City Council

LODI CITY COUNCIL AGENDA – Shirtsleeve Session Date: March 28, 2023 Carnegie Forum Time: 7:00 a.m. 305 West Pine Street, Lodi For information regarding this Agenda please contact: Olivia Nashed City Clerk Telephone: (209) 333-6702 Notice Regarding Public Comments Public Comment may be submitted in the following ways: • In-person • Email – councilcomments@lodi.gov  Received no later than 4:30 p.m. on the business day prior to the meeting. • Mail – City Clerk’s Office, P.O. Box 3006, Lodi, CA 95241 • Hand delivered to: City Clerk’s Office, 221 W. Pine Street, Lodi, CA 95240  Received no later than 4:30 p.m. on the business day prior to the meeting Public comment received via email, mail, or hand delivery will be provided to the City Council and included in the official minutes record of the meeting, but will not be read aloud at the meeting. A. Call to Order / Roll Call B. Topics B-1 Receive Information on Lodi’s Storm Drainage System and Recent Storm Events (PW) C. Comments by Public on Non-Agenda Items THE TIME ALLOWED PER NON-AGENDA ITEM FOR COMMENTS MADE BY THE PUBLIC IS LIMITED TO FIVE MINUTES. Public comment may only be made on matters within the Lodi City Council's jurisdiction (Government Code Section 54954.3, Lodi City Council Protocol Manual Section 6.3l). The Council cannot take action or deliberate on items that are not on this agenda unless there is an emergency and the need to take action on that emergency arose after this agenda was posted (Government Code Section 54954.2(b)(2)). All other items may only be referred for review to staff or placement on a future Council agenda. If you wish to address the Council, please refer to the Notice at the beginning of this agenda. Individuals are limited to one appearance during this section of the Agenda. D. Adjournment Pursuant to Section 54954.2(a) of the Government Code of the State of California, this agenda was posted at least 72 hours in advance of the scheduled meeting at a public place freely accessible to the public 24 hours a day. ______________________________ Olivia Nashed City Clerk Revised 1/2023 3/20/2023 3:22 PM All staff reports or other written documentation relating to each item of business referred to on the agenda are on file in the Office of the City Clerk, located at 221 W. Pine Street, Lodi, and are available for public inspection. Agendas and staff reports are also posted on the City’s website at www.lodi.gov. If requested, the agenda shall be made available in appropriate alternative formats to persons with a disability, as required by Section 202 of the Americans with Disabilities Act of 1990 (42 U.S.C. Sec. 12132), and the federal rules and regulations adopted in implementation thereof. To make a request for disability-related modification or accommodation contact the City Clerk’s Office as soon as possible and at least 72 hours prior to the meeting date. Language interpreter requests must be received at least 72 hours in advance of the meeting to help ensure availability. Contact Olivia Nashed at (209) 333-6702. Solicitudes de interpretación de idiomas deben ser recibidas por lo menos con 72 horas de anticipación a la reunión para ayudar a asegurar la disponibilidad. Llame a Olivia Nashed (209) 333-6702. Meetings of the Lodi City Council are telecast on SJTV, Channel 26. The City of Lodi provides live and archived webcasts of regular City Council meetings. The webcasts can be found on the City's website at www.lodi.gov by clicking the meeting webcasts link. Members of the public may view and listen to the open session of this meeting at www.facebook.com/CityofLodi/.  AGENDA ITEM B-01 COUNCIL COMMUNICATION AGENDA TITLE: Receive Information on Lodi’s Storm Drainage System and Recent Storm Events MEETING DATE: March 28, 2023 PREPARED BY: Public Works Director RECOMMENDED ACTION: Receive information on Lodi’s storm drainage system and recent storm events. BACKGROUND INFORMATION: Over the past few years, the City has experienced several “atmospheric river events”. These once rare, but significant rainfall events have tested the City’s existing network of pipes, basins and pump stations on a more frequent basis. Staff will provide Council with an overview of the City’s storm drain system and current design standards; outline the impacts of more compact development on the storm drain system; and discuss potential long-term solutions for addressing climate change as it relates to providing appropriate storm drain service. FISCAL IMPACT: Not applicable FUNDING AVAILABLE: Not applicable ________________________________________ Charles E. Swimley, Jr. Public Works Director APPROVED: ________________________________ Stephen Schwabauer, City Manager \\cvcfilv02\pubwks$\WP\COUNCIL\2023\CC Storm Drain System SS 032823.docx 3/20/2023 Lodi’s Storm Drainage System and Recent Storm Events Mills Ave & Tokay St (Oct 2021)  Storm Drainage & Recent Events Overview • Causes of Street Flooding • Rain Event Terminology • Lodi’s Storm Drainage System • Recent Storm Events • Specific Areas Prone to Street Flooding • Potential Projects to Minimize Impacts • Questions  Storm Drainage & Recent Events General Street Flooding Causes • Pipe / Inlets Blocked (Debris, Leaves, Gravel Bags, etc.) • Rain Flow is more than the Pipe Capacity • Nowhere for the Water to Go • Basin Full • Flow is Higher than Pump Station Can Handle  Storm Drainage & Recent Events Rain Event Terminology • Frequency & Duration • Frequency Curves = % Chance Happening • 5-Year = 20% (1/5) Chance / Year • 100-Year = 1% (1/100) Chance / Year • Developed by Historical Data & Models • Duration • “48-Hour” = Amount of water dropped over the Duration • 100-Year, 48 Hour Rain Event • Different than 100-Year River Floodplain  Storm Drainage & Recent Events Rain Event Terminology 4.8” 48 Hr  Storm Drainage & Recent Events Lodi’s Storm Drainage System 17 River/Lake Outlets (#s) 12 Basins (Letters) 2 WID Outlets WID Outlets  Storm Drainage & Recent Events Lodi’s Storm Drainage System • Pipe Sizing • Older Areas (Pre-2000): 2-Year Storm Flows w/ Full Basin • Newer Areas: 2-Year Full Basin Higher 5-Year Empty Basin 1’ 2-Year Full Basin Full Basin 1’ 5-Year Empty Basin Empty Basin  Storm Drainage & Recent Events Lodi’s Storm Drainage System • Basin Sizing • 100-Year, 48-Hour Event (4.8”) • Pre-1980 Basins • Reduction for Outflow • Pump Stations • WID Agreement • 60 CFS / Location • 160 CFS Total (Currently 2 Connections, Ultimately 3)  Storm Drainage & Recent Events Lodi’s Storm Drainage System • Newer Subdivisions (Since 2013) Require “Street Breakovers” in Design Lowest House Elevation • Even if Streets Flood, the Houses Shouldn’t “Bathtub & Soap Dish Comparison” Street Breakover Elevation  Storm Drainage & Recent Events Pause for Questions Rain Event Terminology or Lodi’s Storm Drainage System  Storm Drainage & Recent Events Recent Storms • Short Intense • December 10, 2022 • January 14, 2023 • High Volume • October 24-25, 2021 • December 30-31, 2022  Storm Drainage & Recent Events Short Intense Storms Expect short-term street flooding  Storm Drainage & Recent Events High Volume Storms Expect longer street flooding Expect short-term street flooding 48  Storm Drainage & Recent Events October 2021 Storm Time (Saturday - Sunday - Monday) 7.0'' ~6.6” in 32 Hours 6.5'' 6.0'' 5.5'' 4.8” @ ~9:00PM (22 Hours) 5.0'' 4.5'' “Atmospheric River” 4.0'' 3.5'' Rainfall 100-Year 48 Hour Rainfall 3.0'' 2.5'' Cumulative Rainfall 2.0'' Hourly Rainfall 1.5'' 1.0'' 0.5'' 0.0'' 10:00 PM 6:00 AM 2:00 PM 10:00 PM 6:00 AM  Storm Drainage & Recent Events October 2021 Storm (DeBenedetti) 150% 7.0'' Basin Storage vs Cumulative Rainfall 140% 6.5'' Time (Saturday - Sunday - Monday) 130% 6.0'' 120% 5.5'' 110% 5.0'' 100% 4.5'' 50%-120% in 5 Hours 90% 4.0'' Basin Storage 80% Rainfall 3.5'' 70% 3.0'' 60% 2.5'' 100-Year 48 Hour Rainfall 50% 2.0'' Hourly Rainfall (in) 40% Cumulative Rainfall 1.5'' 30% DeBenedetti (G Basin) 1.0'' 20% 0.5'' 10% 0.0'' 0% 10:00 PM 6:00 AM 2:00 PM 10:00 PM 6:00 AM  Storm Drainage & Recent Events October 2021 Storm • Timing (Length of Storm) Matters • Kofu 6.6” @ 32 Hours • Beckman • Vinewood 4.8” @ 22 Hours • Henry Glaves ~200% Volume • Salas ~150% Volume  Storm Drainage & Recent Events October 2021 Storm • How’d the Basins Fare? Above HW % Full • Kofu (A-1) 2.0’ 140% • Beckman (A-2) 2.5’ 150% • Vinewood (B-1) 2.5’ 170% • Henry Glaves (B-2) 1.0’ 130% • Pixley (C) 4.5’ 150% • Salas (D) 1.0’ 120% • Peterson (E) 1.0’ 120% • Rose Gate 1 (F-1) N/A N/A • DeBenedetti (G) 3.0’ 145%  Flooding Photos Kofu (Oct 2021) DeBenedetti (Oct 2021)  Flooding Photos Mills & Tokay (Oct 2021) Vinewood Park (Oct 2021) 1711 W Tokay (Oct 2021) Vinewood Park (Oct 2021)  Flooding Photos Ham Lane (Oct 2021) Lower Sacramento (Oct 2021) Lower Sacramento (Dec 2022) Cabrillo Circle (Oct 2021)  Flooding Photos Vineyard Terrace (Dec 2022) Vineyard Terrace (Dec 2022) Vineyard Terrace (Dec 2022) Storm Drainage & Recent Events Pause for Questions Recent Rain Events  Storm Drainage & Recent Events Flood-Prone Areas • 100+ Flood Calls in Major Events • Short Intense Storm • Spread Out • High Volume Storm • Near Basins • Other Known Areas (Without Many Calls)  Storm Drainage & Recent Events Specific Flood-Prone Areas • Vinewood (B-1) Both Types of Events • DeBenedetti (G) (Vineyard Terrace) Primarily “High Volume” Events (Basin is Full)  Storm Drainage & Recent Events Specific Flood-Prone Areas • Why does this happen? • High Volume Storms = Basins Too Full 1’ Design Street Flooding High Volume Storm  Storm Drainage & Recent Events Specific Flood-Prone Areas • Short Intense Storms = More Complicated • Design Storms • Frequency  Storm Drainage & Recent Events Specific Flood-Prone Areas • Short Intense Storms Street Flooding > 2-Year Design Flow 1’ 2-Year Full Basin Full Basin Street Flooding > 5-Year Design Flow 1’ 5-Year Empty Basin Empty Basin  Storm Drainage & Recent Events Specific Flood-Prone Areas • Short Intense Storms Design Flow = A x I x C • (A) Area “How much area is going to that specific inlet or pipe” • (I) Rainfall Intensity “How much water is falling in a period of time” • (C) Runoff Coefficient “How much water is running off the site”  Storm Drainage & Recent Events Specific Flood-Prone Areas • Short Intense Storms Design Flow = A x I x C • (I) Rainfall Intensity • Time of Concentration • Length of Time from Furthest Point to a Specific Inlet/Pipe • Shorter Time = Higher Design Intensity • What Impacts the Time of Concentration?  Storm Drainage & Recent Events Time of Concentration • Type of Surface • Roof • Back yard • Front yard  Storm Drainage & Recent Events Time of Concentration • Type of Drainage Collection • Over-Land • Area Drains • Roof Drains • Outlet Location  Storm Drainage & Recent Events Rainfall Intensity • Does this Make of a Difference? • City’s Design Standard: 25 Minutes (Res) • If Tc is 5 minute less, the design Intensity (I) is up to 16% higher 1.26 1.09  Storm Drainage & Recent Events Rainfall Intensity Summary • Faster it Gets There = Higher the Flows  Storm Drainage & Recent Events Runoff Coefficient • Design Flow = A x I x C • (C) Runoff Coefficient • Ratio of rainwater runs off the site 0.8 = 80% Running Off • Higher C Factor = Higher Flow into Inlet/Pipe • What Impacts the Runoff Coefficient? 0.4 Min. (1963-2019) Land Uses Surface Types  Storm Drainage & Recent Events Runoff Coefficient • (C) Runoff Coefficient Example Conc x = x = Bldg x = x = Conc Land Check Larger Area: Pvmt Composite C = 0.73 > “0.4 - 0.6”  Storm Drainage & Recent Events Runoff Coefficient • Why So High? • Trend of Larger Houses on Smaller Lots • Smaller Front & Rear Yard Setbacks over Time • Concrete Back Yards • Concrete Front/Side Yards • Synthetic Grass  Storm Drainage & Recent Events Runoff Coefficient • Not Unique to One Location • Analysis 20 Residential Locations (1950-2021) • Style of Development Over Time • +10% 1950s Into 1960s, Steady from 1960s through 1990s • +5% Early 2000s, +5% ~2017 • Increase in Hardscape over Time. Rarely Opposite 5% 5% 10%  Storm Drainage & Recent Events Storm Drainage Flows • What does this all mean? • Rainfall Intensity (I) • Tc is 5 Minutes Shorter • 16% Higher Intensity • Runoff Coefficient (C) • Design = 0.50, Actual = 0.73 • 46% Higher • Design Flow = A x I x C • (A) Area • 1.16 (I) Rainfall Intensity • 1.46 (C) Runoff Coefficient • Actual Flow almost 70% Higher Than Design  Storm Drainage & Recent Events Storm Drainage Flow Summary • Faster Water Gets There = Higher the Flows • The More Water Runs Off = Higher the Flows  Storm Drainage & Recent Events Pause for Questions Specific Flood Prone Areas or Flow Calculations  Storm Drainage & Recent Events Potential Projects • So What Now? • Increase Awareness • Reviewed Areas Most-Impacted by Major Storms • Created a List of Potential Projects • Will Return to Council With Full List / Timing / Costs • Sample of Potential Projects by Location  Storm Drainage & Recent Events Potential Projects • Kofu Park (A-1 Basin) • Add Passive Connection to Skate Park Area • Adds 23% Basin Capacity (without Flooding Ham Lane) • Vinewood Park (B-2 Basin) • Minor Pump Station Improvements • Increase the Pump Capacity (Drain the Basin Quicker) • Shady Acres Pump Station • Minor Modifications • Increase Pumping Capacity  Storm Drainage & Recent Events Potential Projects • Pixley Park (C Basin) • Square-Off • Adds 58% Basin Capacity $$$ • Rose Gate Park (F-1 Basin) • Deepen Basin (~1.5’) • Adds 30% Capacity • Rose Gate 2 Basin (F-2) • Deepen Basin • Adds 13% Capacity  Storm Drainage & Recent Events Potential Projects • DeBenedetti Park (G) • Add Century Outfall • Reduce Pressure on the Century Line • Deepen Middle Area • Add 6% Capacity • Vineyard Terrace • Additional Pipe Connection • Reduce Pressure on the onsite storm drainage system Questions?