Drainage and Erosion
~
PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FOR
O'REAR INDUSTRIAL PLAT
Prepared by" Dennis Cochran, P E.
2626 12th Court SW
OlympIa, WA 98502
(206) 754-1495
Applicant: Mike O'Rear
3105 Marvin Road NE
Olympia, WA 98506
(206) 491.2500
Representative: Randy Orth
2626 12th Court SW
Olympia, WA 98501
(206) 786.1864
December 1, 1994
O'Rear Industrial Plat page 1
DRAINAGE REPORT TABLE OF CONTENTS
DRAINAGE REPORT
ENGINEER'S CERTIFICATE.. .page 4
SECTION 1 Proposed project descrlptlon.....page 5
SECTION 2. EXisting conditions. .page 5
SECTION 3. Infiltration rates and soil report.. .page 5
SECTION 4 Wells. .page 5
SECTION 5 Fuel tanks.....page 5
SECTION 6 Sub-basin description.... page 6
SECTION 7 AnalysIs of the 100 year flood conditlOn.....page 6
SECTION 8 Aesthetic considerations for the facilities.... page 6
SECTION g. Downstream analysIs. .page 6
SECTION 10: Covenants, DedicatIOns and easements... page 6
SECTION 11 Property owner's association articles of incorporation... page 6
EROSION CONTROL REPORT TABLE OF CONTENTS
SECTION 1 Construction sequence and procedure.... page 7
SECTION 2: Trapping sediment. page 8
SECTION 3' Permanent erosion control and site restoration.. page 8
SECTION 4 Geotechnical report and analysIs. .page 8
SECTION 5 Inspection Sequence... page 9
O'Rear Industrial Plat page 2
TABLE OF CONTENTS continued
APPENDICES
APPENDIX A. CalculatlOns.....page 10
APPENDIX B. Soils Information... .page 11
APPENDIX C Work Maps.....page 12
APPENDIX D Basm map.....page 13
APPENDIX E. Mamtenance plan.....page 14
APPENDIX F' Facility summary plan.....page 15
O'Rear Industrial Plat page 3
Dennis Cochran, P E.
2626 12th Court SW
Olympia, WA 98502
(2061 754.1495
I hereby certify that this dram age and erosion control plan and report for'
O'Rear Industrial Park
has been prepared by me or under my superVISion and meets the minimum standards of'
DramaQe Design and Erosion Control Manual for the City of Yelm, WA
and normal standards of engineering practice. I understand that the JUrisdiction does not and will not assume
liability for the sufficiency, sUitability, or performance of the dramage facilities designed by me.
Dennis Cochran, P E.
O'Rear Industrial Plat page 4
SECTION 1 PROPOSED PROJECT DESCRIPTION
The proposal IS to subdivide approximately 13.2 acres into 12 separate commercial lots. The Internal
roadway shall be a private roadway and create about 0.71 acres of Impervious paving and about 042 acres
of disturbed pervIous area. The stormwater management proposal IS to treat and dispose of runoff from the
roadway and right-of-way via a wetpond and a retention pond located In the southwest corner of the site.
The Internal roadway .shall convey runoff via curb and gutter to catch basins and Into to a piping network
which ultimately drams to the wetpond for treatment. Treated runoff will flow into the retention pond via
an overflow weir set at three feet above the bottom of the wetpond.
IndiVidual site runoff will be handled by each commercial development on indiVidual lots. As the various
businesses that will occupy the lots created by thiS subdivision are unknown at thiS time, thiS current
proposal deals only With the runoff created by the private roadway
SECTION 2 EXISTING CONDITIONS
The site is located on Rhoton Road north of N.P Road and south of Rhoton Court. Recently the site was
cleared of most vegetation. The topography IS such that surface flow would be In a southwesterly direction
across the site. The site high point IS located in the southeast corner at an elevation of 336 while the site
low elevations are located along the westerly boundary at 324 There are no roadways across the property
at thiS time.
SECTION 3 INFILTRATION RATE(SlISOILS REPORT
Site and area soils are identified as being Spanaway gravelly sandy loam at depths to 15 Inches while at a
depth of 20 - 60 inches soils are described as being Spanaway extremely gravelly loamy sand (Soil Survey of
Thurston County, WA) Infiltration rates are expected to exceed 20 Inches per hour In the zone associated
With the retention pond that IS targeted for this proposal. Prior to final engineering design, soil logs will be
excavated and the soils confirmed for their Infiltration ability If for some unforeseen reason the soils do not
Infiltrate at a rate of 20 mches per hour, the area reqUired for retention will need to be enlarged. As thiS
proposal is unaffected by the space reqUired for stormwater storage, the confirmation of site soils IS not
provided at thiS time
A copy of the appropriate soils map is included In Appendix B of thiS report.
SECTION 4 WELLS
There are no wells associated with thiS parcel and none were discovered during the topographic survey
SECTION 5: FUEL TANKS
There are no fuel tanks associated With thiS parcel and none were discovered during the topographic survey
Q'Rear Industrial Plat page 5
SECTION 6: SUB.BASIN DESCRIPTION
Site topography is such that any runoff from the site will flow towards the southwest corner of the
property There are no sub-basins located on the site. Area soils are such that no offsite runoff is expected
to enter the site and there currently IS no eVidence of any off site flow entering the site.
The site IS located In the Yelm Creek drainage basin.
SECTION 7 ANALYSIS OF THE 100 YEAR FLOOD CONDITION
There IS no area on this parcel that is associated With any 100 year flood plain.
SECTION 8- AESTHETIC CONSIDERATIONS FOR THE FACILITIES
Treatment and disposal facilities are located together to minimize the visual impact to the project.
Additionally, a Single set of facilities are proposed as opposed to several regional facilities scattered across
the site.
SECTION 9- DOWNSTREAM ANALYSIS
As thiS proposal retains all stormwater onsite, no downstream analYSIS IS provided.
SECTION 10: COVENANTS, DEDICATIONS AND EASEMENTS
Easements to the stormwater facilities shall be shown on the final plat. Covenants will be created giving
responsibility for operation and maintenance of the conveyance system, the wetpond and the retention pond
to the Homeowner's Association. Stormwater facilities located Within road rights-of-way will be maintained
by the Homeowner's ASSOCiation as will the wetpond and the retention pond.
SECTION 11 PROPERTY OWNER'S ASSOCIATION AND ARTICLES OF INCORPORATION
The owner will prOVide these for the City's review pnor to final plat.
O'Rear Industrial Plat page 6
EROSION CONTROL REPORT
SECTION 1 CONSTRUCTION SEQUENCE AND PROCEDURE
Place siltation fencing.
2. Clear the areas associated with roadway construction.
3 Cut the roads to subgrade.
4 Install the stabilized construction entrances.
5 Build temporary shallow ditches to carry the runoff away from the roadways.
6. Excavate the wetpond.
7 Partially excavate the retention pond.
8. Install stormwater lines and utilities.
9 Install catch basins and provide inlet protection.
10 Ballast the roadways.
11 Construct the curb.
12. Crush the roadways.
13 Abandon the temporary drainage ditches.
14 Pave the roadways.
15 Complete the retention pond.
16 Distribute any collected sediments Into the bottom of the wetpond.
17 Stabilize all disturbed areas, the wetpond and the retention pond.
O'Rear Industrial Plat page 7
SECTION 2 TRAPPING SEDIMENT
Siltation fencing placed along the east side of the retentIOn pond will protect the pond from any sediments
during subdivisIOn construction. Additional siltation protection for the retention pond will be provided by the
wetpond located upstream. Inlet protection provided at each catch basin will protect the stormwater
collection system. Temporary ditches located at subgrade will collect sediment as well as convey sediment
to the excavated wetpond.
Sediment that IS trapped may be distributed Into the bottom of the wetpond at the close of constructIOn.
SECTION 3 PERMANENT EROSION CONTROL AND SITE RESTORATION
All disturbed areas, the wetpond and the retention pond will be stabilized With grass at the close of
construction. Though not permanent In nature, the siltation fence at the retention pond may be left "up" to
provide additional protection once the lots begin to develop.
SECTION 4 GEOTECHNICAL REPORT AND ANALYSIS
This site does not warrant a geotechnical report and/or analYSIS.
O'Rear Industrial Plat page 8
SECTION 5" INSPECTION SEQUENCE
Siltation fencing (placement and locatIOn)
2. Roadway subgrade (grade and alignment)
3. Stabilized construction entrances.
3. Temporary sediment control devices.
4 Wetpond (size, grade and depth)
5 Overflow weir from the wetpond (size and depth)
6 Partially excavated retention pond (size and depth)
7 Stormwater lines and utilities (grade and alignment)
8. Catch basins (grade and location)
9 Roadway ballast (grade and amount)
10. Roadway curbing (grade and alignment).
11 Roadway CSTC (grade and amount)
12. CompletIOn of the retention pond (size, grade and depth)
13. Roadway asphalt (grade and amount)
14 Seeding of all disturbed areas.
Q'Rear Industrial Plat page 9
APPENDIX A
Calculations
a/Rear Industrial Plat page 10
O'REAR INDUSTRIAL PLAT CALCULATIONS
SITE AREA SUMMARY
SITE AREA COMPONENT AREA (ACRES)
TOT AL SITE AREA 13.2
ONSITE RIGHT-OF-WAY 1 13
IMPERVIOUS AREA 0.71
DISTURBED PERVIOUS AREA 0.42
REOUlRED STORAGE.
ImpervIOus area = 3,000 cf/acre(0.71 acres) = 2,130 cf
Disturbed pervious area = 1,000 cf/acre(0.42 acres) = 420 cf
Total required project storage = 2,130 cf + 420 cf = 2,550 cf
PROVIDED STORAGE.
VOLUME OF A TRAPEZOIDAL POND
Vo/ume=1/3~B+b+J Bb)
Where: H IS the depth of the pond
B IS the area of the bottom base
b is the area of the top base
Given that H = 2 feet, side slopes = 3 1, L = 65 feet, W = 12 feet, B = 780 sf, b = 1,848 sf, the
resulting volume is 2,552 cf
O'Rear Industrial Plat Appendix A page 1
REOUlRED TREATMENT
Wetpond surface area at a depth of three feet = 0.025(0 71 acres) = 773 sf
PROVIDED WETPOND SURFACE AREA AT A DEPTH OF THREE FEET
12 feet(65 feet) = 780 sf
SUMMARY OF REOUlRED STORAGE AND TREATMENT vs PROVIDED STORAGE AND TREATMENT
REQUIRED I PROVIDED
STORAGE = 2,550 CF 2,552 CF
TREATMENT = 773 SF 780 SF
CALCULATE THE TIME NEEDED TO DRAWDOWN THE STORAGE:
Assume an Infiltration rate of 20 inches per hour, bottom area of 780 sf; the time reqUired to drawdown
the storage is:
((780)(20/12)) = 1,300 cf/hour
NOW diVide by the volume and Inverse to get the time. 2,552/1,300 = 1 96 hours, say 2 hours
O'Rear Industrial Plat Appendix A page 2
APPENDIX B
Soils Information
O'Rear Industrial Plat page 11
----- ~
states
(\\ellt 01
Iture
\n cooperatloll wit"
'IN as\lingtoll State
oe?art(\\ent 01 Natural
r.esources and
'lNas\lington State
unl\J8r5lW Agncul\ure
Researc\l center
50n 5Uf"e,/ ot
,hurston count)',
\J\l3sh\ngton
.eNa\iOn
Ice
--_/ -~-- - --------::
SOIL SURVEY Of ,\4URS,ON COUI
\ '
o
o
\12
3/'
0')
266 Soil Survey
TABLE 14.--ENGINEERING INDEX PROPERTIES--Continued
I I Class if ica tion : Frag- I Percentage passing I
I I I I
Soil name and lDepth: USDA texture I :ments I sieve number-- I Liquid P1as-
I I
map symbol , , UnH ied I AASHTO I > 3 I I I I limit tiei ty
I I I I I I I I
I , I I inehes , 4 I 10 40 I 200 I
I I I I I , index
I In I I I Pet I I I Pet
, I I I I I I
- \ I I I I I I I
1 I I I , I I
110, 111----\----: 0-15:Grave11y sandy GM, SM :A-l, A-2 I 0-5 55-85 50-75 30-50 :15-25 , 35-50 NP-10
I I
Spanaway : : loam. I I I I I
I , I I I
115-20iVery gravelly :GM lA-I, A-2 I 0-10 35-55 25-50 15-45 110-35 I 35-50 NP-10
I I
, I loam, very I I I I I
Thurston County Washington
TABLE 15.--PHYSICAL AND CHEMICAL PROPERTIES OF THE SOILS--Continued
I I
, ,
Soil name and IDepthl
map symbol : :
, ,
I I
: In :
, 1
, I
109--------------: 0-22:
Spana 122-26 I
:26-38:
:38-60:
, I
, ,
110, 111--~------: ~-15:
Spanaway, :15-20:
._,~_.,.~"'.".mi : 20-60:
I ,
, 1
112, 113---------' 0-16:
Spanaway 16-221
22-60:
,
1
114*: I
Spanaway-------- 0-15:
15-201
,20-601
, ,
, I
Nisqually-------I 0-5 :
: 5-31:
:31-60:
1 ,
I ,
115--------------: 0-7 :
Sultan : 7-601
, I
1 ,
116--------------: 0-7 :
Tacoma I 7-50:
:50-60'
,
,
117, 118, 119----: 0-11
Tenino 111-36
: 36-40
:40-60
,
,
120--------------: 0-111
Tisch Ill-50:
150-601
I I
I ,
121, 122---------: 0-10:
Vai1ton 110-15:
:15-48:
: 48 :
I ,
, ,
123, 124---------: 0-111
Wilkeson 111-47:
:47-60:
1 I
I I
1 I
, ,
I ,
, I
1 ,
I ,
126, 127, 128----1 0-8 :
Yelm : 8-461
: 46-60:
, 1
I I
.~
~.... ~,~.. '~:;;J~" ~ .f-
_~___~I!""'';~' lli
125.
Xerorthents
Clay
15-20
20-30
5-18
5-18
20-50
10-15
10-15
10-25
25-35
18-35
0-5
Pct
7-15
5-15
5-15
2-5
0-5
0-5
0-5
0-5
0-5
0-5
2-10
I
,
I Permeability
I
I
,
I
I
,
,
,
,
I
1
I
,
I
,
,
1
,
1
,
1
1
,
,
I
,
,
,
,
,
,
,
,
1
1
1
,
I
,
I
,
I
,
,
,
,
I
1
,
,
I
I
I
I
,
,
I
,
,
I
I
,
,
,
I
I
,
I
,
I
,
I
I
,
,
,
1
I
,
I
I
,
,
,
I
I
I
I
1
I
I
I
I
I
,
I
I
,
,
,
,
,
,
,
I
,
I
I
I
I
,
,
1
1
I
I
In/hr
2.0-6.0
2.0-6.0
2.0-6.0
6.0-20
2.0-6.0
2.0-6.0
>20
2.0-6.0
2.0-6.0
>20
2.0-6.0
2.0-6.0
>20
2.0-6.0
2.0-6.0
>20
0.6-2.0
0.6-2.0
0.6-2.0
0.2-0.6
0.2-0.6
0.6-2.0
0.6-2.0
>20
0.6-2.0
0.2-0.6
0.6-2.0
0.6-2,0
0.6-2.0
0.6-2.0
0.6-2.0
o 6-2.0
0.6-2.0
2.0-6.0
2 0-6.0
6 0-20
Available
water capacity
In/in
0.12-0.14
0.14-0.17
0.09-0.12
0.05-0.08
0.11-0.13
0.09-0.12
0.03-0.05
0.11-0.13
0.09-0.12
0.03-0.05
O. 11-0.13
0.09-0.12
0.03-0.05
0.09-0.12
0.08-0.12
0.04-0.07
0_18-0.20
0.18-0.20
0.25-0.35
0.20-0.30
0.19-0.21
0.12-0.14
0.12-0.14
0.06-0.07
0.25-0.35
0.25-0.35
0.30-0.40
0.25-0.35
0.25-0.35
0.20-0.30
0.17-0.20
0.12-0.17
0.15-0.20
0.25-0.35
0.15-0.25
0.04-0.09
I
I
: Soil ,
: reaction:
,
,
I
,
I
I
'5.6-6.0
5.6-6.0
5.6-6.0
5.6-6.0
5.1-6 0
5.1-6 5
6.1-7 3
5.1-6.0
5.1-6 5
6.1-7.3
5.1-6.0
5.1-6.5
6.1-7.3
5.6-6.5
5.6-6.5
6.1-7.3
6.1-7.3
6.1-7 3
3.6-5.5
3.6-5.5
3.6-5.0
,5.1-6.0
:5.1-6,0
1
I
15.1-6.0
I
I
:5.6-7.3
15.6-7.3
15.6-7.3
1
I
:5.1-6.0
:5.1-6.0
:5.1-6.0
,
I
,
1
:5.1-6.0
:5.1-6.0
15,1-6.0
,
5,6-6.5
5 6-6.5
5.6-6.5
pH
Shrink-swell
potential
I
I
K :
I
1
,
,
Low------------ 0.241
Low------------:0.171
Low------------lo.l0:
Low------------:0.051
, 1
, ,
Low------------:0.15:
Low------------:0.101
Low------------:0.02:
I ,
1 ,
'Low------------10.I51
Low------------:O,10:
Low------------:0.021
, ,
, 1
, I
1 I
Low------------:0.15 I
Low------------:0.l0:
Low------------:0.02:
I I
I ,
lLow------------:0.20:
:Low------------Io.28:
:Low------------:0.241
, "
, "
:Low------------:0.37:
:Xoderate-------:O 32:
I "
, "
ILow------------io.28:
:Low------------Io.321
iModerate-------lo.32:
I "
I 1 1
ILow------------:0.20:
ILow------------:O,201
1______---______1____'
1 "'
:Low------------Io 021
, "
, I
Low------------lo.28:
Low------------io.281
Low------------'o.ool
,
,
0.24:
0.24:
0.151
I
--------------- ----I
I
,
:Low------------ 0.321
IModerate-------,O.20:
IModerate-------10.20'
, ,
, ,
, ,
I 1
, I
1 ,
, ,
1 ,
:Low------------io.32
:Low------------Io.32
ILow------------10.l0
, 1
I ,
Low------------
Low------------
Low------------
* See description of the map unit for composition and behavior characteristics of the map unit,
Erosion
factors
273
T
I
,
iOrganic
I matter
I
I
: Pct
I
1
: 5-15
I
1
,
1
5
2
5-15
2
5-15
2
5-15
5
3-10
5
5-10
5
10-20
2
5-10
5
3-10
3
5-10
5
5-10
5
3-9
~_.......c,;:.::'.~!:.~
APPENDIX C
Work Maps
O'Rear Industrial Plat page 12
O'REAR INDUSTRIAL PLA T
TRIBUTARY AREA
!
--------
DRAINAGE WORK MAP
APPENDIX 0
Basin map
O'Rear Industrial Plat page 13
R 1
R 2 E
R 3 E
R .
R . E
~@ COMPREHENSIVE PLAN ~@
THURSTON COUNTY, WASHINGTON
T
20
N
(
DRAINAGE BASINS
)
19
N
flsacl\
I.QuoIIlly F...t.
__.--".D
, ,\"",--,
..-" ! /" /
~ NLS'QUAL1. Y
-","{'
-~
~
~
MAJOR RNER DRAINAGE BASINS
:0
1t""'
N
w.'
PACIFIC OCEAN/PUGET SOUND DRAINAGE DIVIDE
T
s
"
DRAINAGE SUB-BASIN
N
Map prepared by Thurston County Planning Department.
t
- --
SCALE
il1 mU..
; .:-
T
17
N
T
,.
N
M-4
Page
T
15
N
R 1
R 2
R
E
R .
R
APPENDIX E
Maintenance plan
(provided at the time of final engineering plan submittal)
O'Rear Industrial Plat page 14
APPENDIX F
Facility summary form
Q'Rear Industrial Plat page 15
THURSTON REGION
FACILITY SUMMARY FORM
Complete one for each facility (detention/retention, coalescing plate filter etc.,) on the project site. Attach
8% x 11 sketch showing location of facility
Proponent's Facility Name or Identifier (e.g , Pond A)' Wetpond and Retention pond
Name of Road or Street to Access Facility' Prrvate Internal roadway
Hearings Examiner Case Number
Development Rev Project Number/Building Permit Number'
Parcel Number'
64300800300
To Be Completed by Utility Staff.
Utility Facility Number
Parcel Number Status, (num, 1 chI
0, Known; 1, Public; 2, Unknown, 3, Unassigned
Basin and Sub-basin: 9num, 6ch)
(2ch for basin, 2ch for sub-basin, 2ch future)
Responsible JurrsdictlOn: (alpha, 1 chI
(Ollympla, (C)ounty, (TJumwater, (l)acey
Part 1. Project Name and Proponent
Project Name: O'Rear Industrral Plat
Project Owner' Mike O'Rear
Project Contact: Randy Orth
Address: 3105 Marvin Road NE, Olympia, W A 98506
Phone: 206-491-2500
O'Rear Facility Summary Form page 1
Project Proponent (if different).
Address:
Phone.
PrOject Engineer' Dennis Cochran. P. E.
Firm: Dennis Cochran. P.E. Civil Engineer
Phone: (206) 754-1495
Part 2. Project Location
Section
19
Township
17N
Range
2E
Name and Addresses of Adjacent Property Owners:
Part 3. Tvpe of Permit Application
Type of Permit (e.g., Commercial Building)
Other Permits (Circle)
DOF/W HPA
COE 404
COE Wetlands
DOE Dam Safety
FEMA
Floodplain
Shoreline Management
Rockery/Retalning Wall
Encroachment
Grading
Other
Other Agencies (Federal, State, Local, etc.,) that have had or will review this Drainage and Erosion Control
Plan:
O'Rear Facility Summary Form page 2
Part 4. Proposed Proiect Description
What stream basin is this project in (e.g , Percival, Woodland)' Yelm Creek
Zoning
On-Site:
Industrial SubdivIsion:
Number of Lots:
12!
Lot Size (average), Acres:
V ARIES
Building Permit/Commercial Plat:
Building(s) Footorlnt, Acres:
Asphalt Concrete Paving, Acres:
071
Lattice Block Paving, Acres:
Public Roads (including gravel shoulder), Acres:
Private Roads (including gravel shoulder), Acres:
1 13
On-Site ImpervIous Surface Total, Acres:
0.71
O'Rear Facility Summary Form page 3
Part 5: Pre-Developed Project Site Characteristics
Stream Through Site y/n
Name:
DNR Type:
Type of feature thIs facility discharges to (Le., lake, stream, mtermlttent stream, pothole, roadsIde ditch,
sheet flow to adjacent private property, etc: GROUNDWATER
Swales, Ravine yln:
Steep Slopes (steeper than 10%) vln:
ErOSIon Hazard, yln:
100 Year Floodplam, y/n:
Wetlands, y/n:
Seep/Springs, yln:
HIgh Groundwater Table, yln:
Groundwater Sensitive Area, y/n:.
Other
O'Rear Facility Summary Form page 4
N
N
N
N
N
N
N
N
y
Part 6: Facility Description
Total Area Tributary to Facility Including Off-Site (Acres)'
Total On-Site Area Tributary to Facility (Acres)'
Design ImpervIous Area Tributary to Facility (Acres)'
Design Landscaped Area Tributary to Facility (Acres)'
Design Total Tributary Area to Facility (Acres)'
Enter 1 for the Type of Facility-
Wet Pond Detention
Wet Pond Water Surface Area, Acres
Dry Pond Detention
Underground Detention
Infiltration Pond
Dry Well InfiltratIOn.
Coalescmg Plat Separator
Centrrfuge Separator
Other
1 13
1 13
071
042
1 13
0018
O'Rear Facility Summary Form page 5
Outlet Type (enter 1 for Each Type Present)
Filter
Oil Water Separator
Smgle Orifice
Multiple Orifice
Weir
Spillway
Pump(sl
Other
Part 7. Release to Groundwater
Design PercolatIOn Rate to Groundwater (if applicablel
Part 8: Release to Surface Water (if applicablel
Thurston
County MSL
Elevation
(ft.l
Percent
Design Full
Empty-
_0_
_25_
_50_
100_
Volume
(cu ft.l
_0.0_
O'Rear Facility Summary Form page 6
20 INCHES PER HOUR
Discharge
to Surface
Water
(cfsl
_0.0_