HomeMy WebLinkAboutSec B Ch 4 03-08-33
Section B - Chapter 4
Dutchmans Creek, McDowell Creek and Mountain Island Lake
Catawba River Subbasin 03-08-33
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4.1 Subbasin Overview
This subbasin is located in the Southern Outer Piedmont
ecoregion. The largest watershed in this subbasin is
Dutchmans Creek, formed by the confluence of Leepers
and Killian Creeks. Dutchman's Creek flows into the
Catawba River just downstream of Mountain Island Lake.
Streams in the subbasin are often sandy, low gradient
streams. Land use is primarily forested. The largest
discharger in this subbasin is the Charlotte/Mecklenburg
Utilities District which discharges 3 MGD into McDowell
Creek.
Urbanization is a significant threat to water quality in this
basin as some of the fastest growing communities in the
state are located within it (Table A-7). Recognizing this
threat, local governments have begun implementation of
innovative management strategies to reduce
urbanization’s negative impact on water quality.
There are six facilities in this subbasin required to monitor
effluent toxicity. Five facilities have passed all required
toxicity tests. The CMUD/McDowell Creek WWTP has
had three failing tests since 1997. The most recent
failings were in 2000 and thought to be due to sample
contamination. Otherwise, there have been no toxicity
failures since the plant disinfection process was converted from chlorine to ultra-violet (UV) in
1998.
Land and Water Area
Total area: 220 mi2
Land area: 216 mi2
Water area: 4 mi2
Population Statistics
2000 Est. Pop.: 117,621 people
Pop. Density: 546 persons/mi2
Land Cover (percent)
Forest/Wetland: 69%
Surface Water: 2%
Urban: 2%
Agriculture: 27%
Counties
Catawba, Gaston, Lincoln and
Mecklenburg
Municipalities
Cornelius, Huntersville, Mount
Holly and Stanley
Subbasin 03-08-33 at a Glance
There are three ambient monitoring sites located in this subbasin: Mountain Island Lake above
Gar Creek, Dutchmans Creek at SR 1918, and the Catawba River at NC 27. All three sites have
exhibited elevated conductivity since the middle and late 1990s.
There were four benthic macroinvertebrate community samples and four fish community
samples (Figure B-4 and Table B-7) collected during this assessment period. Three sites had
lower bioclassifications, and one site was sampled for the first time during this assessment
period. Refer to 2003 Catawba River Basinwide Assessment Report at
http://www.esb.enr.state.nc.us/bar.html and Section A, Chapter 3 for more information on monitoring.
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 137
Table B-7 DWQ Assessment and Use Support Ratings Summary for Monitored Waters in Subbasin 03-08-33
Biological Ambient Other 2004 1998
CATAWBA RIVER (Lake
Wylie below elevation 570)11-(117) WS-IV CA 375.3 ac.AL C3900000 nce L-1 nce NR FS
CATAWBA RIVER
(Mountain Island Lake below
elevation 648)11-(112) WS-IV CA 389.4 ac.AL C3699000 nce L-1 nce S FS
CATAWBA RIVER
(Mountain Island Lake below
elevation 648)11-(114) WS-IV & B CA 1,937.1 ac.AL C3699000 nce L-1 nce S FS
Dutchmans Creek 11-119-(0.5) WS-IV 7.4 mi.AL C3860000 nce S FS
Killian Creek 11-119-2-(0.5)a C 11.6 mi.AL
F-2 G--97
F-2 GF--02 SFS
Killian Creek 11-119-2-(0.5)b C 3.2 mi.AL
B-3 G--97
B-3 F--02 IFS
McDowell Creek 11-115-(1.5)a WS-IV 4.4 mi.AL
F-1 F--97
F-1 P--02 IPS
McDowell Creek 11-115-(1.5)b WS-IV 2.9 mi.AL B-1 F--02 IPS
CATAWBA RIVER (Lake
Wylie below elevation 570)11-(117) WS-IV CA 375.3 ac.REC C3900000 nce S -
CATAWBA RIVER
(Mountain Island Lake below
elevation 648)11-(114) WS-IV & B CA 1,937.1 ac.REC C3699000 nce S -
Dutchmans Creek 11-119-(0.5) WS-IV 7.4 mi.REC C3860000 nce S -
Assessment Unit Number - Portion of DWQ Classified Index where monitoring is applied to assign a use support rating.
Use Categories:Monitoring data type: Use Support Ratings 2004:
AL - Aquatic Life F - Fish Community Survey E - Excellent S - Supporting, I - Impaired, NR - Not Rated
REC - Recreation B - Benthic Community Survey G - Good
L - Lakes Assessment GF - Good-Fair Use Support Ratings 1998:
F - Fair FS - fully supporting
P - Poor PS - partially supporting, NS - not supporting
nce - no criteria exceeded
ce - criteria exceeded
Bioclassifcations:
Ambient Data
DWQ Classification
Assessment Unit
NumberWaterbody Length / Area
Data Type with Map Number
and Data Results
Use Support Rating
Category
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 139
Based on past benthic macroinvertebrate data, Dutchmans and Killian Creeks received either
Excellent or Good bioclassifications, and McDowell Creek a Good-Fair. In 2002, benthic
macroinvertebrate data from Dutchmans Creek declined to Good-Fair, and Killian and
McDowell Creeks declined to Fair. Similar trends were observed for the fish community at
McDowell Creek, which declined from Fair in 1997 to Poor in 2002; and in Killian Creek, which
declined from Good in 1997 to Good-Fair in 2002. The lower benthic macroinvertebrate and
fish bioclassifications were likely the result of the prolonged drought in Killian Creek, while the
lower bioclassifications in McDowell Creek were likely the result of expanding urbanization
surrounding the City of Charlotte. Remaining benthic macroinvertebrate sites which declined in
2002 from previous samples were likely due to extended low flows from the drought.
Mountain Island Lake is located on the Catawba River downstream of Lake Norman. In 2002, it
was classified as oligotrophic and received the lowest trophic scores since 1981. Nutrient levels
in 2002 were generally lower than measured in the past, and lakewide Secchi depths were
correspondingly high. These improved conditions might have been due to decreased runoff as a
result of the drought. The noxious exotic macrophyte, Hydrilla, is established and covers more
than 600 acres. To manage it, grass carp were stocked in 2000 and 2002.
Waters in Parts 4.3 and 4.4 are identified by assessment unit number (AU#). This number is
used to track defined segments in the water quality assessment database, 303(d) Impaired waters
list, and the various tables in this basin plan. The assessment unit number is a subset of the
DWQ index number (classification identification number). A letter attached to the end of the
AU# indicates that the assessment is smaller than the DWQ index segment. No letter indicates
that the assessment unit and the DWQ index segment are the same.
Use support ratings are summarized in Part 4.2 below. Recommendations, current status and
future recommendations for waters that were Impaired in 1999 and newly Impaired waters are
discussed in Part 4.3 below. Supporting waters with noted water quality impacts are discussed in
Part 4.4 below. Water quality issues related to the entire subbasin are discussed in Part 4.5.
Refer to Appendix III for use support methods and more information on all monitored waters.
4.2 Use Support Assessment Summary
Use support ratings in subbasin 03-08-33 were assigned for aquatic life, fish consumption,
recreation and water supply. All water supply waters are Supporting on an Evaluated basis based
on reports from DEH regional water treatment plant consultants. Refer to Table B-8 for a
summary of use support ratings by use support category for waters in the subbasin.
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 140
Table B-8 Summary of Use Support Ratings by Use Support Category in Subbasin 03-08-33
Use Support
Rating
Aquatic
Life
Fish
Consumption Recreation Water
Supply
Monitored Waters
Supporting 18.93 mi
2,701.7 ac 0 7.4 mi
2,312.4 ac 0
Impaired 10.4 mi 0 0 0
Not Rated 3.4 mi.0 0 0
Total 32.7 mi
2,701.7 ac 0 7.4 mi
2,312.4 ac 0
Unmonitored Waters
Supporting 0.0 mi 0 0 53.5 mi
2,701.7 ac
Impaired 0.0 mi 133.88 mi
375.29 ac 0 0
Not Rated 37.2 mi 0 0 0
No Data 92.2 mi 28.2 mi
2,326.41 ac
154.8 mi
389.3 ac 0
Total 129.4 mi 162.1 mi
2,701.7 ac
154.8 mi
389.3 ac
53.5 mi
2,701.7 ac
Totals
All Waters 162.1 mi
2,701.7 ac
162.1 mi
2,701.7 ac
162.1 mi
2,701.7 ac
53.5 mi
2,701.7 ac
Note: All waters include monitored, evaluated and waters that were not assessed.
4.3 Status and Recommendations of Previously and Newly Impaired
Waters
The following waters were identified in the 1999 basin plan as Impaired or are newly Impaired
based on recent data. The current status and recommendations for addressing these waters are
presented below. These waters are identified by assessment unit number (AU#). Refer to the
overview above for more information on AUs.
4.3.1 McDowell Creek [AU# 11-115-(1.5)a and 11-115-(1.5)b]
Current Status and 2004 Recommendations
McDowell Creek is a tributary to the upper reaches of Mountain Island Lake and drains the
rapidly growing suburban areas of the towns of Cornelius and Huntersville and the lands
between Interstate 77 and Lake Norman.
In 1999, DWQ noted that bank erosion in McDowell Creek was severe and instream habitat was
generally poor. The basinwide plan also mentioned that upgrades to the Charlotte-Mecklenburg
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 141
Utilities WWTP had resulted in reduced nutrient loads. DWQ suggested that local initiates be
pursued to find solutions to habitat degradations.
Site B-1 was added in 2002 by DWQ as a basinwide monitoring site to track this rapidly
developing portion of Mecklenburg County. The site was previously monitored in 1990 and was
given a Good-Fair bioclassification. In 2002, the bioclassification declined to Fair. Upstream at
site F-1, the bioclassification declined from Fair in 1997 to Poor in 2002. The upper 7.2 miles of
McDowell Creek (US Hwy 21 to SR 2136) are Impaired for aquatic life because of the
bioclassifications at site B-1. The downstream 2.7 miles (SR 2136 to Mountain Island Lake) are
Not Rated because there is no sample site on this segment. It should be noted that no visible
difference in stream quality exists between the up and downstream segments.
Water quality data colleted by the Mecklenburg County Water Quality Program (MCWQP) since
1988 also indicates a significant decline in water quality conditions in McDowell Creek and the
cove in Mountain Island Lake where the creek drains. These declining water quality conditions
are being caused by the increased discharge of pollutants carried in stormwater runoff from
rapidly increasing impervious cover (parking lots, roads, houses, etc.) and construction activities
in the McDowell Creek watershed. Sediment from construction sites, nutrients from lawn
fertilizers, and heavy metals (lead, chromium and zinc) from parking lot and road runoff are the
primary culprits. Currently, water quality in McDowell Creek Cove is ranked as "POOR" by
Mecklenburg County and consistently ranks as one of the lowest water quality sites in the
county.
To assess the impacts from future development in this watershed, MCWQP completed a water
quality model for the McDowell Creek watershed that indicates a significant increase in pollutant
loads as the area approaches build out. If left unchecked, the poor water quality conditions in
McDowell Creek and McDowell Creek Cove will persist and could impact the quality of the
water at Charlotte-Mecklenburg Utilities (CMUD) drinking water intake located downstream.
The quality and usability of McDowell Creek Cove as a recreational area are also threatened by
sediment depositions that decrease water depth and impair navigation.
Town of Huntersville Role:
In October 2002, the Huntersville Town Board adopted a "non-degradation" goal for the
McDowell Creek watershed to halt the declining water quality trends. The board later expanded
this goal to include all the surface waters within its jurisdiction. The board further requested that
the MCWQP work with town staff to develop a post-construction ordinance to ensure that this
was fulfilled. In response to this request, a Low Impact Development (LID) Ordinance was
drafted by staff and approved by the Town Board in February 2003.
Huntersville’s decision to adopt LID standards is based on the fact that a developed site can be
designed as an integral part of the environment, and thus, serves to protect existing water quality
conditions through the careful use of design principles that seek to mimic natural site hydrology.
In some applications, LID designs can also significantly reduce development costs with the
reduction of impervious surfaces (roadways), curb and gutters; use of less storm drain piping;
and elimination of large stormwater ponds. Reducing site development infrastructure also
reduces associated project, bonding and maintenance costs. Refer to Section A, Chapter 4, Part
4.11.
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 142
Mecklenburg County’s Role:
Mecklenburg County’s Water Quality Program is providing support to the Town of Huntersville
through plan reviews and inspections to ensure compliance with the new ordinance. In addition,
Mecklenburg County has agreed to install BMPs in critical areas of the McDowell Creek
watershed to remove nonpoint source pollutants from development activities that occurred prior
to the adoption of the Huntersville ordinance. The combination of the implementation of
Huntersville’s new water quality ordinance and the installation of retrofit BMPs will work
toward reversing negative water quality trends in McDowell Creek and result in the ultimate
improvement of overall water quality conditions. Mecklenburg County has already purchased
properties at several locations in the watershed and is currently working to secure Clean Water
Management Trust Fund grants to install BMPs at these sites.
Charlotte-Mecklenburg Utilities Role:
Charlotte-Mecklenburg Utilities (CMUD) received a permit modification to expand the
McDowell Creek WWTP (NC0036277) located in the lower reaches of the watershed near
Mountain Island Lake. In its plans for stepped plant expansion to 12 MGD (6.6, 9.0, 12.0
MGD), CMUD has included the treatment systems necessary to prevent an increase in existing
pollutant loads. In addition, CMUD will be expanding current nutrient removal systems at the
plant. The schedule is to complete construction to treat 9.0 MGD in 2005 and finish construction
to treat 12.0 MGD in 2007.
North Carolina’s Role:
Without state assistance, Huntersville and Mecklenburg County will be unable to fund the efforts
necessary to reverse the negative water quality trends in McDowell Creek. Funding from
programs such as the Clean Water Management Trust Fund and the Section 319 Program is
essential. State support is needed to ensure that this funding is made available.
DWQ applauds the cooperation, foresight and initiative demonstrated by all the parties involved
in the effort to reverse water quality impairment in McDowell Creek. The McDowell Creek
watershed offers several unique opportunities. MCWQP has over 20 years worth of water
quality data for McDowell Creek and Cove and continues to maintain a very extensive
monitoring network to measure the effectiveness of efforts to restore water quality. This
provides an opportunity to test the effectiveness of LID on a watershed scale and also to test the
effectiveness of regional BMPs as a retrofit in a developing watershed. This also creates a
unique opportunity to evaluate modeling as a tool for ordinance development and
implementation.
Over the next basin cycle, DWQ will work to provide Huntersville and Mecklenburg County
with the necessary support to continue their BMP implementation program. Additionally, DWQ
will seek guidance from Huntersville and Mecklenburg County as it encourages the development
of similar programs across the Catawba River basin.
4.3.2 Killian Creek [AU# 11-119-2-(0.5)b
Current Status and 2004 Recommendations
Killian Creek is a tributary to upper Dutchmans Creek in southeastern Lincoln County. In 1992
and 1994, the stream received an Excellent bioclassification, Good in 1997, and Fair in 2002.
Because of the Fair bioclassification at site B-3 in 2002, 3.2 miles (from Anderson Creek to a
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 143
point 1.2 miles upstream of mouth) are Impaired. Flows were less than 20 percent of historical
median flow during the 2002 sampling and likely influenced the water quality decline. The
decrease in bioclassification may also be due to reduced dilution of instream wastes from the
Forney Creek and Fa Be Enterprises WWTPs. These facilities discharge to Forney Creek, a
tributary to Killian Creek. There is no evidence to suggest these facilities are operating
improperly or violating their current permits. DWQ will continue to monitor this creek in the
next basin cycle.
4.4 Status and Recommendations for Waters with Noted Impacts
The surface waters discussed in this section are not Impaired. However, notable water quality
problems and concerns have been documented for some waters based on this assessment. While
these waters are not Impaired, attention and resources should be focused on these waters to
prevent additional degradation or facilitate water quality improvement. Waters in the following
section are identified by assessment unit number (AU#). See overview for more information on
AUs.
4.4.1 Mountain Island Lake [AU# 11-(112) and 11-(114)]
Current Status and 2004 Recommendations
Mountain Island Lake is operated by Duke Power and is located on the Catawba River
downstream from Lake Norman. The reservoir is used as a water supply for the City of
Charlotte and to generate electricity at the Riverbend Steam and Mountain Island Stations.
The reservoir was most recently monitored by DWQ in 2002. The lake was classified as
oligotrophic; nutrient concentrations were generally lower than those observed in the past, and
lake-wide Secchi depths indicated good water clarity. Decreased nutrient concentrations and
greater water clarity may have been due to the drought conditions, which decreased nonpoint
source runoff throughout the basin. Prior to 2002, the most recent monitoring was conducted in
1997.
Hydrilla is established in the reservoir and covers approximately 625 acres (Bonham, 2001).
The exotic macrophyte was observed in the upper end of the reservoir in 2002. Grass carp were
first stocked in 2000 as a possible biological control agent for this plant. In 2002, an additional
20,000 fish were stocked. Duke Power, along with stakeholders and DWQ, will continue to
develop and implement an invasive plant management program for the reservoir.
Extensive management efforts are underway in the McDowell Creek Cove area of Mountain
Island Lake. Please refer to the discussion of McDowell Creek (Section B, Chapter 4, Part 4.3.1)
for a detailed description of those activities.
4.5 Additional Water Quality Issues within Subbasin 03-08-33
4.5.1 Water Quality Threats to Streams in Urbanizing Watersheds
Subbasins in and around the Greater Charlotte Metropolitan Area are experiencing rapid growth
as new homes and businesses sprout up on old farms and forests. This development places
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 144
intense pressure on the sensitive stream communities within those basins. In order to prevent
aquatic habitat degradation and Impaired biological communities, protection measures should be
put in place immediately. Refer to Section A, Chapter 4, Parts 4.11 and 4.13 for a description of
urban stream water quality problems and recommendations for reducing impacts and restoring
water quality.
Section B: Chapter 4 - Catawba River Subbasin 03-08-33 145