Fundamental to the FloCis process is comprehending how the sanitary and storm collection systems respond to wet weather. This procedure is best accomplished with many meters placed in the collection system gathering flow behavior data throughout seasonal weather differences encountered by the utility. Traditional metering programs have a pricing structure that is beyond the reach of many small communities. Priced at $ 70 to $ 90 per day per manhole, the metering program for three months at ten manholes can cost $65,000 to $ 85,000! Hopefully it rains during that three month period and those rains are representing the types of wet weather conditions that generate excessive ground water intrusion. Because of the difficulty, risk and cost of confined space entry, traditional meters placed at the bottom of manholes are not moved to seek out the specific sections of the collection system that contribute the largest portions of I & I flows. Considering the limitations of cost and flexibility, FloCis set out to find a better way to analyze and isolate where storm water enters the sanitary system. If it was possible to isolate specific pipe segments that leak, then the rehabilitation costs would be better controlled.

FloStik meters are patent-pending, small wireless data collection sensors that are one of the most valuable tools used in the FloCis investigation process for I & I abatement. FloStiks collect data in short intervals in order to measure changes in sewer collection systems within manholes.

FloStiks measure three important features in the flow: the change in flow depth or hydraulic head, the change in flow temperature, and wobble or tilt change as the sensor hangs within the flow. These three measurements are important for the following reasons:

As ground water leaks into the sanitary sewer, this contribution of fluid, added to the normal flow, will raise the flow depth or hydraulic head. The FloStik sensor measures the flow depth at five minute intervals. Each sensor has a clock that is synchronized with all the other FloStiks placed in the collection system. As a result, every five minutes a "picture" is collected of the flow depths at manholes where the FloStiks are placed.

Rapid changes in the flow temperature at different times of the year are strong indicators of intrusion from nearby groundwater sources. Warmer weather is an indicator of I & I arriving from paved areas during a "first flush" of a summer rain; whereas cold water from localized snowmelt is an indicator of the presence of antecedent I & I. The tilt or wobble of the sensors is a function of the velocity and turbulence of the flow. A rise in hydraulic head, associated with a small tilt and turbulence is an indicator of minor ground water contribution from upstream of the meter, accompanied with flow obstructions downstream. When analyzing the hydraulic behavior, the maintenance supervisor can identify conveyance problems using the FloStik. By contrast, during the onset of wet weather, a rapid rise in flow depth, with significant sensor movement is a strong indicator of nearby ground water intrusion.

 

FloStiks have the following features and benefits:

Unlike conventional meters, installation does not require confined space entry precautions, equipment or trained personnel. The sensor hangs in a manhole at ground level supported by a temporary but sturdy crossbar mounted at the top of the manhole vault. No special tools or electricity are required.

Though drive time and traffic control procedures are needed, the actual time required for typical sensor installation alone is approximately ten minutes. A two-person crew can typically install 12 to 16 meters in a day. FloStik sensor ends hang in the flow, just touching the manhole invert. A support tube is extended with standard ¾" CPVC pipe and clamped to the crossbar at street level.

The sensor tube is curved such that, as the meter wobbles in the flow, ragging is sloughed off thus keeping readings accurate and the drainage free of obstruction.

To prevent moisture damage to the electronics, a desiccant module is required. It lasts about six weeks and is replaced at ground level.

The sensor is lightweight, durable and collects approximately 125,000 records without a battery charge, helping to ensure infrequent maintenance and downloading requirements.

A standard hand-held computer collects data wirelessly in a matter of minutes using the most common wireless protocol. The data collection process is quick and easy because the meter does not need to be removed from the manhole in order to be read.

A wide variety of Windows compliant portable computers and devices can load the software, saving on the investment costs due to custom data collection hardware and wiring connections.

FloStiks are currently available for use by our FloCis clients as a value-added part of our consulting practice. Interested parties may contact us for information as to when FloStik will be ready for sale. Measurements from FloStik are ideally designed to be displayed in our FloViz software package but Excel or other data analysis programs can also be used.