14_Painted_Hills_Drywell_Testing_Report_6-28-16IPEC
Inland Pacific Engineering Company
Geotechnical Engineering and Consulting
P.O. Box 1566, Veradale, WA 99037
Phone 509-209-6262
June 28, 2016
Project No. 16-249A
NAI Black
c/o Mr. Bryan Walker
107 South Howard
Suite 500
Spokane, WA 99201
Re: Full-Scale Drywell Testing
Proposed Stormwater Management Facility
4403 South Dishman-Mica Road
Spokane Valley, WA
Dear Mr. Walker:
As you authorized, we have completed a full-scale drywell test on the drywell installed at the
above-referenced site in Spokane Valley, Washington. The purpose of the testing was to
establish a design flow rate. This report summarizes the results of our site investigation,
engineering analyses and recommendations.
AVAILABLE INFORMATION
We were provided a topographic survey for the project site by Whipple Consulting Engineers, Inc.
(WCE). This topographic survey showed the existing roadways, existing structures, property lines,
and existing ground surface elevation contours. This plan was prepared by WCE and was dated
November 7, 2013. The site was used as a golf course prior to our evaluation. The site is relatively
level with some elevated golf greens and excavated areas for water hazards. The site is primarily
grass-covered with scattered trees along the fairways and pine trees in the undeveloped area to the
northwest. The clubhouse building is present at the southwest corner.
In addition, we performed a preliminary geotechnical evaluation for the property in December 2013.
The results of that evaluation, along with our opinions and recommendations, are summarized in our
Preliminary Geotechnical Evaluation dated December 31, 2013.
Full-Scale Drywell Testing Project No. 16-249A
Painted Hills Golf Course 4403 South Dishman-Mica Road
Spokane Valley, WA June 28, 2016
Inland Pacific Engineering Company Page 2
We also performed a geotechnical evaluation for certification of the existing levee along Chester
Creek in April 2014. The results of that evaluation are summarized in our Geotechnical Evaluation
report dated February 12, 2015.
Lastly, we performed a geotechnical evaluation in July 2015 consisting of ten 50-foot borings in the
south half of the property. The results of that evaluation are summarized in our Geotechnical
Evaluation Phase 2 report dated July 23, 2015.
FIELD EVALUATION
A geotechnical engineer from Inland Pacific Engineering Company (IPEC) performed a full-scale
drywell test on the Type 2 drywell on May 6, 2016. The drywell test was performed in accordance
with the Spokane Regional Stormwater Manual, Appendix 4B procedures.
ANALYSIS AND RECOMMENDATIONS
We calculated a design outflow rate for the existing drywell using the results of the recent and
previous laboratory tests and the procedures described in the SRSM manual, Appendix 4B (Full-
Scale Drywell Test Method). Based on the test performed, we recommend using a design flow rate
of 1.05 cfs for design. This recommended design outflow rate includes a safety factor of 1.1 as
required by the SRSM.
REMARKS
This report is for the exclusive use of the addressee and the copied parties to use in design of the
proposed project and to prepare construction documents. In the absence of our written approval, we
make no representations and assume no responsibility to other parties regarding this report. The
data, analyses, and recommendations may not be appropriate for other structures or purposes. We
recommend that parties contemplating other structures or purposes contact us.
Services performed by the geotechnical engineers for this project have been conducted in a manner
consistent with that level of care ordinarily exercised by members of the profession currently
practicing in this area under similar budget and time restraints. No warranty, expressed or implied,
is intended or made.
FIGURE 1
Site Location Map
Project No. 16-249A
June 28, 2016 Painted Hills Golf Course
4403 South Dishman-Mica Road
Spokane County, WA
FIGURE 2
NRCS Map
Project No. 16-249A
June 28, 2016 Painted Hills Golf Course
4403 South Dishman-Mica Road
Spokane County, WA
0
5
10
15
20
25
30
35
40
45
50
55
60
65
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0.0010.010.1110100
PI Cc CuLLPL
5.761.00
GRAIN SIZE DISTRIBUTION
COBBLES GRAVEL
3.550
SAND
GRAIN SIZE IN MILLIMETERS
coarse fine
SP Poorly Graded Sand with Gravel
Classification
D100 D60 D30 D10 %Gravel
5.212
L16-057
coarse SILT OR CLAYfinemedium
20.0
%Sand %Silt %Clay
2.167 0.904 42.9 53.6
BOREHOLE DEPTH
BOREHOLE DEPTH
3 100
L16-057
24 16 301 200610501/2 HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS 1403420406601.5 8 143/4 3/8
20.0PERCENT FINER BY WEIGHTCLIENT NAI Black
PROJECT NUMBER 16-249A
PROJECT NAME Painted Hills Drywell Test
PROJECT LOCATION 4403 South Dishman-Mica Road
GRAIN SIZE - GINT STD US LAB.GDT - 6/28/16 15:32 - J:\_IPEC PROJECTS\_2016 PROJECTS\16-249A PAINTED HILLS DRYWELL TESTING\GINT\16-249A PAINTED HILLS DRYWELL TEST.GPJInland Pacific Engineering Company
3012 North Sullivan Road, Suite C
Spokane Valley, WA 99216
Telephone: 509-209-6262
Fax: 509-290-5734
Full-Scale Drywell Test Results
Time
Elapsed
Time
(seconds)
Depth to
Water
(feet)
Flow
Meter
Reading
(ft3)
Volume
of Water
(ft3)
Flow Rate (cfs)
10:00 0 19.5 596.6
11:00 3600 18.2 1171.5 574.90 1.60E-01
11:10 600 18.2 1261.0 89.50 1.49E-01
11:20 600 18.2 1350.7 89.70 1.50E-01
11:30 600 18.2 1441.1 90.40 1.51E-01
11:35 18.3
11:40 18.6
11:45 19.1
11:50 19.5
1.50E-01
5/6/2016
Test Location: Existing Drywell
Average Flow Rate:
Project Name: Painted Hills Drywell Test
Project Number: 16-249A
Test Date:
Client: NAI Black Depth: 20'
17.5
18.0
18.5
19.0
19.5
20.0
Depth to Water (feet)
Depth to Water
1.42E‐01
1.44E‐01
1.46E‐01
1.48E‐01
1.50E‐01
1.52E‐01
1.54E‐01
1.56E‐01
1.58E‐01
1.60E‐01
1.62E‐01
11:00 11:10 11:20 11:30
Flow Rate (cfs)
Flow Rate (cfs)
P.O. Box 1566, Veradale, WA 99037
Phone 509-209-6262