NCG140462_Complete Submittal with Site Plan_20180416

Speer Concrete Design, Inc.

NPDES NCG140000 - Notice of Intent

Narrative Description

Waste Sources
Speer Concrete Design, Inc. intends to open a ready mixed concrete facility, using a
standard portable mixing plant to be installed onsite. The company will operate a small
fleet of transport trucks for distribution, which will also be housed onsite. Domestic
wastewater from the office building will be collected and treated by the onsite septic
system (located along the eastern property line). Industrial wastewater will be created
during typical plant operations. These sources include wetting of raw material stockpiles,
vehicle/equipment cleaning, mixing drum cleaning, as well as stormwater runoff from the
site.

Solid Waste Management
Solid waste, in the form of excess or improperly mixed concrete, will be dumped onsite
and allowed to cure. When feasible, said excess concrete will be formed into precast
blocks, dividers, barriers, wheelstops, etc. In other instances, cured concrete will be
ground and recycled as aggregate. In no case shall raw, uncured concrete be dumped into
the wash pit or outside of the watershed area which drains to the wash pit.

Fluid Waste Management
Fluid waste is largely a combination of cleaning efforts and stormwater, both of which
result in runoff that picks up contaminants from the site. Through the use of directional
grading and diversion berms, all runoff from the facility will be collected and transported
to the wash pit. The wash pit is a three-chamber device where contaminated water enters
through the first chamber and travels through subsequent chambers via a series of screens
and filters. This system treats the runoff for Total Suspended Solids (TSS) and settleable
solids. As a result, the quality of water is improved from one chamber to the next. In
addition, the wash pit will be monitored for pH balance and treated with muriatic acid or
other chemical additives as necessary to control the alkalinity.

A pump and piping system located in the final chamber of the wash pit will allow water
to be reused for vehicle and equipment cleaning. For cleaning of the mixing drums the
facility will use Delvo ESC or similar chemical additive to limit the volume of water
required. This alternative solution does not need to be emptied from the drum before the
next use, which means less runoff into the wash pit.

During unusually heavy rainfall events and periods of little water reuse it is possible for
the wash pit to fill to capacity. A rectangular weir on the final chamber allows excess
(treated) water to be released from the wash pit. This water is collected by an existing
diversion berm and is transported to an existing detention basin (along the western
property line). These existing features remain in place as a secondary defense to ensure
no untreated wastewater is discharged from the site.