AgdaPkt 2020-08-24 Joint SA PFA - Laserfiche WebLink

Browse Search

A] DESCRIPTION UNIT COST UNIT Excavation/Removal $50 CY Rubber Dam System - LS Diversion Structure - LS Pretreatment $6,000 CFS Diversion Pump Structure $56,000 CFS Diversion Pipe (24" RCP) $200 LF Subsurface Gallery $300 CY Restoration $5 SF CONSTRUCTION SUBTOTAL Mobilization (10% construction) design components, such as structure depth and capacity. Additional uses of captured runoff, such as irrigation or Contingency (15% construction) greywater, may contribute to 72 -hr drawdown requirement. Design (10% total) 'Maximum 72 -hr drawdown time is recommended in the SMCWPPP renovations/redevelopment at nearby John Gill Elementary School, the California Envirostor database shows no C.3 Stormwater Technical Guidance. Using a larger footprint and a TOTAL COST QUANTITY 63,000 1 1 20 20 100 50,000 113,000 SUBTOTAL $3,150,000 $80,000 $150,000 $120,000 $1,120,000 $20,000 $15,000,000 $565,000 $20,475,000 $2,048,000 $3,071,000 $2,559,000 $28,153,000 Phase I — McGarvey Field design values QUANTITY SUBTOTAL bWAMSiM 29,000 $1,450,000 Footprint 1 $150,000 23 $138,000 23 $1,288,000 100 $20,000 20,000 $6,000,000 78,000 $390,000 require the structure to be placed below the storm drain invert, increasing the required excavation depth. As-builts $9,436,000 for the storm drain will need to be obtained from the City to determine this depth. For a 2.6 -acre footprint, capital $944,000 cost may increase $300,000 per foot of additional excavation. In comparison, the O&M associated with a pump $1,415,000 diversion may be around $50,000 annually ($1.4 million projected over 20 years with 2.5% inflation). A break-even $1,180,000 analysis should be performed to determine if a gravity -flow alternative is more cost-effective. All cost estimates are $12,975,000 Design Height Depth of Excavation Pumping Requirements Infiltration Rate Drawdown Time Infiltration Rate Needed for 72 -hr Drawdown Time* 2.6 acres 12 ft 15 ft 18.6 cfs Needs further investigation Needs further investigation 2 in/hr Phase I Capacity 31.2 ac -ft This project concept is planning -level and subject to review and revision during project design. A % Design Storm Managed 72 % variety of confounding factors, including geotechnical and environmental considerations, will need to be further investigated to inform project design. Factors to be considered include but are not limited to the following: Phase II — Griffin-Bechet Fields design values • Drainage delineation: the drainage was delineated using best available data in GIS analysis. Field examinations Item Description of the upstream storm drain network should be performed to confirm drainage area. Footprint 1.8 acres • Utilities: a utilities survey at the park should be performed to minimize the disruption of utilities during construction. Design Height 6.67 ft • Groundwater levels: the distance between the bottom of the infiltrating structure and the seasonal high groundwater level should be at least 10 feet apart to allow for adequate infiltration. Depth of Excavation 10 ft • Pumping Requirements: pumping is generally assumed for large-scale regional projects. However, gravity -flow Pumping Requirements 22.6 Cfs diversion alternatives may be possible, reducing O&M costs associated with pumping. Gravity diversions would require the structure to be placed below the storm drain invert, increasing the required excavation depth. As-builts Infiltration Rate Needs further investigation for the storm drain will need to be obtained from the City to determine this depth. For a 2.6 -acre footprint, capital cost may increase $300,000 per foot of additional excavation. In comparison, the O&M associated with a pump Drawdown Time Needs further investigation diversion may be around $50,000 annually ($1.4 million projected over 20 years with 2.5% inflation). A break-even analysis should be performed to determine if a gravity -flow alternative is more cost-effective. All cost estimates are Infiltration Rate Needed for preliminary and will need to be reevaluated during a feasibility analysis when project details are developed further. 72 -hr Drawdown Time* 1.10 in/hr • Infiltration rates: the NRCS Soil Survey did not contain an infiltration rate estimate for the Red Morton Community Park area. Infiltration tests should be performed during a feasibility study to ensure the structure is sized Phase II Capacity 12 ac -ft appropriately. It is recommended that infiltrating structures drain within 72 hours. The infiltration rate may determine design components, such as structure depth and capacity. Additional uses of captured runoff, such as irrigation or % Design Storm Managed 28 % greywater, may contribute to 72 -hr drawdown requirement. • Environmental factors: with the exception of an active environmental investigation from 'Maximum 72 -hr drawdown time is recommended in the SMCWPPP renovations/redevelopment at nearby John Gill Elementary School, the California Envirostor database shows no C.3 Stormwater Technical Guidance. Using a larger footprint and a active cleanup sites near the project site. Additional investigation should be performed at the project site to assess smaller design height, while keeping storage capacity constant, will the possibility of existing contamination interfering with stormwater infiltration. lower the infiltration requirement for 72 -hr drawdown. Regional Stormwater Capture Project at Red Morton Community Park Design Details and Itemized Cost Estimate (Sheet 3 of 3) Water Pollution PAR�DIC,M Prevention Program E N V I R O N MEN T A S