19-074-RPT-Drainage-2025.01.06 (8819)
DEUTSCHER - YELM COMMERCIAL
Project #2022-0096
Drainage Report
Prepared for: Marijke Deutscher
1401 Marvin Road NE, Suite 307
Lacey, WA 98516
360 402 6871
almst421@comcast.net
Report Date: January 6, 2025
Prepared by: Ahmad Kamyab
Reviewed by: Chloe P. McIntyre, PE
HATTON GODAT PANTIER
3910 Martin Way E., Suite B
Olympia, WA 98506
(360) 943-1599
Project No: 19-074
Project Name: DEUTSCHER - YELM COMMERCIAL
H:\Office\JOBS\2019\19-074 Deutscher-Yelm Commercial\PERMIT\Reports & Calculations\DRAINAGE
I hereby state that this Drainage Control Plan for, Deutscher - Yelm Commercial located at 15152 Berry
Valley Road, Yelm 98597, Thurston County, WA, has been prepared by me or under my supervision and
meets the standard of care and expertise which is usual and customary in this community for professional
engineers. I understand that the CITY OF YELM does not and will not assume liability for the sufficiency,
suitability, or performance of drainage facilities prepared by me.
Signature
Date
Seal
January 8, 2025
TABLE OF CONTENTS
Section 1 – Project Description ................................................................................... 1
Vicinity Map ...................................................................................................................................... 3
Site Plan ........................................................................................................................................... 4
Basin Map ........................................................................................................................................ 5
Minimum Requirement #1: Preparation of Stormwater Site Plans ............................................... 7
Minimum Requirement #2: Construction Stormwater Pollution Prevention ................................. 7
Minimum Requirement #3: Source Control of Pollution ............................................................... 7
Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls ................... 7
Minimum Requirement #5: On-Site Stormwater Management ..................................................... 7
Minimum Requirement #6: Runoff Treatment .............................................................................. 8
Minimum Requirement #7: Flow Control ...................................................................................... 8
Minimum Requirement #8: Wetlands Protection .......................................................................... 9
Minimum Requirement #9: Operation and Maintenance .............................................................. 9
Minimum Requirement #10: Financial Liability ............................................................................. 9
Minimum Requirement #11: Off-Site Analysis and Mitigation ...................................................... 9
Section 2 – Existing Conditions Description .............................................................. 9
Section 2.1 Topography ................................................................................................................ 9
Section 2.2 Ground Cover ............................................................................................................ 9
Section 2.3 Drainage .................................................................................................................... 9
Section 2.4 Soils ......................................................................................................................... 10
Section 2.5 Critical Areas ........................................................................................................... 10
Section 2.6 Adjacent Areas ........................................................................................................ 10
Section 2.8 Reports and Studies ................................................................................................ 10
Section 2.9 – Wells and Septic Systems ....................................................................................... 10
Section 2.10 – Fuel Tanks ............................................................................................................. 11
Section 2.11 – Analysis of 100-Year Flood .................................................................................... 11
Existing Conditions Map................................................................................................................. 12
Section 3 – Vicinity Analysis and Sub-Basin Description ....................................... 13
Section 4 – Flow Control and Water Quality Facility Sizing .................................... 14
Water Quality Treatment Facility Sizing ......................................................................................... 14
Flow Control Facility Sizing ............................................................................................................ 14
Section 5 – Aesthetic Considerations for Facilities ................................................. 15
Section 6 – Conveyance System Analysis and Design ............................................ 15
Section 7 – Covenants, Dedications and Easement ................................................. 15
Section 8 – Agreements and Guarantees .................................................................. 15
Section 9 – Other Permits or Conditions Place on the Project ............................... 15
APPENDIX 1 – Design Calculation ............................................................................. 16
APPENDIX 2 – Supplemental Reports and Information ........................................... 17
DEUTSCHER - YELM COMMERCIAL 01.06.2025 PAGE 1
DRAINAGE REPORT
Section 1 – Project Description
The Deutscher - Yelm Commercial project is located northeast of the intersection of Tahoma Boulevard
SE and Berry Valley Road SE in the City of Yelm. The site is located in Section 24, Township 17, Range
1E Quarter SW on tax parcel numbers 21724131001 and 21724130800, separated by a portion of
21724131201. See Vicinity Map on page 3.
This project will construct Phase 2 of an earlier project that completed frontage improvements along Berry
Valley Road SE. Phase 2 construction includes three (3) new commercial buildings. Two of the proposed
buildings will be 7,638 sf each and one building will be 15,002 sf. Construction also includes asphalt
paved parking areas, sidewalks, concrete pads, and landscaping areas. See proposed Site Plan on page
4.
The proposed project will require grading, building, and utility permits. Water and sewer will be provided
via connection to the City of Yelm’s utilities. Zoning for the property is C-1 (Commercial).
Stormwater runoff mitigation measures for the entire site were designed and constructed with Phase 1
“Yelm Day Care”. Criteria followed the Department of Ecology Stormwater Management Manual for
Western Washington (SMMWW). The construction of Phase 1 allocated 1.40 acres runoff from
impervious areas for the Phase 2. Phase 1 included approximately 9,600 sf Day Care building, ~31,000 sf
paved private roadway, sidewalks, and parking area between Phase 1 and Phase 2, ~42,000 sf
landscape and infiltration areas, as well as ~16,600 frontage improvement along the Berry Valley Rd. SE.
See the attached Yelm Day Care Drainage Report in Appendix 2.
Phase 2 construction consists of two (2) basins for stormwater modeling, the Phase 2 South Basin, and
the Phase 2 North Basin. The northern property (parcel number 21724130800) shown on the Basin Map
as the Phase 2 North Basin, is an addition to the original Phase 2 plan. In order to keep the stormwater
runoff from impervious areas under 1.40 acres, Hatton Godat Pantier has separated the stormwater
runoff from the 3 proposed building’s roof aeras to infiltrate in two (2) individual roof infiltration trenches.
Stormwater runoff from proposed Phase 2 South and Phase 2 North basins include 1.05 acres asphalt
paved parking areas, 0.02-acre concrete pads, and 0.25-acre sidewalks. The total Phase 2 runoff from
pollution-generating pervious surface (PGPS) areas is 1.32 acres, well below the 1.40 acres allocated.
Runoff from both basins of Phase 2 will be collected via catch basins and conveyed by stormwater
pipes to the existing stormwater facilities located at the southeast corner of Day Care building for
treatment and 100% infiltration.
Roof runoff does not require treatment as it is non-pollution generating surface. The total Phase 2 roof
areas are 0.69-acre and will be connected to two (2) roof infiltration trenches sized per Infiltration
Trenches (Ecology BMP T7.20). In addition to the roof area, 0.05-acre of non-pollution generating
impervious pedestrian area between buildings 1 and 2 will be conveyed to infiltration trench 1 for
infiltration. All new and disturbed lawn/landscape areas will be amended per Postconstruction Soil
Quality and Depth (Ecology BMP T5.13) to retain greater stormwater functions, including increased
infiltration potential and treatment. A summary of pre-developed and proposed pervious and impervious
areas are included in Table 1.1. See the attached Basin Map on page 5.
DEUTSCHER - YELM COMMERCIAL 01.06.2025 PAGE 2
Table 1.1 – Area Summary*
All areas measured in acres
Pre-Developed Ph 1 Ex. Yelm
Day Care
Ph 2 South
Basin
Ph 2 North
Basin Total Site
Forest (A/B Flat) 2.51 1.74 1.11 5.36
100-Year Developed Flow Rate (cfs) 0.024
Developed Ph 1 Ex. Yelm
Day Care
Ph 2 South
Basin
Ph 2 North
Basin Total Site
Landscape/Lawn (Flat) 0.96 0.59 0.23 1.77
Road (Flat) 0.39 - - 0.39
Parking (Flat)** 0.25 0.62 0.47 1.31
Concrete Pad** - 0.01 0.01 0.02
Sidewalk (Flat)** 0.09 0.17 0.07 0.34
Frontage Improvement 0.38 - - 0.38
Roof 0.22 0.35 0.34 0.92
Pond 0.23 - - 0.23
Total 2.51 1.74 1.11 5.36
100-Year Developed Flow Rate (cfs) 0 0 0 0
*Areas reflect rounding.
**Total Phase 2 PGPS impervious areas 1.35 acres, Phase 2 allowed is 1.40.
DEUTSCHER - YELM COMMERCIAL
15152 BERRY VALLEY RD. SE, YELM, WA 98597
N
HATTON
PANTIER
GODAT
VICINITY MAP
SITE
Y
E
L
M
A
V
E
S
E
/
H
W
Y
5
1
0
KIL
L
I
O
N
RD
S
E
TA
H
O
M
A
B
L
V
D
.
S
E
BE
R
R
Y
V
A
L
L
E
Y
R
D
S
E
BERRY VALLEY RD SE
N.T.S
N.T.S