|(a) The design of a new wastewater treatment facility
must be based on the flows and loadings in paragraphs (1) - (3) of
this subsection, unless subsection (b) of this section applies.
(1) Design flow.
(A) If the flow is greater than or equal to 1.0 million
gallons per day, as determined by multiplying the per capita flow
in Table B.1. in paragraph (3) of this subsection by the number of
individuals in the service area, then the design flow is the flow
calculated from the table.
(B) If the flow is less than 1.0 million gallons per
day as determined by multiplying the per capita flow in Table B.1.
in paragraph (3) of this subsection by the number of individuals in
the service area, then the design flow is determined by multiplying
the average annual flow calculated from the table by a factor of at
(C) The design flow must be based on the flow authorized
in the wastewater treatment facility's wastewater permit.
(2) Peak flow. When site-specific data is unavailable,
the peak flow must be determined by multiplying the design flow by
a factor of at least 4.0. If site-specific data or projections are
available, the peak flow must be based on the site-specific data.
(A) If the average daily peaking factor at a wastewater
treatment facility exceeds 4.0, the actual daily peaking factor must
be used to calculate the peak flow, unless flow equalization is provided.
(B) If a wastewater treatment facility experiences
occasional peak events with a peaking factor that exceeds 5.0, the
event-based peaking factor must be used to calculate the peak flow,
unless flow equalization is provided.
(C) In a wastewater treatment facility with flow equalization,
the subsequent treatment units may be designed for a lower estimated
peak flow. The engineering report shall include data that supports
the lower estimated peak flow.
(D) A treatment unit, pipe, weir, flume, disinfection
unit, or any other treatment unit that is flow limited must be sized
to transport or treat the peak flow.
(3) Design organic loading. If available, actual organic
loading data must be used as the basis for the design of the wastewater
treatment facility. If actual organic loading data is not available,
the design organic load must be determined by using the following
table. The design organic load is determined by multiplying the annual
average flow from the projected uses by the corresponding influent
(b) An owner designing a new wastewater treatment facility
that will serve the same service area as an existing wastewater treatment
facility must use historical data from the existing wastewater treatment
facility to design the new wastewater treatment facility, if there
is enough historical data to meet the needs of §217.34 of this
title (relating to Organic Loadings and Flows for Existing Wastewater
Treatment Facilities, Re-Ratings, and Alterations). The engineering
report must justify the design conclusions that are based on existing