HomeMy WebLinkAboutStudies APPLICANT 4/2/2021STORMWATER ANALYSIS REPORT FOR:
NINTH ST PROPERTIES, LLC
431 35TH STREET
Map 17-02-31-24, Tax Lots 11900
Springfield, OR 97478
(Pre -Submittal Case #
Prepared by
%WENGINEERS.
CIVIL STRUCTURAL BUILDING DESIGN
SURVEYING LAND USE PLANNING
2350 Oakmont Way, Suite 105
Eugene OR 97401
(547)485-8383
Contact: Michael A Cox, PE
Job #20-7774
RENEWS: �
Based on the City of Springfield
Engineering Design Standards and Procedures Manual —2012
City of Eugene Stormwater Management Manual 2014
Contents
ProjectOverview............................................................ ...................................... 1
Methodology.........................................................................................................3
Analysis................................................................................................................3
Engineering Conclusions......................................................................................4
Attachments:
Appendix A: Stormwater Scooping Sheet
Appendix B: Stormwater Plan
Appendix C: Stormwater Design Calculations
Appendix D: Web Soil Survey Map
Appendix E: Geotechnical Infiltration Report
Appendix F: Stormwater Planting Schedule Exhibit
Project Overview
Location: 431 35" Street, Springfield, OR.
Map and Taxlot: Lot 11900 of Assessor's Map 17-02-31-24
Vicinity Map:
dWl s
EF, Efl [n
Tyson Ped
r
ZiN041
_ _ fo�-yc Taquerie.p
Development:
The property is a 0.93 acre parcel of land comprised of Tax Lot 11900 of Lane County Assessor's
Map 17-02-31-24. The subject property is currently under residential use and developed with an
existing single-family dwelling and detached garage to remain (431 35th Street). The subject
property is bounded on the West by 35th Street, and is bounded on the North, South and East by
previously developed private properties. Said adjacent private properties are under separate
ownership. The subject property is currently designated "Low Density Residential" per the
Comprehensive Plan, and is currently zoned LDR Low Density Residential.
The applicant desires to subdivide the subject property into six lots, each of which is proposed to
accommodate one single-family dwelling for a total of 6 dwelling units following subdivision
approval. This results in a proposed net density of 6.45 dwelling units per acre, which complies
with the permitted density range of 6 to14 dwelling units per net acre within the LDR zoning
district per Section 3.2-205 of the Springfield Development Code (SDC).
The project site lies within 10 year travel time of the Maia potential wellhead (Wellhead Map -
2013 City of Springfield Development & Public Works — Technical Services Division) with the Q
Street Floodway subbasin. The public stormwater follows the drainage system in catchments
10/135. According to the 10 -Year Future model (Figure 3-10 of the Stormwater Facility Master
1
Plan — 2008), the nearest major piped system has no excess capacity. The stormwater scoping
sheet, dated 10/21/2020 indicates that detention is not applicable (See Appendix A).
Permits required for the project include local building, electrical, and mechanical. Stormwater
discharge is covered under the City of Springfield MS4 NPDES permit.
Methodology
The downstream capacity of the public system is not sufficient. New impervious surface runoff
will not be detained per the Stormwater Scooping Sheet (Appendix A). The stormwater treatment
facility will treat all proposed impervious surfaces, with design overflow directed to the existing
stormwater system located to the north of the property. Facility layout can be seen on plans
found in Appendix B and a planting exhibit (Appendix F)
SITE SOIL CLASSIFICATIONS
The entirety of the soil at the project site is hydrologic soil group D. Infiltration testing performed
by K&A Engineering (Project: 20066) produced no infiltration over a 24 hour period. Infiltration will
not be used on this site. (See Appendix E: Geotechnical Infiltration Report)
2226A—Awbrig-Urban Land Complex Hydrologic Soil Group D
(See Appendix D: Web Soil Survey Map, USDA NRCS Web Soil Survey, and accessed 3/30/21)
STORMWATER BMP—
Stormwater planters will be used to treat the complete runoff from the property. Three planters
located on the north side of the access road will be used to collect all runoff. Lott and the
existing garage on Lot 6 shall be treated at Planter 1, Lots 2 & 5 shall be treated at Planter 2, and
Lots 3&4 shall be treated at Planter 3. A portion of the access road will be divided between the
three planters for treatment. Planters were designed using the presumptive method using a
maximum buildout area including roof and driveway surfaces. Actual size of planters exceeds the
required area of the proposed planters. Individual lots shall, at time of construction, demonstrate
that the produced impervious area is less than what the proposed planters are capable of.
Analysis
Design Storms: Water Quality Storm = 0.25 Inches per hour (in/hour)
Conveyance Storm = 10Y-10 Min Storm 3.60 in/hour
Computation Methods:
Rational Method Stormwater Quality
Retention Volume
Storm Pipe Conveyance
Software Used: Excel
Design Coefficients: C = 0.90 Impervious Pavement
1.1 = 25Y Adjustment Factor
Design Calculations:
See Appendix C: Stormwater Design Calculations
Flood Control & Conveyance
Conveyance of runoff is based on a minimum of 3.0 feet per second flow at 10 year —10 minute
design storm conditions and minimum pipe slope of 1.0 percent.
Engineering Conclusions
Stormwater design and plans conform to the City of Springfield Development Code sections 4.3-
110 and Chapters 3 & 4 of the Springfield Design Standards and Procedures Manual, adopted
2012. Stormwater from all proposed impervious pavement areas will be treated and infiltrated
consistent with vegetated stormwater planter design. For conveyance, the system is designed to
handle flow beyond the 10 year 10 minute design storm to the planter.
An O and M agreement specific to the facilities must be filed. Stormwater facilities constructed
must be properly operated and maintained for the life of the facility.
Stormwater Plans
See attached Appendix 8: Stormwater Plan
APPENDIX A
DEVELOPMENT AND PUBLIC WORKS
SPRINGFIELD
+F \ 225 FIFTH STREET
OREGON SPRINGFIELD, OR 97477
PHONE: 541.726.3753
FAX 541.726.1021
www.spnngheldorgov
STORMWATER MANAGEMENT SYSTEM SCOPE OF WORK
------- -- (Area below this tine filled out by Applicant) --------- __---_--_
(Please return to Clayton McEachern ® City ofSprbullield Development and Public Works, Pax # 736-1021, Phone # 736-1036),
email: omceachern(ibspringfield-or.gov
Project Name: Tentative Subdivision for Ninth St. Properties, LLC Applicant
Assessors Parcel #: 17-02-31-24, Tax Lot 11900 Date:
Land Use(s): Residential Phone #:
Project Size (Acres):
Approx. Impervious Area:
0.93 Acres Fax #:
Roof: +1- 6,800 to 8,500 sf Email:
Other: +/- 8,600 sf
Jason Goshert, SSW Engineers Inc.
10/21/2020
541-485-8383
541-485-8384
jasong@sswengineens.com
Project Description (Include a copy of Assessor's map):
Proposed blot residential subdivision for 1 existing dwelling and 5 new / future dwellings. See attached Site
Assessment of Existing Conditions and preliminary Land Division Tentative Plan.
Drainage Proposal (Public connection(s), discharge location(s), etc. Attach additional sheets) if necessary:
New impervious areas are proposed to drain to privately maintained on-site vegetated stormwater treatment facilities
(and detention facilities if necessary) that collect and discharge treated runoff into the public system via piped
connections to the existing 30" public stormwater main which runs along the north side of the proposed subdivision.
Proposed Stormwater Best Management Practices:
Raingardens and/or vegetated planters.
---(Area below this line filled out by the City and Returned to the Applicant) —
(At a minimum, all boxes checked by the City on the front and back of this sheet shall be submitted
_ or an application to he complete for submittal, although other requirements may be necessa
Drainage Study Type (EDSPM Section 4 03.2) (Note UH may be substituted for Rational Method)
® Small Site Study—(use Rational Method for calculations)
❑ Mid -Level Development Study — (use Unit Hydrogfaph Method for calculations)
❑ Full Drainage Development Study — (use Unit Hydrograpb Method for calculations)
Environmental Considerations:
❑ Wellhead Zone: 10 year TOT ❑ Hillside Development: N/a
❑ Wetland/Riparian: N/a ❑ Floodway/Floodplain: N/a
❑ Soil Type: 6-Awbirg Urban Land Complex -likely a ❑ Other Jurisdictions N/a
Downstream Analysis yrdrologic group C/D soil -infiltration test
—required
® N/A
❑ Flow line for starting water surface elevation:
❑ Design IIGL to use for starting water surface elevation:
❑ Manhole/Junction to take analysis to:
Return to Clayton McEachern Q City of Springfield, email. criceachern@springfield-orgov, FAX- (541) 736-1021
COMPLETE STUDY ITEMS I For Official Uw Only.
* Based upon the information provided on the front of this sheet, the following represents a minimum ofwhat is needed for an
application to be complete for submittal with respect to drainage,' however, this list should not be used in lieu of the Springfield
Development Code (SDC) or the City's Engineering Design Manual. Compliance with these requirements does not constitute site
approval, Additional site specific information may be required Note: Upon scoping sheet submittal, ensure completedfnon has been
signed in the space provided below:
Interim Design Standards/Water Quantity (EDSPM Chapter 3
Req'd N/A
Z ❑ All non -building rooftop (NBR) impervious surfaces shall be pre-treated (e.g. multi-chambered eatchbasin wood filtration
media) for stonnwater quality. Additionally, a minimum o&50% of the NBR impervious surface shall be treated by
vegetated methods.
Z Where required, vegetative stormwater design shall be consistent with design standards (EDSPM Section 3.02), set forth
in Chapter 2 of the Eugene Stormwater Management Manual.
For new NBR impervious arca less than 15,000 square feet a simplified design approach may be followed as specified
by the Eugene Stormwater Management Manual (Sec2.4.1).
V1 ❑ If a stormwater treatment Swale is proposed, submit calculations/specifications for sizing, velocity, flow, side slopes,
bottom slope, and seed mix consistent with City of Springfield or Eugene's Stormwater Management Manual.
Z ❑ Water Quality calculations as required in Section 3.03.1 of the EDSPM, only required a proposed area don't meet COE
st�naaids (or treat M
All building rooftop mounted equipment, or other fluid containing equipment located outsi�c of the building, shall
be provided with secondary containment or weather resistant rnalnsnrn.
Z
❑
Drainage study prepared by a Professional Civil Engineer licensed in the state of Oregon.
Z
❑
A complete drainage study, as required in EDSPM Section 4.03.1, including a hydrological study map.
ZE]
Calculations showing system capacity for a 2 -year storm event and overflow effects of a 25 -year storm event.
7
n
The time of concentration (Tc) shall be determined using a l0 minute start time for developed basins.
E] Z A downstream drainage analysis as described in EDSPM Section 4.03A.C. On-site drainage shall be governed by the
Oregon Plumbing Specialty Code (OPSC).
E] 0 Elevations of the HCI. and flow lines for both city and private systems where applicable.
Design of Storm Systems (EDSPM Section 4.04).
Flow lines, slopes, rim elevations, pipe type mil sizes clearly indicated on the plan set.
Minimum pipe cover shall be 18 inches for reinforced pipe and 36 inches for plahn concrete and plastic pipe materials, or
proper engineering calculations shall be provided when less. The cover shall be sufficient to support an 80,000 Ib load
without before of the pipe structure.
Z E Manning's "n" values for pipes shall be consistent with Table 4-1 of the EDSP. All storm pipes shall be designed to
achieve a minimum velocity of three (3) feet per second at 0.5 Dice full based on Table 4-1 as well.
Z Ej Existing and proposed contours, located at one foot interval. Include spot elevations and site grades showing how site
drains.
7 F-1 Private stormwater easements shall be clearly depicted on plans when private stormwater flows from one property to
another.
2 ❑ Drywells shall not receive runoff from any surface w/o being treated by one or more BMPs, with the exception of
residential buildutg roofs (EDSP Section 3.03.4.A). Additional provisions apply to this as required by the DEQ. Refer to
the website: htto://w v.deg.smle.or uywq/uic/uic htm for more information.
Detention ponds shall be designed to limit runoff to pre -development rates for the 2 through 25 -year storm events.
onsite soils may limit infiltration of treatment areas, but should still be maximized as much as possible to limit downstream discharge.
"This form shall be included as an attachment, inside the front cover, of the stormwuter study.
'IMPORTANT. • ENGLVEER PLEASE READ BELOWAND SIGN.r
As the engineer of record, I hereby certify the above required items are complete and included with the submitted stormwater study
and plan set. Signature Date
Form Version 5: June 2015
APPENDIX B
m—
I
SITE STORMWATER PLAN
SCALE 1 -20 A
e
A'
q
IN
m 1.55'—•w a
�@
a
T 8800 I. O 850' FACN) R
IRiUOSri P P
as -ncw
.0 -mss
c x,
I
TP
aII
X BY2 E
L
LOT .
4"`n
u
IIY
—
T.
\
NET
I
I 7
ANUT+I
. L Y.R� „soR
-Ol
\q
\
LN]PIT
_
"I
e
0
w.xo•
n.xa•
°
FL
73B
g
i
SITE STORMWATER PLAN
SCALE 1 -20 A
e
A'
q
IN
m 1.55'—•w a
�@
a
T 8800 I. O 850' FACN) R
IRiUOSri P P
as -ncw
SITE STORMWATER PLAN
SCALE 1 -20 A
e
NOT TO SCALE
MSYMBOLS
p^ PROPOSED CLEANOUT, SEE 1C/1
SS PROPOSED DOWNSPOUT
—ST— PROPOSED STORM LINE
------ PROPOSED PERFORATED STORM LINE
PROPOSED STORMWATER PLANTER
NOTES
1 ALL STORMWATER PIPE ARE PVC UNLESS OTHERWISE
NOTED
2. PLANTING FOR S70EMWATER FACILITIES BY OTHERS.
MALYMUM LOT IMPERVIOUS SURFACE 1
LOT 2 049 SO ET
LOT 2 1 OU SO Fi
LOTS 2, 575 SO FT
LOT I 21551 SO FT
LOTS 2,ACEDF
NOTE LOT MAX IMPERVIOUS SURFACE IS THE
PROPOSED BUILDING & DRIVEWAY SURFACE.
CCC�MM`�
ENGINEERSI®
P.. LNC Xs..._SE
OJo
Z J rn
J � �
IL F P,
>aOwm
W
QaF�o
F h0
Z O V7=-
W N�–
F� MLL
z z
U)
pia
pz<
Z-�
EVISO 5
SITE
STORMWATER
PLAN
wxnX
MAC
01312011
MAC
6H
LET
q
i
m 1.55'—•w a
_ 1_1S 13295•
as -ncw
.0 -mss
c x,
I
TP
aII
L
LOT .
4"`n
EST.
u
IIY
I
I 7
_
_
e
w.xo•
n.xa•
s 9P0.5'm. w,
ss
i
+
_
e
I
i
Tw 1011-1
NOT TO SCALE
MSYMBOLS
p^ PROPOSED CLEANOUT, SEE 1C/1
SS PROPOSED DOWNSPOUT
—ST— PROPOSED STORM LINE
------ PROPOSED PERFORATED STORM LINE
PROPOSED STORMWATER PLANTER
NOTES
1 ALL STORMWATER PIPE ARE PVC UNLESS OTHERWISE
NOTED
2. PLANTING FOR S70EMWATER FACILITIES BY OTHERS.
MALYMUM LOT IMPERVIOUS SURFACE 1
LOT 2 049 SO ET
LOT 2 1 OU SO Fi
LOTS 2, 575 SO FT
LOT I 21551 SO FT
LOTS 2,ACEDF
NOTE LOT MAX IMPERVIOUS SURFACE IS THE
PROPOSED BUILDING & DRIVEWAY SURFACE.
CCC�MM`�
ENGINEERSI®
P.. LNC Xs..._SE
OJo
Z J rn
J � �
IL F P,
>aOwm
W
QaF�o
F h0
Z O V7=-
W N�–
F� MLL
z z
U)
pia
pz<
Z-�
EVISO 5
SITE
STORMWATER
PLAN
wxnX
MAC
01312011
MAC
6H
LET
SYMBOLS
.,�..� EXISTING ELEVATION TOP OF CURB
...... EXISTING ELEVATON
® PROPOSED SPOT ELEVATION
/.asc P ROPOS EO SPoT ELEVATION-TOPOFCURB
wa uc PROPOSe05POTELEVATION-MATCHEXISTING
jos=i PPO.EBSPOl DLEVATIGN-FLCI
0
�, SITE GRADING PLAN m
csa ® NOT TO SCALE N.�
Y
JJrr
ENGINEERS
®t
97401
O J o
Z J rn
J C
d W F
W�Owm
w
QW�O
F d 4.9i
ZO Vy
W
Z aMr,Z
O�Npaa
oFo_
OZa
gz�
REVISIONS
SITE GRADING
PLAN
2677]4
MAC
099 Q021
MAC
(�Moo
iV
t,
•
�
w
I�
I
m
Fw._M_
G.Sir
_
s
n_
NI.R�•_
n y
n
_
cl
v
f
o
Lvw;
Ito
a
?
R
I
t
IF
eon'
`w
-.fit zcao
ff o vsrc uvM
T
aa�vss,
?. -
^
w
t
a
I{
XXI
A.
8
,.. rw z>ao
i
I
I
I~o
fR
Lm •
2
o,§
14 1
�gti
ru wrx®�
_
ON.
0
�, SITE GRADING PLAN m
csa ® NOT TO SCALE N.�
Y
JJrr
ENGINEERS
®t
97401
O J o
Z J rn
J C
d W F
W�Owm
w
QW�O
F d 4.9i
ZO Vy
W
Z aMr,Z
O�Npaa
oFo_
OZa
gz�
REVISIONS
SITE GRADING
PLAN
2677]4
MAC
099 Q021
MAC
(�Moo
APPENDIX C
Stormwater Surface Filtration/Infiltration Facility Sizing Spreadsheet
24 Hour Storm, NRCS Type 1A Rainfall Distribution
City of Eugene
Version 2.1
Name: NINTH ST PROPERTIES Date: 3/17/21
Add.; 43135TH STREET Permit Number:
SPRINGFIELD. OR 87478 CatchmeatlD: PLANTERI
art MICHAEL A COX. P.E.
ay: SSW ENGINEERS INC
Complete this bourn for each drainage catchment in the project she that is to be sized per the Presumptive Approach.
Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate
calculations with the facility.
The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF)
=or infiltration facilities in Class A or B soils where no infiltration testing has been perfromed use an infiltration rate of 0.5 in/h r.
For all facilities use a maximum soil infiltration rate of 2.5 in/hr for topsoil/growing medium.
hoose "Yes" from the dropdown boxes below next to the design standards requirements for this facilely.
Pollution Reduction (PR) FYes
FlowControl(FC)l No
Destination(DT) No an ii ancon hurt, Maar be moue as he really rse to Meet castrare,eyei,meme
Total Square Footage Impervious Area= 7217 sqft
Total Square Footage Pervious Area-
0
sgft
Impervious Area CN=l 98
Pervious Area CN=
85
3.6 inches
Total Square Footage of Drainage Area=
7217
at
Time of Concentration Post Development- 10 min
Weighted Average CN=
98
Site Dattel Development (Data in this section is only used if Flow Control is required)
Pre -Development CN= 85
Time of Concentration Pre -Development= rain
Soil Data
Tested Soil Infiltration Rate=
5
iNhr(See
N l Destination Design= l�.•.•••rin/hr
Design Sell Infiltration Ratas=l
2.5
in/hr
Soil Infiltration Rate
Re vire-ant
Rainfall Depth
Desi nStorm
Pollution Reduction
1.4 inches
Water OUal'
Flow Control
3.6 inches
IFlootl Control
Destination
I 3.6 inches
IFlootl Control
Surface Width=If
SurFdce Length=It
Facility Type=RIB
Facility Side Slopes=to
Max. Ponding Depth
in Stormwater Facility=in
Depth of Growing Metlium (Soip=in
tonnwater Planter Facility Surface Area=
FacilitySurface PedmeW
Facility Bottom Area=
1 Facility Bottom Perimeter-
Basin Volume=
Ratio of Facility Area to Impervious Area=
250
sgft
ft
sgft
ft
cf
110
250
110
125.0
0.035
3/30/21-12:24 PM
Pollution Reduction-Calculation Hesults
Peak Flow Rate to Slormwater Facility= 0051 cis
Peak Facility Overflow Rate= 0.000cfs
Total Runoff Valume to S[ormwater
Facility= 707 cf
Total Overflow Volume= 0 cf
Max. Depth of Stormwater in Facility= 4.0 in
Drawdown Time= 02 hours
Facility Sizing Meets Pollution Reduction Standards?
Meets Requirement of No Facility Flooding?
Meets Requirement for Maximum of 18 Hour Drawdown Time?
Flow Control-Calculation Results
Peak Flow Rate to Stormwater Facility=Ncfs
Peak Facility Overflow Rate= 0.125 cis
Total Runoff Volume to St. an
Facility=cf
Total Overflow Volume= 725 cf
Peak Off -Site Flow Rate
Max. Depth of Stormwater in Facility=in
Filtration Facility Undentrain= 0.014 cfa
Drawdown Time=hours
Pre-Development Runoff Data
Peak Flow Rate= 0.086 cis
Total Runoff Volume= 1265 cf
NW Facility Sizing Meets Flow Control Standards?
NA Meets Requirement for Post Development offsite flow less or equal to Pre-Development Flow?
NA IMests Requirement for Maximum of 18 Hour Drawdown Time?
Destination-Calculation Results
cfs
Peak Flow Rate to Stormwater Facility =INIA
Peak Facility Overflow Rate= N!A cis
Total Runoff Volume to Stormwater
Facility-cf
Total Overflow Volume= NIA cf
Max. Depth of Stormwater In Facility=in
Drawdown Time=hours
N/A Facility Sizing Meets Destination Standards?
NIA Meets Requirement of No Facility Flooding?
N!A Meets Requirement for Maximum of 30 hour Drawdown Time?
3/30/21-12:24 PM
Stormwater Surface Filtration/Infiltration Facility Sizing Spreadsheet
24 Hour Storm, NRCS Type 1A Rainfall Distribution
City of Eugene
Name: ntntrlbt m<urbHnr Date: 3/17/21
Address: 431 36TH STREET Permit Number:
SPRINGFIELD. OR 97478 CatchmentlD: PLANTER2
:r: MICHAEL A CO%PE
ay: SSW ENGINEERS INC
Complete this form for each drainage catchment in the project site that is to he sized per the Presumptive Approach.
Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate
calculations with the facility.
The maximum drainage catchment to be modeled per the Presumptive Approach is t acre (43,560 SF)
=or infiltration facilities in Class A or B sails where no infiltration testing has been perfromed use an inti thation rate of 0.5 With,
For all facilities use a maximum soil infiltration rate of 2.5 in/hr for topsoil/growing medium.
loose "Yes" from the dropdown boxes below next to the design standards requirements for this facility.
Pollution Reduction (PR)Yes
Flow Control (FC)l No
Destination(DT) No 'An initiation radaly horn be u,ixec as the Isoll"pe to MWdececetmc rensnamems
Total Square Footage Impervious Area= 7292 sgft Total Square Footage Pervious Area= 0 sgft
Impervious Area CN=l 98 Pervious Area CN=j 85
Total Square Footage of Drainage Area= 7292 sfl Time of Concentration Post Development= 10 min
Weighted Average Ci 98
Time of Concentration
Tested Soil Infiltration Rate= inim(Seenote,l) Destination Design-®inlhr
Design Soil Infiltration Ratemi 2.5inlhr Soil Infiltration Rate
Requirement
Rainfall Death
IDeadamStorm
Pollution Reduction
1 4 incM1es
Water Qual'
Flow Cordrol
3.6 inches
I Flood Control
Destination
1 3.6 inches
I Flood Control
Surface Lengl
Facility Side Slope
Max. Pending Depth
in Stormwater Facility=
Depth of Growing Medium (Soi
3/30/21-12:24 PM
Facility Surface
Facility Surface Perir
Facility Bottom
Facility Bottom Pedr
Ratio of Facility Area to
Pollution a uchon- alculanon esu
Peak Flow Rate to Stonnwater Facility 0.051 cfs
Peak Facility Overflow Rate= 0.000 cfs
Total Runoff Volume to Stormwater
Facility 715 of
Total Overflow Volume= 0 cf
Max. Depth of Stormwater in Facility_ 5.9 in
Drawdown Time= 0.2 hours
Yes Facility Sizing Meets Pollution Reduction Standards?
FY—EF-17111fileets, Requirement of No Facility Flooding?
VE` Meets Requirement for Maximum of 18 Hour Drawdown Time?
Flow Control -Calculation Results
Peak Flow Rate to Stormwater Facility= 0.141 cfs
is
Peak Facility Overflow Rate=plis
Total Runoff Volume W Stormwas"
Facility= 203] cf
Total Overflow Volume=f
Peak Off-site Flow Rate
Max. Depth of Stormwater in Facility= 6.0 in
Filtration Facility llnderdrain=
Drawdown Time= 25 hours
Pre-Develo ment Runoff Data
Peak Flow Rate = 0.087 cls
Total Runoff Volume =1 1278 d
NW Facility Sizing Meets Flow Control Standards?
NW Meets Requirement for Post Development offsite flow lessor equal to Pre -Development Flout!
NW Meets Requirement for Maximum of 18 Hour Drawdown Time?
Destination -Calculation Results
cfs
Peak Flow Rate to Stormwater Facility =R",
Peak Facility Overflow Rate= WA cfs
Total Runoff Volume to Stormwater
Facilitycl
Total Overflow Volume= N/ Cf
Max. Depth of Stormwater in Facility=in
Drawdown Time=hours
N/A Facility Sizing Meets Destination Standards?
W77IMe.ts Requirement of No Facility Flooding?
r—
N/A Meets Requirement for Maximum of 30 hour Drawdown Time?
B1!<ll/ii6PJPZf9�Gl
Stormwater Surface Filtration/Infiltration Facility Sizing Spreadsheet
24 Hour Storm, NRCS Type to Rainfall Distribution
City of Eugene
Version 2.1
Name: NINTH ST PROPERTIES Date: 3/17121
Address: 431 35TH STREET Permit Number:
SPRINGFIELD, OR 97478 Catchment ID: PUNTER
)r: MICHAELA COX, P.E.
ty: SSW ENGINEERS INC
Complete this form for each drainage catchment In the project site that is to be sized per the Presumptive Approach.
Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate
calculations with the facility.
The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF)
:or infiltration facilities in Class A or B soils where no infiltration testing has been perfromed use an infiltration rete of 0.5 in/hr.
For all facilities use a maximum soil infiltration rete of 2.5 in/hr for topsoil/growing medium.
loose "Yes" from the dropdown boxes below next to the design standards requirements for this facility.
Pollution Reduction (PR) Yes
Flow Control (FC) No
Destination(DT) No 'nn saltation tenity Ten be chosen as the Miry nine to meet destination regovememe
Total Square Footage Impervious Area= 6974 sgft Total Square Footage Pervious Area= 0 act
Impervious Area CN= 98 Pervious Area CN= 85
Total Square Footage of Drainage Aress-1 6974 sit Time of Concentration Post Development- 10 min
Weighted Average CN= 98
Site Data -Pre Development (Data in this section is only used if Flow Control is required)
Pre -Development CN= 85 Time of Concentration Pre -Development= t nrn
Soil Data
Tested Soil Infiltration Rate= inlhr(See Note 4) Destination Design=®inlhr
Design Soil Infiltration Ratismi 2.5 in/hr Soil Infiltration Rate
Requirement
Rainfall De th
Design Storm
Pollutlon option
1.4 inches
Water Quality
Flow Control
3.6 inches
Flood Control
Destination
I 3.6 inches
Flood Control
Surface Wid
Surface Long
Facility Side Slops
Max. Ponding Depth
in SWrmwater Facility=
Depth of Growing Medium (So
3/30/21-12:25 PM
Planter I Facility Surface
Facility Surface Perir
Facility Bottom
Facility Bottom Perir
Ratio of Facility Area to
Pollution Recluction-Calculation Results
Peak Flow Rate to Stormwatrr Facility 0.049 chic
Peak Facility Overflow Rate= 0.000 cfs
Total Runoff Volume to Stormwater
_
Facility 684 cf
Total Overflow Volume= 0 cf
Max. Depth of Stormwater in Facility= 5.9 in
Drewdawn Time= 0.2 hours
Yes Facility Sizing Meets Pollution Reduction Standards?
YES Meets Requirement of No Facility Flooding?
YES Meets Requirement for Maximum of 18 Hour Drawdown Time?
Flow Control-Calculation Results
Peak Flow Rate to Stormwater Facility =Ecis
Peak Facility Overflow Rate= 0.123 cfs
Total Runoff Volume to Stormwater
Facility=of
Total Overflow Volume= 905 cf
Peak Off -Site Flow Rate
Max. Depth of Stormwater in Facility=in
Filtration Facility Underdmin= p 1112 cfs
Drawdown Time=hours
Pre-Develo mentRunoff Data
Peak Flow Rate - 0.083 ofs
Total Runoff Volume =1 1223 cf
NW Facility Sizing Meets Flow Control Standards?
Nw Meets Requirement for Post Development offsite flow less or equal to Pre-Development Flow,
EE
MA Meatr Requirement for Maximum of 18 Hour Drawdown Time?
Destination-Calculation Results
Peak Flow Rate to Stormwatrr Facility= N/A cis
Peak Facility Overflow Rate= N/A cis
Total Runoff Volume to Stormwatrr
Facility N/ ' of
Total Overflow Volume= N/A cf
Max. Depth of Stormwater in Facility= N/ in
Drawdown Time= N/ hours
N/A Facility Sizing Meets Destination Standards?
N/A Meets Requirement of No Facility Flooding?
N/A Meets Requirement for Maximum of 30 hour Drawdown Time?
3/30/21-12:25 PM
nmuni��i
�iini�eeM
■iii��
�ioi�in
■�uA
n�n�iw
n
��ie�'
N�i�i'dn�
IlO�i
nui
u�
�Alinm��
A
Nninid
��u■i■
viii
i
i
���R���
v....
�
m
un°
�i
a�iiiiiiiiii��
nnn
Ooi
���
�ivai
��
nnA�
imm��
APPENDIX D
70
Md 8 d
ma
N
2N
N
N
p
g
n
E
�
5
�O
$2
VG
z�
2 U
Ms[,us .s
d
�
/
! .2E
!
E A 8 9
»mea, } {!|> \■
)[2g�,�4«ao>+z,_*
•
!!,r
)
-
_
\/{
\
){/
\);<A
®
!
�#f19
!|
)\
\
-
21
T
q){1
b;
»mea, } {!|> \■
)[2g�,�4«ao>+z,_*
Soil Map—Lane County Area. Oregon 431 35th St, Springfield, Oregon
Map Unit Legend
Map Unit Symbol Map Unit NameAcres in AOI Percent of AOI
2226A Awbng-Urban land complex, 0 2.2 100.0%
to 2 percent slopes
Interest
2.2 I 100.0%
USDn Natural Resources Web Soil Survey 3/30/2021
:G Conservation Service National Cooperative Soil Survey Page 3 of 3
APPENDIX E
K & A ENGINEERING, INC.
91051 S. WILLAMETTE STREET *a
P.O. Box 8486, COBURG, OR 97408
(541) 684-9399 KAENGINEERS.COM
enginee-ing
November 30, 2020 Project: 20066
Ninth St. Properties, LLC
17605 NW Autumn Ridge Dr.
Beaverton, OR 97006
Subject: Infiltration Test Summary
43135" Street, Springfield, Oregon.
PURPOSE AND SCOPE
At the request of the Lane County, K & A Engineering, Inc. has completed one (1) infiltration test for the
purpose of determining allowable infiltration rates for the design of stormwater facilities associated
with the subject development.
The scope of our services included one (1) infiltration tests, conducted on November 19, 2020 and this
Written Report.
INFILTRATION TEST RESULTS
Locations and Depths
One (1) shallow infiltration test were made at the subject project site to characterize the Infiltration
rates for design and specification of stormwater retention/detention facilities for the project. The test
location and depth (3 -feet) were specified by the project architect. The test location has been labelled
as IT 1. The testwas made at an approximate depth of 3 -ft below the existing ground surface.
See the attached Site Plan drawing for approximate location.
Procedure
• 6 -inch diameter borings were pre -drilled to a 3 -foot depth using 6 -inch solid stem auger and our
geotechnical drill.
• 5 -inch diameter PVC casing was placed in the holes and pushed approximately 6 -inches into the
soil at the bottom of the hole to form the requisite soil plug.
• Water was placed in the casing to a minimum height of 1 -foot above the bottom of the
borehole.
• Measurement of drawdown commenced within approximately 4 -hours of initial filling.
• Observations continued for a period of 24 -hours after initial filling
Subsurface conditions
Subsurface soils, based on visual inspection of the soil cuttings during the advancement of the auger,
consist of (approximately):
Infiltration Test Results ma
43135`^ Street, Springfield OR
November 30, 2020-K& A Engineering, Inca Project No.: 20066 en s.n Pe .n
• Undocumented FILL: 1.5 -feet of dark gray,damp, soft organic SILT with woody debris, over
• Organic CLAY: 1.5 -feet of dark brown, damp, soft, silty -CLAY.
In general, the soil layer at the depth of infiltration test can be described as silty -CLAY.
Infiltration Observations
Infiltration was observed in the casing over a period of 24 -hours. No changes in the water column
height inside the casing could be detected over the test period.
SUMMARY AND RECOMMENDATIONS
Test indicates extremely poor infiltration capacity of the organic silty -CLAY at the depth tested and we
recommend that these soils are not suitable for conventional on-site storm water disposal systems such
as soakage trenches. We recommend that detention or retention facilities can be used but should not
be designed to incorporate any significant infiltration back into soils at the site, at least at this depth.
Based on our research of logs for nearby wells', groundwater is likely to be found as shallow as 10 -feet.
Further testing at greater depths may find increased infiltration capacity, but additional testing should
also be accompanied by at least one deep boring to determine actual groundwater levels at the site.
Deep infiltration testing, if successful, requires deeper stormwater handling facilities, which cost more
to construct.
K & A Engineering, Inc. should be contacted if further exploration and testing is desired to improve the
viability of on-site stormwater disposal or storage.
1 Oregon Water Resources Department Well Report Query. See Well Report Query (state.or.us)
Page 12
Infiltration Test Results. kea
431 35`^ Street, Springfield OR
November 30, 2020 K & A Engineering, Inc. - Project No.: 20066
engineering
LIMITATIONS AND USE OF GEOTECHNICAL RECOMMENDATIONS
This report has been prepared for the exclusive use of Ninth St. Properties, LLC for the subject project.
The geotechnical testing, analysis, and recommendations for this report meet the standards of care of
competent geotechnical engineers providing similar services at the time these services were provided.
We do not warrant or guarantee site surface subsurface conditions.
Infiltration testing in this case was made without investigating the depth of groundwater, which can
have a significant effect on seepage characteristics. We made reasonable assumptions of groundwater
depth from well log report of nearby sites.
The scope of our services does not include construction safety precautions, techniques, sequences, or
procedures, except as specifically recommended in this report. Our services should not be interpreted
as an environmental assessment of site conditions.
Thank you for the opportunity to be of service. Please call me if you have any questions.
Sincerely,
/% Xe'-41�
Michael Remboldt, P.E., G.E.
K & A Engineering, Inc.
SPED PROF'S
G IN E X02
19,474 9
FN OREGON 1
icy TF418ER ib', p�O
qF! dfNNls'RE�O
EXPIRES'. DECEMBER 31. 2020
Page 1 3
APPENDIX F
I
+ + JUNCUS EFFUSUS (COMMON RUSH) 4" POTS - 12" O.C.
+ 3/8" TO 3/4" ROUND ROCK NON-FLOATABLE MULCH
4" TO 8" COBBLES AT INLET LOCATIONS
PIPE INLET OVERFLOW
PLANTER 1 PIPE INLET
io. . . . . . . . . . . . . . .
v
83'-22'
4 12" INLET IN CURB m A
@ 12' O.C., TYP,
47'-04" 6" 4'-6'12,-10"
.........} ............................ J 4' YIW�tlN iii WN 4
3
......... 6''
... ....PLANTER 2
'IPE INLET PIPE INLET
C T
12" INLET IN CURB
NOTES @ 12'0.C., TYP.
PLANTINGS PER CITY OF SPRINGFIELD, OREGON: ENGINEERING DESIGN ���D
STANDARDS AND PROCEDURES MANUAL (2012) APPENDIX 6B, ZONE A; PAF
MOIST TO WET CONDITIONS & CITY OF EUGENE STORMWATER
MANAGEMENT MANUAL (2014); APPENDIX D, ZONE A ,S?
2� a ] 0 r
STORMWATER PLANTING SCHEDULE'c Zo CO
EX1 SCALE: V= 5'-0" ygFL ALpN
RENEWS: 12/31/21
o -m4
LAND DIVISION TENTATIVE PLAN FOR: oarsvzoz0
SSWENGINEERS. i
NINTH ST. PROPERTIES, LLC ""°
r CIVIL STRUCTURAL -BUILDING DESIGN MAP 17-02-31-24, TAX LOT 11900
SURVEYING LANDUSEPLANNING 43135TH STREET xEE��'({�
es" wsv� e<"<o,<e4 ,4o SPRINGFIELD OR 97478 LSLN u
so1)4e �(5., 4M-aea."