(C) Technical report. A technical report shall be prepared
for any system using surface application and shall be submitted with
the planning materials required in §285.5(a) of this title. The
technical report shall describe the operation of the entire on-site
sewage facility OSSF system, and shall include construction drawings,
calculations, and the system flow diagram. Proprietary aerobic systems
may reference the executive director's approval list instead of furnishing
construction drawings for the system.
(D) Effluent disinfection. Treated effluent must be
disinfected before surface application. The effluent quality in the
pump tank must meet the minimum required test results specified in §285.91(4)
of this title. All new disinfection equipment shall be listed as approved
dispensers or disinfection devices for wastewater systems by NSF International
or by an ANSI accredited testing institution under ANSI/NSF Standard
46, or approved by the executive director. After January 1, 2016,
all new disinfection equipment shall be listed as disinfection devices
for wastewater systems by NSF International or by an ANSI accredited
testing institution under ANSI/NSF Standard 46, or approved by the
executive director. Installation of disinfection devices on new systems
shall be performed by a licensed installer II. Tablet or other dry
chlorinators shall use calcium hypochlorite properly labeled for wastewater
disinfection. The effectiveness of the disinfection procedure will
be established by monitoring either the fecal coliform count or total
chlorine residual from representative effluent grab samples as directed
in the testing and reporting schedule. The frequency of testing, the
type of tests, and the required results are shown in §285.91(4)
of this title. Replacement of disinfection devices on existing systems
may be considered an emergency repair as described in §285.35
of this title (relating to Emergency Repairs) and shall be performed
by either a licensed installer II, a licensed maintenance provider,
or a registered maintenance technician.
(E) Minimum required application area. The minimum
surface application area required shall be determined by dividing
the daily usage rate (Q), established in §285.91(3) of this title,
by the allowable surface application rate (Ri = effective loading
rate in gallons per square foot per day) found in §285.90(1)
of this title or as approved by the permitting authority.
(F) Landscaping plan. Applications for surface application
disposal systems shall include a landscape plan. The landscape plan
shall describe, in detail, the type of vegetation to be maintained
in the disposal area. Surface application systems may apply treated
and disinfected effluent upon areas with existing vegetation. If any
ground within the proposed surface application area does not have
vegetation, that bare area shall be seeded or covered with sod before
system start-up. The vegetation shall be capable of growth, before
system start-up.
(G) Uniform application of effluent. Distribution pipes,
sprinklers, and other application methods or devices must provide
uniform distribution of treated effluent. The application rate must
be adjusted so that there is no runoff.
(i) Sprinkler criteria. The maximum inlet pressure
for sprinklers shall be 40 pounds per square inch. Low angle nozzles
(15 degrees or less in trajectory) shall be used in the sprinklers
to keep the spray stream low and reduce aerosols. If the separation
distance between the property line and the edge of the surface application
area is less than 20 feet, sprinkler operation shall be controlled
by timers set to spray between midnight and 5:00 a.m.
(ii) Planning criteria. Circular spray patterns may
overlap to cover all irrigated area including rectangular shapes.
The overlapped area will be counted only once toward the total application
area. For large systems, multiple sprinkler heads are preferred to
single gun delivery systems.
(iii) Effluent storage and pumping requirements.
(I) For systems controlled by a timer and required
to spray between midnight and 5:00 a.m., there shall be at least one
day of storage between the alarm-on level and the pump-on level, and
a storage volume of one-third the daily flow between the alarm-on
level and the inlet to the pump tank.
(II) For systems not controlled by a timer, the minimum
dosing volume shall be at least one-half the daily flow, and a storage
volume of one-third the daily flow between the alarm-on level and
the inlet to the pump tank.
(III) Pump tank construction and installation shall
be according to §285.34(b) of this title.
(iv) Distribution piping. Distribution piping shall
be installed below the ground surface and hose bibs shall not be connected
to the distribution piping. An unthreaded sampling port shall be provided
in the treated effluent line in the pump tank.
(v) Color coding of distribution system. All new distribution
piping, valve box covers, and sprinkler tops shall be permanently
colored purple to identify the system as a reclaimed water system
according to Chapter 210 of this title (relating to Use of Reclaimed
Water).
(3) Mound drainfields. A mound drainfield is an absorptive
drainfield constructed above the native soil surface. The mound consists
of a distribution area installed within fill material placed on the
native soil surface. The required area of the fill material is a function
of the texture of the native soil surface, the depth of the native
soil, basal area sizing considerations, and sideslope requirements.
A description of mound construction, as well as construction requirements
not addressed in this section can be found in the North Carolina State
University Sea Grant College Publication UNC-SG-82-04 (1982).
(A) A mound drainfield shall only be installed at a
site where there is at least one foot of native soil; however, approval
for installation on sites with less than one foot of native soil may
be granted by the permitting authority on a case-by-case basis.
(B) Mounds and mound distribution systems must be constructed
with the longest dimension parallel to the contour of the site.
(C) Soil classification, loading rates (R(a)), and
wastewater usage rates (Q) shall all be obtained from this chapter.
(D) The depth of soil material (with less than 30%
gravel) between the bottom of the media and a restrictive horizon
must be at least 1.5 feet to the restrictive horizon or two feet to
groundwater. The soil material includes both the fill and the native
soil.
(E) The distribution area is defined as the interface
area between the media containing the distribution piping and the
fill material or the native soil, if applicable. The distribution
length is the dimension parallel with the contour and equivalent to
the length of the distribution media which must also run parallel
with the contour. The distribution lines within the distribution media
must extend to 12 inches of the end of the distribution media. The
distribution width is defined as the distribution area divided by
the distribution length.
(i) The formula A(d) = Q/R(a) shall be used for calculating
the minimum required distribution area of the mound where:
Attached Graphic
(ii) The area credited toward the minimum required
distribution area can be determined in either of the following ways.
(I) If the distribution area consists of a continuous
six-inch layer of media over the fill, the credited area is the bottom
interface area between the media and soil beneath the media.
(II) If the distribution area consists of rows of media
and distribution piping, the credited area can be calculated using
the formulas listed in paragraph (1)(C)(i)(I) or (II) of this subsection
depending on the depth of the media.
(iii) For sites with greater than 2% slopes and solid
bedrock, saturated zones, or class IV horizons within two feet of
the native soil surface, the length to width ratio of the distribution
area must be at least 7:1. For sites with greater than 2% slopes and
no solid bedrock, saturated zones, or class IV horizons within two
feet of the native soil surface, the length to width ratio of the
distribution area must be at least 4:1. No length to width ratio is
required on a site with 2% slope or less.
(iv) Effluent must be pressure dosed into the distribution
piping to ensure equal distribution and to control application rates.
(v) If a continuous layer of media is used, the dosing
lines must not be spaced more than three feet apart. If rows of media
are used, the rows may be as close as three feet apart, measured edge
to edge.
(vi) The dosing holes must not be greater than three
feet apart.
(F) The basal area is defined as the interface area
between the native soil surface and the fill material. The formula
A(b) = Q/R(a) must be used for calculating the minimum required basal
area of the mound where: A(b) = minimum required basal absorptive
area in square feet; Q = design wastewater usage rate in gallons per
day; R(a) = application rate of the native soil surface in gallons
per square foot per day.
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