Ver _COMPLETE FILE_19930422

S&
EC

Soil & Environmenta.1Consultants" Inc.
3818 Blari(iRoad.Raleigh, North Carolina 27609. [phone] . Fa:x,(919)79D-1728

"'August 9 , 1993'

U.S. Army Corps of Engineers
Attn: Mr. Eric Alsmeyer
6512 Falls of the NeuseRoad, suite 105
Raleigh, NC 27615~6846

DEM
Attn: Mr. John Dorney
POBox 29535
Raleigh, NC 27626

Dear Messrs. Alsmeyer and Dorney:

The purpose of this brief note is to update you on recent changes
in the Town of Garner Stormwater Management Project and to respond
to Mr. Wright's 8/4/93 letter.

The Towns plans have now changed, so that uponds" R7 and R9, instead
of ponds RTand:R~are th~onef;lUostlikely.t,o):)e built initialty,.
ThiSl'!()1.l1qi:r;7sult .,in. rOl.lgp.ly, a..).~.l,aq:r;eCibo'Ve,head\'f'~~7:r:e;~mpag~C. ..' ... '.
Joa:,E;~~"Orl".C:>1.l{[".'.'.pr7J.'~11l,il'lCi~}7''W'():r;k(q.~e;p:J:'i,Jo,7~,.i'n. .tP.7;.",~nf9~a:t!i9n'.'.,.....,...i>':,,~. . '
, previouslyproV'igedto YC)'t1<anddisctisSedwithiKenJoll:yua1'ldEri~
Alsmeyer. '

II wouldals() like to respond, to Mr. Wright's, letter to cl'arify
that we believe that all pond sites are above headwaters,impacf:.s
have been minimized and avoided and every attempt possibl~ is
being made to permit the sites, especially the initial 2,'under
Nationwide rather, than individual permits and therefore his
comments regarding mitigation, and other individual permit
requirements may not apply. Areas identified in our' study to'have
significant impacts will be further studied to assess
alterna.tives.

We realize'the study has identified SotIle pond sites ,with ,
significant.' impa-cts but that was the purpose of the, study, {i.,e.
Identify "g()od" sites to move forward with and identify problem
sites tobEffurther examined at a later, date). Please call if you
have questions or if any of my statements are in error.

Sincerely,

e~ 'IYl~ (6:J~J

m.mf~ ~UW m@
AUG I 31993
WETLANDS GROUP
WATER'(j'UAlITY SECTION

j1~

Kevin,C.Martin,
President

Soil/Site Evaluation . Mapping and Physical Analysis . Wetlarids Mapping and Mitigation . Environmental Audits;
On-Site Waste Treatment Systems" Evaluation and D,?sigll .", ,,'<,'(

August 3, 1993

MEMO

TO:

Beth McGee
Steve Zoufaly

John Dorne;~{)

Review of Preliminary Stormwater ponds for Garner

FROM:

RE:

Attached for your (and others?) review is a preliminary plan
for the Garner stormwater ponds from the wetlands viewpoint.
Kevin Martin has asked for comments soon so the city can finalize
their plans. If my faulty memory serves (doubtful), the main DEM
players in this issue were you two. Please review and advise
whether we need an internal meeting or just want me to coordinate
comments. Please comment by August 9 (next Monday). Thankx

Garner.pnd

cc: Boyd DeVane
Greg Thorpe

(' .. --~ .... '.

S&
EC

Soil & Environmental C

J c.
'! J

9O-3~)F !l8Ff993J1~ i~~~1728

3818 Bland Road . Raleigh, North Carolina 27609 . (

WETLANDS GROUP j
WATER UAlITY SECTjON~_,_j
June 3, 1993

U.S. Army Corps of Engineers
Attn: Mr. Eric Alsmeyer and Mr. Ken Jolly
6512 Falls of the Neuse Road, suite 105
Raleigh, NC 27615-6846

NCDEHNR-DEM
Attn: Mr. John Dorney
PO Box 29535
Raleigh, NC 27626

Re: Town of Garner - Stormwater - Proposed Pond sites
Preliminary Wetland Review (9 sites Evaluated)

Dear Messers: Alsmeyer, Jolly and Dorney:

The purpose of this letter is to request a written response to the
current methodology employed in preliminary evaluation of wetland
issues related to the project known as The Town of Garner
Stormwater Management Project, Garner, N.C. We have met on several
occasions previously to discuss preliminary delineations and
discuss permitting. The attached maps and this report describe
the approximate locations of Wetlands and Waters of the u.s. as
preliminarily determined by S&EC on the property, proposed
impoundment sites and the areas of Wetlands and Waters of the U.s.
to be impacted at each fill site. We would like this input so
that we can best advise the Town on the best way to approach the
more detailed evaluations and permitting process that must follow
prior to construction. For your information impoundments R7 and
R8 are the ones most certain to be built in the foreseeable
future, while the fate of the other proposed sites are uncertain
at this time.

In the recent past, when dealing with wetland areas above
headwaters which require fill covered under Nationwide Permits the
Corps and DEM have issued permits/certifications on a routine
basis unless the wetlands are of exceptional quality or if
endangered species are involved. We would like to point out that
significant efforts have already gone into reducing impacts "up-
front" based on our recommendations and input from previous
meetings with you. Therefore, I hope you will consider that we
have already made considerable changes to the original plans to
minimize the project's impacts as much as possible. This is
especially true for all impoundments except R1, R4 and R6.

Cumulative impacts are addressed below for individual impoundments
and for various scenarios of impoundments. We felt this approach

Soil/Site Evaluation . Mapping and Physical Analysis . Wetlands Mapping and Mitigation . Environmental Audits
On-Site Waste Treatment Systems, Evaluation and Design

. ... . "t

would be easier for all of us to follow and be more informative.

There are several items that I would like to point out that you
may want to discuss with me in further detail:

(1) The larger streams in the area (e.g. Swift Creek) with the
highest values from a water quality or wildlife standpoint
were preliminarily omitted from the study because we felt
impoundments in such areas would cause significant adverse
impacts based on our professional judgement.

(2) Based on conversations with your staff and the Corps under
current "policy" non-vegetated areas of Waters of the u.s. to
be inundated by creation of lakes are not considered to be
adversely impacted except for the dam area. Therefore such
areas have not been included as negative impacts except for
the dam areas. These areas are either "gully-like" channels
with little or no vegetation or small intermittent stream
channels.

The following lists each pond site and essentially what was found.
This was only a preliminary wetlands evaluation of general areas
because the potential pond sites were drawn on a standard topo map
1:24,000 scale and therefore could not be exactly located. We
would like to point out that only the most recent work performed
is being presented here. A significant amount of work was
performed to assist the client in minimizing impacts and selecting
the best sites available along specified drainageways.

County and or city topojairphoto maps were obtained at a 1" = 200'
scale and show the locations evaluated and the general findings
(copies enclosed). In cases where air photos were used, a "hand
traced" drawing is substituted for the original because the air
photo does not copy legibly. In other cases the topo was copied.
The following is a brief verbal description of each site examined
to date.

site R1:

On map number 160902 scale 1" = 200' approximately 40% of the
floodplain area is wetlands, plus a channel, 15 feet wide and 500
feet long. Moving the dam site upstream 450' to 750' would
minimize wetland impacts. This is a good site if dam is moved and
is fair if it is not. The current impoundment location shown
would result in roughly 3.2 acres of wetland impacts.

" ..

site R2: Map number, 0699.02 1" = 200'

Contains Approximately 7,000 sq. ft. of wetland area (see map) and
a 10 to 12 foot wide channel running through the site.

Most of this site is non-wetlands in the floodplain area. This
appears to be a good location from a wetland permitting
standpoint. Moving the dam site upstream 500' would further
reduce wetland impacts.

site R3: Map number 0699.02, 1" = 200'

contains Approximately 12,000 sq. ft. of wetland area (see map).
There is a 15' wide channel running through the site. Most of the
floodplain area is non-wetlands. This appears to be a good
location. The dam would have to be moved at least 1000' upstream
to minimize impacts further.

site R4: Map - 655 and 656 1" = 200'

Approximately 30 to 40 % of the floodplain area within the pond
site is wetlands. Moving the dam site 1000' upstream would
minimize impacts to wetlands. Fair site if dam not moved. Good
site if dam moved. Current impoundment location would impact
approximately 3.2 acres of wetland.

site R5: Map 655 and 656 1" = 200'

Approximately 30 % of floodplain area is wetlands. The wetlands
follow the channel and the area is about 50 feet wide. On the
north side of this proposed site is a dirt road with a sewer line
on the southern side of road which does not show up on the maps.
This road goes to a pump station next to the railroad track.
There is little potential to move the dam upstream due to the
presence of an existing pond. This is a fair to good site.
Current impoundment location would impact approximately 1.4 acres
of wetland.

site R6: Map 20 1" = 200'

90% of this proposed pond site is wetlands. This is a poor site.
An alternate site was investigated and contained a similar
percentage of wetlands. The current impoundment location would
impact approximately 13.2 acres of wetland. There is not a good

...

alternative location on this drainageway.

site R7: Map

Approximately 1.3 acres of wetlands exist in this proposed pond
site plus a 15 foot wide channel running through the site (see
map). Enlarging this pond from its originally proposed size to
the currently proposed dimensions increased the wetland impacts
from 8000ft2 to 1.3 acres, mainly along the upper reaches at the
head of the lake.

Note - Sewer line is present on western side of floodplain. An
upland break that does not show on map is roughly sketched in.

site R8: Maps 4 and 15 scale 1" = 200'

Approximately 10,000 sq. ft. of wetlands exist in the site plus a
12 foot wide channel running through the site (see map). A dirt
road crossing this drainage way does not show on the map - but is
sketched in on the map. This is where the proposed pond site
would begin - north of this road. This appears to be a good site.
Wetland impacts could be minimized even further by moving dam
upstream 350'.

site R9: Maps 14 and 15 1" = 200'

Most of the floodplain of initial area (90%) was wetlands. Most
probably due to back waters of Lake Benson. This was a poor site,
so an alternate site was evaluated and is shown on the attached
map. It contains roughly 0.8 acres of wetland and is a better
site even though less drainage area would be served.

PLEASE NOTE: Estimated Wetland Impacts assume that impounding ~
water over a stream channel is not an. adverse
impact. This assumption is consistent with current
Corps policy.

S&EC discovered that the impact to wetlands under the 9
impoundment proposal would be significant for impoundments R1, R4
and R6. (See attached maps.) The proposed impoundments at R5 and
R7 may be feasible. It appears that proposed lakes on R2, R3, R8
and R9 are clearly feasible from a wetlands permit standpoint.

Significant wetland areas do exist, however, at proposed Lakes R1,
R4 and R6 which would amount to a significant impact if inundated

.'

.'

permanently. Options to reduce these impacts on existing wetlands
were discussed with the US Army Corps (Eric Alsmeyer and Ken
Jolly) and DEM (John Dorney) and resulted in potential alternative
plans.

option one involves one major change: 1) reduce the number of
large earthen dam impoundments and restrict them to areas of least
wetland impact. Additionally, in the earthen dam impoundments,
include alternately shallow areas in the upstream portion and
along lake edges to create an aquatic habitat which would help in
pollutant attenuation and habitat creation. Also forbays for
sediment removal may be required as discussed. The total wetland
impact under the lake plan for two lakes (R7 and R8) will be
approximately 1.5 acres under current "rules". The inclusion of
lakes R2, R3, R5, R9 would increase impacts (to roughly 4 acres)
but more field work is needed to determine if impacts would be
increased to the point of requiring mitigation (a recent Corps
requirement in some cases) for a Nationwide permit. The inclusion
of all 9 lakes would total approximately 24 acres of impact which
would have to be permitted under an individual permit. Most of
these impacts are due to Lakes R1, R4 and R6 alone which total
19.8 acres. Exclusion of R6 would result in roughly 10 acres of
impact.

Option Two involves pursuing all 9 lakes and an individual permit
with associated mitigation.

option Three involves substituting more numerous smaller basins on
tributaries of the larger streams that have significant wetlands
(i.e. R1, R4 and/or R6). These smaller basins would have to be
placed to minimize impacts to wetlands on the small tributaries
also.

option Four involves a combination of the above options but we
would suggest avoiding an individual permit if at all possible.

We feel that this will be a unique and precedent setting approach
to water resource development in the area. The Town of Garner is
acutely aware of its responsibility and position in the
development of the land in this progressive region and appears
interested in working to balance the needs of that development
with environmental concerns.

The detailed field wetlands work required for permitting anyone
or all of the impoundments would build upon the preliminary
wetlands evaluation but will be significantly more detailed with
wetland boundaries located on the ground. Also required will be
some general design drawings of typical impoundment and proposed

t.. 4..

lake waterlines on each of the proposed lakes. The surveying work
will support both the detailed wetlands map and the need for data
required for lake design.

Please call if you have questions or require further information.
As mentioned earlier the town would appreciate written comments on
the information presented above.

sincerely,

~e~'-

Kevin C. Martin,
President

KM/jb

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TOWN OF GARNER WATERSHED PROTECTION PROGRAM

Background Information

1 Unlike most North Carolina municipalities, most of land area within Garner's
corporate limits is within a water supply watershed. This fact leads to the
unavoidable decision to embrace the high density development option in the
Town's watershed planning.

2 Most of the undeveloped areas within Garner's planning jurisdiction are either
west of NC401 or are situated near the limits of the watershed critical area (~orth
of Lake Benson). Most undeveloped lands in the older part of town are "in-fill"
areas, mostly small isolated tracts.

3 Garner, as well as other legal entities with jurisdiction in the Swift Creek I Lake
Benson watershed, have adopted, and DEM has approved, the Swift Creek Land
Management Plan, which in essence results in the management of a WS-III
watershed as if it were a WS-II watershed.

Master Plan

4 The Town of Garner has developed a master plan for the management of the
undeveloped areas that are within the jurisdiction of the Town and within the
watershed protection area. The master plan was developed based on:
. planning maps (land use and density zoning);
. aerial photography;
. soils maps; and
. field reconnaissance.

5 The basis for all preliminary structural storm water control siting decisions was
the location, zoning, and size of undeveloped land areas.

6 On-site and small regional control sites were field checked to assure that identified
strategic open areas were indeed undeveloped properties. The preliminary siting
resulted in 50 ponds with drainage areas ranging from 10 to 100 acres.

7 Due to the number of small facilities and the related construction, inspection, and
maintenance costs, a decision was made to look at larger regional opportunities
where economies of scale could be balanced with watershed protection.

8 Preliminary regional pond siting resulted in the location of 15 possible ponds with
drainage areas ranging from 150 to almost 2000 acres.

Watershed Protection
Town of Garner

April 22, 1993
Page - 1

,.

'...

9 Screening of the fifteen sites using soils maps (hydric soils) and aerial
photography (proximity of development with high flooding potential) reduced the
number of sites requiring field checks to 9.

10 Field verification ~f the sites was performed to determine whether or not wetlands
were present at the preliminary pond locations and whether or not the ponds
could be moved upstream or downstream a short distance and thereby avoid
significant wetland disturbance.

11 A meeting was held where the following decisions were made:
. one of the nine sites is zoned for lower density than required;
. two sites were dominated by undeveloped lands where the burden of building
regional controls will be placed on the development community;
. the bulk of the undeveloped land in the drainage areas of two of the sites
were under single ownership and !t was decided that these areas too would
be left to the developer/owner to develop storm water runoff controls;
. one site was found to have extensive wetland areas in both the immediate
and nearby areas; and
. three sites were found to be feasible for the siting of large regional basins
based on the presence of less than 10 acres of wetlands collectively at the
three sites.

The Proposed Management Program _---"'P'J ~JJ} L~

-~'
12 After completing th~eps, it was determined that the drainage areas in the
basins identified a~ R7, R8, and R9 should be dealt with by the Town for
several reasons, primarily because this is the area where much of the development
will be in-fill development at which it will be difficult for individual developers to
address the water quality issues.

13 Within the Garner planning area (limits plus ET J) there are approximately:
. 4,000 acres of undeveloped area
. 1,300 undeveloped acres in sub-basin R6, R7, R8, and R9
. 1,890 developed acres in R7 and R8
. 725 undeveloped acres in R6 and R9

14 The following table shows the relative levels of undeveloped and developed areas
within the four drainage areas that contain much of the commercially-zoned
property in Garner. As is shown by the table, a decision to build the ponds in
basins R7 and R8 would result in treating existing development in those drainage
areas that total 2.6 times the undeveloped drainage areain basins R6 and R9. The
ratio of existing imperviousness in R7 and R8 to planned imperviousness in R6
and R9 is also approximately 2.6.

v

Watershed Protection
Town of Garner

April 22, 1 993
Page - 2

""

"'

Pond Drainage Built Upon Not Yet Developed
Location Area Drainage Area Impervious Drainage Area Imp - Planned
ID (ac) (ac) (ac) (ac) (ac)
R6 1200 840 353 360 180
R7 1120 840 353 280 126
R8 1400 1050 441 350 140
R9 1040 676 284 364 120
R6,R9 2,240 1,516 637 724 300
R7,R8 2,520 1,890 794 630 266
R6, R7, R8, R9 4,760 3,406 1 ,431 1,354 566

15 Garner proposes to build the two ponds at R7 and R8, and in exchange for both
treating the runoff from the existing developed acreage in these basins and for
controlling the remainder of the town's jurisdiction according to the Swift Creek
Plan (WS-II controls in a WS-III watershed), the undeveloped areas in the R6 and )...P
R9 basins would be exempt from controls.

16 The following advantages to this plan should be considered:
. control not only of runoff from older urban development (found to be more
polluted than from new development in virtually all studies of urban runoff
quality), but at a 2.6: 1 ratio;
. providing for capture of potential spills along 60% of the US70 corridor within
the basin;
. development of multi-purpose ponds will help to ensure proper maintenance
and operation;
. fewer ponds means lessened risks due to poor construction and maintenance;
. R9 basin has large existing pond near the US70 corridor that will provide
some settling;
. R6 has wetlands impacts; and
. cost effectiveness ($3 million construction price tag represents $2200/acre
for undeveloped land, much less than cost of providing on-site control).

Watershed Protection
Town of Garner

April 22, 1 993
Page - 3