Prelim Storm Drain and Erosion Control Report 10-27-06 001PRELIMINARY STORM DRAINAGE AND EROSION
CONTROL REPORT
FOR
August 18, 2006
Proponent: Mr. Jack Long
Contact: Jack Long
Pacific Frontier
The One Eleven Building
Prepared by: Jeff McInnis, P.E.
Petra Engineering, LLC
1306 NorthlStreet
Tacoma, WA 98403
Ph: (253)752-7617
1300 NO H'I H I S1 ftEPr I TACOMA i WA I Jri4U3 i PHON F X241752-"141] I FAX Qi3pG1-SSH2 i W W WPETFAF NG.N Ei
TABLE OF CONTENTS
PRELIMINARY STORMWATER MANAGEMENT AND EROSION/SEDIMENTATION CONTROL
REPORT
Section 1 -Proposed Project Descrip[ion ....................................................................................... ...........................4
Section 2 -Existing Hydrology ....................................................................................................... ...........................4
Section 3 -Developed Hydralogy .................................................................................................... ...........................4
Section 4 -Hydrologic Analysis ...................................................................................................... ...........................5
Section 5 -Conveyance System Analysis &Design ....................................................................... ...........................5
Section 6 -Special Reports &Studies ............................................................................................ ...........................5
Section 7 -Other Permits ................................................................................................................ ...........................5
Section R -ESC Analysis &Design ................................................................................................. ...........................5
Section 9-Bond Quantities, Facility Summaries, & Declaration of Covenant ......................... ...........................6
Section 1R -Conclusions ................................................................................................................... ...........................6
Appendix ........................................................................................................................................... ...........................7
1 hereby state that this Preliminary Drainage and ErosioNSediment Control report for Crystal Springs has been
prepared by me or under my supervision and meets the minimum standards of care and expertise which is usual and
customary in [his community for professional engineers. 1 understand that The City of Yehn does not and will not
assume liabi]iry for the sufficiency, suitability, or performance of drainage facilities designed by me.
Preliminary Stormwater Management and Erosion/Sedimentation Control Report
Section 1 -Proposed Project Description
This report accompanies the Planned Residential Development (PRD) submittal for the development of
the 29 unit mulit-family project named Crystal Springs on Crystal Springs Road in Yelm, WA. The site is
located east of Crystal Springs Road in the northern extremity of the City of Yelm, directly across from the
intersection between Crystal Springs and Coates Street in Section 19 of Township 17N and Range 2E.
The project involves the creation of 29 residential units on 6 lots, approximately 17,000 Sq. Ft. of
associated private roads, and the associated recreation tracts and open space areas to satisfy the PRD
requirements of the City of Yelm.
Section 2 -Existing Hydroloav
The appendix contains apre-developed hydrology map showing the site as it exists today. As can be
seen from that map, the site remains undeveloped and covered in grasses and a small number of trees.
The overall site proposed for development is 180, 790 Square Feet, or 4.15 Acres. Although the overall
parcel is significantly larger than 4.15 acres, the western portion of the site is being segregated through a
Boundary Line Adjustment process and sold to a third parry.
The site is sloped [o [he east, fairly steeply at the western portion and fairly shallow farther to the east.
The site is entirely contributory [o the small creek bed known as Yelm Creek. This creek bed has been
dry during the duration of this project, but historically has flowed through the rainy season. There is an
associated Floodplain to elevation 330 which is noted on the PRD plans submitted with this report.
Yelm Creek is considered a Critical Area, and therefore a Critical Areas Report is being compiled and
submitted by Talasaea Consultants to accompany this submittal. This Critical Areas Report will address
the reduction of the CAO buffer to accommodate the proposed design.
Section 3 -Developed Hydroloav
In the developed condition, we are proposing the installation of a 22' wide internal road system consisting
of approximately 14,622 Sq. Ft. of new impervious. In addition, the building pads will comprise
approximately 31,776 square feet of impervious area, with the driveways encompassing approximately
10,247 square feet of impervious area. When tallied, the impervious area created by the project will total
56,645 square feet, or 1.30 acres.
The proposed storm drainage system, designed to comply with the 1992 DOE Stormwater Management
Manual for the Puget Sound Basin, will include a detention pond at the eastern portion of [he project site.
This storm pond has been sized to receive runoff from the site. The developed 2, 10, and 100-year
storms have been estimated using the SBUH methodology using [he Stormshed® software. The pond
was [hen sized to reduce flows to the pre-developed flows of 50 % of the 2-year, and the 10 and 100-year
flowrates. Prior to entering [he storm pond, the flow will be routed through a Leaf Compost Filler for
stormwaler treatment. Once through the water quality device and attenuated by the 6,700 cubic foot
storm pond, the stormwaler will be released to the Yelm Creek system through a spreader trench system
located just outside of the 100-year flood plain elevation.
Section 4 -Hydrologic Analysis
A hydrologic analysis of the developed conditions has been completed using StormShed software and the
SBUH methodology using a Type 1A hyetograpli. On-site soil has been classified as Hydrologic Soil
Group C as a result of the on-site soil exploration compelled by Gary Flowers, LEG. Although the SCS
mapping (included in appendix) shows [he site as containing both Spanaway and McKenna soils, the on-
site exploration did not turn up any infiltratable soils on the site.
The results of the detention analysis, showing the expected runoff values from the impervious areas
contributing to the WO and detention systems, are tabulated below:
Event Pre-Develo Flow cfs Develo ed Flow cfs Attenuated Flow cfs
2- r124-hr .1960 (50 % - .0980) .5991 .0990
10- r/24-hr .4183 .9366 .4179
100- r/24-hr .6667 1.2448 .6660
The detention pond sizing was performed utilizing the rates presented above and is presented in the
appendix. The appendix contains the hydrology calculations as well as pre and post-development maps.
Section 5 -Conveyance System Analysis 8 Design
The on-site conveyance systems (pipes, and roof drain tightline) will be designed to convey the 25-year
peak Flows in accordance with the 1992 DOE manual.
Section 6 -Special Reports 8 Studies
A geotechnical report was prepared by Gary A. Flowers, PLLC for this project and has been submitted
under separate cover. This report was prepared only for use by the design engineer in designing
pavement and for exploration of [he feasibility of on-site infltration.
A Critical Areas Report is also currently being completed and will be submitted supporting the location of
the setback from Yelm Creek as shown on the PRD plans submitted with this application.
Section 7 -Other Permits
Building Permits will be obtained to construct the buildings.
Section 8 -ESC Analysis & Design
Erosion and sediment control will be provided through the use of silt fence, Catch Basin Protection, and a
stabilized construction entrance. Since the site slopes to the southwest, silt fence will be concentrated on
the southwest portion of the site. With [he soil types present on the site, a sediment pond is neither
practical nor preferred, as runoff will not reach it prior to infiltration. Instead, treatment al the point of
runoff is preferred and will be employed on this project.
The ESC features employed on this project include.
• Stabilized construction entrances
• Catch basin inlet protection
• Silt fence
• Track-walking and hydro-seeding as necessary.
It is important to note that the responsibility for erosion control rests with the contractor, as only he can
respond to changing site conditions. The measures included on the ESC plan should be considered a
starting point, only.
Section 9 -Bond Quantities Facility Summaries. & Declaration of Covenant
These Items will be supplied at the time of complete CD submittal, as will the declaration of covenant.
Section 70 -Conclusions
The storm drainage system, as designed, will control stormwater runoff quantity and quality and will work
well with the proposed residential PRD and the surrounding areas. The detention system will operate in
accordance with the requirements of the City of Yelm and the 1992 DOE manual. This system will be
designed in accordance with the standards of care and quality typical in [his area for projects of this type.
Appendix
Exhibits
1. Sails Map and description
2. Pre-Developed Hydrology Map
3. Developed Hydrology Map
4. Stormshed ^" Calculations, including pond sizing
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Soil Survey ofThurston County, Watihington Crystal Springs SCS Soils Map
Map Unit Legend Summary
Thurston County, Washington
Map Unit Symbol Map Uni[ Name Acres in AOI Pcrccnl of AOI
110 Spanaway gravelly sandy 0.7 34.7
.loam, 0 to 3 percrnt slopes
113 Spanawey smny sandy loam, 1.3 653
3 to 15 percent slopes
USDA n.um xno.mn W eh Snil Survcy LI 8/18RW6
!~ tao...wnm~9ervl.r Nalonal Cooperative Soil Survey pugcJ o(3
Appended on: 11:17:34 Friday, August 18, 2006
Pre-100-Year Event Summary
Event Peak Q (cfs) Peak T (hrs)',Hyd Vol (acft) Area (ac) Method Raintype
__
6 month 0.0526 8.17 0.0374 '. 1.3000 -- --
SBUH TYPEIA
2 year 0.1960 8.17 0.0981 1.3000 SBUH TYPEIA
]0 year 0.4183 8.00 0.1884 1.3000 SBUH TYPE]A
25 yeaz 0.5409 8.00 0.2364 '. 1.3000 SBUH TYPEIA
100 year 0.6667 8.00 0.2856 1.3000 SBUH TYPE]A'
Record Id: Pre-100-Year
Design Method SBUH Rainfall type '.. TYPE]A
Hyd Into 10.00 min Peaking Factor 484.00
Abstraction Coeff 0.20
Pervious Arca (AMC 2) 1.30 ac DCIA 0.00 ac '.
Pervious CN 87.00 DC CN 0.00
Pervious TC 19.32 min DC TC 0.00 min
Pervious CN Calc -- --..
Description SubArca Sub en
Herbaceous 1.30 ac 87.00
Pervious Composited CN (AMC 2) 87.00
_.
_-_
Pervious TC Calc _
_
_..
Type Description Length Slope Coeff _ __ _.
Misc '. TT
Sheet Dense grasses :0.24 50.00 ft 22.00% 0 2400 .2.00 in 3.97 mm
Sheet Dense grasses :0.24 100.00 1t 3.00% 0.2400 2.00 in 15.35 mm
Pervious TC 19.32 min
Licensed to: Petra Engineering, LLC
History Cleared: 10:55:59 Friday, August 18, 2006
Post ]00-year Eveut Summary
Event Pcak Q (cfs) Peak T (hrs) Hyd Vol (acfr) Area (ac) Method Raintype
6-month 0.3386 7.83 0.1078 1.3000 SBUH TYPEIA
2 year
0.5991
7.83
0.1922 __
1.3000
', SBUH
TYPEIA
10 year
0.9235
7.83
''. 0.2999
1.3000 _
''.. SBUH _ _.
TYPE]A
25 year 1.0844 7.83 0.3539 1.3000 SBUH TYPE]A'
100 vear 1.2448 7.83 0.4079 1.3000 SBUH TYPE]A
Record Id: Post ]00-year
Design Method SBUH Rainfall type TYPEIA '.
Hyd Inty 10.00 min Peaking Fac[or 484.00 ',.
Abstraction Coeff 0.20
Pervious Area (A MC 2) 0.00 ac DCIA 1.30 ac
Pervious CN 0.00 DC CN 98.00
Pervious TC 0.00 min DC TC 0.56 min
Directly Connected CN Calc
____
__. Description
_
_.._ SubArea '. Sub cn '..
_.. __.
Impervious surfaces (pavements, roofs, etc) 1.30 ae ~. 98.00
DC Composited CN (AMC 2) 98 00
Directly Connected TC Cale
___
Type
Description Leng[h '.. Slope
Coeff I Misc TT
Sheet Smooth Surfaces.: 0.011 30.00 ft ] 0.00% 0.0110 -0.00 in 0.00 min
Channel (mtenn) ,Concrete pipe (n~.012) 200 00 ft 2.00% 0.0120 0.56 mm
Directly Connected TC 0.86mm
LPOOLCOMPUTE ~N-001 SUMMARY using Puls
Start of live storage: 100.0000 ft
Event Mach Q (cfs) Peak Q (cfs) Peak Stg (ft) Vol (ct) ,Vol (acft) Time to Empty
2 year (1.0980 0.0990 102.1232 2865.71 0.0658 39.33
10 year 0.4183 0.4179 102.4328 3476 86 0.0798 42.17 '.
100 yeaz 0.6667 0.6660 102.8451 4377.40 0.1005 42.67
Licensed to: Petra Engineering, LLC
Appended on: 11:02:43 Friday, August 18, 200E
Record Id: MH Release
Descrip: Prototype Structureincrement
_
_.___ 0.10 fi '.
__ ___,
Start EL 100.0000 ft ,Max El. 105.0000 fl.
Orif Coeff 0.62 Lowest Orif El. 98.00
Lowest Diam
1.5820 in _
.Dist to next __
2.2300 ft
_.___
D2
_
._ _
5.0684 in
_
..Dist to next
--___.
0.3100 ft
D3 0.5859 in Dist to next 0.0000 fl
Stage Discharge Rating Carve I
100.0000 ft 0.0000 cfs 102.6000 ft 0.5358 cfs'
100.1000 ft 0.0215 cfs 102.7000 ft 0.5932 cfs
100.2000 ft '.0.0304 cfs 102.8000 ft 0.6447 cfs
100.3000 ft 0.0372 cfs 102.9000 ft 0.6919 cfs'...
100.4000 ft '..0.0430 cfs 103.0000 ft 0.7357 cfs '..
100.5000 ft'0.0480 cfs 103.1000 ft 0.7768 cfs
100.6000 ft 0.0526 cfs 103.2000 ft 0 8156 cfs
100.7000 ft..0.0568 cfs 103.3000 ft 0.8526 cfs
100.8000 ft 0.0607 cfs 103.4000 ft 0.8879 cfs
100.9000 ft 0.0644 cfs 103.5000 fr 0.9218 cfs'.
101.0000 ft 0.0679 cfs ] 03.6000 fr 0.9544 cfs
101.1000ft 0.0712 cfs 103.7000 ft 0.9859 cfs ''..
10] .2000 ft 0.0744 cfs 103.8000 ft 1.0163 cfs
101.3000 ft 0.0774 cfs 103.9000 ft 1.0458 cfs
101.4000 ft -0.0804 cfs 104.0000 ft 1.0745 cfs
101.5000 ft.0 0832 cfs 104.1000 ft 1.1024 cfs
101.6000 ft',0.0859 cfs 104.2000 ft 1 1296 cfs'..
101.7000 ft 0.0886 cfs 104.3000 ft 1.1562 cfs''
101.8000 ft 0.0911 cfs 104.4000 ft 1 182] cfs
101.9000 ft Q0936 cfs 104.5000 ft 1.2074 cfs
102.0000 ft 0.0961 cfs ] 04.6000 ft 1.2322 cfs
102.1000 ft,0.0984 cfs 104.7000 ft 1.2565 cfs.
_._ _.._
102.2000 ft 0.1007 cfs 104.8000 ft 1.2804 cfs
102.3000 ft b.2874 cfs 104.9000 ft 1.3037 cfs'
102.4000 ft 0 3926 cfs 105.0000 ft 1.3267 cfs
102.5000 ft 0 4696 cfs 105. ] 000 fl 1.3493 cfs
105.0000 ft 1.3267 cfs
Licensed to: Petra Engineering LLC
Appended on: 11:02:55 Friday, August 18, 20116
Record Id: N-00]
Descrip: Prototype Record Increment 0.10 ft
Start EI. 100.0000 ft Max El. 105.0000 ft
Storage Node Pond Dischazge Node MH Release
Record Id: Pond
Descrip Prototype Record ',Increment 0.10 ft
Start EL ''.100.0000 ft .Max EI. 103.0000 fr'....
Length 17.3300 ft Width 50 0000 ft ''...
Length ss]
3.OOhav _____
Lenbrth ss2 3.OOOOhav '...
Width ss] 3.OOhav Width ss2 3.OOOOh']v ''.
Record Id: MH Release
Descrip: Prototype Structure d7ncrement 0.10 ft
Start El. 100.0000 ft '.Max El. 105.0000 ft
Orif Coeff 0.62 '.Lowest Orif EL 98.00
Lowest Diam 7.5820 in Dist to next 2.2300 ft
D2 5.0684 in Dist to next 0.3100 ft
D3 0.5859 in Dist to next 0 0000 ft
Licensed to: Petra Engineering LLC
Appended on: 11:05:53 Friday, August 18, 2006
Record Id: Pond
Descrip: 'IPrototype Record Increment 0.10 ft
Start El. .100.0000 ft Max El. 103.0000 ft
Len1,Rh 17.3300 ft Width 50.0000 ft
Length ssl 3.OOhav Length ss23.0000hav
Width ssl ''3.OOhav Width ss2 3.000Ohav
StageStorage Rating Curve
100.0000 fr ' 0.0000 cf 101.6000 ft 19526464 cf
100.]000 ft'. 88.6819 cf 101.7000ft 2715.7571cf
]00.2000 ft'.. 781.4756 cf 101.8000fl 2284.1316cf
100.3000 ft 278.4531 cf 101.9000 ft 24528419 cf
100.4000 fl .379.6864 cf 102.0000 ft 2636.9600 cf
_. _. _..
100.5000 ft' 485.2475 cf 102.1000 ft 2821.5579 cf
100.6000 ft' 595.2084 cf 102.2000 ft 30] 1.7076 cf
100.7000 ft 709.64] 1 cf 102.3000 ft 3207.4811 cf
100.8000 R' 828.6176 cf 102.4000 ft 3408.9504 cf
100.9000 ft 952.2099 cf 102.5000 ft 3616.1875 cf
101.0000 ft 1080.4900 cf 102.6000 ft 3829.2644 cf
_. _ _.
.701.1000 ft 9213.5299 cf 102.7000 ft 4048.2537 cf
101.2000 ft 1351.4016 cf 102.8000 ft 4273.2256 cf
901.3000 ft 1494.1771 cf 102.9000 ft 4504.2539 cf
101.4000 ft ] 641.9284 cf 103.0000 ft 4741.4100 cf
101.5000 ft 1794.7275 cf 103.1000 fi 4984.7659 cf
Licensed to' Petra Engineering, LLC