UNISTORM™ Information Sheet

The UNISTORM Stormwater Treatment System offers the advantages of Environment 21 technology and the cost savings obtained from using locally available precast concrete structures. Product pricing includes Environment 21 Technical Support and preparation of a site-specific Site Data Sheet/Sketch Plan, analysis of Sediment Removal Efficiency and Pumpout Interval, Design Storm Backwater Analysis, and Precaster Detail Drawing in Autocad.

 

UPSTREAM STRUCTURE

(as applicable)

CURB INLET

PARKING LOT INLET

STORM MANHOLE

POND OR SWALE

 

Important operating and design features
of the UNISTORM configuration:

Two options for treatment

§         Treats flow from upstream structures Sediment

§         Treats flow from UNISTORM inlet grate

First stage pollutant storage

§         Floatables readily visible for inspection and removal

§         Sediment sump sized for 5-10 year pumpout interval

Baffle wall with SIte-SpecIfIc Flow Control Configuration

§         Prevents carry-over of floating oil and debris

§         Openings configured to provide improved flow distribution for sedimentation process

§         Openings configured to reduce turbulence at surface of sediment pile

§         Openings configured to provide less than 0.20 ft head loss at Design Storm chamber.

 

Second stage treatment chamber

  § Provides additional removal of fine sediment

       § Provides maintenance access to outlet pipe

       § Pipe orientation -- inlet and outlet piping orientation readily adapted to unusual site constraints

 

Inspection and Pumpout access -- sediment and fIoatables accumulation is easily measured and/or removed using the access openings provided in each treatment chamber.

Manufacturing Cost --use of locally available standard precast concrete structures provides lowest cost.

Site Hydrology used to Estimate 80% Average Annual Removal Efficiency for Sandy Sediment

▪ Intensity = 0.80 inches/hr     ▪ Pavement Washoff Intensity = 0.70 cfs/ acre pavement

▪ Runoff depth = 0.50 inches   ▪ Frequency = 3-5 significant washoff events/yr (varies with location)

Selection of UNISTORM Manhole Models

§         Sizing based on 10-year Design Storm
  

UNISTORM Model No./Diameter ft

5

6

7

8

9

10

12

10-yr Design Storm cfs

4.3+

6.2+

8.5+

11.0+

14.0+

17.3+

25.0+

§         Sizing based on Impervious area
  

UNISTORM Model No./Diameter ft

5

6

7

8

9

10

12

Treatment capacity, impervious acres

1.0+

1.4+

2.0+

2.7+

3.4+

4.2+

6.0+

.Site specific Technical Report and Precaster DetaIl Drawing Provided by Environment 21
   

  • Site Data/Sketch Plan drawing prepared to provide basis for Technical Report and Precaster Detail Drawing
  • Site-specific Technical Report for (a) sediment removal efficiency, accumulation, and pumpout frequency, and (b) Design Storm Hydraulics and Backwater Analysis
  • Precaster Detail Drawing available in Autocad Release 14 and 2000

Precast Concrete Structure SpecIfications

§         Precast concrete structures are fabricated in accordance with ASTM standards for H-20 loading.

§         Cast iron frames and covers are standard cast iron for H-20 loading.

Field Installation
UNISTORM structures and flow control baffle wall are installed using standard practice for precast concrete.

Maintenance

Semi-annual inspection is recommended to determine rate of accumulation of fIoatables and sediment. UNISTORM sediment storage capacity is estimated to be adequate for several years of service (based on annual sediment washoff of 400# per acre of pavement).

Applications and Technical Assistance

 
For additional UNISTORM information, contact Stormwater Solutions.