20150378 Ver 1_Stormwater Approval_20150420

Engineering and
Environmental Services
December 5, 2014
Oliver Sherrill
ARE — NC Region No. 14, LLC
7020 Kit Creek Road
Suite 100
Research Triangle Park, NC 27709
Re: Stormwater Collection Systems Plan Approval
6 Davis Drive — Hamner Institutes
DRB Number D1400055
Durham County Stormwater Project #SW -1408
Dear Mr. Sherrill:
On October 27, 2014, we received a stormwater construction drawing package submittal
package for the 6 Davis Drive project located at 6 Davis Dr, Durham, NC. This construction
drawing set is approved by this office on December 3, 2014. Enclosed is a copy of the plans
and calculations, stamped approved by this office.
The approved stormwater collection system consists of:
1. Installation of a wet detention facility with a design permanent pool volume of
13,589 CF.
2. Installation of a bio-retention facility with a design volume of 7,603 CF.
3. Installation of a bio-retention facility with a design volume of 1,928 CF.
4. Installation of a bio-retention facility with a design volume of 6,165 CF.
Our office will issue a Stormwater Operation and Maintenance Permit for the stormwater
control measures after the following are completed:
1. The stormwater system is constructed and final construction inspected by a registered
professional engineer, a registered land surveyor, or a registered landscape architect. A
signed and sealed copy of the inspection report must be submitted to this office.
2. The final As -Built Plans sealed and signed by a registered professional engineer, a
registered land surveyor, or a registered landscape architect must be submitted.
3. An operation and maintenance plan sealed and signed by a registered professional
engineer, a registered land surveyor, or a registered landscape architect must be
submitted.
4. An operation and maintenance agreement signed and notarized by the property owner.
This will be drafted near the end of the project.

5. An improvement security must be provided to our office in accordance with Ordinance
Section 14- 155(e). Our calculations indicate a performance bond in the amount of
$56,106.64 is necessary to ensure construction, and continuing operation, maintenance
and inspection of the facilities. Performance bond forms and information can be found
on the Durham County Engineering / S &E Webpage. If you believe this bond amount is
incorrect please contact me. See Attached.
Please feel free to contact me if you have any questions pertaining to this approval at (919)
560 -7992.
Sincerely,
- —rc::�
D�
Ryan D. Eaves
Stormwater Manager
cc: Curtis M. Blazier, PE
McKim & Creed, INC

BMP Performance Bond Calculations
BMP:
Wet Detention Pond Performance Bond Calculations
Project Name:
6 Davis Dr - Hamner
Facility Name
Wet Detention 1
Bio- Retention 3
Bio- Retention 3A
Bio- Retention 4
Facility Drainage Area AC
5.10
3.08
0.77
2.77
Facility Volume CF
39,220
7,603
1,928
6,165
Capital Costs' ($)
$ 30,382.75
$ 9,635.21
$ 3,687.62
$ 8,320.03
$
$
O &M Costs 2 ($)
$ 1,215.31
$ 385.41
$ 147.50
$ 332.80
$
$
Inspection Costs s ($)
$ 500.00
$ 500.00
$ 500.00
$ 500.00
$
$
Total ($)
$ 32,098.06
$ 10,520.62
$ 4,335.13
$ 9,152.83
$
$
Total Bond
Date
Notes:
$ 56,106.64
121512014 13:54
1) Capital Costs = 18.5 * Volume
2) O &M Costs = 4% Capital Costs
3) Inspection Costs = By Durham County
Source: NCDENR Stormwater BMP Manual