Bobcat Meadows Metropolitan District

Originally constructed in 1998, Bobcat Meadows is a small subdivision of 178 homes outside of Falcon, Colorado. The subdivision is supplied with water from a small facility within the district and has a demand of ~24,000 gallons per day. Water is drawn from two wells, treated with chlorine, and stored in a 120,000 gallon storage tank. Treated water is pumped to the district through one of three pressure pumps at any time. There is one pump for primary use, another for backup and a fire protection pump as well. The building also has a backup generator for emergencies.


One of the wells, the Laramie Fox well, has a high iron content. This well is drilled 1,600 feet deep and uses a 50 HP motor to bring water to the surface at 100 gallons per minute(GPM). While the iron is not a health concern it is a nuisance as it increases the cost of treatment and causes odor and discoloration issues. The other well, the Arapahoe well, is drilled 1,200 feet deep into an aquifer producing clean water with a low iron content at 30 GPM. Prior to the upgrades these wells were both turned on at the same time in order to fill the water tank; mixing clean water with iron rich water. This is more than enough water yet is not energy  efficient. Demand is only high enough to require both wells three months out of the year during watering or during a fire. Chlorination of the water in this system is done by pumping liquid sodium hypochlorite into the water. This small chemical pump was originally powered on with the well relays then pulsed for each gallon of flow by a flow meter. 


Treated water is pumped using a 10 HP motor for normal operation, and a 20 HP motor for emergency fire pumping. Originally these pumps were driven by pressure switches and relay logic. While this was effective at keeping the system pressurized, the constant on/off cycles were costing the district on their electric bill. To make matters worse the hammering of the pipes from those on/off cycles were causing leaks in service lines. 


Upon our arrival there was no auto dial system or remote monitoring present. 


We need to know what is going on during a blizzard and we need to cut our monthly bottom line

Operations Manager - Bobcat Meadows Metropolitan District

Our Design

Each project carries its own unique challenges. Our primary challenge on this job was the total budget, set at just $55,000. That sum total had to cover all parts, the electrician, and Stanford Engineering for system integration. After interviewing the operations manager at length and examining the system we arrived at the following requirements.      


  • The wells must function independently 
  • The Laramie well should only run when the tank is low (preferably at night)
  • Tank level should be visible to operator 
  • Email and/or text alarms needed for low pressure, low tank etc.
  • Continual chlorine monitoring with automated chemical pump control
  • Continuous treated water pressure monitoring and adjustment
  • Operator must be able to change system pressure easily 
  • Attempt to reduce chemical and electrical costs
  • Interface backup generator with control system for email/text alarms when it is running
  • Enable remote off site monitoring of the water plant


To monitor tank level a custom level transducer was installed in the water tank. The transducer puts out a variable signal based on water level above the sensor. The Arapahoe well was placed on a variable frequency drive (VFD) and the Laramie well was left with on/off soft start control. The nature of how a VFD operates allows it to drive a motor a varying speeds while running the motor more efficiently, thus lowering energy cost. The treated water pressure pumps were also placed on VFD's. Water pressure is monitored by a pressure transmitter inserted in the treated water pipe in the plant. The old pressure switches were removed entirely.

  

Chlorine monitoring is done by a Hach CL17 chlorine monitoring system and a variable signal is put out by the device related to the amount of chlorine in the water. The existing chemical pump was reused as it could accept a variable signal for pulsing speed. Connections were found in the existing generator for alarm output on general alarms and transfer switch engage. Internet connection was brought in to the plant for use by the operators as well as the control system.


All of the plant control signals were brought back to one single control panel running on 110 volt AC power from an outlet. This was made possible by exclusively using 24 volt DC signals to and from every device in the process.  Since it was small we constructed the main control panel in the shop here at SEA to save the customer money. Once the panel was built it was delivered on site and installed by our staff and the electrician.  


These signals in and out of various sensors and switches were all brought back to an Opto 22 PAC within the control panel for monitoring and control. If the wires and sensors could be considered the nervous system then the Opto 22 PAC is the brain. For remote access and monitoring a groov server was put in place to serve up the operator interface and a firewall to guard the plant network from internet intruders. (groov is a box that connects to the PAC controller and allows you to view what is going on and much more). Operators securely connect to the plant network from the internet through an encrypted virtual private network (VPN), and by using groov they can view plant interface from any device they have anywhere in the world. The groov system also serves the HMI (visual interface) on the main plant control panel as well. The HMI is shown on a 10 inch Google Nexus tablet fixed on the front of the control panel.


The entire system was built to be expanded with greater input/output if needed, and groov will allow the system to automatically gather plant data and put it into a database or excel file if the customer ever wishes to. One feature that was quite popular was the ability of the PAC to send text messages to the operators' smart phone if an alarm is thrown.     


Once the PAC system was connected to the relays and sensors it was custom programmed to make the system function exactly as the operator needed it to. When the tank drops to 9 feet the Arapahoe well comes on and remains at full speed until it approaches the full point of 14 feet. As it approaches the full point the PAC slows the water flow from the well. This serves the purpose of regularly turning the water in the tank over to keep it fresh during peak usage times. If the tank is still filling at night, the Laramie will come on and top off the tank but that is all. If the system hits 7 feet the Laramie comes on regardless of the time and sends an alarm . These wells can be controlled manually with the push of a button on the operator HMI. During the fill cycle the PAC is also watching the chlorine concentration and driving the speed of the chlorine pump up or down based on the desired concentration setting given by the operator. 


The PAC also watches the system pressure and adjusts pressure pump speed based on the pressure setting given by the operator. If the drive idles for too long it will shut down and wait for pressure to drop, it will also shut down if the system sees high pressure and send an alarm. If the pressure drops too low an alarm is sent out, the regular pressure pump shuts off and the fire pump starts. If the fire pump runs too long the operator is notified. Each pressure pump can be controlled from the HMI on the plant tablet. Generator alarms, water on the floor, and high/low chlorine also send text alarms.  



The Bottom Line​ 


After construction our customer monitored their electric and chemical usage closely and reported back with excellent results. Chemical consumption dropped by a whopping 2/3! Suddenly they were using water with low mineral content and high pH from the Arapahoe well without the heavy amount of iron from the Laramie that reacts with chlorine. The electric bill was equally dramatic. Prior to the upgrade the district paid $1,900-$2,200 per month for electric in the plant and wells. Today their bill is steadily about $950. These numbers shocked not only the operations manager, but our designer as well. 

But what about that pesky budget we mentioned? What did it cost to install? In the end it cost $53,491.

We always aim high, but with this project we knocked it out of the park!  Have a look at our project pictures below.