20171073 Ver 1_3.1 SA Corps comments June 27, 2017-RESPONSE_20170825

Corps comments June 27, 2017
1. Please provide a clear overall drawing of the project. The Grading and Utility plans show the overall
development; however, these are not sufficient for the purpose of reviewing project impacts as they relate
to the entire development. The new drawing should include all aquatic resources and their boundaries,
the location, type, and amount of each impact, stormwater facilities and intakes/discharge outlets, all
subdivision amenities (sidewalks, walking trails, community buildings, and recreation or open space
areas), clear project boundary, easements, and lot lines, correctly numbered lots, etc. Unnecessary data
layers, such as contour lines, that may hinder the ability to see pertinent information should be removed.
Please show the utility line in color for easier review. Ensure all drawings are legible in either 8.5 x 11" or
11 x 17" format.
See the attached drawings
2. In accordance with Regional Condition 4.1.7 of NWP 29, utility lines must comply with the terms and
conditions, including Regional Conditions, of NWP 12. To address Regional Condition 4. 1.1 of NWP 12,
please provide a brief discussion as to why horizontal directional drilling is not being used as a method to
avoid impacts to wetlands and waters of the US.
Wetland W2 (WT)
Directional drilling was evaluated for the crossing of the proposed 8 -inch diameter water line
pipe of Wetland WT near Neills Creek. An evaluation of the water line route survey profile, and
subsequent field of evaluation to verify existing conditions was performed to gather information
related to the potential to directional drill. The assessment yielded field topographical
constraints that would require an approximately 250 foot long directional drill length to go
under Wetland WT. At a unit rate of $175/1inear foot, the cost to directional drill Wetland WT is
$43,750. The project cost for installation of 8 -inch waterline using open cut is $17/LF or
$4,250 (250 linear feet). Based on project budget constraints, and that directional drilling this
location would be more than 10 times the open cut cost, the open cut methodology was selected.
Wetland WI (WSO
Directional drilling was evaluated for the crossing of the proposed 8 -inch diameter water line
pipe and Wetland WS which is located on either side of the power transmission line easement
crossing. An evaluation of the water line route survey profile, and subsequent field of evaluation
to verify existing conditions was performed to gather information related to the potential to
directional drill. The assessment yielded field constraints including the required avoidance of
major power transmission line towers and guy wires that would necessitate an approximately
400 foot long directional drill length to go under Wetland WS. At a unit rate of $175/1inear foot,
the cost to directional drill Wetland WS is $70,000. The project cost for open cut installation of
8 -inch waterline is $17/LF or $6,800 over the estimated 400 linear feet. Based on project
budget constraints, and that directional drilling this location would be more than 10 times the
open cut cost, the open cut methodology was selected.
3. Please provide a brief discussion addressing the need for this type of project for this area. Additionally,
the applicant must address indirect adverse environmental effects of the proposed impacts on local
resources and the watershed.
Project Need
The area around the project is growing and a need for single family homes is increasing. The Southern
Acres subdivision will fill part of that need.

Corps comments June 27, 2017
Indirect Adverse Environmental Effects
The indirect environmental effects of this project are increased site runoff and pollutions resulting from
residential land use.
Watershed
Beyond the project, other increases in density will add additional pressure to provide services requiring
additional development of infrastructure such as roads, restaurants, and retail stores. The size of this
development, while not small, will not be large enough to require additional development by itself, but
may add to the pressure to provide these services in the future. Many of these additional services may
result in cumulative impacts to the watershed that could adversely impact water quality.
Impacts in this project were minimized by reducing impacts that includes use of headwall at stream
crossing to reduce impacts, avoiding wetland impacts directly within the subdivision design, limiting
impervious surface area, and removal of an existing crossing.
4. Please provide an approximate total in acres/linear feet of aquatic resources avoided by the use of
headwalls and retaining walls.
The road crossing (SI) is for a 50' paved roadway with curb and gutter with a S' sidewalk (see
attachments Sl and cross section of stream crossing drawing). The use of headwall at SI reduced impacts
from the road culvert from 98 LF to 75 IF while retaining necessary roadway width and sidewalk. The 35
IF of rip -rap diffuser meets the calculated need to dissipate erosive forces based on slope and watershed.
Total impact was reduced from 133 IF to 110 IF due to the use of headwalls at this crossing.
5. Please provide a discussion regarding the continued viability of the 0.296 -acre wetland within the
"Open Space Nature Preserve" once the hydrology source from the relatively permanent water, which
discharges into this wetland, is entirely removed as proposed. Please note that the Corps may require
monitoring of this wetland to ensure secondary adverse impacts are not occurring over time due to the
removal of hydrology.
A design modification has been added to provide drainage from the post -construction watershed to this
wetland. The preconstruction watershed was calculated to be 12.3 acres. The post -construction
watershed is estimated to be 8.2 acres. Impervious surface will be less than 24 percent. Stormwater
runoff is collected along through the street culvert system and discharged into the Open Space lot into a
Swale with a diffuser pad above the wetland. The watershed will include approximately 75 percent of the
original area with under 24 percent impervious area. Much of the surface drainage will be divert through
culverts, but surface flows from the adjacent lots will drain directly to the wetland. No attempt will be
made to reduce localized groundwater seepage. This design should provide adequate hydrology to
maintain this wetland in addition to providing opportunityfor functional treatment of runoff.
6. Please further discuss the removal of the existing 42" HDPE as it relates to avoidance and minimization
of project impacts and identify the location of the restoration work.
The existing 34.14 IF of 42"HDPE used as a farm crossing will be removed and banks graded to a
stable grade. Native grasses will be planted to provide long-term stabilization. Grade control will only be
used if streambed stabilization is needed. All stream work will be done in the dry.
N

Corps comments June 27, 2017
7. For the purpose of coordinating for the Northern long-eared bat, please provide the following
information:
a. Will the proposed project require tree cutting/removal at the proposed impact locations? If so,
please provide either an estimated number of trees or the area of cutting/removal in acreage.
Within the Southern Acres development, the site is absent of trees due to past agricultural use. The
waterline extension traverse areas of forested land and will result in a minimal number of trees cut to
install the waterline and maintain access. The project will cut up to 0.162 acres of forest as a result of the
waterline extension for this project.
Temporary forest removal= 0.081
Permanent forest removal= 0.081
Total forest removal= 0.162
b. Will the project require blasting at the proposed impact locations?
No blasting for construction of this project are anticipated. With the wetland crossing locations
for the water line, they are outside areas needed for vehicular traffic or future construction.
compaction equipment will not be utilized or required.
c. Will there be other percussive activities conducted by machines, such as jackhammers or
mechanized pile drivers?
Jackhammers and mechanized pile drivers are not expected to be used for construction of this
project. Compaction of the roadbed is necessary and standard roller compaction equipment for
the construction will be utilized.
3

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NOTE: FOR ANY RIP -RAP TO BE PLACED IN
THE STREAM BED - THE FINISHED TOP
ELEVATION OF THE RIP -RAP SHOULD NOT
EXCEED THAT OF THE ORIGINAL STREAM BED
NOTE: TEMPORARY FILLS MUST BE REMOVED IN
THEIR ENTIRETY AND THE AFFECTED AREAS
RETURNED TO PRE -CONSTRUCTION ELEVATIONS.
THE AREAS AFFECTED BY TEMPORARY FILLS
MUST BE RE -VEGETATED, AS APPROPRIATE.
® PERMANENT IMPACTS (S1)
GRAPHIC SCALE
30 0 15 30 60
( II\ FEET )
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SWALE CALCULATION TABLE
LOT #
01O(CFS)
SWALE SLOPE
n
NORVAL DEPTH
(FT)
VELOCITY SHEAR STRESS
(FT/S) REQUIRED (PSF)
SWALE TYPE
SHEAR STRESS
PROVIDED (PSF)
OS
23.6
1.5%
0.03
0.94
3.7 0.88
A
1.45
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"STRAW W/NET" TEMP.
LINER AS
SHOWN
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4'
SEE PER
PERMANENT SWALE "A" PROJECT
NTS SPECS
5�
60
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CB28-1
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CB26
(28
CB24
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AREA FLOWING TO OPEN SPACE WETLANDS F.-rz
PRE—CONSTRUCTIONDRAINAGE AREA TO WETLANDS=12.3 AC. \\58 d
ROW CROPS (C=0.35)
Q=CIA=(0.35)(7.2 IN/HR)(12.3AC.)=31.0 CFSElY
POST CONSTRUCTIONUvmm ll
27 ` 2�lo
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24% MAX. IMPERVIOUS\ 5
— IMPERVIOUS C=0.95 5p0
LAWN C=0.20 T4
WEIGHTED C FACTOR
C=(0.24*0.95)+(0.76*0.20)=0.38 (USE 0.40) \ \ \ \ \ \ \
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253
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265
264
263
262
261
260
259
258
257
256
255
254
253
252
251
250
249
248
247
246
1 +00 245
CROSS SECTION OF STREAM CROSSING
1" = 30' HOR.
1" = 3' VER.
STREET
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259
258
257
256
255
254
253
252
251
250
249
248
247
246
1 +00 245
CROSS SECTION OF STREAM CROSSING
1" = 30' HOR.
1" = 3' VER.