Loading...
PC - Item 3A - Exhibit E - Appendix D - 3001 Walnut Grove Pre-LID PlanCal Land Engineering, Inc. dba Quartech Consultants Geotechnical, Environmental, and Civil Engineering 576 E. Lambert Road, Brea, California 92821 Tel: 714-671-1050 - Fax: 714-671-1090 - Email: callandeng@yahoo.com LOW IMPACT DEVELOPMENT PLAN PROVIDES DATE 05/08/2020 JOB ADDRESS: 8589 GARVEY AVE. AND 3001 WALNUT GOVE AVE. ROSEMEAD, CA 91770 BY CAL LAND ENGINEERING, INC. TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 2 I. Introduction This report has been provided in order to determine the best capability of the project to use stormwater quality measures to manage and capture stormwater runoff. The 85th percentile 24 hr rainfall is 0.9” per attached Hydrology map. That is greater than 0.75”. The 85th percentile 24 hr rainfall was used for this On-site LID Report. Per Geotechnical recommendation, infiltration is possible for on site. The infiltration trench will be provided to detain the 85th percentile 24 hr rainfall on site. The infiltration dry-well will be constructed under the basement. Project Data Project Name: TAIWAN CENTER Address: 8589 Garvey Ave. & 3001 Walnut Grove Ave., Rosemead, CA APN: 5390-002-004, 041, 042 and 043. Project Area: 46,059.06 SF (1.057 acres) Disturbed Area: 46,059.06 SF (1.057 acres) Impervious Area: 44,896.17 SF (1.031 acres) (97%) Pervious Area: 1,162.89 SF (0.026 acres) (3 %) Owner: TAIWAN CENTER / MR. ALAN THIAN, PRESIDENT Existing Land Use: Commercial Proposed Land Use: Mix-use residential and commercial Scope of Work The project includes demolition of all structures and construction of mix-use residential and commercial building. Project Designation This project equal to one acre or greater of disturbed area and adding more than 10,000 square feet of impervious surface area. This will result in the designation of “Designated Project” All “Designated Projects” must retain 100 percent of the SWQDv on-site through infiltration, evapotranspiration, stormwater runoff harvest and use, or a combination thereof unless it is demonstrated that it is technically infeasible to do so. To meet these requirements, Designated Project must: - Conduct site assessment and identify design considerations, including determining the feasibility of on-site infiltration - Apply site-specific source control measures - Calculate the Stormwater Quality Design Volume - Implement stormwater quality control measures TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 3 II. Report Proposed Disturbed area 1.057 acres Type of Development Mix-use Residential and Commercial Predominate Soil Type No. 003 Using HydroCalc Length of Flow Path 65’ 85th percentile rainfall depth: 0.9 Proportion Impervious Values 0.9748 Qpm = 0.4263 cfs VProp. = 3013.17 CF TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 4 TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 5 Stormwater Quality Design Volume Calculation Current water quality requirements are based on treating a specific volume of stormwater runoff from the project site (stormwater quality design volume [SWQDv]). By treating the SWQDv, it is expected that pollutant loads, which are typically higher during the beginning of storm events, will be reduced in the discharge to or prevented from reaching the receiving water. The design storm, from which the SWQDv is calculated, is defined as the greater of: - The 0.75 inch, 24-hour rain event; or - The 85th percentile, 24-hour rain event as determined from the Los Angeles County 85th percentile precipitation isoheytal map For this project, the 85th percentile, 24-hour rain event will be used, which is 0.9 inch. Using Hydrocalc: SWQDv = 3031.17 cu.ft. TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 6 Hydrology Map TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 7 Infiltration Calculation SWQDv = 3013.17 cu.ft. fdesign (Infiltration rate) = 1 in/hr Dry Well Calculation: V = πr2h Where: V = Volume [ft]; r = radius of drywell [ft]; and h1 = depth of dry well [ft] (Storage) h2 = depth of dry well [ft] (Infiltration) nt = Dry well fill porosity (40%) V1 = πr2 h1 V1 = 3.1416 x 22 x 20 V1 = 251.33 ft3 V2 = πr2 h2 V2 = 3.1416 x 22 x (16 x 0.4) V2 = 80.42 ft3 Total Volume = 251.33 + 80.42 = 331.75 ft3 _______________________________________________________________________ Storage Tank Use Concrete Storage Tank = 2350 CF Volume of Dry well + Volume of Storage Tank = 331.75 ft3 x2 + 2350 ft3 = 3013.50 ft3 > 3013.17 ft3 _______________________________________________________________________ Infiltration Rate = 1 inch. / hr. = 0.083 ft. / hr. Perimeter of Drywell = 2 x 3.1416 x r = 12.57 ft. Capacity = 12. 57 ft. x h2 = 12.57 x 16 = 201.12 ft2 Infiltration rate x Capacity = 0.083 x 201.12 = 16.69 ft3 / hr. Drain in 96 hrs. = 16.69 ft3 / hr. x 96 hr. = 1602.24 ft3 x 2 = 3204.48 ft3 V = 3204.48 ft3 > 3013.17 ft3 TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 8 CONCLUSION Storage Volume: Per LID request =3013.17 CF Total provide= 3013.50 CF Volume (Total provide 3013.50 CF) > Volume (Total request 3013.17 CF) OK The Dry-well will be installed on the project site to reduce the peak discharge rate, volume, and duration of the flow. These BMP’s are designed to collect the site drains from the corresponding Tributary Drainage Areas and to soak water on site prior to draining to pump pit, pump drainage to street. TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 9 Vicinity Map TAIWAN CENTER LID Plan – 8589 Garvey Ave. & 3001 Walnut Grove Ave. August 02, 2019 Cal Land Engineering, Inc. 576 E. Lambert Road, Brea, California 92821; Tel: 714-671-1050; Fax: 714-671-1090 Page 10 III. Infiltration report Cal Land Engineering, Inc. dba Quartech Consultants Geotechnical, Environmental, and Civil Engineering 576 East Lambert Road, Brea, California 92821; Tel: 714-671-1050, Fax: 714-671-1090 November 18, 2019 Taiwan Center 3001 Walnut Grove, Rosemead, CA 91770 Attention: Mr. Alan Thian Subject: Percolation Feasibility Testing for the Proposed Infiltration System, 4-Story Mixed Use Development, with One-Level of Subterraneous Garage, 3001 Walnut Grove Avenue and nearby lots, APN: 5288-001-040, 041, 042, 043, Rosemead, California, QCI Project No.: 19-221-001Per References: County of Los Angeles, Department of public works, 2017, Guidelines for Design, Investigation and Reporting, Low Impact Development Stormwater Infiltration, GS200.2, dated June 30, 2017. Gentlemen: As requested and authorized, Cal Land Engineering, Inc. (CLE) has performed a feasibility percolation evaluation for the above project located at the subject site. The purpose of this report is to aid in the design and construction of the required storm water infiltration system. The professional opinions and geotechnical information contained in this report are not intended to imply total performance of the project or guarantee that unusual or variable conditions will not be discovered during or after construction. The scope of our study is limited to the area explored, which is shown on Figure 2, (Site Plan). SITE CONDITIONS The project site is located on the northwest corner of Garvey Avenue and Walnut Grove Avenue, in the City of Rosemead, California. The approximate location of the site is presented in the attached Site Location Map (Figure 1). The lot size is approximately 46,075 square feet (1.060 acres). The site is relatively flat and is currently occupied by constructions. No major surface erosions were observed during our subsurface investigation. FIELD EXPLORATION Field exploration for this investigation consisted of drilling one-percolation boring (P-1) to the depth of approximately 35-36 feet below existing site grade (depth corresponds to the bottom the proposed of infiltration system) on October 4, 2019 and two additional borings to the maximum depth of 51.5 feet below the existing grade on October 3, 2019 . Approximate boring locations are presented on Figure 2, Site Plan Description of the soil materials encountered during drilling was entered into the boring logs in accordance with the Unified Soil Classification System (USCS) and Hydraulic Soil Group (HSG). The boring logs are included in Appendix A. SUBSURFACE CONDITION The onsite near surface soils consist predominantly of clayey sand (SC). In general, these soils exist in the loose and moist condition. Underlying the surface soils, fine grained clayey sand (SC), silty sand (SM), poorly graded sand (SP) and sandy clay (CL) were disclosed in the borings to the Taiwan Center Page 2 QCI Project Number: 19-221-001 November 18, 2019 576 East Lambert Road, Brea, California 92821; Tel: 714-671-1050, Fax: 714-671-1090 depths explored (51.5 feet below the existing ground surface). These soils exist in medium dense to very dense and very stiff and slightly moist to very moist conditions. In general, the soils become denser as depth increases. GROUNDWATER Ground water level was not encountered to the depth explored (approximately 51.5 feet below the existing grade) during our subsurface investigation. In our opinion, groundwater will not be a problem during the near surface construction. Based on our review of the “Historically Highest Ground Water Contours and Borehole Log Data Locations, El Monte Quadrangle”, by CGS (formerly CDMG), it is estimated that the highest historical ground water level is approximately 10 feet below the existing grade. LABORATORY TESTING Laboratory testing including Expansion Potential and Mechanical Analysis were performed on selective soil samples: EXPANSION INDEX Laboratory Expansion Index test was conducted on the existing onsite near surface materials sampled during QCI’s field investigation to aid in evaluation of soil expansion potential. The test is performed in accordance with ASTM D-4829. The testing result is presented below: Sample Location Expansion Index Expansion Potential P-1 @ 35’-36’ 2 Very Low PARTICLE-SIZE ANALYSIS & PERCENT PASSING #200 SIEVE Particle-size analyses were determined for selected soil samples in accordance with ASTM D442 standard. The results were plotted and presented in appendix C. Percent of soil passing #200 sieve were determined for selected soil samples in accordance with ASTM D1140 standard. The test results are presented in the following table: PERCOLATION RATE/ PERMEABILITY Percolation rate and permeability of the subsurface material, encountered in Boring P-1, was drilled to a depth of 35’-36’ feet (advanced 12 inches more) at previously assigned locations and a 2-inch diameter perforated PVC pipe casing with a solid end cap was installed in each boring after the completion of the drilling. Gravelly filter materials were placed between the PVC pipe and the drill holes. The test boring was pre-soaked on October 4, 2019 prior to percolation testing, to ensure the sand around the perforated pipe is fully saturated. After the presoak, the time interval for recording the water drop was determined between the readings for P-1, hole. For P-1 the hole was filled with water 12 inches above the bottom of the excavated hole and PVC end cap. Water remained in the hole after 10 minutes and drain before 30 minutes and the time interval between the readings was determined to be 10 minutes. Therefore, rate of surface water drop was measured every 10 minutes for P-1 and testing stopped after a minimum of eight readings and after noticing a stabilized rate of drop was obtained. Upon completion of tests, the boring was backfilled with the soil cuttings. Sample Location % Passing #200 P-1 @ 35’-36’ 30.5 Taiwan Center Page 3 QCI Project Number: 19-221-001 November 18, 2019 576 East Lambert Road, Brea, California 92821; Tel: 714-671-1050, Fax: 714-671-1090 Numerous measurements recorded within the test period indicated an average percolation rate of 8.50 inch/hour for P-1. The results of percolation test for boring P-1, provided in Appendix B. The percolation rates were reduced and readjusted to account for the discharge of water from both the sides and bottom of borings (i.e., non-vertical flow). The following formula was used to determine the infiltration rates, GS200.2, dated June 30, 2017: Reduction Factor (Rft) = (2d1-Δd) + 1 (Reference GS200.2, dated June 30, 2017) DIA Where: d1=Initial Water Depth (in) Δd = Water level drop of the final period of stabilized rate (in) DIA = Diameter of boring (in) Infiltration Rate = Pre-adjusted Percolation Rate divided by Reduction Factor Total Reduction Factor RF = RFt x RFv x RFs P-1, Reduction Factor (Rft) = (2d1-Δd) + 1 or (2 x 18)-8.50 + 1 = 5.583 DIA 6.0 The site is underlain by relative uniform of alluvial deposits. It is our understanding that stormwater infiltration BMPs with pretreatment components and regular maintenance programs will be implemented. The following presents the calculations of the recommended infiltration rate for the onsite stormwater system Total Reduction Factor RF = RFt x RFv x RFs = (5.583x3x3) = 50.24 Boring P-1 Design Infiltration Rate = 51.00 / (5.583x3x3) = 1.01 in/hr CONCLUSIONS AND RECOMMENDATIONS Our review and analysis of collected data and percolation testing indicate that the proposed infiltration system is feasible from geotechnical viewpoint and permeability rates exceed the required minimum 0.3 inch/hour for onsite soils. It is our opinion that the infiltration rate of 1.0 inch/hour may be used for the design of the onsite infiltration. LIMITATIONS Soil materials vary in character between excavations. Site conditions may vary due to seasonal changes or other factors. Therefore, we assume no responsibility or liability for work, testing or recommendations performed or provided by others. Site geotechnical or environmental factors, are not part of the scope of this work. Since our study is based upon the site materials observed, engineering research and analyses, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is expressed or implied. Standards of practice are subject to change with time.