NCS000430_Water Quality Assessment_20210630

Montreat Stormwater Inventory and Management Plan
Land of Sky Regional Council
NC Department of Environmental Quality, Division of Water Resources
2050) FY2020-2021 I Contract #8095 1 January 24`^, 2020 —June 30th, 20211 $28,685
Mary Roderick
June 30th, 2021

Contents
ExecutiveSummary.......................................................................................................................................1
Introductionand Background.......................................................................................................................2
Purposeand Goals........................................................................................................................................2
Deliverables...................................................................................................................................................
2
Methodologyand Execution.........................................................................................................................5
Stormwater System Inventory ..................................................................................................................5
WaterQuality Monitoring.........................................................................................................................
5
Watershed Assessment and Analysis........................................................................................................6
Steep -slope SCM Project Opportunities...................................................................................................7
Resultsand Conclusions................................................................................................................................8
Stormwater System Inventory..................................................................................................................8
WaterQuality Monitoring.........................................................................................................................8
Watershed Assessment and Analysis........................................................................................................9
Steep -slope SCM Project Opportunities.................................................................................................10
References..................................................................................................................................................11
Appendices..................................................................................................................................................12

Executive Summary
Through this grant, the Land of Sky Regional Council (LOSRC) focused on the Town of Montreat in the
Upper Swannanoa River Watershed (USRW) along Flat Creek and its tributaries to augment the USR
Watershed Management Plan. The plan, developed from 2014-2016, included Montreat geographically,
but all of the proposed SCMs and stream restoration projects were located in Black Mountain and did
not address the steep -slope conditions in Montreat.
LOSRC developed a detailed, web -based stormwater inventory, as well as supported water quality
monitoring and a watershed -wide hydrologic and hydraulic study to identify opportunities for steep -
slope stormwater management. The inventory included existing stormwater infrastructure (e.g. inlets,
outfalls, pipes, and SCMs). LOSRC worked with town staff to locate facilities, document their condition,
and identify areas of concern in order to facilitate maintenance and capital improvements. Overall, the
stormwater system is in good condition and handles typical storm events well.
Water quality monitoring was carried out by Montreat College Professor Joshua Holbrook and his
students at three locations (reference and above and below Lake Susan) and included four sampling
events (two in the summer, one in the fall and one in the spring). The engineering team, Blue Earth, also
assessed physical conditions in the watershed and recorded 62 field observations as well as evaluated
over 4,200 linear feet of streambank and 10 aquatic habitat areas. Together, they found that Flat Creek
and its tributaries have good to excellent streambank stability, streamflow, chemistry, habitat and
diversity.
Blue Earth also developed a hydrologic and hydraulic (H&H) model for the Flat Creek subwatershed
encompassing 4.8 square miles with 158 catchments and 129 conduits. The H&H model revealed that
most options for stormwater storage in the public ROW are along creeks at road crossings, which
reinforces the need for widespread stormwater management on private property since it is damaging
both the stream ecology and the road infrastructure to intentionally collect stormwater in these public
ROW areas.
While we did not identify any major projects to pursue on public land or in the public ROW, the
analyses supported by the 205j grant program have been very helpful in developing a more detailed
understanding of the overall health of and stressors in the Flat Creek watershed, of the functional status
of the town's stormwater system, and of potential partnerships to pursue to maintain the current level
of water quality.

Stormwater Features
• Inlet %
■ Issue 1 •
■ function Lbrat
• Dutfall
■ SCM
•
0 ■
w wwmm Ie,
Pipes
Town Boundary • _
Lhdrv.n01-0�•
tl
■ •"•10
Rolxn P�
Wk L'an `a
Igo
n
300tt
Buncombe County, NC, State of North Carolina DDT, Esri, HERE, Gamin, INCREMENT P, NGA, USGS
Figure 1. Montreat stormwater inventory map. Source: Jon Beck, GIS Coordinator, LOSRC.
3

Macroinvertebrate Assessment
It
1C
8
6
4
2
0
North Central South
■Diversity ■Family Richness ■EPTS
Figure 3. Macroinvertebrate assessment scores. Source: Josh Holbrook, Professor, Montreat College.
Methodology and Execution
The following sections describe the approach taken for each project deliverable. The stormwater system
inventory and map were completed first to provide a common basis for evaluating potential stormwater
runoff issues found during water quality monitoring and the watershed assessment, both of which
occurred in tandem over a period of several months. Results from the biological monitoring and physical
assessment were shared between teams to cross-check and verify each other's findings.
Stormwater System Inventory
To create the inventory and map the infrastructure, a data dictionary was first created for each aspect of
the infrastructure. Inlets, junction boxes, and outfalls are represented as points with 18 attributes: type,
subtype, material, depth, condition; inflow pipe direction, material and diameter (x2); outflow pipe
direction, material and diameter; perch height; presence of erosion; comment; and a photo. The pipes
are represented as polylines with 3 attributes: material, diameter, and comment. The perch height and
erosion attributes were added in this project to help identify catchments and infrastructure that may be
negatively impacting stream health.
The next step involved field work and site visits with the public works department to locate each point
(inlet, junction box, and outfall) using a GPS device. This data was then imported into GIS. Based on the
pipe attribute information, the pipe network was then created to connect the inlets, junction boxes, and
outfalls. All of the information was then uploaded to AGOL to create an interactive web map.
Water Quality Monitoring
Water quality monitoring can indicate areas where stormwater runoff and non -point source pollution
are negatively impacting aquatic health. Three locations on Flat Creek were selected for biological anc
physical monitoring:

vegetative cover and land use type. Soils within the watershed were identified primarily as either
hydrologic soil group (HSG) Type A or Type B. HSG Type A indicates a "low runoff potential when
thoroughly wet" while HSG Type B indicates a "moderately low runoff potential when thoroughly wet."
Runoff curve numbers (CNs) were computed for each of the subwatersheds along with the percent
imperviousness.
The stormwater management approach for Montreat was to identify green infrastructure storage
opportunities throughout the community. Approximately 80% of all storm events in Montreat consist of
1 inch of rainfall or less and approximately 90% of all storm events consist of 1.5 inches of rainfall or
less. Therefore, the focus of the modeling effort was to evaluate the rainfall -runoff response of the Flat
Creek watershed for these more frequent storm events.
The computer model selected to evaluate the hydrologic response of the Flat Creek watershed was the
EPA Stormwater Management Model (SWMM) version 5.1. SWMM is a dynamic hydrology -hydraulic
simulation model used for evaluation and design of both urban and non -urban stormwater and
watershed systems. GIS data, including the high -resolution digital elevation model was used as the basis
for the model development. A total of 129 conduits representing streams and other surface
conveyances, 130junctions, and one outfall were characterized and incorporated into the model. The
node diagram which represents the Flat Creek watershed is shown Figure 2. Appendix A describes the
model in more detail.
Steep -slope SCMs
Input was obtained from both Montreat's public works staff and residents (through an online survey) in
order to better understand any problems with the existing stormwater management system of
Montreat and to identify opportunities for SCMs and other potential improvements. Once the PC-
SWMM model was developed, it was used in combination with the high -resolution DEM to identify
potential stormwater storage areas. The first iteration for identifying storage areas employed a
threshold with a minimum depth of 6 inches and a minimum area of 25 square feet. This threshold
resulted in a total of 587 storage areas.
Because the first iteration yielded such a large number of potential storage areas, a second iteration was
performed by employing a threshold with a minimum depth of 3 feet and a minimum area of 100 square
feet. This threshold resulted in a total of 58 storage areas. The 58 larger storage areas were then
evaluated with the PC-SWMM model to determine the maximum reduction in stormwater volume that
might be achieved by utilizing each area as compared to the runoff volume for the 1-inch and 1.5-inch
storms. Other characteristics such as the location of the storage with respect to private or public
property were also considered in the evaluation. An example of this evaluation is provided in Table 3.1
of Appendix A.
This desktop evaluation was then used to determine the top priority areas for field verification. Each
priority storage area was uploaded into a smart phone application to facilitate the efficiency of the field
verification. An example of the field verification is shown in Figure 5.

kick nets, the 0.32cm-mesh seine used for this project likely did not capture some of the smaller species
that kick net samples would have uncovered.
Macroinvertebrate family richness and standing stock increased in an upstream -downstream gradient
North to South, and Shannon -Weiner Diversity followed a similartrend, except that it decreased at Central
Site. This overall increase in three metrics can be attributed to the increase in number of species that are
able to survive in the more voluminous southern reaches of Flat Creek while good water quality is still
maintained. The dip in Shannon -Weiner Diversity at Central Site is due to a high abundance of a couple of
species relative to others, as S-W Diversity is a measure of both richness and evenness of catch.
It is possible that a higher macroinvertebrate diversity and productivity could be partially due to increased
Nitrogen and Phosphorus runoff downstream. Although all sampled N and P levels are within normal
regulatory boundaries, levels of these fertilizer -borne nutrients do increase downstream of the Lake Susan
(Seaman; Holbrook, Unpublished Data, Appendix B), which possesses a fertilized lawn, has a fish
population which is artificially fed, and has a healthy waterfowl population, all of which can contribute to
downstream eutrophication. Indeed, the output from Lake Susan causes a noticeable increase in algal
growth downstream of the dam, which in turn increases food availability for herbivorous
macro! nvertebrates. The increase in EPT family richness downstream indicates that despite the increase
in N and P levels, water quality at these sites remains good, thus there is no apparent biological indication
that water quality is being significantly affected by stormwater runoff in Montreat, NC with the caveat
that the sampling period did not occur during any particularly heavy rain event, where siltation events are
known to occur from residences or mudslides (Holbrook, unpublished).
Watershed Assessment and Analysis
The stream habitat throughout the study area varies from good to excellent. Although the stream is
impacted by built -upon areas and infrastructure, the low impervious percentage and large undisturbed
areas of the overall watershed provide good water quality and natural hydrologic conditions. The physical
characteristics of the streams are impacted by the town's built -upon area and infrastructure, but the
adverse consequences of those factors are limited by natural conditions. For example, the streams exhibit
some degree of entrenchment but most of the streambeds lie upon bedrock. Increased frequency and
intensity of stormflows due to impervious area and stormwater infrastructure have resulted in some
stream widening but little increase in depth. Similarly, stream alignments have been altered by road
construction and stormwater infrastructure, but the narrow, steep valleys of the area naturally limit the
lateral movement of streams and the ability to relocate streams. Even where the streams have been
significantly shifted and their movement constrained, e.g. Little Piney creek, current habitat and stream
stability are good.
The stream assessment findings are consistent with the biological surveys conducted by Joshua Holbrook
of the Department of Natural Science, Montreat College. Holbrook noted that water quality data
corroborates his assessment that physical stream quality is good to excellent throughout his study sites
on Flat Creek.
It is recommended that monthly chemical water quality sampling continue to be conducted on Flat Creek
using the methods and constituent list developed by the Volunteer Water Information Network (VWIN)
supported by the Environmental Quality Institute (the Montreat Stream Team has had a grant to do
sampling over the past year). Samples should be collected from a site above Lake Susan and from a site
below the confluence of Little Piney creek. In addition to the chemical sampling, we recommend annual

linear filtration trench could be installed adjacent to the parking area to prevent sediment
release and provide infiltration and temperature reduction of the parking lot runoff.
Encouraging green infrastructure practices to mitigate increased impervious surfaces and serve
as demonstration sites at the proposed Montreat Lodge development on Georgia Terrace
adjacent to Flat Creek.
General Project Takeaways
While we did not identify any major projects to pursue on public land or in the public ROW, the analyses
supported by the 205j grant program have been very helpful in developing a more detailed
understanding of the overall health of and stressors in the Flat Creek watershed, of the functional status
of the town's stormwater system, and of potential partnerships to pursue to maintain the current level
of water quality. There has been some discussion in the community around the restrictive requirements
of the stormwater ordinance; however, these appear to be effective in protecting water quality and
should not be changed without performing detailed, subwatershed sensitivity analysis, which can be
facilitated by the H&H model developed in this project.
Within the larger Upper Swannanoa River Watershed, it appears that the Montreat section of the Flat
Creek subwatershed is not contributing to the impairments in the Swannanoa River. However, lower
portions of Flat Creek that run through more highly developed areas of Black Mountain do show signs of
stress such as excessive streambed sedimentation. This need to be addressed in future work to improve
both in -stream conditions for aquatic species as well as the overall health of the Swannanoa River.
References
Equinox. 2016. Upper Swannanoa River Watershed Management Plan. Available from:
httr)s://files.nc.gov/ncdeo/WateN`20Quality/Planning/NPU/319/WatershedMGTPlans 9element/Final-
Upper SwannanoaR WMP012016.odf
11

Or

.Stream Assessment and Stormwater Management Evaluation
Town of Montreat. North Carolina
Executive Summary
The Town of Montreat experienced significant storm damage from Tropical Storm Alberto in
2018. In an effort to support Montreat with its stormwater management program, Land of Sky
Regional Council (LOSRC) applied for, and received, 2050) grant funding from the North Carolina
Department of Environmental Quality (NCDEQ). The grant funds were awarded in order to
inventory and assess Montreat's stormwater management system and identify opportunities for
stormwater control measures (SCMs) within a steep slope environment. The scope of work in the
grant application included the following major tasks:
1) Mapping existing stormwater infrastructure (culverts, pipes, outfalls, area drains, catch
basins, dry ponds, wet ponds, and ditches). A component of the stormwater infrastructure
mapping is an interactive map product to enable Montreat staff to identify and assess
priority facilities for maintenance, water quality improvements, and flood mitigation.
2) Stream assessment to establish baseline conditions for Flat Creek, the primary stream
that flows through Montreat. The stream assessment included 6,000linear feet of stream
using a simplified BEHI and the DWR stream & riparian habitat assessment methodology.
3) Stormwater management evaluation and concept plan which included watershed
assessment and stormwater control measure (SCM) opportunity investigation. Where
applicable, the plan included conceptual design of SCMs and cost estimation.
LOSRC contracted with Blue Earth Planning, Engineering and Design, PC (Blue Earth) to lead the
effort on Tasks 2 and 3, the stream assessment and stormwater management evaluation and
concept plan. Beginning in June 2020,62 stream and stormwater system observations were made
by Blue Earth and over 6,000 linear feet of stream conditions were assessed for stream habitat
and bank stability. The major finding was that little bank instability was found along Flat Creek
and its major tributaries.
The stormwater management system evaluation conducted by Blue Earth included the following
tasks:
• Extensive field observations of the stormwater management system
• Discussions with Town staff to identify existing problems and capacity issues
• Reviewing and field verification of resident surveys and complaints
• Developing a detailed PC-SWMM model of the Flat Creek watershed and creek network
• Evaluating opportunities for potential storage and SCMs using high -resolution digital
elevation model (DEM) of the Flat Creek watershed
• Providing recommendations for improvements to the stormwater management system
• Developing planning level cost estimates for potential recommended projects
In general, the opportunities to implement SCMs within public property and public right-of-way is
very limited. However, there are opportunities to enhance stormwater management through
improvements in operations and engaging property owners within the Town as detailed in the
subsequent report.
e BlueEarth

•Stream Assessment and Stormwater Management Evaluation
Town of Montreat. North Carolina
The Flat Creek watershed at the Town boundary comprises an area of approximately 4.8 square
miles. Lake Susan, owned and operated by the MRA, is located centrally within Montreat and
provides some flood attenuation as well as sediment capture on Flat Creek.
In 2018, the Town experienced significant damage from a mudslide triggered by Tropical Storm
Alberto which caused an estimated $915,000 in damages to public property and infrastructure.
As a result, the Town was interested in identifying measures, including stormwater control
measures (SCMs) for steep slope environments, that could help provide more resilience during
extreme storm events.
In an effort to support Montreat with its stormwater management program, Land of Sky Regional
Council (LOSRC) applied for, and received, 205(j) grant funding from the North Carolina
Department of Environmental Quality (NCDEQ). The grant funds were awarded in order to
inventory and assess Montreat's stormwater management system and identify opportunities for
stormwater control measures (SCMs) within a steep slope environment. The scope of work in the
grant application included the following major tasks:
1) Mapping existing stormwater infrastructure (culverts, pipes, outfalls, area drains, catch
basins, dry ponds, wet ponds, and ditches). A component of the inventory mapping is an
interactive map product to enable Montreat staff to identify and assess priority facilities
for maintenance, water quality improvements, and flood mitigation.
2) Stream assessment to establish baseline conditions for Flat Creek, the primary stream
that flows through Montreat. The stream assessment included 4,000linear feet of stream
using a simplified BEHI and the DWR stream & riparian habitat assessment methodology.
3) Stormwater management evaluation and concept plan which included watershed
assessment and stormwater control measure (SCM) opportunity investigation. Where
applicable, the plan included conceptual design of SCMs and cost estimation.
LOSRC contracted with Blue Earth Planning, Engineering and Design, PC (Blue Earth) to lead the
effort on Tasks 2 and 3, the stream assessment and stormwater management evaluation and
concept plan. The following report sections provide detailed documentation of methodology that
was employed, the findings, and recommendations from the evaluations conducted by Blue Earth.
® BlueEarth

-Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
2.1 Habitat
The following habitat assessment scores are presented for ten sites and are representative of the
conditions found within a reach spanning approximately 300 feet upstream to 300 feet
downstream of the site (Table 2.1). The scores fall within a relatively narrow range, all considered
to represent good to excellent habitat. The highest scoring (best habitat) site was in Flat Creek in
the Montreat Wilderness which is upstream of the Town's developed parcels. The reaches near
the Montreat College campus and Puncheon Creek were rated lowest. Those lower ratings were
mostly due to loss of riparian vegetation and proximity of roads, buildings, and parking lots.
Table 2.1. Habitat Assessment Scores for Flat Creek and Trihutnripc
Date
Time
Site ID
Lat
Long
- - ------_--
Name
Habitat
Score
20200624
14:23
1
35.642861
-82.305947
Flat Creek upstream of Little Piney
79
20200624
15:28
2
35.64335
-82.306828
Little Piney
77
20200624
16:02
3
35.641964
-82.306889
Flat Creek downstream of Little Piney
82
20200624
16:50
4
40.645744
-82.300508
Flat Creek upstream of Puncheon Branch
74
20200624
10:06
5
35.645525
-82.299944
Puncheon Creek above Flat Creek
74
20200624
11:20
6
35.644811
-82.301903
Flat Creek downstream of Puncheon
74
20200625
9:59
7
35.659725
-82.294603
Flat Creek in Montreat Wilderness
88
20200625
11:39
8
35.652989
-82.296392
Flat Creek upstream of Big Piney
86
20200625
14:00
9
35.653369
-82.297586
Big Piney Branch
78
20200625
13:05
10
3.5.651753
-82.296789
Flat Creek downstream of Big Piney
79
2.2 Bank Erosion
The BEHI method was applied at a representative location in proximity to the habitat assessment
sites (Table 2.2). The left and right banks (facing upstream) were scored, and a subjective
classification was also assigned. BEHI scores rate the susceptibility of the bank to erosion. A low
score represents stable bank conditions with higher scores representing unstable conditions. In
steep, rocky mountain streams, where the streambed often lies on bedrock and banks have a large
amount of cobblestone and boulders, it is common that the score and subjective evaluations
sometimes diverge.
Table 2.2. Bank Erosion Hazard Index (BEHI) Scores for Flat Creek and Tributaries
Date
Site -ID
Name
BEHI Right
Bank
BEHI -RB
Subjective
BEHI Left
Bank
BEHI - LB
Subjective
20200624
1
Flat Creek upstream of Little Piney
12
Low
15
Low
20200624
2
Little Piney
20
Low -Moderate
23
Moderate
20200624
3
Flat Creek downstream of Little Piney
21
Low -Moderate
21
Low -Moderate
20200624
4
Flat Creek upstream of Puncheon Branch
-
Low
19
Low -Moderate
202006241
5
1 Puncheon Creek above Flat Creek
26
Moderate
22
Moderate
20200624
6
1 Flat Creek downstream of Puncheon
19
Low -Moderate
-
Low
20200625
7
Flat Creek in Montreat Wilderness
24
Moderate
15
Low
20200625
8
Flat Creek upstream of Big Piney
12
Low
-
Low
20200625
9
Big Piney Branch
16
Low
11
Low
20200625
10
Flat Creek downstream of Big Piney
16
Low
12
Low
e BlueEarth

•Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
The stream assessment findings are consistent with the biological surveys conducted by Professor
Joshua Holbrook of the Department of Natural Science, Montreat College. Mr. Holbrook noted
that water quality data corroborates his assessment that physical stream quality is good to
excellent throughout his study sites on Flat Creek. While Mr. Holbrook found macroinvertebrate
family richness to be less than other sites in Western North Carolina, he expects that the findings
were the effect of sampling methods instead of a significant difference in site species richness.
We recommend that monthly chemical water quality sampling be conducted on Flat Creek using
the methods and constituent list developed by the Volunteer Water Information Network (VWIN)
supported by the Environmental Quality Institute (EQI). Samples should be collected from a site
above Lake Susan and from a site below the confluence of Little Piney Creek. In addition to the
chemical sampling, it is recommended that annual macroinvertebrate analysis and habitat
assessments be performed at the most upstream and the most downstream sites assessed by Mr.
Holbrook. With the assistance of volunteers, the annual cost of these assessments should be
between $1,000 and $2,000.
Blue arth

•Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
Much of the Flat Creek watershed is forested and mountainous, with the majority having slopes
between 30 to 60 percent. The maximum elevation in the watershed was determined to be
approximately 5,393 feet, which is approximately 2,922 feet higher than the invert elevation of
Flat Creek at the Town boundary of approximately 2,471 feet. In order to evaluate the hydrologic
response, the overall watershed was delineated into 158 subwatersheds based on contributing
tributary areas and drainage features, as shown in Figure 3.2.
3.2 Watershed Parameters
Parameters which characterize the rainfall -runoff response were computed for each of the 158
subwatersheds, based on the drainage flow paths, slopes, roughness of the conveyance system,
vegetative cover and land use type. Soils within the watershed were identified primarily as either
hydrologic soil group (HSG) Type A or Type B as shown in Figure 3.3. HSG Type A indicates a "low
runoff potential when thoroughly wet' while HSG Type B indicates a "moderately low runoff
potential when thoroughly wet." Runoff curve numbers (CNs) were computed for each of the
subwatersheds along with the percent imperviousness.
e BlueEarth 11

•Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
GIS data, including the high -resolution digital elevation model, was used as the basis for the model
development. A total of 129 conduits representing streams and other surface conveyances,130
junctions, and one outfall were characterized and incorporated into the model. The node diagram
which represents the Flat Creek watershed is shown Figure 3.4.
Stream conveyances were created using the DEM elevation data by averaging transects spaced at
a distance of approximately 100 feet (Figure 3.5). A Manning's roughness coefficient of 0.04 was
assigned to these conveyances to correspond with the roughness typical of a wooded mountain
stream. A typical stream cross section created from the DEM is shown in Figure 3.6.
eBlueEarth 13

•Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
The PC-SWMM model is fully integrated with the Town's GIS data and can provide valuable
evaluation, planning and design information by overlaying hydrologic results with stormwater
infrastructure, parcel data, public right-of-way data, resident complaints and other GIS data. An
example of the GIS overlay is provided in Figure 3.8.
3.6 Storage Evaluation
Once the PC-SWMM model was developed, it was used in combination with the high -resolution
DEM to identify potential stormwater storage areas. The first iteration for identifying storage
areas employed a threshold with a minimum storage depth of 6 inches and a minimum area of 25
square feet. This threshold resulted in a total of 587 storage areas as depicted in Figure 3.9.
BlueEarth 15

Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
The 67larger storage areas were then evaluated with the PC-SWMM model to determine the
maximum reduction in stormwater volume that might be achieved by utilizing each area as
compared to the runoff volume for the 1-inch and 1.5-inch storms. Other characteristics such as
the location of the storage with respect to private or public property were also considered in the
evaluation. An example of this evaluation is provided in Table 3.1 and the full tables are provided
in Appendix A.
Table 3.1. Example of Evaluation of Potential Storaee Areas
Name
Minimum
Dee(it)
Maximum
Fev.(ft)
Depth �ft�
Area
(ft')
Vdume
(it')
''
Storm
Vduma
ft3
Ratio ofr
Storage to ].5-
iMh Volume
Subcatchment
Area (ac)
LSdrKh
5u8wtchment
Runoff (ft3)
Ratioof5torage
to 1.5-1 Mh
SubcatchmeM
Runoff
Feld
Pnority
(Y/N)
Secondary
priority
(Y/N)
SP3
3014.53
3019.96
5.43
762
1393
46.978
3%
10
1556
90%
N
Yes
SP2
2940.89
2944.94
4.05
508
731
3,111
23%
14
4,667
16%
Yes
Yes
SP3
3343.08
3346.62
3.53
3555
$051
SP4
3340.57
3346.27
5.70
4883
17408
SPS
2915.06
2924.62
9.56
8262
24922
4,978
501%
12
7.778
320%
Yes
I Yes
SP6
2825.91
2834.80
8.89
2910
8756
72,334
12%
14
7,778
113%
Yes
Yes
SP7
2843.67
2847.38
3.71
557
751
19,911
4%
12
7,778
10%
N
Yes
Spit
2934.70
2942.37
7.67
1680
2246
81.979
ef
13
4.667
48%
N
Yes
SP9
2895.37
2902.67
7.31
566
1802
81,979
2%
13
4,667
39%
N
Yes
SPI0
2789.52
2794.10
4.59
1230
2067
19,911
10%
12
7.778
27%
Yes
Yes
SP11
2904.47
2908.02
3.54
674
593
121,646
0.5%
30
18,667
3%
N
N
SP32
2857.36
2862.57
5.20
1348
2362
121.646
2%
30
18,667
13%
N
Yes
SP13
2802.46
2807.41
4.96
908
1928
121,646
2%
30
18.667
10%
N
Yes
SP34
2763.47
2767.18
3.71
322
335 1
103,134
0.3%
30
18,667
2%
N
N
SP15
2909.02
2913.94
4.92
1387
1956
7,311
27%
16
4.667
42%
Yes
Yes
SP36
2672.98
2604.27
11.29
10586
38672
160.224
24%
7
4,667
829%
Yes
Yes
SP17
3076.94
3080.68
3.74
215
308
3,422
9%
11
3,111
10%
Yes
Yes
Sp18
3021.35
3026.73
5.38
488
719
16,333
4%
11
4,667
15%
N
Yes
51,39
2862.83
2866.99
4.16
313
646
199,113
0.3%
22
14.000
5%
N
N
SP20
2629.80
2640A2
10.33
8340
33856
199.113
17%
13
9,333
363%
Yes
Yes
This desktop evaluation was then used to determine the top priority areas for field verification.
Each priority storage area was uploaded into a smart phone application for efficient field
verification. An example of the field verification is shown in Figure 3.12.
eBlueEarth 17

•Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
4.0 Project Opportunities
The watershed -wide storage evaluation approach did not identify reasonable, cost-effective
public locations for stormwater storage to enhance the function of the Montreat stormwater
management system. These findings were not unexpected within a steep mountain watershed
with very limited public land and right-of-way. Therefore, other project opportunities were
considered in the evaluation, as described in the following sections.
4.1 Green Infrastructure and Property Owner Assistance
Green infrastructure, which employs stormwater control measures that mimic natural hydrologic
processes, often by employing permeable soils and vegetation, can have substantial benefit,
especially when distributed on a larger watershed scale. There are several existing examples of
green infrastructure within Montreat, including rain garden/detention area located at the new
Town Hall building, as shown in Figure 4.1.
Many stormwater management problems are best addressed by engaging residents in the
development of green infrastructure. That approach can be very cost-effective in comparison to
trying to build large, municipally constructed and maintained, stormwater control measures.
Stormwater departments and utilities in many municipalities have programs that provide
technical and financial assistance to property owners who want to reduce and/or improve the
quality of stormwater running off their buildings and land. These programs have been shown to be
cost effective means of addressing water quality problems in receiving waters, in helping maintain
the stability of stream banks, and addressing municipal stormwater maintenance issues.
Not only do these assistance programs leverage the funds that a stormwater department has
available to address water quality issues, but they also provide a mean of formalizing and
eBlueEarth 19

-Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
4.1.3 Project Resources
Raleigh, North Carolina - Water Quality Cost Share Program:
https:Hraleighnc.gov/prof ects/content/PWksStormwater/Articles/StormwaterQualityCostShare
Program.html
Cedar Rapids, Iowa: httr)://www.cedar-rapids.org/local government/departments e -
v/public works/stormwater best management practices cost -share prog ar m php
U.S. Environmental Protection Agency- Green Infrastructure Funding Opportunities:
https•//www eoa gov/green-infrastructure/green-infrastructure-funding-opportunities
U.S. Environmental Protection Agency- Urban Waters Small Grants Program:
https:Hwww.epa.gov/sites/production/files/2016-10/documents/uwsg flyer october2016 odf
4.2 Lake Susan
Lake Susan is centrally located in the Flat Creek watershed and is owned and operated by the
MRA. The lake currently provides some flood attenuation and sediment capture (Figure 4.2).
According to the MRA, the original lake and dam construction included a forebay and the lake has
not been dredged since prior to the year 2004. Lake Susan's function could be improved for both
sediment capture and flood attenuation by dredging the accumulated sediment and potentially
lowering the normal pool to allow for additional flood storage. A design concept and planning
level cost estimate are presented below. Additional analysis of the lake and dam should be
conducted before making any operational modifications.
eBlueEarth 21

Stream Assessment and Stormwater Management Evaluation
Town of Montreat. North Carolina
Table 4.1. Planning Level Cost Estimate for Lake Susan Dredging and Modifications.
DredgingMontreat/ Land of Sky
Lake Susan
OpinionBudgetary
Item Item Description Scheduled Units Unit Price Total Amount
Quantit
Site Preparation, Demolition and Mlsc
1
Bonds, Mobilization, Demobilization and Insurance
1
LS
$ 20,000.00
2
surveying and Site Staking
1
LS
$ 2,500.00
7
Cleadng and Grubbing
0.15
AC $ 7,300.00
$ 1,095.00
5
Traffic and Packing Control
1
LS $ 2,500.00
$ 2,500.00
92
Water Management and Pump Around
1
ILS $ 7.500.00
$ 7,500.00
Site Preparation, Demolition and Misc Subtotal
$ 33.595.00
Excavator, Backfill & Hauling
35
Drell in
9444
CY
$ 32.50
$ 306,930.00
117
Dewatedn Dredged Material
9444
CY
$ 1.75
$ 16,527.00
34
Earth Work - Fine Grading
8
AR
1 $ 176.31
$ 1,410.46
14
IHaul off -site disposal -general)
9444
CY
1 $ 15,87
$ 149,853.90
Excavation and Backfill Subtotal
$ 474,721.35
Piping
40
"-'no' RCP
75
LF
$ 63.47
$ 4,760.29
1010
Trash Rack
1
li LS
1 $ 1,000.00
$ 1,000,00
Piping Subtotal
$ 4,760.29
Structures
103
GI Store a Basin - Outlet Structures
JEA
1 $ 4.095.00
$ 4,095.00
1119
ijDann Modifation-Boring &Pipe Installation
ILS
1 $ 10,000.00
$ 10,000.00
i
Structures Subtotal
$ 14,095.00
ESC Measures and Bank Protection
90
1 Silt Fence
500
LF
$ 4.15
$ 2,074.20
93
Temporary Gravel Construction Entrance
i
LS
$ 3,500.00
$ 3,500.00
112
Soil Preparation
100
ISIF
BY
$ 29.25
$ 2,925.00
113
IPlug Planting
100
BY
$ 35.10
$ 3.510.00
18
lWetland Seed Ma
5000
$ 0.36
$ 1,814.93
ESC Measures
and Bank
Protection Subtotal
$ 13,824.13
Construction Sub -Total
Engineering, Dam Safety Inspection, Construction Planning & Update
Permitting
Construction Services (5%)
Contingency (30%)
of EAP
$ 541,000.00
$ 25,000.00
E 15,000.00
E 27,000.00
$ 182,000.00
Total Estimate of Cost
$ 775,000.00
4.3 Rainbow Terrace and Parking Area
Rainbow Terrace is a North Carolina Department of Transportation (NCDOT) road that connects
through Montreat at the southern Town limit. One of Montreat's parking areas is located along
Rainbow Terrace and Flat Creek. The surface of both Rainbow Terrace and the parking area
include fine material that is currently being washed into Flat Creek during storm events. There
may be an opportunity for the Town to coordinate with NCDOT to resurface both Rainbow
Terrace and the parking area with a material that does not release fine particulate into Flat Creek.
Additionally, a stormwater control measure, such as a linear filtration trench, could be installed
adjacent to the parking area to prevent sediment release and provide infiltration and temperature
reduction of the parking lot runoff. A photograph of the parking area and sediment migration is
shown in Figure 4.3.
eBlueEarth 23

Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
4.3.3 Project Benefits
The project will result in a decrease in sediment delivered to Flat Creek, treatment of oils and
other pollutants washing off the gravel parking lot, and create both a safer and more aesthetic
parking area. Until improvements are made to the roadway above the parking lot (a heavy
sediment contributor), the forebay area likely will have to be maintained annually. Once the
incoming sediment load is reduced, then required maintenance likely will be reduced to a 3-year
period or longer.
4.3.4 Cost Estimate
The planning level cost estimate for the project as conceptualized is between $50,000 and
$65,000. The detailed cost estimate is included in Table 4.2.
Table 4.2. Planning Level Cost Estimate for Parking Lot Resurfacing and SCMs.
Parking Lot Grading, Resurface, Field Swale & Level Spreader
Budgetary OpinionMontreal / Land of Sky
Kern Item Description Scheduled Units Unit Price Total Amount
Quantity
Site Preps'on, Demolition and Mlac
1 Bonds, Mobilirst'n, Demubil¢allon and Insurance
1
LS
$ 3,500.00
2 Surveying and Site Staking
It
ILS
$ 2,000.00
1 $ 2000.00
Site Preparation, Demolition and Misc Sulatotell
$ 5,500.00
Excavation
and Backfill
30
Unclassilied Excavation
200
icy
1 $ 21.78
$ 4,355.82
Too
GI Storaqe Basin- Initial Grading, Excavation and Tree Removal
3500
ISF
$ 3.11
$ 10,889.55
34
1 Earth Work - Fine Gmdhg
116
JHR
$ 176.31
$ 2,820.91
109
Shrubs
190
lEa
Is 36.30
$ 3,266.87
Excavation and Backfill Subtotal
$ 18,066.28
PI In
107
IGI Blobasin - Outlet Structures
1
EA
1 $ 4.095.00
$ 4,095.00
40
18-inch RCP
25
ILF
1 $ 63.47
$ 1,586.76
25
10oncrelas Level Spreader
118
ILF
1 $ 30.00
$ 540.00
Pi2In2 Subtotal
$ 6221.76
ESC Measures
and Bank Protection
'
90
Sift Fence
250
LF
$ 4.15
$ 1,037.10
94
Install, Inspect, Maintain and Remove Temporary ESC Measures
1
LS
$ 2,000.00
$ 2,000.00
112
Soil Preparation
130
SY
$ 29.25
$ 3,802.50
37
Pea Gravel
125
CY
$ 29.62
$ 3,702.45
98
Seed Ma General
7500
ISF
$ 0.16
$ 1,166.74
ESC Measures
and Bank
Protection Subtotal
$ 11,708.78
Construction Sub -Total
Engineering(15%)
Permitting (5%)
Construction Services (10%)
Contingency 30%
$ 41,500.00
$ 6,200.00
$ 2,100.00
$ 4.200.00
$ 12,500.00
Total Estimate of Cost
I s 64,400.00
4.4 Montreat Lodge and New Construction
Opportunities for stormwater management coincide with new construction. Montreat's current
stormwater ordinance allows a range of green infrastructure practices to be implemented as part
of the stormwater requirements for new construction. One significant project in the Town is the
proposed Montreat Lodge that will be located on Georgia Terrace (Figure 4.4). The project
® BlueEarth 25

Stream Assessment and Stormwater Management Evaluation
Town of Montreat, North Carolina
5.0 References
Holbrook, Joshua D. (2021). Macroinvertebrate Community Assessment of Three Sites in Flat Creek in
Montreat, North Carolina, USA. Department of Natural Science, Montreat College, Report to
Land of Sky Regional Council, June 2021.
United States Department of Agriculture.(1986). Urban Hydrology for Small Watersheds. Technical
Release No. 55 (TR-55). Natural Resources Conservation Service, USDA, June 1986.
Raleigh, North Carolina - Water Quality Cost Share Program:
https://ra leighnc.gov/proiects/content/PW ksStormwater/Articles/StormwaterOual ityCost
ShareProgram.html
Cedar Rapids, Iowa: http://www.cedar-rar)ids.oriz/local government/departments g=
y/public works/stormwater best management practices cost -share pro ram.php
U.S. Environmental Protection Agency - Green Infrastructure Funding Opportunities:
httos://www.ei)a.gov/green-infrastructure/green-infrastructure-fund i ng-000pportu n iti es
U.S. Environmental Protection Agency - Urban Waters Small Grants Program:
https://www.er)a.gov/sites/prod uction/fi I es/2016-
10/documents/uwsg flyer october2016.pdf
NCDEQ-DWR. Biological Assessment Unit's Habitat Assessment Field Data Sheet-
Mountain/Piedmont Streams.
Rosgen, P.H. (2001). A Practical Method of Computing Stream Bank Erosion. Wildland Hydrology Inc.,
Pagosa Springs, Colorado.
eBlueEarth 27
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Appendix B
Macroinvertebrate community assessment of three sites in Flat Creek in Montreat, NC, USA
Joshua D. Holbrook, Dept. of Natural Science, Montreat College
Background
Flat Creek is a second order stream bisecting the town of Montreat, NC between 3,400
and 2,400 feet above sea level and emptying into the Swannanoa River and French Broad
watershed. Due to its extreme elevational heterogeneity, managing stormwater runoff along
Flat Creek is difficult given anthropogenic disturbances such as residences, new construction
and roads. Aquatic macroinvertebrates are a valuable tool used by environmental, regulatory
and other organizations to assess stream condition. Some taxa, particularly the mayflies
(Ephemeroptera), stoneflies (Plecoptera) and caddisflies (Trichoptera) are relatively intolerant
of turbidity, nutrient load and other runoff -borne pollutants.
Methods
Study Sites
In order to assess potential stormwater runoff -related impacts of human development
in Montreat, three sites along Flat Creek representing a gradient of potential impacts
throughout the town were selected. The first site, North Site, was located at the Greybeard
trailhead (35.6597,-82.2949) and was chosen due to its low potential for anthropogenic
impacts (e.g., there are few houses upstream). The second site, Central Site, was at the
Assembly Circle Bridge (35.6485,-82.2978) and was selected because it is downstream of a
number of Montreat houses, but occurs upstream of Lake Susan. Lake Susan is likely the source
of some nutrient runoff (e.g. fertilizer) to downstream parts of the creek. The final site, South
Site, is located at the south side of Montreat (35.6386,-82.3113), thus representing the entirety
of any stormwater runoff impact in Flat Creek.
Macroinvertebrate Inventory Methods
Macroinvertebrates were inventoried at the three sites along Flat Creek in Summer
2020 (n=2), Fall 2020 (n=1) and Spring 2021(n=1) using a 2m seine with .32 cm mesh. At each
site, between 2 and 5 areas of the creek were selected to sample a representative of the
available habitats. At each sampling area, cobble and rocks were perturbed beginning 2m
upstream of the seine to sample 4M2 of stream bottom. Macroinvertebrates were then picked
from the seine and preserved in 70% EtOH until they were later identified to the lowest
possible taxonomic group in the lab. Crayfish species were not included in identified samples
due to permit constraints. Macroinvertebrate catch at each site was divided by the number of
areas sampled at each site to correct for effort (effort = catch / total number of seines).
Additionally, macroinvertebrate catch from two of the summer samples was dried and weighed
to estimate standing stock at each site.
Macroinvertebrate data were analyzed by determining family richness (S, the number of
families represented at each site), family richness of Ephemeroptera, Plecoptera and
Trichoptera (EPT S), as well as Shannon -Weiner Diversity (H) at each site. Site diversity was
calculated using the formula H=Ep; In(pi) where p; is proportion of individuals belonging to the
ith family.

Central Site had the lowest diversity (H=1.00) and North Site had an intermediate diversity
(H=1.05, Fig. 4). Standing stock mass was lowest at North Site (8mg/mz), intermediate though
much higher at Central Site (29.5mg/mz), and highest at South Site (49.2mg/m2, Fig. 5).
Discussion
The three sites sampled along Flat Creek in Montreat largely exhibited typical upstream -
downstream trends in physical characteristics and biodiversity measures. Upstream -
downstream increases in flow rate and temperature were observed and are explained by the
input of other tributaries into Flat Creek between the North and South Site, as well as a possible
effect of Lake Susan on mean temperature. Water quality data taken concurrently by Seaman
et. al. (see Appendix 2) corroborates our assessment that physical stream quality is good to
excellent throughout our sites at Flat Creek. Water level fluctuations were also unremarkable,
with all three sites varying a maximum of -20cm during rain events.
Macroinvertebrate family richness was ostensibly less than other sites in Western NC.
For example, macroinvertebrate family richness ranged from 14 to 20 species at three sites in
Old Fort, NC <20km from Flat Creek (Reece 2019, unpublished data). However, this is likely an
effect of sampling method instead of a significant difference in site species richness.
Macroinvertebrate surveys often entail the use of-0.06cm kick nets, our 0.32cm-mesh seine
likely did not capture some of the smaller species that kick net samples would have uncovered.
Macroinvertebrate family richness and standing stock increased in an upstream -downstream
gradient North to South, and Shannon -Weiner Diversity followed a similar trend, except that it
decreased at Central Site. This overall increase in three metrics can be attributed to the
increase in number of species that are able to survive in the more voluminous southern reaches
of Flat Creek while good water quality is still maintained. The dip in Shannon -Weiner Diversity
at Central Site is due to a high abundance of a couple of species relative to others, as S-W
Diversity is a measure of both richness and evenness of catch.
It is possible that a higher macroinvertebrate diversity and productivity could be
partially due to increased Nitrogen and Phosphorus runoff downstream. Although all sampled N
and P levels are within normal regulatory boundaries, levels of these fertilizer -borne nutrients
do increase downstream of the Lake Susan (Seaman, see Appendix 2; Holbrook, Unpublished
Data), which possesses a fertilized lawn, has a fish population which is artificially fed, and has a
healthy waterfowl population, all of which can contribute to downstream eutrophication.
Indeed, the output from Lake Susan causes a noticeable increase in algal growth downstream of
the dam, which in turn increases food availability for herbivorous macro invertebrates. The
increase in EPT family richness downstream indicates that despite the increase in N and P
levels, water quality at these sites remains good, thus there is no apparent biological indication
that water quality is being significantly affected by stormwater runoff in Montreat, NC with the
caveat that the sampling period did not occur during any particularly heavy rain event, where
siltation events are known to occur from residences or mudslides (Holbrook, unpublished).

Figure 1c.
South Site - Avg. Depth
45
40
35
u 30
s 25
ii
p 20
own 15
Q 10
5
0
O° O° O° .O° O° O° O° O° O° .O°
O° O° 00 O°
e�V o\��ti o�e�ti�\� a�ti�\� ti°~\� ti°°\� tio�ti�\� 10tio\ti
Figure 2: Mean flow rate based on n=3 samples (August -October, 2020) of three sites along Flat
Creek in gallons per minute.
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
Mean Flow Rate
Flow Rate (GPH)
■ North Site ■ Central Site t. South Site

Fig. 3c
South Site - Temp
As]
55
45
40
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Fig. 3d
18.5
18
17.5
16
15.5
15
Mean Water Temp.
North Site Central Site South Site
■ Avg. Water Level

AIk
pH
M91L
22.3"
7.0"
1•
4.0
6.6
5.0
6.6
7.0
6.8
7.0
6.7
11.0
7.1
9.0
6.9
9.0
7.0
11.0
7.0
13.0
7.2
6.5
6.5
6.7
6.7
6.8
6.0
6.8
5.0
6.8
5.0
6.7
6.0
6.8
8.0
6.9
5.0
6.6
6.0
6.6
6.0
6.7
6.0
6.7
6.0
6.7
8.0
6.6
6.0 ---
6-1-
10.0
6.7
12.0
6.7
8.0
6.8
4.0
6.5
4.0
6.6
5.0
6.6
6.0
6.7
5.0
6.7
6.0 7.1
6.0 7.0
4.0 6.8
&0 6.8
7.0 6.8