NC0036277_Environmental Assessment_19950109

MPDE5 D0Ci WEMT ';CAMM1M6 COVER SHEET
NPDES Permit:
NC0036277
McDowell Creek WWTP
Document Type:
Permit Issuance
Wasteload Allocation
Authorization to Construct (AtC)
Permit Modification
Complete File - Historical
Engineering Alternatives (EAA)
Correspondence
Instream Assessment (67b)
Speculative Limits
Environmental Assessment (EA)
Document Date:
January 9, 1995
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content on the reverse side

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State of North Carolina
Department of Environment,
Health and Natural Resources
Division of Environmental Management
James B. Hunt, Jr., Governor
Jonathan B. Howes, Secretary
A. Preston Howard, Jr., P.E., Director
January 9, 1995
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TO: Coleen Sullins, Permits and Engineering
FROM: Monica Swihart,.�nWater Quality Planning
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SUBJECT: EA/FONSI- McDowell Creek Wastewater Treatment Plant
Expansion, NPDES No. NC0036277, Catawba Basin 03-08-34
The subject document was circulated through the State
Clearinghouse for review. Based on the results of this review,
Chrys Baggett issued a January 5, 1995 letter (copy attached)
stating that the EA/FONSI for the subject project has met the
requirements of the NC Environmental Policy Act (NCEPA) and that no
further environmental review action under the NCEPA is required.
In light of the State Clearinghouse Director's letter, permit
processing and issuance, if appropriate, may proceed. The EA
includes a number of mitigation measures aimed at minimizing the
adverse direct and secondary environmental impacts associated with
the proposed project. Therefore, it is recommended that the permit
incorporate a condition that the work be done in accordance with
the mitigation measures outlined in the EA/FONSI.
Please do not hesitate to contact me if you have any
questions.
Attachment
cc: Rex Gleason
Melba McGee (reference #671)
David Parker, Black & Veatch
Barry Gullet, CMUD
P.O. Box 29535, Raleigh, North Carolina 27626-0535 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50%recycled/ 10% post -consumer paper

James B. Hunt Jr., Govemor
North Carolina
Department of Administration
January 51 1995
Ms. Monica Swihart
N.C. Department of Environment, Health,
and Natural Resources
Division of Environmental Management
Archdale Building
Raleigh, North Carolina 27611
Dear Ms. Swihart:
Katie G. Dorsett, Secretary
Re: SCH File #95-E-4300-0297; Environmental Assessment and Finding
of No Significant Impact for the Charlotte -Mecklenburg Utility
Department - McDowell Creek Wastewater Treatment*Plant Expansion
The above referenced environmental impact information has been
reviewed through the State Clearinghouse under the provisions of the
North Carolina Environmental Policy Act. No comments were made by
any state/local agencies in the course of this review. Therefore, no
further environmental review action on your part is required for the
compliance with the Act.
Best regards.
Sincerely,
Ms. Chrys Baggett, Director
State Clearinghouse
CB/jf
cc: Region F
116 West Jones Street • Raleigh, North Carolina 27603-8003 • Telephone [phone]
State Courier 51-01.00
An Equal opportunity / Affirmative Action Employer

Vl. ENVIRONMENTAL CONSEQUENCES AND MITIGATIVE
MEASURES
Expansion of the McDowell Creek WWTP utilizes the existing facilities on the
existing
site as well as the construction of new facilities on the existing site. The
,
following impacts have been considered:
Changes in band Use. The expansion of the McDowell Creek WWTP will be
constructed on the existing plant site. No additional land will be required, so no
change in land use will result. This WWTP expansion was anticipated by the
Mg
ecklenbur County Planning Commission as described in the "NorthDistrict Plan,
and is allowed according to the zoning ordinances for the Mountain island Lake
Watershed Overlay District.
(Changes es in land use in the McDowell Creek service area are addressed as
secondary impacts in the following section.)
Mitigative measures: None required.
rbing activities for the construction of the WWTP
Wetlan
ds. All land distu
exp
ansion will occur in upland areas. Potential wetland sites along Mountain Island
Lake McDowell Creek, and an unnamed tributary to McDowell Creek will not be
impacted. Two letters were sent to the Department of the Army, Corps of Engineers
informing them of the proposed WWTP expansion and soliciting comments or
concerns regarding the effect the proposed expansion would have on wetlands in the
g g
surrounding urroundin area. A copy of each letter sent to the Department of the Army Corps
of Engineers is found in Appendix A.
Mitigative measures: None required.
Prime 'and Unique Agricultural Lands. The site of the plant expansion is owned
by
CMUD. There is no change in land use and no adverse impact to prime and
unique uniqagricultural lands. The solids management modifications proposed will not
affect the areas where the solids are accepted for land `application. A copy of the
letter sent to the North Carolina Division of Soil and Water Conservation soliciting
concerns and comments regarding this issue is included in Appendix A.
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Mitigative measures: None required.
Public Lands. No public lands will be affected because all construction work will
be confined to the existing site. The public land in the service area includes a wildlife
refuge along the Catawba River between Mountain Island Lake and Lake Norman.
Mitigative measures: None required.
Scenic and Recreational Areas. Because the project is an expansion of an existing
plant, there will be no impact on the scenic or recreational value of the area other•
than the potential for continued improvements to water quality in McDowell Creek
and Mountain Island Lake.
Mitigative measures: None required.
Areas of Archeological or Historic Value. Just north of the McDowell Creek
WWTP is the site of an old plantation owned by the Davidson family. The plantation
is known as "Rural Hill." This historic site will not be impacted by the expansion.
All construction activity related to the expansion will occur onsite; therefore, potential
archeological or historic sites in the area will not be affected. A copy of a letter sent
to the North Carolina Department of Cultural Resources Division of Archives and
History soliciting concerns and comments regarding this issue is included in
Appendix A.
Mitigative measures: None required.
Air Quality. Construction -related activities may have a temporary impact on air
quality in the vicinity of the WWTP. Air pollution that may occur includes
windblown dust and engine exhaust. The McDowell Creek WWTP expansion will not
create any increased odor potential associated with the treatment process. Odor
control is a lesser concern than it might otherwise be due to the remote location of
the facility.
Mitigative measures: Control measures for construction -related air pollution must
be enforced.
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i • ' 11/01/94 21: 43 a.AC� & VEATC H y 919 733 �. 99.19
I
Groundwater Qualrt�. Groundwater quality will not be affected. All process
basins are fully contained. By expanding the treatment capacity, groundwater quality
in the area served may improve because of the reduction in the number of septic
systems.
Mitigative me,,asuresj None required.
Noise Levels, Except during construction, noise levels generated by the plant will
not be appreciably changed. Some additional noise will be generated by the use of
additional process equipment, but this noise will be negligible due to the installation
of the equipment inside the plant's facilities And the remote location of the WWTP.
Construction noise will include that typically associated with industrial
construction (i.e., operation of heavy equipment). This noise is not expected to cause
any problems, primarily' due to the remote location of the W'WTP.
Mitigative meavures{ None required,
Water Supplies. affluent from the expanded treatment plant will enter
McDowell Creek and flow into the Mountain Island Lake, The quality will be
improved over that discharged at present; therefore, the usage potential of
Mountain ,island Lake should not be degraded.
Although the volume of wastewater discharged from the McDowell 'WWTP will
be increased by 3 ingd, this increased flow will not adversely affect any water
supplies. Based on water quality modeling performed by DEM, permit limits will be
established to maintain' and protect the water quality. The improved treatment
capabilities of the expanded plant will ensure that the plant effluent will consistently
meet the permit limits,Isc) no adverse impacts to water supplies will result.
Mitigallve mea rul
operated and that
standards are not
Shel4B-h or Fish at
over the last 30
Mecklenburg County,
based on proximity of i
number of species oo
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EA-RPT.WP5
None required, but it ry essential that the WWTP be well
e of fluent be monitored. This will ensure that the water quality
711eirHabitat. Thirty-six species of fish -have been reported
:ars from the Catawba drainages of northwestern
mother nine species of fish may be expected to occur there
ighboring collections. This is about IS percent less than the
rring in similar -sized drainages of the lower Piedmont of
17

North Carolina and indicates long-term pollution primarily due to siltation from
agriculture.
A survey of fishes, mollusks, and water quality (Environmental Assessment of
Fishes, Mollusks, and Water Quality --North Mecklenburg Water Treatment Plant --
Mecklenburg County, North Carolina, May 1993) was performed for a proposed
drinking water plant along McDowell Creek. The only sign of any mollusks was a
badly eroded shell of an Asiatic clam (Corbicula fluminea). No dead shells were seen
along banks where they tend to accumulate. No exposed siphons were seen in silty
areas where they would be expected to be visible. No mussels were collected by
feeling in silty areas near or under banks.
Effluent from the WWTP expansion will maintain or improve upon current
effluent requirements. No impact to aquatic wildlife is expected from this project.
A letter was sent to the North Carolina Division of Marine Fisheries to solicit
concerns or comments regarding the proposed WWTP expansion. A copy of this
letter is included in Appendix A.
Mitigative measures: None required.
Wildlife and Their Habitat (Including Endangered Species). All activity related to
the WWTP � expansion will occur on the current plant site and will not involve
it
Additional clearing. Therefore, wildlife and their habitat will not be affected by this
WWTP expansion.
As a precaution, letters were sent to the North Carolina Division of Parks and
Recreation and to the North Carolina Division of Wildlife Management specifically
requesting a listing of endangered species (both plant and animal) that may reside
on the WWTP site. A copy of these letters is provided in Appendix A.
Mitigative measures: None required.
Toxic Substances. Anticipated chemicals that will be added in the, treatment
process are lime and polymer. Lime and polymer will be used as coagulants and to
condition sludge. Some toxic substances, such as cleaners, paint, petroleum products,
etc., may enter the wastewater. These are in very low concentrations in the plant
effluent. The WWTP improvements include utilizing UV disinfection to replace
chlorination. This will simultaneously preclude the use of chemical dechlorination
and ensure a chlorine free effluent, which may decrease the toxicity of the plant
effluent.
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Mitigative measures: None required.
Eutrophication of Receiving Waters. Water quality sampling by Mecklenburg
County and modeling by DEM confirm that eutrophication occurs at the confluence
of McDowell Creek and Mountain Island Lake. Both nitrogen and phosphorus are
believed to contribute toward increased eutrophication. As such, both of these
nutrients are of concern, especially in the late summer months when these nutrients
accumulate in the cove. During this time, non -point source pollution is lowest
(because rainfall is low) and the McDowell Creek WWTP becomes the primary
source for these nutrients. More detailed computer modeling of this confluence may
help to confirm this assessment of the sampling data (to be performed by DEM in
late 1994).
Speculative limits assigned by DEM include both a total nitrogen and total
phosphorus limit for the expansion of the McDowell Creek plant to 6.0 mgd. These
new limits will improve water quality in the Mountain Island Lake cove, according to
preliminary modeling by DEM.
Another requirement imposed on the expansion of the McDowell plant pertains
to a zoning regulation promulgated with the development of the "Mountain Island
Lake Watershed Protection Study" for DEP. Mecklenburg County zoning regulations
for the Watershed Protection Overlay District states that 'Discharges associated with
the existing public utilities may be expanded, however the pollutant load shall not be
increased beyond presently permitted levels.". Expansion of the McDowell Creek
plant was anticipated when the Watershed Protection Study was performed, with the
assumption that pollutant loads from the WWTP would not change from existing
levels when the study was performed. The plant expansion was supported over other
alternatives (such as package plants) by local environmental groups participating in
the study. The intent of the zoning ordinance is to allow the WWTP capacity to
increase, while regulating the facility such that the water quality in the lake is
protected. This requirement will be satisfied by establishing more strict effluent limits
which will result in improved water quality in McDowell Creek and Mountain Island
Lake.
The current NPDES permit for the plant includes limits on BOD, NH3, and total
suspended solids (TSS). Preliminary modeling of McDowell Creek and the cove in
Mountain Island Lake has indicated that the permit level of these constituents is
already sufficiently low, even at double the existing capacity, to pose no significant
impact to the water quality. However, this modeling has also indicated that nitrogen
and phosphorus levels in the plant effluent will likely have a significant impact on
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9

water quality. These nutrients, which are not currently regulated, can contribute to
increased algae growth and eutrophication. Limits on total nitrogen and phosphorus,
therefore, have been proposed by DEM to protect and improve water quality.
Mitigative measures: The proposed WWTP expansion shall be designed to comply
with all NPDES permit limits. The speculative limits imposed by DEM for nitrogen
and phosphorus are at the limits of technology for what can be achieved by
conventional treatment. This will require the construction of biological phosphorus
and nitrogen removal, and effluent denitrifying sand falters. A limit on chlorine
residual in the effluent was also included. Ultraviolet disinfection will be installed
as part of the expansion, and the effluent sand filters will provide total effluent solids
well below the speculative limits.
Forest Resources. There will be no impact to the woodlands and related
resources in the area because the proposed construction activity will take place on
land owned by CMUD, currently utilized by the WWTP and previously cleared.
Mitigative measures: None required.
Erosion Control. McDowell Creek will not be directly impacted by construction;
but indirect impacts, such as increased runoff and siltation during construction, may
occur.
Mitigative measures: Appropriate measures will be taken to assure that earth
moving activities required for construction do not adversely impact surface water by
increasing overland flow and the sedimentation and scour that may result. Silt
fences, bales, and other devices will be utilized to prevent sediment from entering the
stream with runoff from the construction areas.
Control of erosion and sedimentation to minimize water quality impacts to
McDowell Creek and Mountain Island Lake will be included in the construction
project. An approved sedimentation and erosion control plan will be obtained from
the North Carolina Department of Environment, Health, and Natural Resources
(DEHNR) Land Quality Section prior to the start of construction.
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V. SECONDARY IMPACTS
In addition to those impacts normally associated with discharge of treated
wastewater effluent (see discussion under "Environmental Consequences"), the
following secondary impacts to the proposed project have been considered:
Increased Plant Operations. The increased VVWTP capacity will result in
continued and increasing expenditure of labor, chemicals, and energy for operation
and maintenance. These adverse impacts should be offset by improved water quality
in McDowell Creek, Mountain Island Lake, and local ground water supplies.
Mitigative, measures: None required.
Land Use Changes in the WWTP Service Area. Land use changes will result in
changes of non -point pollution loading pattern. Increased development is a goal of
the City of Charlotte and Mecklenburg County. The WVVTP facility expansion is
occurring in response to the new growth, and is intended to prevent an inhibition of
development that would_ occur without necessary services such as water and sewer
facilities.
Mitigative measures: Enforcement of the county's land use plan, zoning regulations,
and floodplain management program will minimize adverse impact from
development. The city and county must use local development controls, such as
zoning subdivision regulations, sewer tap permits, and building permits, to prevent
incompatible land uses brought about by future growth and development. The
Watershed Protection Zoning Ordinances for the Mountain Island Lake watershed
dictate acceptable densities for development, require best management practices to
help control runoff and pollution, and establish buffer zones along the lake and
streams These buffer zones will also provide protected areas where development will
be restricted, effectively reserving some undeveloped areas throughout the area.
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