HomeMy WebLinkAbout2nd Submittal - 2022-07-06 - stormwatercontrolplanStormwater Control Plan for Post Construction Requirements Exhibit 4
Application Submittal
■ Where directions state "Done" that means no additional information or forms below that point needs to be
filled out or furnished.
See Exhibits for Watershed Management Zones, Basins, & Urban Sustainability Areas
Use "n/a" where information requested is not applicable. If you are unsure regarding how to fill out any of
the information, please come in and request assistance from a staff person.
Project Information
Step 1
Applicant Name:
San Luis Obispo Repertory Theatre
Application No:
Project Name:
San Luis Obispo Repertory Theatre
Location Address:
630 Montery, San Luis Obispo
Location APN:
APNs 002-415-001, 002, 003, 004, 011, & 012
Site Zoning:
Project Type: ✓
✓
Commercial
Detached Single Family Residential
Industrial
Multi -unit Residential
Mixed Use _V1
Phase i
Public
Project Phase:
Project Description:
The project consists of the demolition and removal of 4 structures and a parking lot to allow for the construction of a parking structure, commercial space, and a theatre.
Total Project Site Area
1 1.38ac
(a)
Total New Impervious Surface Area =
0.33ac
(b)
Total Replaced Impervious Surface Area =
0.94ac
(c)
Total Existing Impervious Area =
0.94ac
(d)
Total Impervious Area of Completed Project =
1.27ac
(e)
Net Impervious Area: (a+b) — (c-d) _
OR where (c-d) is a negative number: (a+b) =
1.27 ac
Your project is NOT subject to Post Construction Requirements if...
2
Area (a+b) of project is < 2,500 square feet —
one OR
Area (a+b) of project is > 2,500 square feet, and is a project type listed below (✓ type) —
DoneE] Road & parking surface repair — slurry & fog & crack seal, pothole & spot patching, overlay &
resurfacing & other damage repair with no expansion
Road & parking shoulder grading
H
Road & parking cleaning, repairing, maintaining, reshaping, regarding drainage systems
Sidewalk & bike path / lane project — no other impervious surface created and runoff is directed to
vegetated area
Curb & gutter improvement or replacement — no other impervious created
Underground utility project — surface replaced in kind
Utility vaults — Ex: lift stations, backflows
Fuel storage — above ground with spill containment
Photovoltaic systems — on existing impervious surface, over pervious surface with vegetated cover,
ffer strip at the most down gradient row of panels
Second story — no increase in building footprint
Decks & stairs & walkways — raised with space below for drainage
Temporary structures — in place less than 6 months
Trails and pathways, where no other impervious surfaces are replaced or created, and built to direct
stormwater runoff to adjacent vegetated areas.
Form revised: July 12, 2016
0
Stormwater Control Plan for Post Construction Requirements
Otherwise, your project is subject to the Post Construction Requirements
Project Site Details
Step 3
Watershed Management Zone:
1
Urban Sustainability Area Name:
n
I ✓ Meet USA Conditions
• See Area calculations in Step 1 to compare to thresholds in each Step below
• Where directions state "Go To". fill out and attach the referenced Form and any supporting documents
itep 4
Project is > 2,500 square feet
❑ Yes - Go To Requirement 1— Site Design & Runoff Reduction - Form 1 AND THEN
Go To Step 5
Detached single family residential project where Area (e) is > 15,000 square feet OR
Project where Area (e) > 5,000 square feet
El Yes - Go To Requirement 2 — Water Quality Treatment - Form 2 AND THEN
Go To Step 6
❑ No - Done
b
Detached single family residential project where Area (e) > 15,000 square feet OR
Project where Area (a+b) > 15,000 square feet
AND is in Watershed Management Zone 4,7,10 over a ground water basin OR in Zone 1,2,5,6,8,9
El Yes - Go To Requirement 3 — Runoff Retention - Form 3 AND THEN
Go To Step 7
❑ No - Done
itep 7
Project where Area (a+b) > 22,000 square feet AND is in Watershed Management Zone 1,2,3,6,9
❑ Yes -Go To Requirement 4— Peak Management -Form 4
❑ No -Done
Exhibits
1. Watershed Management Zones
2. Groundwater Basin Location
3. Watershed Management Zone Revision Request
4. Urban Sustainability Conditions and Maps of Approved Areas
Stormwater Control Plan for Post Construction Requirements Form 1
Requirement 1- Site Design and Runoff Reduction:
Identify the strategies used to reduce runoff through site design. Strategies 1-5 required.
Describe or attach simple plan details for 1. - 5.
1. Limit disturbance of creeks and natural drainage features and setback development from these features.
Disturbed area has been limited as requested.
2. Minimize compaction of highly permeable soils
Compaction has been minimized in where feasible.
3. Minimize clearing of native vegetation and grading, conserving natural areas and maximizing undisturbed
areas, and developing along natural landforms.
Project is an infill develpment project. There are no natural areas.
4. Minimize impervious surfaces including roadways and parking lots
Impervious areas have been minimized where possible.
5. Do one of the following: ✓
❑✓ Direct roof run off into cistern, rain barrel, or vegetated area
❑Direct driveway, walkways, patios, and/or parking area into vegetated area
❑Construct surfaces (bike lanes, walks, driveways, parking areas,patios) with permeable surfaces
6. Other (Optional): Identify strategy(s) and describe or show how it will be done in the project.
Stormwater Control Plan for Post Construction Requirements Form 2
Requirement 2 — Water Quality Treatment:
(Reference Post Construction Stormwater Management Requirements for Development Projects in the Central
Coast Region — Adopted July 12, 2013 California Regional Water Quality Control Board Central Coast Region —
for details regarding requirements — Section B.3 and Section C. Alternative Compliance.)
Treatment
Location ✓ El On Site ❑ Off Site - Alternative Compliance
Measure Used ✓ El 1. Harvesting, infiltration, evapotranspiration
❑ 2. Bio-filtration Treatment (Document inability to use 1.)
❑ 3. Non -Retention Based Treatment (Document inability to use 1. or 2.)
Description of structural controls:
Stormtech under ground detention chambers.
Alternative compliance measures:
Attachments
■ Attach treatment/sizing calculations, including any volume treated with off -site compliance.
■ Attach construction and planting details and specifications for bio filtration options
■ Attach documentation regarding Treatment Measure selection
■ Attach infeasibility analysis where alternative compliance is proposed.
Certification
I Daniel Sotelo certify that the systems selected and sized, as demonstrated in the attached
calculations, meet the Water Quality Treatment required for this project per the Post Construction
Requirements adopted by the Central Coast Regional Water Quality Control Board. Where identified in the
attached documentation, Water Quality Treatment will be met through alternative compliance.
7/6/2022
Signature Date
Stormwater Control Plan for Post Construction Requirements Form 3
Requirement 3 — Runoff Retention:
(Reference Post Construction Stormwater Management Requirements for Development Projects in the Central
Coast Region — Adopted July 12, 2013 California Regional Water Quality Control Board Central Coast Region —
for details regarding requirements — Section B.4 and Section C. Alternative Compliance.)
■ If a revision to the site's Watershed Management Zone is being requested, attach Watershed Management
Revision Request Form (Exhibit) and supporting documentation.
■ Rainfall maps are available from the Regional Water Quality Control Board
Site Assessment Measures Summary
0 Attach documentation of the following information:
■ Site topography
■ Development envelope
■ Hydrologic features including natural areas, wetlands, watercourses, seeps, springs, and required setbacks
■ Vegetative cover including trees
■ Open space requirements
■ Location of groundwater wells used for drinking water
■ Depth to seasonal high groundwater
■ Soil types and hydrologic soil groups
■ Depth to impervious layer such as bedrock
■ Presence of unique geology (e.g. karst)
■ Geotechnical hazards
■ Existing structures, utilities, and drainage infrastructure including municipal storm drain system
components
■ Existing easements and covenants
■ Documented soil or groundwater contamination
■ Source and estimated stormwater run-on from offsite, coming to project area
■ Drainage Management Areas (B.4.d.iii)
■ Drainage management strategies by Drainage Management Area
■ Runoff reduction measures and any structural control measures by Drainage Management Area (or full site
as appropriate)
❑ Technical infeasibility limits on -site compliance
❑ 10% of equivalent impervious surface area is dedicated to retention based stormwater control
measures — No alternative compliance for retention
Runoff volume - compliance not achieved on -site:
❑ Alternative compliance for retention proposed
Runoff volume — compliance not achieved onsite:
Runoff volume — alternative compliance used:
Analysis and Sizing
0 Attach calculated Tributary Areas and Design Volumes per the Post Construction Stormwater Management
Requirements —Attachment D
0 Adjustment made for redevelopment
❑ Adjustment made for being in, and meeting requirements of, an Urban Sustainability Area
Stormwater Control Plan for Post Construction Requirements Form 3
Control Mechanism
Site in Zone 1, 4, 7, and/or 10 and over groundwater basin
0 95th percentile event retained via infiltration 2.01 iNCHES
❑ Finding of technical infeasibility — Structural Stormwater Measure proposed
Site in Zone 2
❑ 95" percentile event retained via storage, harvesting, infiltration, and/or evapotranspiration
❑ Finding of technical infeasibility — Structural Stormwater Measure proposed
Site in Zone 5 and/or 8
❑ 85th percentile event retained via infiltration
❑ Finding of technical infeasibility — Structural Stormwater Measure proposed
Site in Zone 6 and/or 9
❑ 851h percentile event retained via storage, harvesting, infiltration, and/or evapotranspiration
❑ Finding of technical infeasibility — Structural Stormwater Measure proposed
Attachments
■ Attach Attachment D calculations for hydrologic analysis and stormwater control measure sizing
■ Attach discussion of technical infeasibility for structural stormwater measure, where proposed in lieu of
preferred storage, harvesting, infiltration, and/or evapotranspiration, include justification for any non -
retention based controls
■ Attach documentation of technical infeasibility for on -site compliance, including a site specific hydrologic
and/or design analysis supporting findings
■ Attach description of alternative compliance project including a summary description of pollutant and flow
reduction comparing the expected aggregate results of the alternate project to the results that would
otherwise have been achieved by meeting the numeric performance requirements onsite.
■ Attach Attachment E calculations for retention requirement adjustment for technical infeasibility
■ Attach Attachment F calculations for off -site retention requirements
■ Attach agreement for alternative compliance site use, for purposes of achieving compliance
■ Attach Operations and Maintenance Plan for all stormwater control measures (include any Peak
Management facilities)
Post -Construction Owner Identification
At the time of completion of the construction work, and the shift to post -construction stormwater controls,
the below listed owner is responsible for Operations and Maintenance of stormwater control measures:
SLO Rep
(If responsibilities are divided, list all responsible owners and associated measures.)
Certification
I Daniel Sotelo certify that the systems selected, sized, and designed as demonstrated in the
attached calculations, meet the Runoff Retention Performance Requirement for this project per the Post
Construction Requirements adopted by the Central Coast Regional Water Quality Control Board. Where
identified in the attached documentation, Runoff Retention will be met through alternative compliance.
L 5/31 /2022
Signature Date
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User Inputs
Chamber Model:
MC-7200
Outlet Control Structure:
No
Project Name:
SLO REP - DMA 1
Engineer:
Daniel Sotelo
Project Location:
California
Measurement Type:
Imperial
Required Storage Volume:
2204 cubic ft.
Stone Porosity:
40%
Stone Foundation Depth:
9 in.
Stone Above Chambers:
12 in,
Average Cover Over Chambers:
24 in,
Design Constraint Dimensions:
(25 ft. x 32 ft.)
EMBEDMENT STONE SHALL BE A CLEAN, CRUSHED AND ANGULAR
STONE WITH AN AASHTO M43 DESIGNATION BETWEEN #3 AND 44
CHAMBERS SHALL MEET ASTM F2418 "STANDARD
SPECIFICATION FOR POLYPROPELENE (PP) CORRUGATED
WALLSTORMWATER COLLECTION CHAMBERS"_
ADS GEOSYTHETICS 601T NON -WOVEN
GEOTEXTILE ALL AROUND CLEAN, CRUSHED,
ANGULAR EMBEDMENT STONE
PERIMETER STONE
EXCAVATION WALL
(CAN BE SLOPED
OR VERTICAL)
12" (300.
Results
System Volume and Bed Size
Installed Storage Volume:
2353.76 cubic ft.
Storage Volume Per Chamber:
175.90 cubic ft.
Number Of Chambers Required:
6
Number Of End Caps Required:
4
Chamber Rows:
2
Maximum Length:
31.01 ft.
Maximum Width:
19.42 ft.
Approx. Bed Size Required:
602.12 square ft.
System Components
Amount Of Stone Required: 105.59 cubic yards
Volume Of Excavation (Not Including 150.53 cubic yards
Fill):
Total Non -woven Geotextile Required:251.33 square yards
Woven Geotextile Required (excluding21.23 square yards
Isolator Row):
Woven Geotextile Required (Isolator 58.90 square yards
Row):
Total Woven Geotextile Required: 80.13 square yards
GRANULAR WELL -GRADED SOIIJAGGREGATE MIXTURES, 135%
FINES, COMPACT IN 12- (300 mm) MAX LIFTS TO 95% PROCTOR
DENSITY_ SEE THE TABLE OF AOCEPTABLE FILL MATERIALS_
CHAMBERS SHALL BE BE DESIGNED IN ACCORDANCE WITH ASTM F2787
"STANDARD PRACTICE FOR STRUCTURAL DESIGN OF THERMOPLASTIC
CORRUGATED WALL STORMWATER COLLECTION CHAMBERS"_
PAVEMENT LAYER (DESIGNED
BY SITE DESIGN ENGINEER)
21 (21 m)
(600 mm) MIN' MAX
12' (300 mm) MIN y -
60"
(1525 mm)
DEPTH OF STONE TO BE DETERMINED
1, 1 — T- 7 - rmtMWW9TI'� 717�
BY SITE DESIGN ENGINEER 9' (230 Inrn) MIN
MC4500 9"
END GAP (230 mm) MIN 100' (2540 nnn) 12' (30D mm) TYP
SITE DESIGN ENGINEER IS RESPONSIBLE FOR ENSURING
THE REQUIRED BEARING CAPACITY OF SOILS
'MINIMUM COVER TO BOTTOM OF FLEXIBLE PAVEMENT. FOR UNPAVED INSTALLATIONS WHERE RUTTING FROM VEHICLES MAY OCCUR, INCREASE COVER TO 30' (750 mm).
User Inputs
Chamber Model:
MC-3500
Outlet Control Structure:
No
Project Name:
SLO Rep DMA 2
Engineer:
Daniel Sotelo
Project Location:
California
Measurement Type:
Imperial
Required Storage Volume:
1617 cubic ft.
Stone Porosity:
40%
Stone Foundation Depth:
20 in.
Stone Above Chambers:
12 in.
Average Cover Over Chambers:
18 in.
Design Constraint Dimensions:
(20 ft. x 28 ft.)
EMBEDMENT STONE S44LLBE ACLEAN. CR US HED AND ANGULAR
STO N E WIT H AN AAS HT G M43 DES I G NAT IGN BETWEEN 43 AND 44
CHAMBERS SHALL MEET ASTM F2418 "STANDARD
SPECIFICATION FOR POLYPROPLENE(PP) CORRUGATED
WALL STORMWPTER COLLECTION CHAMBERS".
ADS GEG S YNT HET ICS 601T NON WOVEN
G EOT EXT ILE ALL A RO U ND CLEAN, CRUSHED,
ANGULAR EMB ECM ENT STONE
PERIMETER STONE
IX CAVAT IGN WALL
(CAN BE SLOPED
O R LERTI CAL)
6" (150 -) MIN
Results
System Volume and Bed Size
Installed Storage Volume:
1658.56 cubic ft.
Storage Volume Per Chamber:
109.90 cubic ft.
Number Of Chambers Required:
6
Number Of End Caps Required:
4
Chamber Rows:
2
Maximum Length:
31.18 ft.
Maximum Width:
15.33 ft.
Approx. Bed Size Required:
478.11 square ft.
System Components
Amount Of Stone Required: 87.00 cubic yards
Volume Of Excavation (Not Including 113.63 cubic yards
Fill):
Total Non -woven Geotextile Required:207.09 square yards
Woven Geotextile Required (excluding16.73 square yards
Isolator Row):
Woven Geotextile Required (Isolator 29.46 square yards
Row):
Total Woven Geotextile Required: 46.19 square yards
G RANUL4R W AL-G RADED S G IUAGG R EG q E M XT ORES, 135 %
FINES, CCM PACT IN 12"(MO mm)MAX LIFTS TO 95°& PROCTOR
❑ EN S IT Y. SEE TH E TAB LE G F AC CEPTAB LE FI LL MAT ERIALS.
CHAMBERS SHALL BE DES I G NED IN ACCORDANCE WITH ASTM F2787
"STANDARD P RACTIC E F G R ST RU CT URAL DES 10 N G F T HERM G P LAST IC
C G RRU GATED WALL STO RMWATER CG LLECTIGN CHLM B ERS".
PAVEMENT LAYER (DESIGNED
BY SITE DESIGN ENGINEER)
L MC-3500 77"(1950 mm)
END CAP (150 mm)MIN �'1 i"^
SITE DESIGN ENGINEER IS RESPONSIBLE FOR ENSURING
TH E REQ U IR ED BEARING CAPACITY OF SOILS
TA IN M LM COVER TO BOTTOM OF F LE(I B LE PA%ANENT. FOR UNPAVED INSTALLATIONS WHERE RUTTING FR OM LEH IC LES MAY OCCUR, INCREASE COVER TO 24"
8'
8" (2.4m)
(450 mm) MIN" MAX
DEPTH OFSTONETO BE DETERMINED
B Y S ITE DESIGN ENO NEER 9" (230 -) MIN
12"(300 mm)TYP
AADS
User Inputs
Chamber Model:
MC-3500
Outlet Control Structure:
No
Project Name:
SLO REP DMA 3
Engineer:
Daniel Sotelo
Project Location:
California
Measurement Type:
Imperial
Required Storage Volume:
619 cubic ft.
Stone Porosity:
40%
Stone Foundation Depth:
9 in.
Stone Above Chambers:
12 in.
Average Cover Over Chambers:
18 in.
Design Constraint Dimensions:
(10 ft. x 41 ft.)
EMBEDMENT STONE SHALL BE AC LEAN, CR US HEG AND ANGULAR
STONEWITHAN AASHTOM43 DESIGNATION BErAEEN N3 AND N4
CHAMBERS SHALLMEEr ASTM F2418 "STANDARD
SPECIFICATION FOR POLYP ROP LEI E(PP)CORRUGATED
WALL$TO RKWATER COLLECTION CHAMBERS".
ADS GEOSYNTHETICS 601T NONWOVEN
GEDT BBT ILE ALL ARO U NO CLEAN, CRUSHED,
ANGULAR EMB ECM ENT STONE
PERIMETER STONE
E(CAVAT ION WALL
(CAN BE SLOPED
OR V.ERTI CAL)
6" (150 mm)MIN
System Volume and Bed Size
Installed Storage Volume:
720.28 cubic ft.
Storage Volume Per Chamber:
109.90 cubic ft.
Number Of Chambers Required:
3
Number Of End Caps Required:
2
Chamber Rows:
1
Maximum Length:
27.25 ft.
Maximum Width:
8.42 ft.
Approx. Bed Size Required:
229.35 square ft.
System Components
Amount Of Stone Required: 33.41 cubic yards
Volume Of Excavation (Not Including 46.72 cubic yards
Fill):
Total Non -woven Geotextile Required:113.47 square yards
Woven Geotextile Required (excluding0 square yards
Isolator Row):
Woven Geotextile Required (Isolator 29.46 square yards
Row):
Total Woven Geotextile Required: 29.46 square yards
GRANULAR WELL 0 FADED S OIUAGG R EGAT E M LCT URES, 135%
FI NES, C CM PACT IN 12" (300 mm) MAX LI Fr TO 95 % P RO CTG R
❑EJ S IT Y. SEE TH E TAB LE GF AC CEPTAB LE FI LL MAT ERIALS.
CHAMBERS SHALL BE ❑ES IG NED IN ACCORDANCE WITH ASTM F2787
"STANDARD PRACTICE FOR ST RU Cr URA. DESIGN OF THERMOPLASTIC
CORRUGATED WALL $TO RMWATER COLLECTION CHPMBERS".
PAVEMENT LAYER (D ESI G NED
BY SITE DESIGN ENGINEER)
MC-3600 ...... ...... 6..
END CAP (150 ..)MIN 77"(1950-)
STEDESIGN ENGINEER IS RESPONSIBLE FOR ENSURING
TH E RED U IF ED B EAR IN G CAPACITY OF SOILS
'TM INMLM COVER TO BOTTOM OF F LB (I BILE PAVEMENT. FOR UNPAVED INSTALLATIONS WHERE RUTTING FROM VEHICLES MAY OCCUR, INCREASE COVER TO 24'
8" } MAX
(450 mm) MIFP MFUi
DEPTH OF STONE TO BE DETERMINED
BY SITE DESIGN ENGINEER 9" (230 -)MIN
C12"C30O -)TYP
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Stormwater Control Plan for Post Construction Requirements Form 4
Requirement 4 — Peak Management
(Reference Post Construction Stormwater Management Requirements for Development Projects in the Central
Coast Region — Adopted July 12, 2013 California Regional Water Quality Control Board Central Coast Region —
for details regarding requirements — Section B.5)
Show any stormwater control measures used to meet the requirements of this section, in the documentation
and attachments required for Retention (Form 3), including in all mapping and Operations and Maintenance
materials.
Peak Management Compliance
El Post -development peak flows, discharged from the site, do not exceed pre -project peak flows for the 2
through 10 years storm events.
❑ Technical infeasibility limits on -site compliance
❑ Alternative compliance for retention proposed
Runoff volume — compliance not achieved onsite:
Runoff volume — alternative compliance used:
Attachments
■ Attach calculations showing pre -project discharge and post -project discharge for the 2 through 10 year
storm events
■ Attach documentation of technical infeasibility for on -site compliance, including a site specific hydrologic
and/or design analysis supporting findings
■ Attach description of alternative compliance project including a summary description of pollutant and flow
reduction comparing the expected aggregate results of the alternate project to the results that would
otherwise have been achieved by meeting the numeric performance requirements onsite.
■ Attach agreement for alternative compliance site use, for purposes of achieving compliance
Post -Construction Owner Identification
At the time of completion of the construction work, and the shift to post -construction stormwater controls,
the below listed owner is responsible for Operations and Maintenance of the peak management control
measures:
SLO Rep
(If responsibilities are divided, list all responsible owners and associated measures.)
Certification
I Daniel Sotelo certify that the systems selected, sized, and designed as demonstrated in the
attached calculations, meet the Peak Management requirements for this project per the Post Construction
Requirements adopted by the Central Coast Regional Water Quality Control Board. Where identified in the
attached documentation, Peak Management will be met through alternative compliance.
-2,--> / S -u 5/31 /2022
Signature Date
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Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
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Percent of AOI
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complex, 5 to 9
percent slopes
D
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100.0%
Totals for Area of Interest
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
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chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
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thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
USDA Natural Resources Web Soil Survey 3/4/2019
Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group —San Luis Obispo County, California, Coastal Part
Component Percent Cutoff.- None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 3/4/2019
Conservation Service National Cooperative Soil Survey Page 4 of 4
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Hydrologic Soil Group —San Luis Obispo County, California, Coastal Part
SLO LITTLE THEATER
Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
162
Los Osos-Diablo
complex, 5 to 9
percent slopes
D
22.3
17.2
56.3%
43.7%
198
Salinas silty clay loam, 2
to 9 percent slopes,
MLRA 14
C
Totals for Area of Interest
39.5
100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
USDA Natural Resources Web Soil Survey 5/21/2019
Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group —San Luis Obispo County, California, Coastal Part
SLO LITTLE THEATER
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 5/21/2019
Conservation Service National Cooperative Soil Survey Page 4 of 4
PROJECT CLEAN WATER
• Design rainfall depth (95`h percentile storm)
• Total new impervious area
• Total replaced impervious area in a USA
• Total replaced impervious area not in a
USA
• Total pervious or landscaped area
Then for each, DMA, enter the following:
• Name of DMA and type (self -treating, self -
retaining, drains to self -retaining, or drains
to Stormwater Control Measure)
• DMA area in square feet
• Type of surface (roof, landscape, etc.)
• New or replaced and whether in a USA
• For DMAs that are not self -treating or self -
retaining, the connection to a self -retaining
area or Stormwater Control Measure
For each LID Facility/SCM, enter:
• Name of SCM and type (bioretention or
direct infiltration; see discussion below)
• Hydrologic Soil Group or design infiltration
rate for subsurface soils (see discussion
below)
• Surface reservoir volume (may be entered as
an average depth if reservoir area is the
same as facility infiltration area)
• Facility infiltration area (area in contact
with subsurface soils)
The calculator performs the following based
on the Santa Barbara Unit Hydrograph
method:
• Distributes the design storm depth over
time increments (Type 1 unit hydrograph)
• Calculates facility inflow rate and volume
for each time increment
• Calculates facility infiltration rate and, for
each time increment, the corresponding
infiltration volume
• Calculates incremental increase or decrease
in storage and cumulative storage for each
time increment
• Tracks and outputs time for facility to drain
fully
The calculator outputs the maximum
cumulative storage volume required to retain
the design storm. As required by the PCRs,
the calculator multiplies this volume by 1.2
when the drawdown time exceeds 48 hours
(the likely condition when facilities are
located in lower -permeability soils).
This is the Minimum Required Storage
Volume to be used for your design.
Infiltration rate for routing method: You may
use the default option or, alternatively, submit
data from on -site testing.
The default option is to use the Hydrologic
Soil Group (HSG) that best characterizes site
soils. To support your selection of an HSG,
attach to your Stormwater Control Plan on -
site boring logs or other information such as a
geotechnical report for the site. In the
calculator, HSG A/B soils (soils with no
significant clay component) are assigned an
infiltration rate of 0.75 in/hr. and HSG C/D
soils are assigned an infiltration rate of 0.25
in/hr. Should you wish to submit data from
on -site testing, consult in advance with
municipal staff regarding acceptable test
methods.2
z The publication "Native Soil Assessment for Small Infiltration -Based Stormwater Control Measures,"
prepared for the Central Coast Low Impact Development Initiative and available at the Central Coast Water
Board website, outlines some test methods
STORMWATER TECHNICAL GUIDE 4-5 3 FEBRUARY 2017
Stormwater Control Plan for Post Construction Requirements
Exhibit 1
Wo
tersnea Management zones
4—
C
O] (D E
J
f17 CJ C M It n 0 co M
M 0 0114
N IIII
M
75
Stormwater Control Plan for Post Construction Requirements Exhibit 2
Ground Water Basin
Groundwater
Basin
y
Iv-------------
----- --- —
`—
•
fir@ i
�� i
r i
1
Tank Fg! V
iL--- --- ------
n
0 0.5 1 2 w e
Miles
5
Stormwater Control Plan for Post Construction Requirements Exhibit 3
Watershed Management Zone Revision Request
It is understood that Watershed Management Zones were developed through the Central Coast Regional Water
Quality Control Board Joint Effort with available data, at varying degrees of detail and accuracy. Zones may
vary across properties, or be off from verifiable, on the ground data. Applicants may propose revisions to the
designate Watershed Management Zone for the project.
Applicants should carefully review the Post -Construction Stormwater Management Requirements For
Development Projects in the Central Coast Region, California — Technical Support Document for a clear
understanding of the basis of the Watershed Management Zone designations before proceeding with this
application.
Site Information
Project Address:
Current Watershed Management Zone(s):
Proposed Watershed Management Zone(s):
Watershed Management Zone Summary
Copy table for multiple zones in the Project area
• Mark the characteristics supported by geotechnical observation in the column marked "(P)"
■ Identifv the oaae number in anv aeotechnical report reference in the column marked "Pa"
Watershed Management Zone
1
2
3
4
5
6
7
8
9
10
1 (P)
I Pg
Drains to:
Stream
✓
✓
BI
l
Wetland
I
I
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I
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Stream or Wetland
✓
✓
✓
✓
La ke
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✓
Lake or River
-�
Underlain by:
0-10% All types
✓
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> 40% All types
I
I
I
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0-40% Quaternary & Late Tertiary
✓
������
10-40% Quaternary & Late Tertiary
✓
������L
0-10% Early to Mid -Tertiary
I✓
I
I
I
I
I
I
I
��
-�
10-40% Early to Mid -Tertiary
I
I ✓
10-40% Franciscan melange, Pre -Quaternary
crystalline, Early to Mid -Tertiary
✓5
I ICI
> 40% Quaternary, Late Tertiary, Early to Mid -
Tertiary
0-10%Franciscan melange, Pre -Quaternary
crystalline
✓
����
n
I �
> 10% Franciscan melange, Pre -Quaternary
crystalline
10 40%Franciscan melange, Pre -Quaternary
crystalline
I
III
I
I
III
I
✓3
n
I �
> 40% Franciscan melange, Pre -Quaternary
crystalline
Stormwater Control Plan for Post Construction Requirements Exhibit 3
Watershed Management Zone
11
I 2
I 3
I 4
I 5
I 6
7
8
9
10
(P)
Pg
Slope:
Steep
����
✓
✓
✓
✓
L
Moderate
✓
✓
������
✓
✓
L
Low
��
✓
✓
������
Watershed Process:
✓1
I
Infiltration dominant
��
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✓
✓
Infiltration less dominant
Chemical & biological remediation
������
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✓
✓
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Overland flow minimal
✓
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I
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Notes:
3 —Zone 9 Stream or Wetland Draining
1 — Over groundwater basin 4 —Zone 10 Lake Draining
2 — Zone 9 Wetland Draining 5 —Zone 10 Lake or River Draining
Watershed Management Zone Revision Supporting Summary
Provide written summary of geotechnical/geological information supporting revised Watershed Management
Zone designation.
Attachment
■ Attach geotechnical or geological information which supports revision (include page references in table
above)
Stormwater Control Plan for Post Construction Requirements Exhibit 4
Urban Sustainability Areas
Urban Sustainability Areas (USA) encompass high density urban centers where the documented objective is to
preserve or enhance and existing pedestrian -oriented and/or public transit -oriented type of urban design
through the promotion of high density redevelopment and infill.
Requirements for USAs
The City has received approval for certain sub -areas within three land use zoning areas for USAs designation,
superimposed with minimum requirements. The Zones are Retail Commercial, Downtown Commercial, and
High Density Residential. Maps are provided at the end of this document.
Site specific requirements relating to floor areas or dwelling units, surface parking allowance, and alternative
transportation meet or exceed the current Zoning Regulation requirements. To be eligible for reductions of
Post -Construction Requirements, development and redevelopment projects must meet all the USA
requirements listed below for the Zone.
A. Retail Commercial (C-R) USA Requirements
■ Ratio of gross building floor area to site area minimum = 3:1
■ Site area building coverage minimum = 90%
■ Project uses < 10% of area for surface parking
■ Within 8 blocks of local transit route with at least hourly daytime service Monday through Friday, with
connections to regional transit routes and train station
■ Provision of bike parking spaces = minimum 15% of auto parking requirement
■ Sidewalks provided on both sides of the street
B. Downtown Commercial (C-D) USA Requirements
■ Ratio of gross building floor area to site area minimum = 3:1
■ Site area building coverage maximum = 100%
■ Project provides no surface parking, beyond incidental uses for emergency and ADA. Exception is
municipal multi -story structures provided as park -in -lieu facilities for intense site developments
■ Within 8 blocks of local transit route with at least hourly daytime service Monday through Friday, with
connections to regional transit routes and train station
■ Provision of bike parking spaces = minimum 15% of auto parking requirement
■ Sidewalks provided on both sides of the street
C. High -Density Residential (R-4) USA Requirements
■ Dwelling units per net acre (net acre - excludes right-of-way, creeks, endangered & threatened species
habitat) minimum = 24 + a low or moderate income density bonus
■ Site area building coverage minimum = 60%
■ Within 8 blocks of local transit route with at least hourly daytime service Monday through Friday, with
connections to regional transit routes and train station
■ Provision of bike parking spaces = minimum 10% of auto parking requirement
■ Sidewalks provided on both sides of the street or approved alternative connection pathways
Stormwater Control Plan for Post Construction Requirements Exhibit 4
Application of Post Construction Requirements within a USA
Post Construction Requirements will be applied in USAs as follows:
A. Performance Requirement No. 1: Site Design and Runoff Reduction
■ The City will apply those aspects of Site Design and Runoff Reduction that are applicable.
■ Site design activities may be limited by the pre -project condition and density goals.
■ Where complete, or nearly complete lot coverage is proposed, shifting of rainwater to vegetated
areas, or for reuse may not be applicable.
B. Performance Requirement No. 2: Water Quality Treatment
■ The City will apply Water Quality Treatment
■ Where Water Quality Treatment is demonstrated as infeasible, it will be handled per C.3.b
■ Site specific analysis completed and endorsed to show infeasibility per sections C.1.a & c
■ Off -site Project description, location within the same watershed, and scheduled completion date
identified
C. Performance Requirement No. 3: Runoff Retention
■ The City will apply Runoff Retention
■ Per B.4.b.ii, the total runoff volume to be retained from replaced impervious surfaces shall be less
than, or equivalent to, the pre -project runoff volume retained
■ New impervious surfaces will comply with requirements of section B.4, calculated per Attachment D,
where the tributary area is a function of new impervious only
D. Performance Requirement No. 4 — Peak Management
■ The City will apply Peak Management Requirements
■ Post -development peak flows will generally not exceed pre -project peak flows for the 2 through 10
year storm events for redevelopment sites
■ Technical infeasibility will apply where density goals result in space constraints as provided for in
C.1.c.v. Per C.1.a, and no site specific hydrologic or geotechnical analysis will be required.
E. Off -Site Compliance
■ Where an off -site compliance proposal is included in the project submittal
■ Location, analysis for performance requirement compliance, and project mitigation completion
schedule for off -site compliance will be required as part of the submittal.
■ Off -site compliance site will be within the same watershed, unless otherwise approved by the Central
Coast Water Board EO.
Stormwater Control Plan for Post Construction Requirements Exhibit 4
Maps of Approved USAs
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