions: Atlas No. B201400g Page 111 Copyright©2020 Atlas Technical Consultants �TWPM M1`a�11 • Track-mounted vehicles should be used to strip the subgrade of root matter and other deleterious debris. Heavy rubber-tired equipment should be prohibited from operating directly on the native subgrade and areas in which structural fill materials have been placed. Construction traffic should be restricted to designated roadways that do not cross, or cross on a limited basis, proposed roadway or parking areas. • Soft areas can be over-excavated and replaced with granular structural fill. • Construction roadways on soft subgrade soils should consist of a minimum 2-foot thickness of large cobbles of 4 to 6 inches in diameter with sufficient sand and fines to fill voids. Construction entrances should consist of a 6-inch thickness of clean, 2-inch minimum, angular drain-rock and must be a minimum of 10 feet wide and 30 to 50 feet long. During the construction process, top dressing of the entrance may be required for maintenance. • Scarification and aeration of subgrade soils can be employed to reduce the moisture content of wet subgrade soils. After stripping is complete, the exposed subgrade should be ripped or disked to a depth of 1'/2 feet and allowed to air dry for 2 to 4 weeks. Further disking should be performed on a weekly basis to aid the aeration process. • Alternative soil stabilization methods include use of geotextiles, lime, and cement stabilization. Atlas is available to provide recommendations and guidelines at your request. 8.5 Frozen Subgrade Soils Prior to placement of structural fill materials or foundation elements, frozen subgrade soils must either be allowed to thaw or be stripped to depths that expose non-frozen soils and wasted or stockpiled for later use. Stockpiled materials must be allowed to thaw and return to near-optimal conditions prior to use as structural fill. The onsite, shallow clayey and silty soils are susceptible to frost heave during freezing temperatures. For exterior flatwork and other structural elements, adequate drainage away from subgrades is critical. Compaction and use of structural fill will also help to mitigate the potential for frost heave. Complete removal of frost susceptible soils for the full frost depth, followed by replacement with a non-frost susceptible structural fill, can also be used to mitigate the potential for frost heave. Atlas is available to provide further guidance/assistance upon request. 8.6 Structural Fill Soils recommended for use as structural fill are those classified as GW, GP, SW, and SP in accordance with the Unified Soil Classification System (USCS) (ASTM D2487). Use of silty soils (USCS designation of GM, SM, and ML) as structural fill may be acceptable. However, use of silty soils (GM, SM, and ML) as structural fill below footings is prohibited. These materials require very high moisture contents for compaction and require a long time to dry out if natural moisture contents are too high and may also be susceptible to frost heave under certain conditions. Therefore, these materials can be quite difficult to work with as moisture content, lift thickness, and compactive effort becomes difficult to control. Atlas No. B201400g Page112 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 If silty soil is used for structural fill, lift thicknesses should not exceed 6 inches (loose), and fill material moisture must be closely monitored at both the working elevation and the elevations of materials already placed. Following placement, silty soils must be protected from degradation resulting from construction traffic or subsequent construction. Recommended granular structural fill materials, those classified as GW, GP, SW, and SP, should consist of a 6-inch minus select, clean, granular soil with no more than 50 percent oversize (greater than 3/4-inch) material and no more than 12 percent fines (passing No. 200 sieve). These fill materials should be placed in layers not to exceed 12 inches in loose thickness. Prior to placement of structural fill materials, surfaces must be prepared as outlined in the Construction Considerations section. Structural fill material should be moisture-conditioned to achieve optimum moisture content prior to compaction. For structural fill below footings, areas of compacted backfill must extend outside the perimeter of the footings for a distance equal to the thickness of fill between the bottom of foundation and underlying soils, or 5 feet, whichever is less. All fill materials must be monitored during placement and tested to confirm compaction requirements, outlined below, have been achieved. Each layer of structural fill must be compacted, as outlined below: • Below Structures and Rigid Pavements: A minimum of 95 percent of the maximum dry density as determined by ASTM D1557. • Below Flexible Pavements: A minimum of 92 percent of the maximum dry density as determined by ASTM D1557 or 95 percent of the maximum dry density as determined by ASTM D698. The ASTM D1557 test method must be used for samples containing up to 40 percent oversize (greater than%-inch) particles. If material contains more than 40 percent but less than 50 percent oversize particles, compaction of fill must be confirmed by proof rolling each lift with a 10-ton vibratory roller(or equivalent) until the maximum density has been achieved. Density testing must be performed after each proof rolling pass until the in-place density test results indicate a drop (or no increase) in the dry density, defined as maximum density or "break over" point. The number of required passes should be used as the requirements on the remainder of fill placement. Material should contain sufficient fines to fill void spaces, and must not contain more than 50 percent oversize particles. 8.7 Backfill of Walls Backfill materials must conform to the requirements of structural fill, as defined in this report. For wall heights greater than 2.5 feet, the maximum material size should not exceed 4 inches in diameter. Placing oversized material against rigid surfaces interferes with proper compaction, and can induce excessive point loads on walls. Backfill shall not commence until the wall has gained sufficient strength to resist placement and compaction forces. Further, retaining walls above 2.5 feet in height shall be backfilled in a manner that will limit the potential for damage from compaction methods and/or equipment. Atlas No. 13201400g Page 113 Copyright©2020 Atlas Technical Consultants �TWPM M1`a�11 It is recommended that only small hand-operated compaction equipment be used for compaction of backfill within a horizontal distance equal to the height of the wall, measured from the back face of the wall. Backfill should be compacted in accordance with the specifications for structural fill, except in those areas where it is determined that future settlement is not a concern, such as planter areas. In nonstructural areas, backfill must be compacted to a firm and unyielding condition. 8.8 Excavations Shallow excavations that do not exceed 4 feet in depth may be constructed with side slopes approaching vertical. Below this depth, it is recommended that slopes be constructed in accordance with Occupational Safety and Health Administration (OSHA) regulations, Section 1926, Subpart P. Based on these regulations, on-site soils are classified as type "C" soil, and as such, excavations within these soils should be constructed at a maximum slope of 1'/2 feet horizontal to 1 foot vertical (11/2:1) for excavations up to 20 feet in height. Excavations in excess of 20 feet will require additional analysis. Note that these slope angles are considered stable for short-term conditions only, and will not be stable for long-term conditions. During the subsurface exploration, test pit sidewalls generally exhibited little indication of collapse; however, sloughing of plow zone materials and native granular sediments from test pit sidewalls was observed. For deep excavations, native granular sediments cannot be expected to remain in position. These materials are prone to failure and may collapse, thereby undermining upper soil layers. This is especially true when excavations approach depths near the water table. Care must be taken to ensure that excavations are properly backfilled in accordance with procedures outlined in this report. 8.9 Groundwater Control It may be possible to discharge dewatering effluent to remote portions of the site, to a sump, or to a pit. This will essentially recycle effluent, thus eliminating the need to enter into agreements with local drainage authorities. Should the scope of the proposed project change, Atlas should be contacted to provide more detailed groundwater control measures. Special precautions may be required for control of surface runoff and subsurface seepage. It is recommended that runoff be directed away from open excavations. Silty and clayey soils may become soft and pump if subjected to excessive traffic during time of surface runoff. Ponded water in construction areas should be drained through methods such as trenching, sloping, crowning grades, nightly smooth drum rolling, or installing a French drain system. Additionally, temporary or permanent driveway sections should be constructed if extended wet weather is forecasted. Atlas No. B201400g Page114 Copyright©2020 Atlas Technical Consultants �TrTG7Tdr—W� 9. GENERAL COMMENTS Based on the subsurface conditions encountered during this investigation and available information regarding the proposed development, the site is adequate for the planned construction. When plans and specifications are complete, and if significant changes are made in the character or location of the proposed structure, consultation with Atlas must be arranged as supplementary recommendations may be required. Suitability of subgrade soils and compaction of structural fill materials must be verified by Atlas personnel prior to placement of structural elements. Additionally, monitoring and testing should be performed to verify that suitable materials are used for structural fill and that proper placement and compaction techniques are utilized. Atlas No. 13201400g Page115 Copyright©2020 Atlas Technical Consultants �TWPM z1`a�11 10. REFERENCES American Association of State Highway and Transportation Officials (AASHTO)(1993). AASHTO Guide for Design of Pavement Structures 1993.Washington D.C.: AASHTO. American Concrete Institute (ACI) (2015). Guide for Concrete Floor and Slab Construction: ACI 302.1R. Farmington Hills, MI:ACI. American Society of Civil Engineers (ASCE) (2013). Minimum Design Loads for Buildings and Other Structures: ASCE/SEI 7-10. Reston,VA:ASCE. American Society for Testing and Materials(ASTM)(2017). Standard Test Method for Materials Finer than 75-um (No. 200)Sieve in Mineral Aggregates by Washing:ASTM C117.West Conshohocken, PA:ASTM. American Society for Testing and Materials (ASTM) (2014). Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates:ASTM C136.West Conshohocken, PA:ASTM. American Society for Testing and Materials (ASTM) (2012). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort:ASTM D698.West Conshohocken, PA:ASTM. American Society for Testing and Materials (ASTM) (2012). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort:ASTM D1557.West Conshohocken, PA:ASTM. American Society for Testing and Materials(ASTM)(2017).Standard Practice for Classification of Soils for Engineering Purposes(Unified Soil Classification System):ASTM D2487.West Conshohocken, PA:ASTM. American Society for Testing and Materials(ASTM)(2017). Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils:ASTM D4318.West Conshohocken, PA:ASTM. American Society for Testing and Materials (ASTM) (2011). Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs:ASTM E1745.West Conshohocken, PA:ASTM. Desert Research Institute.Western Regional Climate Center. [Online]Available: <http://www.wrcc.dri.edu/> (2020). International Building Code Council (2015). International Building Code, 2015. Country Club Hills, IL:Author. Local Highway Technical Assistance Council (LHTAC) (2017). Idaho Standards for Public Works Construction, 2017. Boise, ID:Author. Othberg, K. L. and Stanford, L. A., Idaho Geologic Society (1993). Geologic Map of the Boise Valley and Adloining Area,Western Snake River Plain, Idaho. (scale 1:100,000). Boise, ID: Joslyn and Morris. U.S. Department of Labor, Occupational Safety and Health Administration. CFR 29, Part 1926, Subpart P: Safety and Health Regulations for Construction, Excavations (1986). [Online]Available: <www.osha.gov>(2020). U.S. Geological Survey (2020). National Water Information System: Web Interface. [Online] Available: <http://waterdata.usgs.gov/nwis>(2020). U.S. Geological Survey. (2009). Seismicity of Idaho 1990-2006. [Online] Available: <http://earthquake.usgs.gov/earthquakes/states/Idaho/seismicity.php> (2020). U.S. Geological Survey. (2011). U.S. Seismic Design Maps: Web Interface. [Online] Available: <https://earthquake.usgs.gov/designmaps/us/application.php> (2020). Atlas No. B201400g Page116 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 Appendix I WARRANTY AND LIMITING CONDITIONS Atlas warrants that findings and conclusions contained herein have been formulated in accordance with generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics, and engineering geology only for the site and project described in this report. These engineering methods have been developed to provide the client with information regarding apparent or potential engineering conditions relating to the site within the scope cited above and are necessarily limited to conditions observed at the time of the site visit and research. Field observations and research reported herein are considered sufficient in detail and scope to form a reasonable basis for the purposes cited above. Exclusive Use This report was prepared for exclusive use of the property owner(s), at the time of the report, and their retained design consultants ("Client"). Conclusions and recommendations presented in this report are based on the agreed-upon scope of work outlined in this report together with the Contract for Professional Services between the Client and Materials Testing and Inspection ("Consultant'). Use or misuse of this report, or reliance upon findings hereof, by parties other than the Client is at their own risk. Neither Client nor Consultant make representation of warranty to such other parties as to accuracy or completeness of this report or suitability of its use by such other parties for purposes whatsoever, known or unknown, to Client or Consultant. Neither Client nor Consultant shall have liability to indemnify or hold harmless third parties for losses incurred by actual or purported use or misuse of this report. No other warranties are implied or expressed. Report Recommendations are Limited and Subject to Misinterpretation There is a distinct possibility that conditions may exist that could not be identified within the scope of the investigation or that were not apparent during our site investigation. Findings of this report are limited to data collected from noted explorations advanced and do not account for unidentified fill zones, unsuitable soil types or conditions, and variability in soil moisture and groundwater conditions. To avoid possible misinterpretations of findings, conclusions, and implications of this report, Atlas should be retained to explain the report contents to other design professionals as well as construction professionals. Since actual subsurface conditions on the site can only be verified by earthwork, note that construction recommendations are based on general assumptions from selective observations and selective field exploratory sampling. Upon commencement of construction, such conditions may be identified that require corrective actions, and these required corrective actions may impact the project budget. Therefore, construction recommendations in this report should be considered preliminary, and Atlas should be retained to observe actual subsurface conditions during earthwork construction activities to provide additional construction recommendations as needed. Since geotechnical reports are subject to misinterpretation, do not separate the soil logs from the report. Rather, provide a copy of, or authorize for their use, the complete report to other design Atlas No. B201400g Page117 Copyright©2020 Atlas Technical Consultants �TWPM M1`a�11 professionals or contractors. Locations of exploratory sites referenced within this report should be considered approximate locations only. For more accurate locations, services of a professional land surveyor are recommended. This report is also limited to information available at the time it was prepared. In the event additional information is provided to Atlas following publication of our report, it will be forwarded to the client for evaluation in the form received. Environmental Concerns Comments in this report concerning either onsite conditions or observations, including soil appearances and odors, are provided as general information. These comments are not intended to describe, quantify, or evaluate environmental concerns or situations. Since personnel, skills, procedures, standards, and equipment differ, a geotechnical investigation report is not intended to substitute for a geoenviron mental investigation or a Phase II/III Environmental Site Assessment. If environmental services are needed, Atlas can provide, via a separate contract, those personnel who are trained to investigate and delineate soil and water contamination. Atlas No. B201400g Page118 Copyright©2020 Atlas Technical Consultants § (ma ƒ & - � ; } E )/co \ ƒ ( d \ CL)-i CD � - 9 ) � } Bo = § L6\ i \ \ E 2 - - _ S E m .. ,w z r 2 \\ 0LU 7 i 2 - � � � 2\ 0CD 9 £ \ �/ CL % I k 6 A /0 2 Alf | SOS maALERn Q� 2,:�,a� N 2 ���an ■ 2 f O ■ � O § 10. J � � § ) � w \ , yEAG�ER: g a E�E sEQ�ERo LU \\ � ) * � § 7 k ` � ® ` ui � = I . � § � i § % _ \ ! � r ) d k ccLL / % ) � �u 2 ElkTI - � u\ e J a Ely \ �.•. • �.Ar-KIMMARMISM MUMPS` I I live milli 1114c , s� II ! J Ono— Up +evil WE joISE I� ME �{ ,0j, or Ili ft�I f .:Imi moll �TWPM Z1`a�11 Appendix IV GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-1 Latitude: 43.5928894 Date Advanced: October 5, 2020 Longitude: -116.3607975 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Weston Jorgenson, GIT Total Depth: 16.2 feet bgs Depth . Description and USCS Soiland Sample Sample Depth Lab . .$) Sediment Classification • bgs) QP Test ID Lean Clay (CL): Brown, dry to slightly moist, 0.0-1.6 medium stiff to very stiff. 1.0-4.0 --Organics noted to 0.2 foot bgs. --Plow zone noted to 1.0 foot bgs. Sandy Silt (ML): Gray, dry to slightly moist, very stiff to hard, with fine to medium-grained 1.6-6.1 sand. 3.5-4.5 --Weak calcium carbonate cementation noted throughout. Silty Sand (SM): Light brown, slightly moist, dense, with fine to coarse-grained sand. 6.1-8.7 --Weak calcium carbonate cementation noted throughout. --Fine to coarse gravel noted below 8.0 feet. Poorly Graded Gravel with Sand (GP): Gray, 8.7-16.2 slightly moist, dense, with fine to coarse- grained sand, fine to coarse gravel, and 8- inch-minus cobbles. Notes:See Site Map for test pit location. Atlas No. B201400g Page 121 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-2 Latitude: 43.5933110 Date Advanced: October 5, 2020 Longitude: -116.3617500 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Weston Jorgenson, GIT Total Depth: 11.9 feet bgs Depth Field Description and USCS Soil and Sample Sample Depth Qp Lab • •s) Sediment Classification • bgs) Test ID Lean Clay (CL): Brown, dry to slightly moist, 0.0-1.4 medium stiff to very stiff. 1.0-3.0 --Organics noted to 0.2 foot bgs. --Plow zone noted to 1.0 foot bgs. Silty Sand (SM): Gray, slightly moist, dense, 1.4-7.3 with fine to medium-grained sand. --Weak to moderate calcium carbonate cementation noted throughout. Poorly Graded Gravel with Sand (GP): Light brown to gray, slightly moist, dense to very 7.3-11.9 dense, with fine to coarse-grained sand, fine to coarse gravel, and 10-inch-minus cobbles. --Moderate calcium carbonate cementation noted from 7.3 to 10.8 feet bgs. Notes:See Site Map for test pit location. Atlas No. B201400g Page 122 Copyright©2020 Atlas Technical Consultants �TrTG7T�-1 GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-3 Latitude: 43.5926134 Date Advanced: October 5, 2020 Longitude: -116.3618227 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Weston Jorgenson, GIT Total Depth: 12.5 feet bgs F"" Lean Clay (CL): Brown, dry to slightly moist, . - . medium stiff to very stiff. GS 0.5-1.0 1.0-2.0 A --Organics noted to 0.2 foot bgs. --Plow zone noted to 1.0 foot bgs. Silty Sand with Gravel (SM):Tan to brown, dry to slightly moist, medium dense to dense, with fine to coarse-grained sand and fine to coarse 1.3-5.2 gravel. --Weak to moderate calcium carbonate cementation noted throughout. --Thin clay layers noted from 2.5 to 5.0 feet bgs. Poorly Graded Gravel with Sand (GP): Light brown to gray, dry to slightly moist,dense,with 5.2-12.5 fine to coarse-grained sand, fine to coarse gravel, and 8-inch-minus cobbles. --Weak to moderate calcium carbonate cementation noted from 5.2 to 8.4 feet bgs. Notes:See Site Map for test pit location. Sieve Analysis (% Passing) Lab Test ID Moistur P1 �M 1j1& #4 1 #40 #100 #200 A 17.3 39 18 95 95 92 89 85.4 Atlas No. B201400g Page 123 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-4 Latitude: 43.5922304 Date Advanced: October 5, 2020 Longitude: -116.3603033 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Weston Jorgenson, GIT Total Depth: 11.0 feet bgs Depth Field Description and USCS Soil and Sample Sample Depth Qp Lab • •s) Sediment Classification • bgs) Test ID Lean Clay (CL): Brown, dry to slightly moist, 0.0-1.3 medium stiff to very stiff. 1.0-2.0 --Organics noted to 0.3 foot bgs. --Plow zone noted to 1.0 foot bgs. Silty Sand with Gravel (SM): Light brown to tan, dry to slightly moist, loose to medium 1.3-6.3 dense, with fine to medium-grained sand. --Weak to moderate calcium carbonate cementation noted from 3.2 to 6.3 feet bgs. Poorly Graded Gravel with Sand (GP): Light brown to gray, dry to slightly moist, dense to very dense, with fine to coarse-grained sand, 6.3-11.0 fine to coarse gravel, and 8-inch-minus cobbles. --Weak to moderate calcium carbonate cementation noted from 6.3 to 8.3 feet bgs. Notes:See Site Map for test pit location. Atlas No. B201400g Page 124 Copyright©2020 Atlas Technical Consultants �TrTG7Tdr-W� GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-5 Latitude: 43.5913198 Date Advanced: October 5, 2020 Longitude: -116.3599593 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Weston Jorgenson, GIT Total Depth: 10.2 feet bgs • - • - . e . Lean Clay (CL): Brown, dry to slightly moist, stiff to very stiff. 0.0-1.5 --Organics noted to 0.2 foot bgs. 1.5-3.0 --Plow zone noted to 1.0 foot bgs. Silty Sand (SM): Light brown to gray, dry to slightly moist, dense, with fine to medium- 1.5-6.9 grained sand. --Weak to moderate calcium carbonate cementation noted from 1.9 to 6.9 feet bgs. Poorly Graded Gravel with Sand (GP): Light brown to gray, dry to slightly moist, dense to very dense, with fine to coarse-grained sand, 6.9-10.2 fine to coarse gravel, and 12-inch-minus cobbles. --Weak calcium carbonate cementation noted from 6.9 to 9.5 feet bgs. Notes:See Site Map for test pit location. Atlas No. B201400g Page 125 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-6 Latitude: 43.5915580 Date Advanced: October 5, 2020 Longitude: -116.3615800 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Weston Jorgenson, GIT Total Depth: 12.4 feet bgs Depth Field Description and USCS Soil and Sample Sample Depth e . Lab • •s) Sediment Classification • bgs) Test ID Lean Clay (CL): Brown, dry to slightly moist, stiff to very stiff. 0.0-1.4 --Organics noted to 0.2 foot bgs. 1.5-2.5 --Plow zone noted to 1.0 foot bgs. Silty Sand (SM): Light brown to gray, dry to slightly moist, loose to medium dense, with 1.4-5.4 fine to medium-grained sand. --Weak to moderate calcium carbonate cementation noted from 2.2 to 5.4 feet bgs. Poorly Graded Gravel with Sand (GP): Light brown, dry to slightly moist, dense to very 5.4-12.4 dense, with fine to coarse-grained sand, fine to coarse gravel, and 8-inch-minus cobbles. --Moderate to strong calcium carbonate cementation noted throughout. Notes:See Site Map for test pit location. Atlas No. B201400g Page126 Copyright©2020 Atlas Technical Consultants �TWPM Z1`a�11 GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-7 Latitude: 43.5907768 Date Advanced: October 5, 2020 Longitude: -116.3609789 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Weston Jorgenson, GIT Total Depth: 11.0 feet bgs Depth Field Description and USCS Soil and Sample Sample Depth e . Lab • •s) Sediment Classification • bgs) Test ID Lean Clay (CL): Light brown to brown, dry to 0.0-2.1 slightly moist, stiff to very stiff. 2.0-2.5 --Organics noted to 0.2 foot bgs. --Plow zone noted to 1.0 foot bgs. Silty Sand (SM): Light brown to gray, dry to slightly moist, dense, with fine to medium- 2.1-6.3 grained sand. --Weak calcium carbonate cementation noted throughout. Poorly Graded Gravel with Sand (GP): Brown to light brown, dry to slightly moist,dense,with 6.3-11.0 fine to coarse-grained sand, fine to coarse gravel, and 6-inch-minus cobbles. --Weak to moderate calcium carbonate cementation noted from 6.3 to 9.8 feet bgs. Notes:See Site Map for test pit location. Atlas No. 13201400g Page127 Copyright©2020 Atlas Technical Consultants �TWPM z1`a�11 Appendix V GEOTECHNICAL GENERAL NOTES Unified Soil Classification System Major Divisions Symbol Soil Descriptions Gravel & GW Well-graded ravels; ravel/sand mixtures with little or no fines Coarse- Gravelly Soils GP Poorly-graded ravels; ravel/sand mixtures with little or no fines Grained < 50% GM Silty gravels; poorly-graded ravel/sand/silt mixtures Soils < coarse GC Clayey gravels; poorly-graded gravel/sand/clay mixtures 50% Sand & Sandy SW Well-graded sands; gravelly sands with little or no fines passes Soils > 50% SP Poorl - raded sands; gravelly sands with little or no fines No.200 coarse SM Silty sands; poorly-graded sand/gravel/silt mixtures sieve fraction Sc Clayey sands; poorly-graded sand/gravel/clay mixtures Fine- ML Inorganic silts; sandy, gravellyor clayey silts Grained Silts & Clays CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium- Soils > LL < 50 lasticit cla s 50% OL Organic, low-plasticity clays and silts passes MH Inorganic, elastic silts; sand ravel) or clayey elastic silts No.200 Silts &Clays CH Fat clays; high-plasticity, inorganic clays sieve LL > 50 OH Organic, medium to high-plasticity clays and silts Highly Organic Soils PT Peat, humus, h dric soils with high organic content Relative Density and Consistency Moisture Content and Cementation Classification Classification Coarse-Grained Soils SPT Blow Counts (N) Description Field Test Very Loose: <4 Dry Absence of moisture, dry to touch Loose: 4-10 Slightly Moist Damp, but no visible moisture Medium Dense: 10-30 Moist Visible moisture Dense: 30-50 Wet Visible free water Very Dense: >50 Saturated Soil is usually below water table Fine-Grained Soils SPT Blow Counts N Description Field Test Very Soft: <2 Weak Crumbles or breaks with handling or Soft: 2-4 slight finger pressure Medium Stiff: 4-8 Moderate Crumbles or breaks with Stiff: 8-15 considerable finger pressure Very Stiff: 15-30 Strong Will not crumble or break with finger Hard: >30 pressure Particlqjffi� ]�� Acronym List Boulders: > 12 in. GS grab sample Cobbles: 12 to 3 in. LL Liquid Limit Gravel: 3 in. to 5 mm M moisture content Coarse-Grained Sand: 5 to 0.6 mm NP non-plastic Medium-Grained Sand: 0.6 to 0.2 mm PI Plasticity Index Fine-Grained Sand: 0.2 to 0.075 mm Qp penetrometer value, unconfined compressive Silts: 0.075 to 0.005 mm strength, tsf Clays: < 0.005 mm V vane value, ultimate shearing strength, tsf Atlas No. B201400g Page128 Copyright©2020 Atlas Technical Consultants �TrTG7T�� Appendix VI AASHTO PAVEMENT THICKNESS DESIGN PROCEDURES Pavement Section Design Location: Proposed Mixed-Use Development,Light Duty Average Daily Traffic Count: 400 All Lanes&Both Directions Design Life: 20 Years Percent of Traffic in Design Lane: 50% Terminal Seviceability Index(Pt): 2.5 Level of Reliability: 95 Subgrade CBR Value: 4 Subgrade Mr: 6,000 Calculation of Design-18 kip ESALs Daily Growth Load Design Traffic Rate Factors ESALs Passenger Cars: 140 2.0% 0.0008 993 Buses: 0 2.0% 0.6806 0 Panel&Pickup Trucks: 55 2.0% 0.0122 5,951 2-Axle,6-Tire Trucks: 4 2.0% 0.1890 6,705 Emergency Vehicles: 1.0 2.0% 4.4800 39,731 Dump Trucks: 0 2.0% 3.6300 0 Tractor Semi Trailer Trucks: 0 2.0% 2.3719 0 Double Trailer Trucks 0 2.0% 2.3187 0 Heavy Tractor Trailer Combo Trucks: 0 2.0% 2.9760 0 Average Daily Traffic in Design Lane: 200 Total Design Life 18-kip ESALs: 53,380 Actual Log(ESALs): 4.727 Trial SN: 2.48 Trial Log(ESALs): 4.728 Pavement Section Design SN: 2.61 Design Depth Structural Drainage Inches Coefficient Coefficient Asphaltic Concrete: 2.50 0.42 n/a Asphalt-Treated Base: 0.00 0.25 n/a Cement-Treated Base: 0.00 0.17 n/a Crushed Aggregate Base: 4.00 0.14 1.0 Subbase: 10.00 0.10 1.0 Special Aggregate Subgrade: 0.00 0.09 0.9 Atlas No. 13201400g Page 129 Copyright©2020 Atlas Technical Consultants �TrTG7T�� AASHTO PAVEMENT THICKNESS DESIGN PROCEDURES Pavement Section Design Location: Proposed Mixed-Use De\elopment,Heavy Duty Average Daily Traffic Count: 400 All Lanes&Both Directions Design Life: 20 Years Percent of Traffic in Design Lane: 50% Terminal Seviceability,Index(Pt): 2.5 Level of Reliability: 95 Subgrade CBR Value: 4 Subgrade Mr: 6,000 Calculation of Design-18 kip ESALs Daily Growth Load Design Traffic Rate Factors ESALs Passenger Cars: 105 2.0% 0.0008 745 Buses: 0 2.0% 0.6806 0 Panel&Pickup Trucks: 75 2.0% 0.0122 8,115 2-Axle,6-Tire Trucks: 15 2.0% 0.1890 25,142 Emergency Vehicles: 2.0 2.0% 4.4800 79,462 Dump Trucks: 1 2.0% 3.6300 32,193 Tractor Semi Trailer Trucks: 2 2.0% 2.3719 42,071 Double Trailer Trucks 0 2.0% 2.3187 0 Hea\,y Tractor Trailer Combo Trucks: 0 2.0% 2.9760 0 Awrage Daily Traffic in Design Lane: 200 Total Design Life 18-kip ESALs: 187,727 Actual Log(ESALs): 5.274 Trial SN: 3.06 Trial Log(ESALs): 5.278 Pavement Section Design SN: 3.07 Design Depth Structural Drainage Inches Coefficient Coefficient Asphaltic Concrete: 3.00 0.42 n/a Asphalt-Treated Base: 0.00 0.25 n/a Cement-Treated Base: 0.00 0.17 n/a Crushed Aggregate Base: 4.00 0.14 1.0 Subbase: 12.00 0.10 1.0 Special Aggregate Subgrade: 0.00 0.09 0.9 Atlas No. 13201400g Page 130 Copyright©2020 Atlas Technical Consultants IMPOPIOnt InfOPM81100 Rhout Geolechnical-Engineeping Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help. The Geoprofessional Business Association (GBA) will not likely meet the needs of a civil-works constructor or even a has prepared this advisory to help you—assumedly different civil engineer.Because each geotechnical-engineering study a client representative—interpret and apply this is unique,each geotechnical-engineering report is unique,prepared geotechnical-engineering report as effectively as solely for the client. possible. In that way, you can benefit from a lowered Likewise,geotechnical-engineering services are performed for a specific exposure to problems associated with subsurface project and purpose.For example,it is unlikely that a geotechnical- conditions at project sites and development of engineering study for a refrigerated warehouse will be the same as them that,for decades, have been a principal cause one prepared for a parking garage;and a few borings drilled during of construction delays, cost overruns, claims, a preliminary study to evaluate site feasibility will not be adequate to and disputes. If you have questions or want more develop geotechnical design recommendations for the project. information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Do not rely on this report if your geotechnical engineer prepared it: Active engagement in GBA exposes geotechnical • for a different client; engineers to a wide array of risk-confrontation • for a different project or purpose; techniques that can be of genuine benefit for • for a different site(that may or may not include all or a portion of everyone involved with a construction project. the original site);or before important events occurred at the site or adjacent to it; e.g.,man-made events like construction or environmental Understand the Geotechnical-Engineering Services remediation,or natural events like floods,droughts,earthquakes, Provided for this Report or groundwater fluctuations. Geotechnical-engineering services typically include the planning, collection,interpretation,and analysis of exploratory data from Note,too,the reliability of a geotechnical-engineering report can widely spaced borings and/or test pits.Field data are combined be affected by the passage of time,because of factors like changed with results from laboratory tests of soil and rock samples obtained subsurface conditions;new or modified codes,standards,or from field exploration(if applicable),observations made during site regulations;or new techniques or tools.If you are the least bit uncertain reconnaissance,and historical information to form one or more models about the continued reliability of this report,contact your geotechnical of the expected subsurface conditions beneath the site.Local geology engineer before applying the recommendations in it.A minor amount and alterations of the site surface and subsurface by previous and of additional testing or analysis after the passage of time-if any is proposed construction are also important considerations.Geotechnical required at all-could prevent major problems. engineers apply their engineering training,experience,and judgment to adapt the requirements of the prospective project to the subsurface Read this Report in Full model(s). Estimates are made of the subsurface conditions that Costly problems have occurred because those relying on a geotechnical- will likely be exposed during construction as well as the expected engineering report did not read the report in its entirety.Do not rely on performance of foundations and other structures being planned and/or an executive summary.Do not read selective elements only.Read and affected by construction activities. refer to the report in full. The culmination of these geotechnical-engineering services is typically a You Need to Inform Your Geotechnical Engineer geotechnical-engineering report providing the data obtained,a discussion About Change of the subsurface model(s),the engineering and geologic engineering Your geotechnical engineer considered unique,project-specific factors assessments and analyses made,and the recommendations developed when developing the scope of study behind this report and developing to satisfy the given requirements of the project.These reports may be the confirmation-dependent recommendations the report conveys. titled investigations,explorations,studies,assessments,or evaluations. Typical changes that could erode the reliability of this report include Regardless of the title used,the geotechnical-engineering report is an those that affect: engineering interpretation of the subsurface conditions within the context - the site's size or shape; of the project and does not represent a close examination,systematic inquiry,or thorough investigation of all site and subsurface conditions. the elevation,configuration,location,orientation, function or weight of the proposed structure and Geotechnical-Engineering Services are Performed the desired performance criteria; the composition of the design team;or for Specific Purposes, Persons, and Projects, . project ownership. and At Specific Times Geotechnical engineers structure their services to meet the specific As a general rule,always inform your geotechnical engineer of project needs,goals,and risk management preferences of their clients.A or site changes-even minor ones-and request an assessment of their geotechnical-engineering study conducted for a given civil engineer impact.The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical conspicuously that you've included the material for information purposes engineer was not informed about developments the engineer otherwise only.To avoid misunderstanding,you may also want to note that would have considered. "informational purposes"means constructors have no right to rely on the interpretations,opinions,conclusions,or recommendations in the Most Of the "Findings" Related in This Report report.Be certain that constructors know they may learn about specific Are Professional Opinions project requirements,including options selected from the report,only Before construction begins,geotechnical engineers explore a site's from the design drawings and specifications.Remind constructors subsurface using various sampling and testing procedures.Geotechnical that they may perform their own studies if they want to,and be sure to engineers can observe actual subsurface conditions only at those specific allow enough time to permit them to do so.Only then might you be in locations where sampling and testing is performed.The data derived from a position to give constructors the information available to you,while that sampling and testing were reviewed by your geotechnical engineer, requiring them to at least share some of the financial responsibilities who then applied professional judgement to form opinions about stemming from unanticipated conditions.Conducting prebid and subsurface conditions throughout the site.Actual sitewide-subsurface preconstruction conferences can also be valuable in this respect. conditions may differ-maybe significantly-from those indicated in this report.Confront that risk by retaining your geotechnical engineer Read Responsibility Provisions Closely to serve on the design team through project completion to obtain Some client representatives,design professionals,and constructors do informed guidance quickly,whenever needed. not realize that geotechnical engineering is far less exact than other engineering disciplines.This happens in part because soil and rock on This Report's Recommendations Are project sites are typically heterogeneous and not manufactured materials Confirmation-Dependent with well-defined engineering properties like steel and concrete.That The recommendations included in this report-including any options or lack of understanding has nurtured unrealistic expectations that have alternatives-are confirmation-dependent.In other words,they are not resulted in disappointments,delays,cost overruns,claims,and disputes. final,because the geotechnical engineer who developed them relied heavily TO confront that risk,geotechnical engineers commonly include on judgement and opinion to do so.Your geotechnical engineer can finalize explanatory provisions in their reports.Sometimes labeled"limitations,' the recommendations only after observing actual subsurface conditions many of these provisions indicate where geotechnical engineers' exposed during construction.If through observation your geotechnical responsibilities begin and end,to help others recognize their own engineer confirms that the conditions assumed to exist actually do exist, responsibilities and risks.Read these provisions closely.Ask questions. the recommendations can be relied upon,assuming no other changes have Your geotechnical engineer should respond fully and frankly. occurred.The geotechnical engineer who prepared this report cannot assume responsibility or liabilityfor confirmation-dependent recommendations fyou Geoenvironmental Concerns Are Not Covered fail to retain that engineer to perform construction observation. The personnel,equipment,and techniques used to perform an environmental study-e.g.,a"phase-one"or"phase-two"enviroranental This Report Could Be Misinterpreted site assessment-differ significantly from those used to perform a Other design professionals'misinterpretation of geotechnical- geotechnical-engineering study.For that reason,a geotechnical-engineering engineering reports has resulted in costly problems.Confront that risk report does not usually provide environmental findings,conclusions,or by having your geotechnical engineer serve as a continuing member of recommendations;e.g.,about the likelihood of encountering underground the design team,to: storage tanks or regulated contaminants.Unanticipated subsurface • confer with other design-team members; environmental problems have led to project failures.If you have not • help develop specifications; obtained your own environmental information about the project site, review pertinent elements of other design professionals'plans and ask your geotechnical consultant for a recommendation on how to find specifications;and environmental risk-management guidance. • be available whenever geotechnical-engineering guidance is needed. Obtain Professional Assistance to Deal with You should also confront the risk of constructors misinterpreting this Moisture Infiltration and Mold report.Do so by retaining your geotechnical engineer to participate in While your geotechnical engineer may have addressed groundwater, prebid and preconstruction conferences and to perform construction- water infiltration,or similar issues in this report,the engineer's phase observations. services were not designed,conducted,or intended to prevent migration of moisture-including water vapor-from the soil Give Constructors a Complete Report and Guidance through building slabs and walls and into the building interior,where Some owners and design professionals mistakenly believe they can shift it can cause mold growth and material-performance deficiencies. unanticipated-subsurface-conditions liability to constructors by limiting Accordingly,proper implementation of the geotechnical engineer's the information they provide for bid preparation.To help prevent recommendations will not of itself be sufficient to prevent the costly,contentious problems this practice has caused,include the moisture infiltration.Confront the risk of moisture infiltration by complete geotechnical-engineering report,along with any attachments including building-envelope or mold specialists on the design team. or appendices,with your contract documents,but be certain to note Geotechnical engineers are not building-envelope or mold specialists. GEOPROFESSIONAL BUSINESS SEA ASSOCIATION Telephone:301/565-2733 e-mail:info@geoprofessional.org www.geoprofessional.org Copyright 2019 by Geoprofessional Business Association(GBA).Duplication,reproduction,or copying of this document,in whole or in part,by any means whatsoever,is strictly prohibited,except with GBAs specific written permission.Excerpting,quoting,or otherwise extracting wording from this document is permitted only with the express written permission of GBA,and only for purposes of scholarly research or book review.Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm,individual,or other entity that so uses this document without being a GBA member could be committing negligent or intentional(fraudulent)misrepresentation.