DRAINAGE REPORT.pdfDrainage Report
Bill Ritter SP
for
Vector One, LLC
SITE LOCATION:
8364 Olympic View Dr.
Edmonds, WA 980260
Tax Parcel: 27041800101000
a
Prepared by:
Joseph M. Smeby, P.E.
Job No: 16-0915
November, 2016
fi 9 dl f,.. Eb WHI-1 APPLICABLz
WT.... 'AT ' � C 0 D
TABLE OF CONTENTS
ITEM PAGE
TABLE OF CONTENTS......................................................... ............ ....,............
........1
LISTOF FIGURES........_............................................. ........ ....................... w 2
1. INTRODUCTION & SITE CLASSIFICATION .................................... ........................ 3
2. PREPARATION OF STORMWATER SITE PLAN ,....,..,.. ............................ 4
3. SWPPP NARRATIVE.,,., ....................... ........ ....... , ............. ,.....................5
RISK ASSESSMENT........ ................. ........,..,.... ,,..,.......,.,.,..,.,... 6
B. SWPPP MINIMUM ELEMENTS...................................................... 7
4. SOURCE CONTROL ..................... ...................... ......... ___ ........................... ,...... 8
5. PRESERVATION OF NATURAL DRAINAGE SYSTEM.,....,, .... ......8
6. ON -SITE STORMWATER MANAGEMENT. ......
7. RUNOFF TREATMENT__- ........... ....... ............. ............. ,,,.,...... 9
8. FLOW CONTROL.....................................................................................................10
9. WETLANDS PROTECTION......................................................................................11
10. MAINTENANCE AND OPERATIONS MANUAL ........................„....., ,,,,.,.............,..11
11. OFFSITE ANALYSIS AND MITIGATION ..................................... ,,.,.,..,.,.,.,,.........
,..11
12. FINANCIAL LIABILITY .......................... ................. .,., _ .... ... , ........................11
APPENDIX A - STORMWATER CALCS, SOILS, PHOTOS, M&O............ .......... ___ ..... A-1
Bill Ritter SP 16-0915
May 2017 Page 1
LIST OF FIGURES
ITEM
PAGE
FIGURE 1 VICINITY MAP ..................... ....... ........ ........ ..... ...,....-...12
FIGURE 2 EXISTING DRAINAGE BASIN MAP.......................................................13
FIGURE 3 DEVELOPED DRAINAGE BASIN MAP .........,,.,., ,...:..,.14
FIGURE 4 SNOHOMISH COUNTY SOILS MAP,.... ............ ................... .............. „ 15
FIGURE 5 UPSTREAM/DOWNSTREAM TRIBUTARY AREA MAP........................16
Bill Ritter SP
May 2017
16-0915
Page 2
1. INTRODUCTION & SITE CLASSIFICATION
This document is intended to provide engineering information necessary to support the
construction permit application submittal to the City of Edmonds for the three lot short plat
proposed on this site. The site covers 1.29 acres, with approximately 14,600 sf allowed to
be disturbed. Lot C will not be disturbed as a result 'of this project so the area of -
disturbance will be on future lots A & B along with some work within the Olympic View
Drive R/W. An existing access is located along the east side of the existing parcel serving
the existing SFR on future Lot C along with some adjacent parcels. A new access point
will be constructed off of Olympic View Drive in the northwest corner of future Lot A and
will serve both Lots A & B.
This report is being prepared for the new owners of this project and as a result of the
original engineer for this project Eric Tietze having retired since the last submittal to the
City. The intent of this report is to provide the necessary project information and confirm
the original code and design assumptions provided in Mr. Tietze's report as well as
provide the necessary design information for the proposed drainage system. It should be
noted that the proposed impervious areas originally included in Mr. Tietze's report have
not changed so the calculations and design included in this report are confirming the
original design was accurate based on our review of his,design compared to our
calculations.
Per the City standards in place at the time of the original permit submittal for this project
(City of Edmonds Stormwater Code Supplement, April 20, 2010) this project would fall
under the Category 2 Small Project requirements based on the proposed impervious
surface areas on future Lots A & B. Refer to Section 8 of this report for flow control design
details.
The proposed SFR project will create 8,050 sf of new impervious surfaces including the
future SFRs and driveway/access. Of the total new impervious less than 2,000 sf is PGIS.
All the remaining pervious areas will be amended per the City standard. All the NPGIS
and PGIS will be mitigated using a small site detention system prior to release from the
site. All site runoff will be collected and discharged to the Olympic View Dr. R/W.
The site is located at 8364 Olympic View Dr., Edmonds, WA 98020, and in Section 18,
Township 27N, Range 4E, Willamette Meridian. See Figure 1 - Vicinity Map.
Bill Ritter SP 16-0915
May 2017 Page 3
2. STORMWATER SITE. PLAN
As noted in Section 1 of this report this project is classified as a Category 2 Small Site
Project. Therefore, this drainage design has been prepared to address the requirements
contained in the City of Edmonds Stormwater Supplement and applicable handouts. The
engineering plan set submitted to the City for review along with this report contains the
required information.This document is intended to provide the supporting information to
justify the sizing of the BMPs and detail how the design of the selected BIVIPS meet the
required standards.
For this project, no LID techniques were used. Geotechnical studies show that water will
not infiltrate into the soils. Therefore, no dispersion or infiltration of runoff will be used.
Runoff from the total impervious surfaces will be directed to an on -site detention system.
This is done to reduce the peak flow rates and volumes from these surfaces. This is
discussed in detail in Section 8 of this report and shown on sheets 5 & 6 of the plan set.
Bill Ritter SP . ............ 16-0915
May 2017 Page 4
3. SWPPP NARRATIVE
Clearing, grading, and temporary erosion and sediment control plans have been prepared
as part of the drainage plan drawings. However, since a construction site is dynamic it will
be necessary to reassess the erosion control BMP's during construction and install
additional measures when necessary.
Proposed temporary measures possible for this project will include the following BMP's:
• Installation of stabilized construction entrance.
• Retention of Existing Vegetation
• Straw mulch, hydroseed or other mulching and planting method to stabilized
unworked areas.
• Silt fencing if necessary
• Inlet protection
Permanent measures to reduce or eliminate erosion or water quality degradation will
include the following BMP's:
• Paving all traffic areas (concrete/asphalt)
• Permanent landscaping in pervious areas.
• Limiting cut and fill slopes to 2:1 maximum and 3:1 maximum where exposed
to standing water.
• Routine maintenance and inspection of the grounds and response to
developing problems.
The listed erosion control BMP's will be engineered for anticipated conditions in
compliance with City of Everett and DOE guidelines. With proper installation,
maintenance and inspection the proposed BMP's should result in minimal impact to the
surrounding environment. The City retains the authority by code to require additional
measures should the existing measures prove insufficient.
Bill Ritter SP 16-0915
May 2017 Page 5
A. SITE GRADING/EROSION CONTROL RISK ASSESSMENT
Area proposed to be cleared/worked: 0.34 acres
Average slope for the site: 15%
Erosion Hazard of Soil Moderate -High
Critical Areas downslope No
Site is upstream of an ESA Stream No
Based on the above information and the fact that the site will retain so much existing
vegetation and construction site runoff will filter through the soil, and that if site conditions
warrant, additional BMP's can be implemented as corrective measures the Risk Category
for this site is Moderate Risk.
B. SWPPP MINIMUM ELEMENTS
1: Mark Clearing Limits
The first step in the "Construction Sequence" included on the clearing and grading plan
sheets is for the limits of clearing to be flagged and to have construction fencing placed
along the limits prior to any other construction activity.
2: Establish Construction Access
The SWPPP calls for the proposed construction entrance to be installed as the second
step after the staking of clearing limits. A detail is provided on the plans.
3: Control Flow Rates
This project will utilize the proposed detention system once it has been constructed.
4: Install Sediment Controls
This site and SWPPP proposes to construct/maintain a construction entrance, retained
vegetation and silt fencing. These features are intended to minimize the opportunity for
sediment to leave the site via stormwater or on vehicles. The construction of these
features is one of the first items required in the "Construction Sequence". Mulch will also
be used on the exposed soil as necessary to limit erosion.
5: Stabilize Soils
The "Construction Sequence" calls for the stabilization of soils that remain unworked for
certain lengths of time based on the time of year. Stabilization techniques may include but
not limited to mulching, plastic sheeting or hydroseeding, notes have been added to the
plan regarding protection for the stock pile area if necessary. A stockpile area has been
identified on the SWPPP and is setback a minimum of 20-feet from any down slope
property line.
6: Protect Slopes
All disturbed slopes on site during construction are required to be protected with mulch or
other means as specified in the construction sequence. No concentrated runoff or
significant amounts of sheet flow will be directed to new cut or fill slopes during
construction.
Bill Ritter SP 16-0915
May 2017 Page 6
7: Protect Drain Inlets
All new catch basins and yard drains will be'protected with inlet protection as specified on
sheet 2 of the engineering plan set. In addition, the nearest downstream catch basins
along the west side of 9'h Ave S will receive inlet protection per standard plan E1.8..
8: Stabilize Channels and Outlets
No new channels or outlets are proposed for this site.
9:- Control Pollutants
No outside chemicals are expected to be necessary for the construction of this project. All
vehicles working on and around the site would need to meet the State requirements for
emissions.
10: Control DeWatering
DeWatering is not expected to be necessary for this project. However, the proposed
detention system would be available to control the release of any water from construction
for disposal.
11: Maintain BMPs
The construction supervisor will be responsible for maintaining all BMPs during
construction and working with the City to relocate or add BMPs as necessary as site
conditions change.
12: Manage the Project
It will be the responsibility of the Contractor and Developer to manage this project and
coordinate with the City Inspector and Engineer.
Inspection and Monitoring:
Site inspections shall be done by a person who is knowledgeable in the principles and
practices of erosion and sediment control. The person must have skills to first assess the
site conditions and construction activities that could impact the quality of stormwater, and
second assess the effectiveness of erosion and sediment control measures used to
control the quality of stormwater discharges.
Whenever inspection and/or monitoring reveals that the BMPs identified in the
Construction SWPPP are inadequate, due to the actual discharge of or potential to
discharge a significant amount of any pollutant, appropriate BMPs or design changes shall
be implemented as soon as possible.
Maintaining an Updated Construction SWPPP:
The construction SWPPP shall be retained on -site or within reasonable access to the site.
The SWPPP shall be modified whenever there is a change in the design, construction,
operation, or maintenance at the construction site that has, or could have, a significant
effect on the discharge of pollutants to waters -of the state.
The SWPPP shall be modified if, during inspections or investigations conducted by the
owner/operator, or the applicable local or state regulatory authority, it is determined that
the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater
discharges from the site. The SWPPP shall be modified as necessary to include
additional or modified BMPs designed to correct problems'identified. Revisions to the
SWPPP shall be completed within seven days following inspection.
Bill Ritter SP 16-0915
May 2017 Page 7
4. WATER POLLUTION SOURCE CONTROL
The City of Edmonds Stormwater Supplement and DOE Drainage manual were reviewed
to determine if the proposed land -use for this project or construction activities required any
site -specific source control BMPs to be constructed. SFR projects are not listed as a
proposed use that requires source control. Therefore, no site/development specific source
control BMPs are required for this project.
5. PRESERVATION OF NATURAL DRAINAGE SYSTEM
The runoff from the on -site basin drains to the north and into the existing RNV. The outfall
from the proposed detention system connects to this same downstream conveyance
system.
6. ON -SITE STORMWATER MANAGEMENT
For this project dispersion and infiltration are not feasible due to site constraints (existing
slopes) and soil conditions.
7. RUN-OFF TREATMENT
This project proposes to construct less than 5,000 sf of new PGIS and is therefore exempt
from this requirement.
Bill Ritter SP 16-0915
May 2017 Page 8
8. FLOW CONTROL
For this project, using the City of Edmonds Stormwater Supplement, traditional methods
were designed.
The total new plus replaced impervious surfaces of 8,050 sf will have the runoff mitigated
using a detention tank sized using the Western Washington Hydrology Model with the
Puget East 36 precipitation data, and Section 5.7 of the Edmonds Stormwater Code
Supplement for a Category 2 small site project. Refer to the design discussion below.
For this project, the detention system was sized based on the total new impervious
surfaces. As noted previously the total roof and driveway area totals 8,050 sf. For the
purposes of sizing the detention tank using the Western Washington Hydrology Model and
Section 5.7 of the Edmonds Stormwater Code Supplement for a Category 2 small site
project. A pipe size of 60" has been selected that will require a total length to be 44' and a
bottom orifice size of and an elbow with orifice size 3". Please see the drainage plans
for more details.
Bill Ritter SP 16-0915
May 2017 Page 9 '
Since the project site is in a creek drainage basin the site is required to meet the following
peak flow control standards:
2-year:
0.07 cfs/acre impervious
10-year:
0.14 cfs/acre impervious
100-year:
0.33 cfs/acre impervious
Based on these standards the allowable discharge rates for the site based on 0.183 acres
of impervious surfaces are:
2-year:
0.013 cfs
10-year:
0.026 cfs
100-year:
0.060 cfs
By preparing a site plan that minimized the disturbed area on this site and sets aside a
large portion of the existing treed areas in open space easements on the future lots, the
overall drainage impacts to the downstream system and surrounding area can be reduced,.
Therefore, this design has been laid out to minimized the disturbance to the existing area
while protecting the existing neighboring properties from flooding or erosive impacts.
Bill Ritter SP 16-0915
May 2017 Page 10
9: WETLANDS PROTECTION
This project will not impact any wetland on or directly downstream- of the site.
10: OPERATIONS AND MAINTENANCE MANUAL
The Property Owner will be responsible for maintaining the stormwater and landscaping
facilities within this development. Included in this manual are checklists for each feature
specific to this project. Copies should be made of the checklists as necessary during
routine inspections and required maintenance. Specific problems can -be recorded along
with the appropriate action taken.
These checklists are a guide for inspections and maintenance. The frequency of the
inspections/maintenance is identified in the left-hand column with the following
abbreviations:
A = Annual (March or April preferred)
M = Monthly
S = After Major Storms (Use 1-inch in 24 hours as a guideline)
Routine inspections and maintenance will improve the long-term performance of the
stormwater facilities. If at any time, you are unsure if a problem exists or how to address a
specific problem, contact a Professional Engineer.
Refer to Appendix A for a list of each facility to be maintained and the appropriate
maintenance checklist.
11. OFFSITE ANALYSIS AND MITIGATION
During the site review and downstream site visit for this project it was determined that the
properties to the west of this site contain existing SFRs and it is not viable draining in that
direction. After further soil analysis, it was also determined that on -site infiltration is not
feasible. Therefore, it has been determined that discharging to the drainage system within
9t' Ave. S. was the best option for this project.
The existing drainage system within the R.O.W. consists of a 12" concrete storm system
that drains from south to north within the Shell Creek basin. There were no indications
from the site observations that any capacity issues exist within this system. The
conveyance system was followed to the north for approximately % mile. Therefore, this
project's downstream system is completely contained within an engineered pipe
conveyance system which was not observed to have any drainage problems.
12. FINANCIAL LIABILITY
Since this is a single-family residential project and it does not fall within a Critical Area, per
the City of Edmonds Stormwater Supplement no bonds or other financial guarantees are
required. A KC engineering cost estimate worksheet is being provided to the City for
Construction bonds.
Bill Ritter SP 16-0915
May 2017 Page 11
APPENDIX A
STORMWATER CALCULATIONS
R&D Masonry 16-1005
Nov. 2016 Page -14
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General Model Information
Project Name: - LOt A-B-36
Site Name:
Carl -Ritter SP
Site Address:
8364 Olympic View Drive
City:
Edmonds
Report Date:
5/24/2017
MGS Region:
Puget East
Data Start:
1901/10/1
Data End:
2058/09/30
Timestep:
15 Minute
DOT Data Number03
Version Date:
2016/02/25
Version:
4.2.12
POC Thresholds
Low Flow Threshold for POC1: 50 Percent of the 2 Year
High Flow Threshold for POC1: 50 Year
LOt A-B-36 5/24/2017 2:13:22 PM Page 2
Landuse Basin Data
Predeveloped Land Use
Basin 1
Bypass:
No
GroundWater:
No
Pervious Land Use
acre
C, Forest, Mod
0.33
Pervious Total
0.33
Impervious Land Use
acre
Impervious Total
0
Basin Total
0.33
Element Flows To:
Surface Interflow Groundwater
LOt A-B-36 5/24/2017 2:13:22 PM Page 3
Mitigated Land Use
Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
Pervious Total 0
Impervious Land Use
acre
ROOF TOPS FLAT
0.138
DRIVEWAYS MOD
0.046
Impervious Total
0.184
Basin Total 0.184
Element Flows To:
Surface
Tank 1
Interflow
Tank 1
Groundwater
LOt A-B-36 5/24/2017 2:13:22 PM Page 4
Routing Elements
Predeveloped Routing
LOt A-B-36 5/24/2017 2:13:22 PM Page 5
Mitigated Routing
Tank 1
Dimensions
Depth:
Tank Type:
Diameter:
Length:
Discharge Structure
Riser Height:
Riser Diameter:
Orifice 1 Diameter:
Orifice 2 Diameter:
Element Flows To:
Outlet 1
5 ft.
Circular
5 ft.
44 ft.
4.9 ft.
8 in.
0.5 in
3 in.
Outlet 2
Tank Hydraulic Table
Stage(feet)
0.0000
0.0556
0.1111
0.1667
0.2222
0.2778
0.3333
0.3889
0.4444
0.5000
0.5556
0.6111
0.6667
0.7222
0.7778
0.8333
0.8889
0.9444
1.0000
1.0556
1.1111
1.1667
1.2222
1.2778
1.3333
1.3889
1.4444
1.5000
1.5556
1.6111
1.6667
1.7222
1.7778
1.8333
1.8889
1.9444
2.0000
Area(ac
0.000
0.001
0.001
0.001
0.002
0.002
0.002
0.002
0.002
0.003
0.003
0.003
0.003
0.003
0.003
0.003
0.003
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
Elevation:0 ft.
Elevation:4.57 ft.
Volume(ac-ft.)
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.001
0.001
0.001
0.001
0.001
0.002
0.002
0.002
0.002
0.002
0.003
0.003
0.003
0.003
0.004
0.004
0.004
0.004
0.005
0.005
0.005
0.005
0.006
0.006
0.006
0:006
0.007
0.007
Discharge(cfs)
0.000
0.001
0.002
0.002
0.003
0.003
0.003
0.004
0.004
0.004
0.005
0.005
0.005
0.005
0.006
0.006
0.006
0.006
0.006
0.007
0.007
0.007
0.007
0.007
0.007
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.009
0.009
0.009
0.009
0.009
Infilt(cfs)
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
LOt A-B-36 5/24/2017 2:13:22 PM Page 6
2.0556
0.005
0.007
0.009
0.000
2.1111
0.005
0.008
0.009
0.000
2.1667
0.005
0.008
0.010
0.000
2.2222
0.005
0.008
0.010
0.000
2.2778
0.005
0.008
0.010
0.000
2.3333
0.005
0.009
0.010
0.000
2.3889
0.005
0.009
0.010
0.000
2.4444
0.005
0.009
0.010
0.000
2.5000
0.005
0.009
0.010
0.000
2.5556
0.005
0.010
0.010
0.000
2.6111
0.005
0.010
0.011
0.000
2.6667
0.005
0.010
0.011
0.000
2.7222
0.005
0.011
0.011
0.000
2.7778
0.005
0.011
0.011
0.000
2.8333
0.005
0.011
0.011
0.000
2.8889
U05
0.011
0.011
0.000
2.9444
0.005
0.012
0.011
0.000
3.0000
0.004
0.012
0.011
0.000
3.0556
0.004
0.012
0.011
0.000
3.1111
0.004
0.013
0.012
0.000
3.1667
0.004
0.013
0.012
0.000
3.2222
0.004
0.013
0.012
0.000
3.2778
0.004
0.013
0.012
0.000
3.33.33
0.004
0.014
0.012
0.000
3.3889
0.004
0.014
0.012
0.000
3.4444
0.004
0.014
0.012
0.000
3.5000
0.004
0.014
0.012
0.000
3.5556
U04
0.015
0.012
0.000
3.6111
0.004
0.015
0.012
0.000
3.6667
0.004
0.015
0.013
0.000
3.7222
0.004
0.015
0.013
0.000
3.7778
0.004
0.016
0.013
0.000
3.8333
U04
0.016
0.013
0.000
3.8889
0.004
0.016
0.013
0.000
3.9444
0.004
0.016
0.013
0.000
4.0000
0.004
0.017
0.013
0.000
4.0556
0.004
0.017
0.013
0.000
4.1111
0.003
0.017
0.013
0.000
4.1667
UO3
0.017
0.013
0.000
4.2222
UO3
0.017
0.013
0.000
4.2778
0.003
0.018
0.014
0.000
4.3333
0.003
0.018
0.014
0.000
4.3889
UO3
0.018
0.014
0.000
4.4444
0.003
0.018
0.014
0.000
4.5000
0.003
0.018
0.014
0.000
4.5556
0.002
0.019
0.014
0.000
4.6111
0.002
0.019
0.064
0.000
4.6667
0.002
0.019
0.090
0.000
4.7222
0..002
0.019
0.110
0.000
4.7778
0,002
0.019
0.126
0.000
4.8333
0.001
0.019
0.140
0.000
4.8889
0.001
0.019
0.152
0.000
4.9444
0.001
0.019
0.230
0.000
5.0000
0.000
0.019
0.394
0.000
5.0556
0.000
0.000
0.590
0.000
LOt A-B-36 5/24/2017 2:13:22 PM Page 7
An,
4�sis Results
w►
POC
M
ff
Par -caret Tam® F:n®aci®o-sg
+ Predeveloped
Predeveloped Landuse Totals for POC #1
Total Pervious Area:
0.33
Total Impervious Area:
0
Mitigated Landuse Totals
for POC #1
Total Pervious Area:
0
Total Impervious Area:
0.184
—A ...
x Mitigated
Flow Frequency Method: Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period
Flow(cfs)
2 year
0.0056
5 year
0.00869
10 year
0.010367
25 year
0.012072
50 year
0.013085
100 year
0.013918
Flow Frequency Return Periods for Mitigated. POC #1
Return Period
Flow(cfs)
2 year
0.011859
5 year
0.018361
10 year
0.024328
25 year
0.034264
50 year
0.043787
100 year
0.055504
Annual Peaks
Annual Peaks for Predeveloped
and Mitigated. POC #1
Year
Predeveloped
Mitigated
1902
0.008
0.012
1903
0.003
0.010
1904
0.005
0.012
1905
0.003
0.011
1906
0.001
0.010
1907
0.009
0.014
1908
0.006
0.011
1909
0.006
0.011
1910
0.010-
0.013
1911
0.005
0.011
.—..,....9G.......... .--- ...... a..... mm . SpA R5 9�!N.6; anon.
LOt A-B-36 5/24/2017 2:13:22 PM Page 8
1912
0.017
0.013
1913
0.008
0.011
1914
0.002
0.012
1915
0.003
0.009
1916
0.005
0.011
1917
0.002
0.011
1918
0.005
0.012
1919
0.004
0.010
1920
0.005
0.011
1921
0.005
0.010
1922
0.006
0.012
1923
0.004
0.012
1924
0.003
0.010
1925
0.003
0.009
1926
0.005
0.011
1927
0.006
0.011
1928
0.004
0.011
1929
0.009
0.013
1930
0,005
0.012
1931
0.005
0.011
1932
0.004
0.011
1933
0.005
0.010
1934
0.012
0.014
1935
0.005
0.010.
1936
0.007
0.012
1937
0.006
0.013
1938
0.006
0.011
1939
0.000
0.010
1940
0.005
0.012
1941
0.005
0.010
1942
0.007
0.013
1943
0.002
0.011
1944
0.006
0.081
1945
0,005
0.012
1946
0.005
0.010
1947
0.003
0.011
1948
0.011
0.027
1949
0.009
0.051
1950
0.005
0.010
1951
0,006
0.010
1952
0.016
0.064
1953
0,015
0.071
1954
OM5
0.011
1955
0.004
0.010
1956
0.003
0.008
1957
0.006
0.011
1958
0.015
0.034
1959
0.009
0.011
1960
0.003
0.009
1961
0.010
0.022
1962
OM5
0.012
1963
O A02
0.009
1964
0.004
0.011
1965
0.011
0.021
1966
0,.002
0.010
1967
0.004
0.010
1968
0.006
0.012
1969
0,004
0.011
LOt A-B-36 5/24/2017 2:14:42 PM Page 9
1970
0.006
0.012
1971
0.012
0.027
1972
0.008
0.014
1973
0.009
0.013
1974
0.005
0.011
1975
0.013
0.035
1976
0.006
0.013
1977
0.004
0.009
1978
0.011
0.014
1979
0.003
0.010
1980
0.006
0.010
1981
0.005
0.011
1982
0.004
0.009
1983
0.009
0.013
1984
0.002
0.011
1985
0.005
0.012
1986
0.004
0.010
1987
0.009
0.020
1988
0.007
0.012
1989
0.005
0.011
1990
0.007
0.012
1991
0.005
0.012
1992
0.008
0.012
1993
0.006
0.012
1994
0.011
0.014
1995
0.003
0.009
1996
0.013
0.013
1997
0.006
0.011
1998
0.006
0.013
1999
0.000
0.010
2000
0.004
0.011
2001
0.003
0.010
2002
0.008
0.011
2003
0.006
0.012
2004
0.006
0.012
2005
0.008
0.011
2006
0.004
0.009
2007
0.004
0.013
2008
0.006
0.010
2009
0.004
0.011
2010
0.003
0.014
2011
0.004
0.009
2012
0.005
0.043
2013
0.004
0.010
2014
0.003
0.010
2015
0.011
0.012
2016
0.002
0.009
2017
0.009
0.088
2018
0.016
0.048
2019
0.017
0.077
2020
0.005
0.010
2021
0.008
0.013
2022
0.003
0.010
2023
0.006
0.011
2024
0.013
0.013
2025
0.005
0.010
2026
0.009
0.012
2027
0.004
0.011
LOt A-B-36 5/24/2017 2:14:42 PM Page 10
2028
0.002
0.009
2029
0.006
0.011
2030
0.012
0.027
2031
0.003
0.009
2032
0.003
0.009
2033
0.003
0.009
2034
0.003
0.011
2035
0.014
0.055
2036
0.007
0,012
2037
0.001
0.010
2038
0.007
0.014
2039
0.001
0..010
2040
0.003
0.012
2041
0.004
0.011
2042
0.014
0.056
2043
0.006
0.012
2044
0.009
0.013
2045
0.005
0.010
2046
0.006
0.011
2047
0.004
0.010
2048
0.005
0.013
2049
0.005
0.012
2050
0.003
0.011
2051
0.006
0.014
2052
0.003
0.012
2053
0.006
0.011
2054
0.008
0.014
2055
0.002
0.009
2056
0.002
0.010
2057
0.004
0.010
2058
0.004
0.010
Ranked Annual Peaks
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank
Predeveloped
Mitigated
1
0.0169
0.0880
2
0.0169
0.0809
3
0.0164
0.0775
4
0.0155
0.0712
5
0.0153
0.0644
6
0.0146
0.0564
7
0.0142
0.0545
8
0.0136
0.0510
9
0.0132
0.0480
10
0.0128
0.0433
11
0.0127
0.0352
12
0.0123
0.0343
13
0.0121
0.0275
14
0.0120
0.0272
15
0.0114
0.0269
16
0.0114
0.0217
17
0.0113
0.0212
18
0.0111
0.0205
19
0.0111
0.0144
20
0.0096
0.0144
21
0.0095
0.0142
22
0.0094
0.0141
23
0.0093
0.0140
LOt A-B-36 5/24/2017 2:14:42 PM Page 11
24
0.0091
0.0138
25
0.0091
0.0136
26
0.0090
0.0135
27
0.0089
0.0135
28
0.0088
0.0135
29
0.0087
0.0134
30
0.0086
0.0134
31
0.0086
0.0132
32
0.0084
0.0131
33
0.0079
0.0131
34
0.0078
0.0130
35
0.0078
0.0130
36
0.0078
0.0130
37
0.0077
0.0130
38
0.0076
0.0129
39
0.0075
0.0128
40
0.0073
0.0127
41
0.0073
0.0127
42
0.0071
0.0126
43
0.0070
0.0125
44
0.0069
0.0124
45
0.0067
0.0123
46
0.0065
0.0123
47
0.0064
0.0122
48
0.0064
0.0122
49
0.0064
0.0122
50
0.0063
0.0121
51
0.0063
0.0121
52
0.0062
0.0121
53
0.0062
0.0121
54
0.0062
0.0121
55
0.0061
0.0120
56
0.0061
0.0120
57
0.0061
0.0120
58
0.0061
0.0119
59
0.0060
0.0119
60
0.0060
0.0119
61
0.0060
0.0119
62
0.0059
0.0118
63
0.0059
0.0118
64
0.0058
0.0117
5
0.0057
0.0117
66
0.0057
0.0116
67
0.0057
0.0116
68
0.0056
0.0115
69
0.0055
0.0115
70
0.0055
0.0115
71
0.0054
0.0115
72
0.0054
0.0115
73
0.0054
0.0114
74
0.0054
0.0114
75
0.0054
0.0114
76
0.0054
0.0114
77
0.0054
0.0113
78
0.0053
0.0113
79
0.0053
0.0112
80
0.0052
0.0112
81
0.0051
0.0112
LOt A-B-36 5/24/2017 2:14:42 PM Page 12
82
0.0051
0.0112
83
0.0051
0.0111
84
0.0051
0.0111
85
0.0051
0.0111
86
0.0050
0.0110
87
0.0050
0.0110
88
0.0050
0.0110
89
0.0050
0.0110
90
0.0049
0.0110
91
0.0049
0.0109
92
0.0049
0.0109
93
0.0049
0.0109
94
0.0049
0.0109
95
0.0048
0.0109
96
0.0046
0.0109
97
0.0045
0.0108
98
0.0045
0.0108
99
0.0045
0.0108
100
0.0044
0.0108
101
0.0044
0.0107
102
0.0044
0.0107
103
0.0044
0.0107
104
0.0043
0.0106
105.
0.0042
0.0106
106
0.0042
0.0106
107
0.0041
0.0106
108
0.0040
0.0105
109
0.0040
0.0105
110
0.0040
0.0104
111
0.0040
0.0104
112
0.0040
0.0104
113
0.0039
0.0104
114
0.0039
0.0103
115
0.0038
0.0103
116
0.0037
0.0103
117
0.0037
0.0103
118
0.0037
0.0103
119
0.0037
0.0103
120
0.0036
0.0103
121
0.0036
0.0102
122
0.0034
0.0102
123
0.0034
0.0102
124
0.0034
0.0102
125
0.0034
0.0101
126
0.0033
0.0101
127
0.0032
0.0101
128
0.0032
0.0100
129
0.0031
0.0100
130
0.0030
0.0100
131
0.0030
0.0099
132
0.0029
0.0099
133
0.0029
0.0099
134
0.0028
0.0098
135
0.0027
0.0098
136
0.0027
0.0098
137
0.0027
0.0097
138
0.0027
0.0096
139
0.0027
0.0096
LOt A-B-36 5/24/2017 2:14:42 PM Page 13
140
0.0027
0.0095
141
0.0026
0.0095
142
0.0026
0.0095
143
0.0025
0.0095
144
0.0024
0.0094
145
0.0023
0.0094
146
0.0023
0.0094
147
0.0022
0.0093
148
0.0022
0.0092
149
0.0020
0.0091
150
0.0020
0.0091
151
0.0019
0.0089
152
0.0015
0.0088
153
0.0014
0.0088
154
0.0013
0.0086
155
0.0006
0.0086
156
0.0004
0.0086
157
0.0003
0.0083
LOt A-B-36 5/24/2017 2:14:42 PM Page 14
Duration Flows
Flow(cfs)
Predev
Mit
Percentage
Pass/Fail
0.0028
53256
533602
1001
Fail
0.0029
49033
519894
1060
Fail
0.0030
45152
506077
1120
Fail
0.0031
41772
492645
1179
Fail
0.0032
38645
479212
1240
Fail
0.0033
35816
465175
1298
Fail
0.0034
33228
451357
1358
Fail
0.0035
30911
438035
1417
Fail
0.0036
28863
424382
1470
Fail
0.0037
26925
410620
1525
Fail
0.0038
25180
397353
1578
Fail
0.0039
23435
384141
1639
Fail
0.0040
21871
371039
1696
Fail
0.0042
20336
358102
1760
Fail
0.0043
18921
345220
1824
Fail
0.0044
17666
332338
1881
Fail
0.0045
16493
319732
1938
Fail
0.0046
15453
307290
1988
Fail
0.0047
14445
294739
2040
Fail
0.0048
13504
282848
2094
Fail
0.0049
12601
271067
2151
Fail
0.0050
11792
259507
2200
Fail
0.0051
11060
248277
2244
Fail
0.0052
10416
237211
2277
Fail
0.0053
9837
226422
2301
Fail
0.0054
9309
215907
2319
Fail
0.0055
8781
205668
2342
Fail
0.0056
8291
195704
2360
Fail
0.0057
7850
185905
2368
Fail
0.0058
7399
176546
2386
Fail
0.0059
7035
167408
2379
Fail
0.0060
6667
158655
2379
Fail
0.0061
6342
150397
2371
Fail
0.0062
6034
142580
2362
Fail
0.0063
5742
134873
2348
Fail
0.0064
5474
127606
2331
Fail
0.0065
5217
120615
2311
Fail
0.0066
4988
114064
2286
Fail
0.0067
4756
107678
2264
Fail
0.0069
4538
101458
2235
Fail
0.0070
4334
95512
2203
Fail
0.0071
4124
89677
2174
Fail
0.0072
3938
84282
2140
Fail
0.0073
3772
79162
2098
Fail
0.0074
3631
74208
2043
Fail
0.0075
3491
69584
1993
Fail
0.0076
3368
65124
1933
Fail
0.0077
3255
60886
1870
Fail
0.0078
3145
56922
1809
Fail
0.0079
3054
53250
1743
Fail,
0.0080
2965
49738
1677
Fail
0.0081
2876
46457
1615
Fail
0.0082
2779
43258
1556
Fail
0.0083
2681
40236
1500
Fail
LOt A-B-36 5/24/2017 2:14:42 PM Page 15
0.0084
2585
37324
1443
Fail
0.0085
2491
34709
1393
Fail
0.0086
2391
32188
1346
Fail
0.0087
2278
29832
1309
Fail
0.0088
2181
27690
1269
Fail
0.0089
2080
25780
1239
Fail
0.0090
1997
24002
1201
Fail
0.0091
1927
22411
1162
Fail
0.0092
1864
20870
1119
Fail
0.0093
1790
19466
1087
Fail
0.0094
1718
18145
1056
Fail
0.0096
1664
16878
1014
Fail
0.0097
1595
15772
988
Fail
0.0098
1536
14748
960
Fail
0.0099
1479
13735
928
Fail
0.0100
1417
12777
901
Fail
0.0101
1361
11929
876
Fail
0.0102
1304
11109
851
Fail
0.0103
1242
10278
827
Fail
0.0104
1188
9617
809
Fail
0.0105
1147
9006
785
Fail
0.0106
1100
8368
760
Fail
0.0107
1047
7817
746
Fail
0.0108
1002
7322
730
Fail
0.0109
954
6782
710
Fail
0.0110
917
6347
692
Fail
0.0111
877
5874
669
Fail
0.0112
835
5476
655
Fail
0.0113
791
5096
644
Fail
0.0114
755
4700
622
Fail
0.0115
710
4401
619
Fail
0.0116
666
4076
612
Fail
0.0117
627
3797
605
Fail
0.0118
595
3515
590
Fail
0.0119
555
3214
579
Fail
0.0120
518
2960
571
Fail
0.0122
461
2696
584
Fail
0.0123
423
2517
595
Fail
0.0124
394
2358
598
Fail
0.0125
360
2197
610
Fail
0.0126
336
2056
611
Fail
0.0127
306
1903
621
Fail
0.0128
286
1743
609
Fail
0.0129
265
1626
613
Fail
0.0130
247
1482
600
Fail
0.0131
234
1327
567
Fail
The development has an increase in flow durations
from 1 /2 Predeveloped 2 year flow to the 2 year flow
or more than a 10% increase from the 2 year to the 50
year flow.
The development has an increase in flow durations for
more than 50% of the flows for the range of the
duration analysis.
LOt A-B-36 5/24/2017 2:14:42 PM Page 16
Water Quality
Water Quality BMP Flow and Volume for POC #1
On-line facility volume:
0 acre-feet
On-line facility target flow:
0 cfs.
Adjusted for 15 min:
0 cfs.
Off-line facility target flow:
0 cfs.
Adjusted for 15 min:
0 cfs.
LOt A-B-36 5/24/2017 2:14:42 PM Page 17
Tank I POC
Total Volume InfilOaled
Compfiance vAth LID
Mandaid 8% of 2 -yr In 50%
2-yr
Used lor TotalVolunne Volurne Infiltrallon
Treatment 9 Needs Through Volume
Treatmenl Fa0% (awe -A)
(ac-ftt (ac-ft)
ME
Cumulafive Percent
�Vbturne Volume
vlffWafion Infiltrated
CredHl
DIPIA
Water Duality Pement Comment
Water Quailly
Treated
BIG
Ounabon
Analysis
Reis ult
Failed
LOt A-B-36 5/24/2017 2:14:42 PM Page 18
Model Default Modifications
Total of 0 changes have been made.
PERLND Changes
No PERLND changes have been made.
IMPLND Changes
No IMPLND changes have been made.
LOt A-B-36 5/24/2017 2:15:05 PM Page 19
Appendix
Predeveloped Schematic
Basin �I i
�1.33ac
LOt A-B-36 5/24/2017 2:15:05 PM Page 20
Mitigated Schematic
ank T
LOt A-B-36 5/24/2017 2:15:05 PM Page 21
No. 3 — Closed Detention Systems (Tanks/Vaults)
Maintenance
Defect
Conditions When Maintenance is Needed
Results Expected
Component
When Maintenance Is
Performed
Storage Area
Plugged Air Vents
One-half of the cross section of a vent is
Vents open and
blocked at any point or the vent is damaged.
functioning'.
Debris and Sediment
Accumulated sediment depth exceeds 10%
All sediment and
of the diameter of the storage area for 1/2
debris removed from
length of storage vault or any point depth
storage area.
exceeds 15% of diameter.
(Example: 72-inch storage tank would
require cleaning when sediment reaches
depth, of 7 inches for more than 1/2 length of
tank.)
Joints Between
Any openings or voids allowing material to
All joint between
Tank/Pipe Section
be transported into facility.
tank/pipe sections
(Will require engineering analysis to
are sealed.
determine structural stability).
Tank Pipe Bent Out
Any part of tank/pipe is bent out of shape
Tank/pipe repaired or
of Shape
more than 10% of its design shape. (Review
replaced to design.
required by engineer to determine structural
stability).
Vault Structure
Cracks wider than 1/2-inch and any
Vault replaced or
Includes Cracks in
evidence of soil particles entering the
repaired to design
Wall, Bottom,
structure through the cracks, or
specifications and is
Damage to Frame
maintenance/inspection personnel
structurally sound.
and/or Top Slab
determines that the vault is not structurally
sound.
Cracks wider than 1/2-inch at the joint of any
No cracks more than
inlet/outlet pipe or any evidence of soil
1/4-inch wide at the
particles entering the vault through the walls.
joint of the inlet/outlet
pipe.
Manhole
Cover Not in Place
Cover is missing or only partially in place.
Manhole is closed.
Any open manhole requires maintenance.
Locking Mechanism
Mechanism cannot be opened by one
Mechanism opens
Not Working
maintenance person with proper tools. Bolts
with proper tools.
into frame have less than 1/2 inch of thread
(may not apply to self-locking lids).
Cover Difficult to
One maintenance person cannot remove lid
Cover can be
Remove
after applying normal lifting pressure. Intent
removed and
is to keep cover from sealing off access to
reinstalled by one
maintenance.
maintenance person.
Ladder Rungs Unsafe
Ladder is unsafe due to missing rungs,
Ladder meets design
misalignment, not securely attached to
standards. Allows
structure wall, rust, or cracks.
maintenance person
safe access.
Catch Basins
See "Catch Basins"
See "Catch Basins". (No. 5).
See "Catch Basins"
(No. 5) 1
1
(No. 5).
Volume V — Runoff Treatment BMPs — December 2014
4-36
No. 4 — Control Structure/Flow Restrictor
Maintenance Defect Condition When Maintenance is Needed results Expected
Component When Maintenance
Is Performed
General
Trash and Debris Material exceeds 25% of sump depth or 1
Control structure
(Includes Sediment) foot below orifice plate.
orifice is not blocked.
All trash and debris
removed.
Structural Damage Structure is not securely attached to
Structure securely
manhole wall.
attached to wall and
outlet pipe.
Structure in correct
Structure is not in upright position (allow up
to 10% from plumb).
position.
Connections to outlet
Connections to outlet pipe are not watertight
and show signs of rust.
pipe are water tight;
structure repaired or
replaced and works
as designed.
Any holes --other than designed holes --in the
Structure has no
structure.
holes other than
designed holes.
Cleanout Gate
Damaged or Missing Cleanout gate is not watertight or is missing.
Gate is watertight
and works as
designed.
Gate cannot be moved up and down by one
Gate moves up and
maintenance person.
down easily and is
watertight.
Chain is in place and
Chain/rod leading to gate is missing or
damaged.
works as designed.
Gate is repaired or
Gate is rusted over 50% of its surface area.
replaced to meet
design standards.
Orifice Plate
Damaged or Missing Control device is not working properly due to
Plate is in place and
missing, out of place, or bent orifice plate.
works as designed.
Obstructions Any trash, debris, sediment, or vegetation
Plate is free of all
blocking the plate.
obstructions and
works as designed.
Overflow Pipe
Obstructions Any trash or debris blocking (or having the
Pipe is free of all
potential of blocking) the overflow pipe.
obstructions and
works as designed.
Manhole
See "Closed See "Closed Detention Systems" (No. 3).
See "Closed
Detention Systems"
Detention Systems"
(No. 3).
(No. 3).
Catch Basin
See "Catch Basins" See "Catch Basins" (No. 5).
See "Catch Basins"
(No. 5).
(No. 5).
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No. 5 — Catch Basins
Maintenance
Defect conditions When Maintenance Is Needed
Results Expected When
Component
Maintenance is
performed
General
Trash & Trash or debris which is located immediately
No Trash or debris located
Debris in front of the catch basin opening or is
immediately in front of
blocking inletting capacity of the basin by
catch basin or on grate
more than 10%.
opening.
No trash or debris in the
Trash or debris (in the basin) that exceeds 60
percent of the sump depth as measured from
catch basin.
the bottom of basin to invert of the lowest
pipe into or out of the basin, but in no case
less than a minimum of six inches clearance
from the debris surface to the invert of the
lowest pipe.
Inlet and outlet pipes free
Trash or debris in any inlet or outlet pipe
blocking more than 1/3 of its height.
of trash or debris.
No dead animals or
Dead animals or vegetation that could
generate odors that could cause complaints
vegetation present within
or dangerous gases (e.g., methane).
the catch basin.
Sediment Sediment (in the basin) that exceeds 60
No sediment in the catch
percent of the sump depth as measured from
basin
the bottom of basin to invert of the lowest
pipe into or out of the basin, but in no case
less than a minimum of 6 inches clearance
from the sediment surface to the invert of the
lowest pipe.
Structure Top slab has holes larger than 2 square
Top slab is free of holes
Damage to inches or cracks wider than 1/4 inch
and cracks.
Frame and/or (Intent is to make sure no material is running
Top Slab into basin).
Frame is sitting flush on
Frame not sitting flush on top slab, i.e.,
separation of more than 3/4 inch of the frame
the riser rings or top slab
from the top slab. Frame not securely
and firmly attached.
attached
Fractures or Maintenance person judges that structure is
Basin replaced or repaired
Cracks in unsound.
to design standards.
Basin Walls/
Bottom
Pipe is regrouted and
Grout fillet has separated or cracked wider
than 1/2 inch and longer than 1 foot at the
secure at basin wall.
joint of any inlet/outlet pipe or any evidence of
soil particles entering catch basin through
cracks.
Settlement/ If failure of basin has created a safety,
Misalignment function, or design problem.
Basin replaced or repaired
to design standards.
Vegetation Vegetation growing across and blocking more
than 10% of the basin opening,
No vegetation blocking
opening to basin.
Vegetation growing in inlet/outlet pipe joints
No vegetation or root
that is more than six inches tall and less than
growth present.
six inches apart.
Contamination See "Detention Ponds" (No. 1).
No pollution present.
and Pollution [ I
Volume V — Runoff Treatment BMPs — December 2014
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No. 5 — Catch Basins
Maintenance
Defect
Conditions When Maintenance Is Needed
Results Expected When
Component
Maintena►ipe is
performed
Catch Basin
Cover Not in
Cover is missing or only partially in place.
Catch basin cover is
Cover
Place
Any open catch basin requires maintenance.
closed
Locking
Mechanism cannot be opened by one
Mechanism opens with
Mechanism
maintenance person with proper tools. Bolts
proper tools.
Not Working
into frame have less than 1/2 inch of thread.
Cover Difficult
One maintenance person cannot remove lid
Cover can be removed by
to Remove
after applying normal lifting pressure.
one maintenance person.
(Intent is keep cover from sealing off access
to maintenance.)
Ladder
Ladder Rungs
Ladder is unsafe due to missing rungs, not
Ladder meets design
Unsafe
securely attached to basin wall,
standards and allows
misalignment, rust, cracks, or sharp edges.
maintenance person safe
access.
Metal Grates
Grate opening
Grate with opening wider than 7/8 inch..
Grate opening meets
(If Applicable)
Unsafe
design standards.
Trash and
Trash and debris that is blocking more than
Grate free of trash and
Debris
20% of grate surface inletting capacity.
debris.
Damaged or
Grate missing or broken member(s) of the
Grate is in place and
Missing. L
grate.
meets design standards.
No. 6 — Debris Barriers (e.g., Trash Racks)
Maintenance
Components
General
Defect
Trash and
Debris
Condition When Maintenance is
Needed
Trash or debris that is plugging more
than 20% of the openings in the barrier.
Results Expected When
Maintenance is Performed
Barrier cleared to design flow
capacity.
Metal
Damaged/
Bars are bent out of shape more than 3
Bars in place with no bends more
Missing
inches.
than 3/4 inch.
Bars.
Bars are missing or entire barrier
Bars in place according to design.
missing.
Bars are loose and rust is causing 50%
Barrier replaced or repaired to
deterioration to any part of barrier.
design standards.
Inlet/Outlet
Debris barrier missing or not attached to
Barrier firmly attached to pipe
Pipe
pipe
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