SW3190703_Geotech Email_20191219

Robby Bell
From: Kerry Cooper, PE <[e-mail]>
Sent: Tuesday, December 17, 2019 11:56 AM
To: Todd Costner; Robby Bell
Subject: RE: Hemby Place Geotechnical Report - Infiltration
Robby: You are absolutely correct, the Elastic Silts and Fat Clay soils encountered in the proposed BMP Pond location
make infiltration virtually impossible at best extremely difficult. Conversely it makes it a great location for a wet pond as
it will hold water very well. The hydraulic conductivity of these type soils is typically 1 x 10-6 to 1 x 10 -8 cm/sec. These
type soils are typically used for landfill liners, earth dam cores, pond liners and other similar uses.
Very Truly Yours,
Kerry Coper, PE
"L�eRATMG 15 YlA�
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SUMMIT
ENG1Mee1:01341r.. LA19OPArCQY & TESTING. P.C.
Kerry C. Cooper, PE - Geotechnical Manager
[e-mail]
Charlotte Office 1 3575 Centre Circle Drive I Fort Mill, SC 29715
704.504.1717 Office 1 704.504.1125 Fax
www.summit-companies.com
Charlotte -HQ I Raleigh I Columbia I Greenville I Charleston
SUMMIT Engineering, Laboratory, & Testing, PC
From: Todd Costner <[e-mail]>
Sent: Tuesday, December 17, 2019 11:15 AM
To: Kerry Cooper, PE <[e-mail]>
Subject: FW: Hemby Place Geotechnical Report - Infiltration
Do you want to reply?
From: Robby Bell <[e-mail]>
Sent: Tuesday, December 17, 2019 11:11 AM
To: Todd Costner <[e-mail]>
Subject: Hemby Place Geotechnical Report - Infiltration
Todd,
We are working on the stormwater permit for the Hemby Place Subdivision (formerly Patterson Property) that you did a
geotechnical report on (see attached). We received one comment from NCDEQ— because this project is in the Sixmile
Creek Watershed, it must comply with stormwater standards that apply to the Goose Creek Watershed. The comment is
attached, and says "15A NCAC 02B .0602 requires development to implement stormwater management measures that
promote infiltration of flows and groundwater recharge. A written explanation is required to explain if and why it is not
practical to use infiltration methods." We looked at your borings report and found stiff clay where the proposed BMP is

located, so I do not believe an infiltration is feasible and am currently drafting up an explanation. Have you had any
experience with this or any recommendations for reporting this to NCDEQ? You can email or call me anytime to discuss.
Thanks for your help,
ROBBY BELL, El
Designer I Charlotte I (o) 704.333.0325 x 1117
Charlotte I Washington DC I Dallas I Orlando I San Francisco I Boulder
LandDesign.com I @LandDesigninc