WQ0002284_Correspondence_20020507

DIVISION OF WATER QUALITY
GROUNDWATER SECTION
May 3, 2002
MEMORANDUM
To: Kim Colson
cc: Willie Hardison, GWS-RO -- —
Through: Debra Watts !J/`^l� MAY 7 2002
From: David GoodrichV,
Subject: Outer Banks — Kinnakeet Shores / Changeover from Rotary to Reuse System
Dare County
W00002284/GW02027
The Groundwater Section is in receipt of the subject application to change an existing
rotary wastewater treatment system which currently treats the domestic wastewater generated by the
Kinnakeet Shore residential subdivision to a higher -capacity reuse system. The present system utilizes
two high -rate infiltration rotary beds. The existing permit was issued on December 13, 2001 and allowed
the applicant to construct and operate a new 220,000 GPD system which could utilize four 100-foot
diameter rotary distributor units. The existing permit requires the sampling of four monitoring wells
(MW-1, 2, 3, and 4) every February, June, and September for Water Levels, pH, Fecal Coliforms, Nitrate
Nitrogen, Chloride, TDS, TOC, Ammonia Nitrogen, and Volatile Organic Compounds (in November
only). These four monitoring wells were destroyed when dredge material was deposited on the site in the
year 2000. The Groundwater Section's comments were issued after the present permit was issued, and
recommended that five new (replacement) wells (MW-5, 6, 7, 8, and 9) be sampled for the parameters
previously listed.
The compliance monitoring data for this facility was examined to determine the effect of
the rotary distributors on the groundwater quality. Data was missing for the 1999 calendar year. The
historical water level data indicated the existence of groundwater mounding at all four of the former
wells. The sampling data indicated elevated concentrations of TSS in monitoring wells MW-1 and MW-
4. Total Dissolved Solids (TDS) were found to be elevated in monitoring wells MW-1 and MW-2, and
exceedances of the Groundwater Quality Standards were detected in monitoring wells MW-3 and MW-4.
Concentrations of Nitrate Nitrogen which exceeded the Standards were detected in all four wells
between 1995 and 1997. The facility is now under new management and improvements to the system
have reportedly been made. The management intends to convert the treatment system from a rotary
system to a spray reuse system, and it is the understanding of the Groundwater Section that the intended
construction activities will destroy the five existing monitoring wells.
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According to the subject application package, wastewater treatment will be performed by
a new 350,000-gallon/day capacity reuse system (see Figures 1 and 2). The wastewater is projected to be
90% domestic and 10% non -industrial, with a portion reportedly taken from strip malls. The new
treatment system will not utilize a rotary distributor system. Under normal operating conditions, the
reuse system will use the 1,800,000-gallon, lined 5-day sidestream pond for the storage of effluent which
does not meet the reuse standards. In addition to meeting the standards of reuse water, the waste stream
will undergo denitrification and the concentration of Nitrate Nitrogen will reportedly be reduced to a
level below the 2L Groundwater Quality Standard concentration of 10 mg/L. The facility will spray
irrigate up to 350,000 gallons of reuse -quality water per day onto approximately 30 acres of lawn areas
in the Kinnakeet Shores residential community. This application rate is equal to approximately 0.43
inches per day over the intended application area.
A 5,097,095-gallon unlined infiltration pond will be utilized (in place of rotary
distributors) under conditions of inclement weather (or a plant upset) and allow the infiltration of
199,027 gallons of treated effluent per day (see Figure 2). The infiltration pond will have an infiltration
rate of 1.49 gallons per day per square foot, which is just below the "High Rate" classification standard
of 1.50 gallons per day per square foot. The mounding beneath the infiltration pond will be controlled by
a drainage ditch to the West and Northwest (see Figure 2). The present chlorination disinfection system
will be replaced by ultra -violet disinfection. A turbidimeter will be used to control the storage of the
effluent and will divert it from the irrigation pond to a non -compliant storage basin if it senses a
reduction in the quality of the effluent.
The treatment requirements for reuse quality effluent, as defined under 15A NCAC 2H
.0219(k)(1)(A)(iii), is met by this system, thus both the Compliance Boundary and the Review Boundary
are situated at the property line. The. maps submitted with the application suggest spray patterns which
include roads, sidewalks, and the berms of proposed ponds. The spray patterns should be examined
upon installation to ensure that the spray patterns are conTned to the lawn areas.
The site was hydrogeologically characterized and modeled by a consultant to evaluate its
ability to accommodate the intended (and potential) loadings from the perspectives of hydraulics and the
potential transport/migration of possible contaminant substances. The previous modeling indicated that
mounding would take place beneath the spray application areas (lawns), the proposed infiltration pond,
and the rotary distributors. Although none of these applications will be continuous, the most nearly
continuous will be the spray applications. The modeling indicated that the mounding beneath the lawns
will likely result in an elevated water table between one foot and three feet beneath the surface of the
ground. The wastewater is 90% domestic and 10% non -industrial, placing it in the domestic wastewater
category. In addition, nitrate nitrogen removal is part of the treatment process and the wastewater is
being treated to meet reuse standards. Contaminant transport does not appear to be an issue, due to the
high level of treatment (which includes denitrifrcation).
The Groundwater Section has reviewed the subject application for the renewal / modification of an
existing permit and recommends issuance of the permit with the following conditions:
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1. Vertical Separation Requirements:
Waste application activities shall not occur when the vertical separation between depth of
application and the water table is at less than one (1) foot. Verification of the water table
elevation can be confirmed by water level readings obtained from the monitor well(s) near the
site or auger boring(s), which must be done within 24 hours, prior to application of wastewater.
Any open borings must be properly filled with native soil, prior to application to decrease the
chance of any waste contaminating the groundwater.
2. Liner Requirements:
The 5-Day Pond shall have either a liner of natural material at least one (1) foot in thickness and
having a hydraulic conductivity of no greater than 1 x 10' centimeters per second when
compacted, or a synthetic liner of sufficient thickness to exhibit structural integrity and an
effective hydraulic conductivity no greater than that of the natural material liner, according to
15A NCAC 2H .0219(f).
3. Applicable Boundaries:
The COMPLIANCE BOUNDARY and REVIEW BOUNDARY for the waste disposal area(s)
is specified by regulations in 15A NCAC 2H, Waste Not Discharged to Surface Waters,
specifically .0219(k)(1)(C)(i)(II). The Compliance Boundary and the Review Boundary for
groundwater shall be established at the property boundary. An exceedance of Groundwater
Quality Standards at or beyond the Compliance Boundary is subject to immediate remediation
action according to 15A NCAC 2L .0106(d)(2).
4. Additional Requirements:
a. Any groundwater quality monitoring, as deemed necessary by the Division, shall be
provided.
*b. Prior to waste disposal, Pe spray patterns of each spray head shall be tested and examined to
ensure that the application of the reuse water is limited to the intended areas of application.
If there are any questions please call David Goodrich at [phone].
*This verbage differs from that of the shell document.
Attachments: Figures 1 and 2.
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Name: BUXTON
Date: 3/21/102
Scale: 1 inch equals 1666 feet
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FIGURE 1
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Location: 035.339! REUSE APPLICATION SYSTEM
Caption: Kinnakeet
Dare Cour DARE COUNTY
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FIGURE 1
IMF K11*4NAKEET SHORES
Location: 035.339! REUSE APPLICATION SYSTEM
Caption: Kinnakeet
Dare Cour DARE COUNTY
WQPQ�4/G�WQ2027
)7, Maptech. Inc. SITE LOCATION MAP
"10
20'
-"M
FIGURE 1
IMF K11*4NAKEET SHORES
Location: 035.339! REUSE APPLICATION SYSTEM
Caption: Kinnakeet
Dare Cour DARE COUNTY
WQPQ�4/G�WQ2027
)7, Maptech. Inc. SITE LOCATION MAP

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