20080867 Ver 2_More Info Received_20090212

LETTER OF TRANSMITTAL
DEVELOPMENT CONSULTING SERVICES, INC. ;?
1401 Aversboro Road, Suite 206 0
Garner, North Carolina 27529 FE B 1 2009
[phone] phone
[phone] fax DENR - WAFER WALITY
WETLANDS AND STQRMWATER BRANCH
oB- rnLv 1
To: Cyndi Karoly
Company: NCDENR-DWQ
Address:
From: Dexter Howell
Date: Thursday, February 12, 2009
RE: Millstone Ridge Phase 2
URGENT F-] Reply ASAP [:] Please Comment A Please Review F-1 For Your Information
COPIES DATE NO. DESCRIPTION
5 02/12/09 Sets of Plans
5 02/12/08 Scour Hole and Grass Swale Calculations
5 02/12/09 Impact Analysis
1 02/12/09 Response Letter

Comments:

DEVELOPMENT CONSULTING SERVICES, INC.
1401 Aversboro Road, Suite 206
Garner, North Carolina 27529
Ph. [phone]
Thursday, February 12, 2009
Cyndi Karoly or Ian McMillan
NCDENR-DWQ
1650 Mail Service Center
Suite 250
Raleigh, NC 27699
Reference: Millstone Ridge Phase 2
1. Overall site plan has been scaled to 1"=50' as shown on sheets C-1 to C-6.
2. Cross section detail was added to sheet C-7.
3. Building envelopes have been shown on all site plan sheets C-1 to C-6.
4. Septic tank and repair are shown on all site plan sheets C-1 to C-6.
5. Impacts have been labeled as A, B, C, and D on sheets C-1 to C-6.
6. Riparian buffers labeled as zone 1 and zone 2 on all sheets.
7. The impact analysis is included with this submittal.
8. Scour holes have been regraded as a cut area and one scour hole was removed and changed to a
grass swale.
9. Level spreader #1 was regarded to a slope less than 8% to the top of bank.
10. Level spreaders #2 and #3 were moved away from the fill slopes.
We appreciate the opportunity to have provided you with our services on this phase of the project. If you
have any questions concerning this letter or if we can assist you on any other phase of the project please do
not hesitate to contact us.
Devel pment nsulting Services, Inc.
exter Howell
QUALITATIVE INDIRECT AND CUMULATIVE IMPACT ANALYSIS
MII.LSTONE RIDGE SUBDIVISION, SECTIONS I & II
1. Indirect Impacts
A. Increased surface water discharges from the development of individual
residential lots and recreational facilities in open spaces.
1.)Impervious Surfaces. - Dwelling Roofs
- Driveways
- Accessory structures and recreational facilities
2.) Alteration of Natural Vegetation - Clearing of native vegetation
- Establishment of lawns (fertilization)
B. Discharges into groundwater
1.) Sewage effluent from septic tasks discharges into drainfield trenches.
2. ) Infiltration of nutrients from fertilized lawns into the soil.
2. Cumulative Impacts
A. Development of adjoining properties, which may result in further direct and
indirect impacts. At present this development will be limited to"lots unless
an additional street outlet can be obtained. The additional outlet will most likely
be obtained from White Memorial Church Road through the adjoining
properties on the west side of the subdivision. Whether or not this happens will
depend upon the economic situation and the willingness of adjoining landowners
to participate. The development may generate about 1,000 additional vehicle
trips per day, which should not significantly impact the current highway system.
NC 210 has less than 6,000 vehicles per day.
3. Analysis
A. Surface Discharges - The impacts on water quality from increased surface water
discharges may be minimal. Surface water from most of the
building lots flows into wooded open spaces, wooded or
vegetated adjoining properties and into wetlands. The
vegetated areas will reduce the intensity of surface sheet flow
and have the potential to absorb nutrients.Also most of the
soils have sandy surfaces, which have high infiltration rates.
There is a high probability that de-nitirification will occur in
the wetlands due to the high organic content and the
anaerobic soil environment. There are some lots (1, 9, 48,
49, 50, 51, 52, 60, 61, 62 & Open Space "D"), where surface
runoff may discharge into the road drainage system. The
effect of these discharges on water quality will depend upon
the effectiveness of the storm water storage and treatment
structures. The volume and significance of these additional
QUALITATIVE INDIRECT AND CUMULATIVE IMPACT ANALYSIS
3. Analysis
A. Surface Discharges (cont.)
discharges will be dependent upon the specific
conditions for development of the lots.
B. Discharges into ground water
The potential impacts from these discharges may
be minimal due to the buffering by open spaces
and wetlands and the potential for seasonal
evapotranspiration. Subsurface ground water flow
is anticipated to be somewhat restricted due to the
nature of some relatively impervious materials
(Carolina Slates) that underlie the Coastal Plain
Sediments. Lateral water movement may be more
significant that verticle movement to the water
table. Design waste water flow for three
bedroom dwellings is 360 gal./day, however
actual usage is often calculated at between
200 dt 250 gal./day. It would appear that there is
less concern for the impact of discharges into
ground waters that for surface water. If for no
other reasons the total volume of waste water
water for the overall area is low and it is dispersed
throughout the entire development on individual
lots.
4. Conclusions Indirect impacts to water quality for this development have the potential to
be minimal due to the presence of open space buffers and wetlands that can
act as filters for increased surface and subsurface discharges. The impact of
additional surface discharges into the stmt drainage system will depend
upon the effectiveness of the storm water containment and treatment
systems.
There are no cumulative impacts anticipated within the property .
Cumulative impacts will be incurred when adjoining properties are
developed, which does not appear to be in the near future. These properties
may need to be developed in order for Millstone Ridge to achieve the
maximum number of lots. The extent of these impacts will depend upon the
kinds of developments that are proposed (residential density) and the kinds
of measures that arc installed to minimize impacts to surface and ground
waters.
GRASS SWALE AND SCOUR HOLE CALCULATIONS
MILLSTONE RIDGE - PHASE 2
JOHNSTON COUNTY, NORTH CAROLINA
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SUBMITTED BY: DEVELOPMENT CONSULTING SERVICES, INC.
1401 AVERSBORO ROAD, SUITE 206
GARNER, NC 27529
[phone]
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cfs Peak Flow
Period ors Velocity (fps) Area (sq.IQ Hydraulic
Radiusfitl Normal
Depthlftl
)2.9 I 0.0 I 119 I _
1.45 0.07 0.07
Utseinlmced Vegetation In-.0.030)
S-0.0550
1 got I1
'Width?0100 ft
61
Not to Scale

Reach Matting Type
StabiftyAnefysis Vegetation Characteristics
Perrrissble
Calculated
Safety Factor
Remarks
Staple Pattern Phase Class Type Density Show Stteu
(pa) Shoat Shass
(psi)
Straight Urrveinlmced Vegetation C Bunch 50.75%. 4,20 0.25 17.01 STABLE
Soil Clay 0.070 0.040 1.75 STABLE