5. INSTALLATION OF EQUIPMENT
This section discusses typical installation and is not specific to a particular manufacturer. It addresses requirements and installation practices for each equipment type.
5.1.1. General Installation Considerations
Installation procedures, materials and field equipment requirements will vary depending on the type of monitoring equipment used and the conditions of the site that was selected for monitoring. Table 5.1 provides a list of the most common tools and equipment used for stormwater monitoring and equipment installation.
Before any installation activity begins in the field, a health and safety plan should be developed, read, and understood by all field personnel. Appendix B provides an example of a health and safety plan.
Once at the site, all safety concerns should be addressed before beginning installation of equipment. This usually involves:
- Setting up traffic control devices around the work area.
- Finding a safe place with a level, smooth surface to stage and assemble equipment.
- Checking for hazardous atmosphere (for manhole or confined space entry).
- Choosing appropriate personal protective equipment (PPE). Only personnel properly trained in confined space entry using proper equipment should enter conveyance systems for installation.
- Setting up winch and lifeline (for manhole or confined space entry) and additional health and safety equipment.
Equipment enclosures, where they are needed, should be selected to contain all monitoring equipment and provide adequate clearance for removal of samples and maintenance of equipment. Prefabricated shelters and large electrical equipment enclosures function well for this purpose. Manufacturers of monitoring equipment often provide prefabricated shelters; however, local sources are often a good low-cost alternative. Garden sheds have been used in some locations where space permits and vandalism is expected to be minimal. Locks should be installed on all equipment shelters. Alternately, portable platforms, such as trailers, have been employed to facilitate setup and transport of equipment. It should be noted that making equipment easily transportable also increases the risk of theft. Trailers should have wheels removed or otherwise immobilized. Stormwater monitoring equipment is susceptible to vandalism and theft due to its installation in isolated areas and the apparent lure of electronic equipment, however unuseful to the thief.
5.1.2. Data Loggers
188.8.131.52. Typical Installation
Data loggers should be installed as near to the sampling site as possible while still maintaining adequate accessibility. The location of the data logger can be dependent on the type of sensors installed. For example, pressure transducers often have vented cables that must not be allowed to sag or dip between the sensor and data logger.
TABLE 5.1 COMMON TOOLS AND EQUIPMENT USED IN STORMWATER MONITORING
- Sample collection jar(s)
- Graduated cylinder for sampler calibration
- Suction line (0.24-in to 0.375-in diameter)
- Masonry anchors & screws
- Masonry drill bits
- Tubing anchors or galvanized steel strapping
- Portable gas monitor
- Safety line
- Tripod, winch, and safety harness
- Flashing lights for vehicle
- Traffic cones
- Protective Gloves
- Hard hat
- Connection cable
- Depth-measuring rod
- Data interrogator or laptop computer
- Bubbler tubing or pressure transducer w/cable
- Cable ties
- Calibration equipment (see flowmeter manual)
- Battery powered drill
- Hand tools (hammer, screwdriver, pliers, knife, hacksaw, wire strippers, measuring tape)
- Manhole hook
- Duct tape
- Distilled water
- Watch or stopwatch
Most commercially available data loggers can be equipped with a weatherproof housing that is useful to shelter field personnel to allow for more comfortable programming, data retrieval, and maintenance of equipment. Commonly, an enclosure is provided that is large enough to house all of the sampling equipment and allow for at least partial entry by field personnel. Enclosures also can provide added security for equipment if they are sturdy and can be locked.
It is recommended that the data logger be mounted off the ground to prevent damage and to make programming and data retrieval easier. A grounding rod should be installed to protect the equipment from lightning damage, especially if the equipment is hooked directly to a telephone or power line. Each manufacturer will provide detailed instructions, schematics, and diagrams that should cover most aspects of installation.
184.108.40.206. Special Cases
Manhole installation can create some challenges for installation of data loggers. In addition to weatherproofing the equipment, it may be necessary to protect it from corrosive atmospheres or submersion. An appropriate housing is required for this type of installation.
Some data loggers can be equipped with an external communications cable that can be attached to a personal computer or keypad for programming and data retrieval. This allows the data logger to be accessed without entering the manhole and can eliminate the problems associated with confined entry.
5.1.3. Flow Measurement Equipment
220.127.116.11. Typical Installation
Although installation of flow measurement equipment varies significantly depending on the type of equipment used, some general principals can help facilitate equipment selection and ease installation.
The most common equipment used in flow monitoring (weirs, flumes, etc.) can be broken down into two components typically referred to as primary and secondary devices. Primary devices are methods for altering flow in a predictable manner so that a known relationship between flow and measured depth can be used. Secondary devices measure the depth of flow in, upstream, or downstream of primary devices and include methods, for example bubblers, pressure transducers, or ultrasonic sensors described in previous sections.
Primary devices are sensitive to proper installation and setup in the field. Installers should have detailed specifications for the following:
- Slope and leveling tolerances for device;
- Minimum tolerances on dimensions for device;
- Proper upstream and downstream conditions;
- Calibration methods (if applicable);
- Proper structural support or anchoring (both hydrostatic and kinetic forces during large events are significant and should be examined and accounted for during design and installation); and
- Proper placement and setup of primary device to work in conjunction with secondary device.
Often these specifications will be provided by the manufacturer of the devices; however, primary devices are often custom-built, particularly in the case of simple devices such as weirs, and may require the designing engineer to compile installation instructions and specifications.
Secondary devices range significantly in their installation requirements. Most of these devices have similar housing and installation needs as data loggers as described above. ,
However, some require significantly more complex setup. Manufacturers of these devices such as ISCO, and American Sigma, provide detailed installation instructions and technical support for their products.
18.104.22.168. Special Cases
Due to the wide range of circumstances surrounding the installation of flow equipment, most installations require custom modification and best engineering judgment in order to obtain accurate, reliable, and repeatable flow measurement.
22.214.171.124. Typical Installation
The installation of sampling equipment is similar in many ways to installation of data loggers. However, location for equipment is more difficult in many instances in that sampling equipment can be quite large compared to the space requirements for data loggers. Most samplers are designed for installation in manholes or in small enclosures. A sampler will typically be collocated with the data logger or flow measurement device.
A maximum height above the water surface is a key factor for sampler location. Typically samplers should be located as close to the sampling point as possible both in elevation and in distance. Maximum heights between water surface elevation should not exceed 20 feet in most cases.
Sample lines should be set up so that there are no sags or dips in the line that would prevent the line from draining when not in use.
Power requirements are similar to data loggers and often samplers have their own battery source that needs to be changed before events.
Access to equipment should be limited to prevent vandalism, yet provide personnel ample room to remove heavy sample bottles and replenish ice, if used.
5.1.5. Rain Gauges
126.96.36.199. Typical Installation
Installation of rain gauges is often a straightforward matter. Manufacturers provide guidelines on the appropriate mounting of the devices. The main concerns during installation are:
- Leveling the device
- Making sure that vegetation (trees) or structures are not obstructing rainfall
- Providing enough height above the ground to prevent vandalism
- Locating rain gauge in close proximity to other monitoring equipment to provide required connections for recording of rainfall depths and/or representative records
5.2. Putting It All Together
The commonly used components of a stormwater monitoring system are described separately in the preceding sections. This section provides an overview of the integration of these components into functional systems for field use. The examples provided are the most common arrangements and should be used only as a general guide.
The configuration of a monitoring system is guided by program objectives including requirements for:
- Grab, composite, or continuous sampling of the discharge
- Sample volumes for laboratory analysis of discharge constituents
- Data logging/PC interface
- Remote communications
- Ease of installation
Three types of common system configurations are described below. The systems differ in degree of automation in that the first system uses entirely manual methods to measure discharge and to collect flow-weighted composite samples for laboratory analysis. The second and third systems use automated equipment but differ in the degree of electronic linkage between the components.
188.8.131.52. Manual Sampling
Inexpensive manual sampling programs have been used by a number of stormwater monitoring programs. When conducting manual sampling, discharge can be collected using high-density polyethylene buckets. Compositing procedures are used to weight the volumetric contribution from each grab by the discharge rate at the time of collection. Discharge is estimated from measurements of the depth of flow and using the Manning equation (incorporating details of the hydraulic configuration at each site).
In some cases the use of manual sampling can reduce capital costs for equipment while improving reliability. Field personnel can ensure that each sample is collected in a manner consistent with program objectives. However, these cost savings are lost as the number of storms increases. The somewhat unpredictable timing of storms can also make it difficult to maintain a dedicated work force of trained field personnel who are often exposed to harsh environmental conditions and safety hazards. Finally, manual sampling when a crew is covering more than one site can be limited in accuracy due to the small number of samples that can be collected as well as the timing of collection.
184.108.40.206. Automated Flow Meter And Sampler - Without Remote Communication
This relatively simple system is used to monitor and collect stormwater runoff from highway sites. The system uses a bubbler flow measurement system to measure discharge via a standard hydraulic method such as the Manning equation. The bubbler is often chosen for its simplicity and low cost and because, unlike a flume or weir, it does not create a potential blockage problem in the conveyance. The bubbler could be linked to an automated sampler that is capable of collecting flow-weighted composite samples. Using this configuration with no telemetry requires field personnel to collect digital field data. This mandates frequent visits to the site before and after storms even for those events that did not require sampling to collect flow data and check equipment if flow measurements were desired.
220.127.116.11. Flume, Automated Flow Meter, And Automated Sampler - With Remote Communication
This more sophisticated system is often used where more control and real time information is required for managing and conducting monitoring. The flow meter receives and logs both rainfall data from a tipping bucket gauge and discharge data from a bubbler inserted into the flow, ideally using primary device (flume) to improve accuracy. A second bubbler could be used as a backup so that discharge can be measured even under pressurized flow. Another option would be to utilize a velocity sensor in combination with a depth measurement device. An automated sampler, capable of collecting flow-weighted composite samples, could be integrated into the system such that flow measurement can be utilized to trigger the sampler. The entire system could be linked to the storm event coordinator through a modem. The coordinator could thus interrogate the flow meter, download data, and even change the programming on this device without mobilizing to the site.
The ability to interrogate the flow meter allows the storm event coordinator to send field personnel to any of several sites in a local area based on the need for inspection, repair, or bottle replacement, thereby increasing the efficiency with which human resources are used. Linkage to a rain gauge at the site also would provide additional local data on storm intensity and volume. Telemetry could be installed using either a cell phone modem or landlines depending on proximity to utilities.
18.104.22.168. Summary and Conclusions
A variety of technologies can be applied to stormwater monitoring. The ability of the user to interface instruments and accessories is one of the most desirable features of equipment used in integrated systems. The best technology is user friendly for installation, operations, and maintenance and is one that provides accurate data at a reasonable cost. The extra costs associated with remote communications can be very valuable to the user in many situations, but they may not be necessary for successful stormwater monitoring.
There is no one best technology that will fit all stormwater monitoring goals and field conditions. Keys to successful stormwater monitoring include:
- establishing clear monitoring goals and objectives;
- selecting a site that meets the requirements of the monitoring goals and the criteria mentioned previously in this document; and
- selecting equipment that fits the site characteristics and monitoring requirements.
Site security is very important to successful operation of a water quality monitoring station. The more mobile the station set-up is, the more this is a challenge. The ability to move the station can be greatly enhanced by making equipment portable; however, portability makes equipment much less secure than installing equipment in either a shed or a manhole.
Steep sloped pipes that created high velocities and turbulent flows make monitoring of both flow and water quality difficult. Some modifications to the pipe bottom may be needed (smooth shallow weir) to allow for the collection of the sample downstream of the flow measurement.
Baseflow in pipes must be accurately accounted for; otherwise, the triggering of sample collection may occur prematurely. For general characterization studies, sites with baseflow should be avoided.
Field programming of equipment that requires a laptop computer is difficult in wet and cold conditions. Laptops that are highly weatherproof should be utilized.
When using different equipment brands, there likely will be some problems with incompatibility of the equipment. Frequent contacts with manufacturers will likely be required to resolve problems and create a workable monitoring station. In addition, as one sets up monitoring equipment for specific sites and applications, there will be software problems that will require manufacturer assistance to resolve.
Complete stations that include a flow meter, sampler, rain gauge, and data logger by one manufacturer eliminate most incompatibility problems and make data collection and analysis easier. However, special site requirements may necessitate specific equipment capabilities that one manufacturer might be unable to supply.
In situ water quality monitors are currently limited in the number of and detection limits of pollutants. It is likely that a subset of this equipment will undergo further development for general application. As yet, in situ monitors for other than some basic parameters (temperature, conductivity, DO, etc.) are not commonly used, but as technology develops and costs decline, these devices are likely to be considered for field applications.
The use of in situ monitoring equipment (probes) is difficult at best in the intermittent flow conditions of stormwater systems. This is due to its need for frequent calibration and the requirement that the probe be submerged at all times, including in-between storm events. Remote operation of this type of equipment does not appear to be practical.
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Questions and feedback should be directed to Deirdre Remley (email@example.com, 202-366-0524).