Page 286 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

SITE UTILITY SYSTEMS

6.8 CHAPTER SIX

Because of sand present in discharge water coming from subsurface drainage piping,
a sand interceptor is usually required by plumbing codes. The sand interceptor should be
placed in the drainage line before it discharges into a building sump or ejector pit for dis-
posal. This will avoid the necessity of installing the sand interceptor at the public sewer,
where discharge of sand is prohibited. There are several commercially available sand inter-
ceptors, or one can be built on site.
The drainage lines should be sized using standard flowcharts, such as nomographs using
the Manning, Kutter, or Hazen-Williams formula, with a roughness coefficient correspond-
ing to the type of pipe used in the system and the pitch of the drainage pipe.

SURFACE DRAINAGE

This section is intended as a guide for development of a storm water drainage system for smaller
2
uncomplicated sites of less than 2mi . Procedures follow established engineering principles
and allow a simplified, conservative method of design and piping layout for small watersheds.
Included is rain water removal from parking lots, roadways, and undeveloped areas of the
site. The selection and location of inlets, catch basins, manholes, and piping along with storm
sewer design must be accomplished. The design of storm water removal, for example, from
building roofs, is discussed in Chap. 9, in the section entitled Interior Storm Water Drainage.
When systems are located on larger sites or complications are encountered, it may be
necessary to request the help of a consultant specializing in this type of work to ensure that
the design is adequate.

PRELIMINARY INVESTIGATIONS

The following investigations must be concluded before designing the proposed system:

1. Determination of the site storm water discharge location or method of disposal, such as
public sewers, waterways, surface absorption, recharge basins, or dry-wells.
2. If streams or rivers are to be used as a final outfall, local, state, or federal agencies must
be contacted regarding permitted flow, outfall structures, and required permits. Such
agencies may be the U.S. Army Corps of Engineers, Environmental Protection Agency
(EPA), or local sewer department. EPA permits are required if such a waterway is con-
sidered navigable.
3. If a public sewer is to be the final outfall, public agencies must be contacted regarding
permitted flow, connection details, plan submittal, and required approvals.
4. High and low water levels of all streams and rivers must be known, including past his-
tory of floods.
5. If site storm water will be discharged directly into smaller streams, it must be deter-
mined whether a possible flood condition downstream could be created.
6. Provision should be made for any future development of surrounding site areas of build-
ing additions.
7. The requirements for the Standard Urban Storm Water Mitigation Plan (SUSMP) must
be checked in your project location.

Layout of System
At this point, it is assumed a survey plan and a preliminary site plan with contours are available
for a general layout of the system. Runouts from buildings should now be located, outfall of the

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