STEP COLLECTION SYSTEMS AND FLOW METERS

SHANE SPARKS, P. GEO

SD CONSULTING GROUP

Part 1

INTRODUCTION/OVERVIEW

Wastewater Collection Systems – Types of Sewers

What is a STEP System?

Recent Step Systems in Alberta

Step System Components

Example Projects

Flow Meters

TYPES OF SEWERS

• CONVENTIONAL GRAVITY

• PRESSURE

• SEPTIC TANK EFFLUENT PUMP (STEP)

• GRINDER PUMPS

• SEPTIC TANK EFFLUENT GRAVITY (STEG)

CONVENTIONAL GRAVITY SEWER

Manholes

200 mm Sewer

CONVENTIONAL GRAVITY SEWER

• Low operation and maintenance costs

• Few mechanical parts

• Conventional, proven method

• Contractors are familiar with gravity installations

Advantages:

• Limited by site topography

• Infiltration and Inflow

• Construction impacts are large

• Sewer lines start at >2.5 m and can get deep

• For onsite treatment, large septic tanks required at treatment site

• Lift Stations may be required

Disadvantages:

SEPTIC TANK EFFLUENT PUMP SYSTEMS

STEP SYSTEMS

• Large tanks for solids handling not required at treatment site

• Pumped system follows contours of site – no topographic limits

• Better pretreatment – BOD levels are typically lower

• No I&I

• Forcemain easier to directionally drill

Advantages:

• Tanks, Pumps, and Controls required at each house

• Homeowners can’t “flush and forget”

• Operations and maintenance costs can be higher

• Gravity flow is easy

• Experienced operators and contractor required

Disadvantages:

SMALL DIAMETER GRAVITY SEWER

SMALL DIAMETER GRAVITY SEWER

• Low operation and maintenance fees

• Few mechanical/electrical parts

• Small diameter pipes and fewer manholes

• Able to connect to existing septic tanks

• Much less surface disturbance

• Not as limited by topography

Advantages:

• Interceptor tanks required for each home

• Might have to be buried deep, depending on service and main line depth

• Infiltration and inflow

• Sewer lines should be buried >2.5 m

Disadvantages:

• ALL OPTIONS ARE EVALUATED ON EVERY

PROJECT

• MOST RECENT APPROVALS ARE STEP:

• MODULAR, LOW COST OPTION FOR

PHASED DEVELOPMENTS

• LARGE PORTION OF COST DEFERRED

TO HOMEOWNERS AT TIME OF

CONSTRUCTION

• ELIMINATES THE NEED FOR LARGE

PRIMARY TREATMENT TANKS AT THE

TREATMENT SITE (CAN BE A HIGH

COST THAT IS RESPONSIBILITY OF

DEVELOPER)

WASTEWATER COLLECTION

SYSTEMS

• SEPTIC TANKS ON EACH LOT

(OR SOME COMBINATION)

WITHIN THE DEVELOPMENT

• SMALL DIAMETER FORCEMAIN

TAKING WASTEWATER TO

TREATMENT, OR REGIONAL

LINES

• EACH TANK OUTFITTED WITH

SUBMERSIBLE EFFLUENT STYLE

PUMP (OR PUMPS) TO

PRESSURE EFFLUENT

• TANKS INCLUDE FILTERS AND

CONTROLS

WHAT IS A STEP SYSTEM?

COMPONENTS OF A STEP SYSTEM

• SERVICE W/CLEANOUT FROM

SOURCE

• SEPTIC TANK (ONE OR TWO

COMPARTMENT

• PUMP VAULT W/FILTER

• SUBMERSIBLE EFFLUENT PUMP

• DISCHARGE PIPING

• CONTROL PANEL

• VALVE ON CONNECTION TO MAIN

LINE

• MAINLINE

PUMP AND DISCHARGE ASSEMBLIES

STANDARD DISCHARGE

ASSEMBLIES

HANGING DISCHARGE

HANGING DISCHARGE ASSEMBLES - INSTALLED

STEP SYSTEM CONTROLS