low impact development (lid) - la stormwater impact development (lid) ... owner certification...
TRANSCRIPT
City of Los AngelesDepartment of Public WorksBureau of SanitationWatershed Protection Division
Low Impact Development (LID)
April 17, 2012Downtown Los AngelesWATERMARKE TOWER
717 W. 9th St
Overview
Road to Adoption
Overview of Requirements & Handbook
Plan Check Process / Submittals
Review & Permitting Process
Small Scale Residential Projects
All Other Development Projects
Examples
Questions
Requirements:
Amends and expands on the existing Standard Urban Stormwater Mitigation Plan (SUSMP) requirements of capturing the first ¾‐inch of a storm event by incorporating LID practices and standards.
Residential (4 units or less):
Projects must chose from prescriptive list of BMPs (Appendix E)
All other developments (commercial, industrial, etc.):
Similar to SUSMP Requirements
Majority of projects implementing SUSMP would satisfy LID requirements
Capture & Use with Rain Barrel
Rain Gardens
Low Impact Development (LID) Ordinance
SECTION 1: INTRODUCTION
SECTION 2: PROJECT REVIEW AND PERMITTING PROCESS
SECTION 3: STORMWATER MITIGATION MEASURES3.1 LOW IMPACT DEVELOPMENT (LID) PLAN3.1.1 SMALL SCALE RESIDENTIAL DEVELOPMENTS (4 UNITS AND LESS)3.1.2 ALL OTHER DEVELOPMENTS
3.2 STANDARD URBAN STORMWATER MITIGATION PLAN (SUSMP)3.3 SITE SPECIFIC MITIGATION3.4 SOURCE CONTROL MEASURES
SECTION 4: BEST MANAGEMENT PRACTICES (BMP) PRIORITY AND RESTRICTIONS4.1 PRIORITIZATION OF BMP SELECTION4.2 INFILTRATION FEASIBILITY SCREENING4.3 CAPTURE AND USE FEASIBILITY SCREENING4.4 INFILTRATION BMPS4.5 CAPTURE AND USE4.6 BIOFILTRATION / BIORETENTION BMPS
SECTION 5: OFFSITE MITIGATION MEASURES
APPENDICIES
Table Of Contents
Development and redevelopment projects are mainly processed through Department of Building and Safety (DBS) & Department of City planning (DCP).
DCP ‐ Projects require discretionary action.
DBS ‐ Building/Grading Permit approvals.
Plan Check ProcessPlan Check Process
DBS Process Submit design plans
Will refer to DCP if necessary
Building / Grading Permit
Will refer to Bureau of Sanitation for all projects 500ft2 of impervious area or more
Bureau of Sanitation Review*
Plan Check ProcessPlan Check Process
* Recommendation: Consult with WPD staff in early stages of the project design
Bureau of Sanitation Review
Step 1: Define project category and identify appropriate BMPs
Small Scale Residential (residential developments less than 4 units)
Prescriptive Option ‐ Appendix E
All Other Development(commercial, industrial, residential developments of 5 units or more)
BMPs adequately sized
Step 2: Submit appropriate Mitigation Plan
Step 3:WPD Review & Approval
Plan Check ProcessPlan Check Process
Bureau of Sanitation ReviewStep 2: Submit Mitigation Plan
Small Scale Residential (residential less than 4 units)First review submittal
1 set of full plans (plot, elevation, utility, mechanical, plumbing, architectural, and landscape plans). Plans must include at least the following:Location, size, and capacity of all BMPs on plansLandscaping areas
Plan Check ProcessPlan Check Process
Final review submittal3 set of full plans (WPD keeps 1 set)Owner Certification (Appendix E ‐ BMP Fact Sheet)Letter of Commitment for SF residential less than 1 acre
WPD will stamp and approve plans and issue clearance thru PCIS
Submit Stormwater Observation Report for Certificate of Occupancy
Bureau of Sanitation ReviewStep 2: Submit Mitigation Plan
All Other Development First review submittal
1 set of full plans (plot, elevation, utility, mechanical, plumbing, architectural, and landscape plans).
Plans must include at least the following:Location of all BMPs on plans, including elevations and drainage patterns.Detailed drawings of all BMPs, including model, size, and capacity. Submit the manufacturer’s product specifications if a manufacturer's product is proposed.Stenciling note and detailTrash enclosure location and detailsLandscaping areasFlow calculations determining the volume of stormwater runoff that must be managed (identifying BMP type and size) ‐ Appendix F. Draft Covenant & Agreement (C&A) Form with an Operation & Maintenance Plan – Appendix D
Plan Check ProcessPlan Check Process
Plan Check ProcessPlan Check ProcessBureau of Sanitation Review
Step 2: Submit Mitigation Plan
All Other Development
Final review submittal3 set of full plans (plot, elevation, utility, mechanical, plumbing, architectural, and landscape plans) ‐WPD keeps 1 set
Submit a copy of the recorded Covenant & Agreement (C&A) filed with the County Recorder’s Office
Operation & Maintenance Plan
WPD will stamp and approve plans and issue clearance thru PCIS
Submit Stormwater Observation Report for Certificate of Occupancy – Appendix D
Residential Prescriptive ExamplesResidential Prescriptive ExamplesLID Requirements
Implement adequately sized LID Best Management Practice (BMP)
Prescriptive Measures – Appendix E
5 BMP ExamplesRain GardensRain BarrelsPlanter BoxesPermeable PavementDry Wells
Residential Prescriptive ExamplesResidential Prescriptive ExamplesProposed addition = 1,000 ft2 Planter Box
Assumes min depth of 2.5ft, 2ft of soil media, 6 inches of freeboard
Rain Garden
Residential Prescriptive ExamplesResidential Prescriptive ExamplesProposed addition = 7,00 ft2
50 ft
120 ftProposed addition
Rain Barrels
Proposed Development
Residential Prescriptive ExamplesResidential Prescriptive Examples
Planter Box
Assumes min depth of 2.5ft, 2ft of soil media, 6 inches of freeboard
Proposed development = 20,000 ft2
Requirement 2,001 – 2,500* = 168 ft2 of planter box area20 ft2 for each additional 500 ft2 thereafter
20,000 ft2 – 2,500ft2 = 17,500 ft2 remaining17,500 ft2 / 500 ft2 = 3520 ft2 x 35 = additional 700 ft2
Total Planter Box Area required = 868 ft2
Infiltration
• Infiltration Trenches• Infiltration Basins• Dry Wells• Permeable Pavement• Underground
Detention Chambers
Road to Compliance Road to Compliance ……
Capture and Use
• Cisterns• Rain Barrels
All other developments(commercial, industrial, etc.)
Currently implemented under SUSMP
Maximize each option
High Efficiency Bio‐filtration
• Bioinfiltration• Bioretention• Planter Boxes• High Flow
Biotreatment
Sample Design Calculations & Worksheet
Appendix F – Sample Design Calculations & WorksheetDetermine the peak mitigated flow rate (QPM) from the development project, use the Los Angeles County Department of Public Works Hydrology Manual. Use the Modified Rational Method for calculating the peak mitigation QPM for compliance with LID Ordinance (consistent with SUSMP).
QPM = CD • IX • ATotal
Sample Design Calculations & Worksheet
Appendix F – Sample Design Calculations & Worksheet
Determine the volume (VM) of stormwater runoff to be mitigated from the new development, use the following equation:
Vm = ( 2,722.5 ft3 / acre ) • [ ( AI )( 0.9 ) + ( AP + AU )( CU ) ]
List the BMP Type(s) to be used in managing the calculated Vm, and size it per the design criteria listen in Section 4.
BMP Sizing – Infiltration Trench
FSK
K MeasuredSatDesignSat
,, =
TKft
inVmA
DesignSat •
•=
,min
12
ratioVoidVV m
Storage =
minAV
D StorageDesign =
Givens:• Vm = 2,492 ft3
• KSat, Measured = 2 in/hr• T = 48 hrs (from Table 4.4)• FS = 3 (from Table 4.4)• Gravel void ratio = 40% ii. Determine Minimum Bottom Infiltration, Amin:
iii. Determine the minimum storage volume, VStorage:
iv. Determine Design Depth:
i. Determine KSat, Design
Costco at Plaza Pacoima (13510 Paxton)
BMP Sizing – Dry Well
rrAh
ππ
2
2min −=
)( RatioVoidVVV DryWellmStorgae •−=
ii. Determine required storage volume, VStorage:
i. Required dry well depth for the infiltration zone, h (ft)
Givens:• Vm = 2,492 ft3 (from step 9)• KSat Measured = 2 in/hr• Gravel void ratio = 40%• Factor of Safety = 3 (per table 4.4)• Amin = 934 ft2• Dia = 6 ft
USC - University Gateway
Capture and Use BMPsNo upper limit size requirement (Encourage larger systems)
As long as 0.75” capacity is available within 72 hours of a storm event
Storm event = a weather pattern that is forecasted to have a 50% or greater probability of providing precipitation to the site. www.srh.noaa.gov/forecast
Otherwise 72 hour drawdown time
LA County Public Health Policy & Operations Manual and Guidelines (Tier I – IV) – Appendix K
Allow spray irrigation if disinfection is provided
LA County Vector Control compliant
Example Capture and Use BMP
Encino Home
ii. Determine Planting Area:
iii. Determine the 7‐month (Oct 1 – April 30) Estimated Total Water Use (ETWU):
i. Determine Design Volume in gallons :
iii. Determine Plant Factor, PF:
galftgalftgalVDesign 640,1848.7492,2)( 3
3 =•=
acftareaLandscapeftAreaPlanting
22 560,43)( •=
AreaPlantingftFactorPlanter •= 4.0)( 2
PFETETWU month ••=− 62.07)7(
BMP Sizing – Planter BoxGivens:• Vm = 2,492 ft3
• Soil media infiltration rate: 5 in/hr (Table 4.5)• TFill = 3 ft (Table 4.5)
ii. Determine KSat, Design
VmftVDesign •= 5.1)( 3
FSK
K MediaSatDesignSat
,, =
( )ft
inhrTk
ftd hrindesignsatp
12
)()( )/(, •=
⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡+⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛ •=
pDesignSatFill
Design
dft
inkT
VftA
12
)(
,
2min
iii. Determine the BMP ponding depth, dp:
* Rule of thumb: With a max ponding depth of 1 ft, area needed is 5 - 6% of impervious area
i. Determine the design volume:
iv. Calculate the BMP Surface Area, Amin*:
717 W. 9th St, Downtown Los Angeles
Additional Information: www.lacity.orgwww.lastormwater.org
Follow us on Facebook: www.facebook.com/lastormwaterprogram
Michael Scaduto, P.E.Michael Scaduto, P.E.Bureau of SanitationBureau of SanitationCity of Los AngelesCity of Los Angeles(213) 485(213) 485‐‐[email protected]@lacity.org