Frost-depth gauge Installation, Maintenance and Observation Instructions This instruction sheet provides guidance on the installation, maintenance and procedure for taking observations utilizing an NWS Model 5 frost-depth gauge. Installation Procedures Storage The inside tube of the frost-depth gauge should be stored in a dark storage area away from any sunlight or indoor lighting prior to installation. Prolonged exposure to light will cause the dye/water solution to lose its consistency and/or body. Tube Length Selection The length of the frost depth tube should be selected to match the maximum frost depth of a geographic location. Figure 1 below should be used as a guide to select the appropriate frost depth tube length. Figure 1. Approximate maximum frost-depth contours. Frost-depth tube length should be selected to capture the appropriate frost depth in a given geographic area. Site Selection The frost-depth gauge is typically co-located with other NWS observing equipment. The frost-depth gauge should not be installed within a 20-ft distance of a heated building. In addition, the gauge should not be installed within 10-ft of any marked underground utilities (see Utility Location). The selected site should be reasonably level. Utility Location All utilities must be located and marked by a professional utility location service, prior to digging a hole for the frost-depth gauge. As a general rule of thumb, all underground utilities must be located within 100-ft of the selected frost-depth gauge location. Contact the local utility location service and make a request to have the utilities located on the property. Place a stake or other marker in the ground at the selected site, prior to the utility location. The stake/marker will serve as a reference when describing the location to the utility location service. Typically, it takes two to four full working days for the utility location service to mark all the utilities. Do not install the gauge in a location that is within a 10-ft radius of any utility line. Installation Supply List NWS Model 5 Frost-Depth Gauge: o ¾-in diameter PVC outer tube with end cap (length varies from 2 ft to 6 ft) o Flexible-clear inner tube assembly with top cap and handle (length varies from 2 ft to 6 ft). The clear tube is filled with green fluorescein dye. o 4-in diameter PVC frost-depth gauge outer tube with lid Sledge hammer Small 4x4 in or similar size piece of scrap lumber Shovel Post hole digger or hand auger or gasoline-powered auger or post-hole driver/black iron pipe. Broom handle or similar flat-bottomed stick Yard stick Bubble level Wooden stake or similar marker Offices must have utilities located by a professional utility location service prior to boring a hole for the frost-depth gages. Equipment Rental or Purchase Procedure Offices may have to purchase or rent equipment to install the frost-depth gage. Central Region will fund the rental or purchase of equipment to install one frost-depth gages on the property of each WFO. There is a budgetary limit of $100 for the installation of a frost-depth gage at each WFO. Offices that must rent or purchase equipment for the installation of frost-depth gages should follow the procedure below: Regional Point of Contact (POC): Bob Brashears (Bob.Brashears@noaa.gov) 816-268-3161 1. Obtain an estimate for the purchase or rental of the necessary equipment required to bore a single hole on WFO property to a depth that will accommodate your WFO frost-depth gage. 2. Once you have obtained an estimate, have the station MIC enter the following information in the Central Region Facilities Project Request System: a. SUBJECT: Frost-Depth Gage Installation b. WFO Name c. The handbook 5 ID (NSWLI) of the frost-depth gage that will be installed on WFO property. d. An itemized list of the equipment to purchase and/or description of the equipment rental that will be ordered and the associated costs. e. The name of the person that will charge the purchase to your local office’s Government Visa Purchase Card (for accounting purposes). 3. The POC will review the parts and/or repair request. Upon review: a. If the purchase request is approved, the POC will approve the request in the system, upon which the MIC and the person who entered the request will be notified via e-mail that the equipment and/or rental have been approved, and the purchase can be ordered. The charge code to be used will be included in the approval email for reconciliation of office bank card statements. b. If the purchase request is not approved, the e-mail generated by the request system will notify the requester that the equipment and/or rental cannot be purchased. 4. Once the request has been approved, make the purchase and/or arrange for the equipment rental. Charge the purchase to the office’s Government Visa Purchase Card. Notify the POC immediately if the final costs are different from the initial estimate previously provided in the Facilities Project Request System. Installation Methodology There are two basic approaches to creating a hole for installation of the frost-depth gage. A hole may be excavated with a manual post-hole digger, gasoline-powered auger, or manual soil auger. A hole may be pierced in the soil with a manual post-hole driver and iron pipe combination. Excavation Method The excavation method requires removal of soil in layers to create a void space for the installation of the frost-depth gage. This method should work in all soil conditions. A manual post-hole digger, gasoline- powered auger, or manual soil auger may be used to excavate the soil layers. During excavation, soil layers should be extracted in sections, and the soil sections should be preserved, in order of extraction from bottom to top. The layers will be used to backfill void space once the gauge has been installed, thus it is important that the layers are replaced in the order that they were extracted. The diameter of the tool used to excavate can range from 1 to 12 inches in diameter. A 1 -in diameter hole is the minimum diameter that will accommodate the frost-depth gauge. A 6-in or 8-in diameter auger is the ideal size. The 6 to 8-in diameter hole may be easily backfilled with a tamping stick. When excavating the hole, it is critical to maintain a 90-degree angle between the auger tool and the ground surface. A bubble level can be used as a guide to ensure that the frost-depth tube is installed at a 90-degree angle. After the gauge has been set in the hole, adjust the gauge depth so that the black ground line mark on the outside of the gauge lines up with the ground surface. Use a yardstick laid horizontally to line up the black line with the ground line. After the gauge is adjusted to the proper height to match the ground surface, backfill the hole slowly making sure the gauge stays as vertical as possible during the backfill process. Using a flat-bottomed stick, tamp the dirt down tightly around the gauge. If possible, return the soil layers back in the hole in the order they were taken out. The soil should be tamped down as closely as possible to the original state of the compactness. Backfill and tamp the soil right up to the black line on the gauge. Figure 2. A frost-depth gauge installed inside the 4-in diameter PVC cover. The tube is positioned so that zero inches of depth reading is level with the ground surface. Piercing Method The piercing method consists of driving a length of threaded black iron pipe into the ground to create a void space for the installation of a frost depth gage. This method may not work in rocky soils or soils with heavy clay deposits. The piercing method requires a single or multiple lengths of threaded black iron pipe, depending on the depth requirement of the gauge, and a two-handled metal post driver. The black iron pipe should be approximately the same diameter or slightly larger than the frost-depth gage PVC casing. A 4-ft to 6-ft length of black iron pipe can be driven into the ground, and a second section may be threaded onto the initial section to keep the above ground length of the pipe at a manageable length for operation of the post driver. Once the desired gauge depth has been reached, remove the entire length of threaded black iron pipe and install the frost depth gage. The black ground line mark on the outside of the gauge should align with the ground surface. No backfilling is required with the piercing method. PVC Cover Installation Using a short piece of scrap lumber and a sledge hammer, pound the 4-in diameter PVC cover into the ground around the gauge. Use the piece of scrap lumber to protect the PVC cover from direct contact with the sledge hammer. Secure the screw-on top. A post, stake or marker can be placed near the gauge so that it can be easily found under deep snow conditions. NWS CSSA Station Documentation The frost-depth gages should be documented in the Cooperative Station Service Accountability (CSSA) system in the "Other Equip Info" section. Complete the CSSA form as follows: Equip Category: MISC Equip: MISCX Owner: NWS Azimuth and Distance: the direction and distance from the primary precip gage Backup: Enter "N" Equipment Description: NWS MODEL 5 FROST DEPTH GAGE / DEPTH "X" FEET / INSTALLED ON "XX-XX-20XX" / DEPTH OF FROST PENETRATION (GD) AND DEPTH OF SURFACE FROST THAWED (GT) REPORTED VIA WXCODER ( "ON MONDAY AND THURSDAY / OR DAILY" ...as appropriate ) FROM NOVEMBER UNTIL THE FROST IS OUT OF THE GROUND IN THE SPRING. Annual Maintenance Once a year, a service check should occur prior to the reporting season (September to October). Key Items to view during the annual inspection: The gauge and the 4-in diameter PVC cover should be removed, inspected and cleaned. Check the elevation of the zero line on the gauge in relation to ground level. Ground settling may have occurred, and readings will be inaccurate if this zero line is higher or lower than the ground level. If the zero line on the gage falls below the ground surface, then add soil so that the ground line matches up with the black line (zero inch line) on the gauge. If the gauge is too high, pound it down in the ground to the proper depth using a piece of scrap lumber and a hammer. The dye/water mixture should be inspected. The dye/water mixture should maintain a green color that is similar in color to automotive antifreeze. The dye should not appear faded, very light green in color or “washed out.” If this is the case, then the dye and water mixture must be drained and replaced. The clear plastic tubing that contains the dye must be visually inspected. If the clear plastic tubing appears foggy or cloudy, the whole inside clear tubing must be replaced. Lubricate the cap threads lightly with white lithium grease or Vaseline. This will prevent the cap from freezing in place. Procedure for Taking Frost-Depth Observations Reporting Season: The objective of the frost-depth gauging program is to capture the formation and degradation of the frost throughout the reporting season. The reporting season begins in Fall and ends in Spring, but may vary widely by geographic region. The WFO must capture a minimum of two weeks of baseline zero- frost depth data prior to the onset of frost. The WFO must capture a minim of two weeks of baseline zero-frost depth data after all frost has melted. The WFO should coordinate with their RFCs to determine the best date to begin and end the frost reporting season for their geographic area. Reading the Instrument: The instrument reports frost depth below ground level in units of inches. Ground level is designated as 0 in and units increase as the distance below ground increases. The inner tube must be removed from the outer tube. Figure 3. A frost-depth gauge being removed from the 4-in diameter PVC cover. Reporting Elements: Frozen ground conditions will cause the liquid in the clear tube to freeze. Ice formation in the flexible- clear tube will change the color of the liquid from a green color to a clear or opaque color, so that the observer may visually identify the depth of frost penetration. In addition, a ball bearing has been installed inside the clear tube. The observer may tip the clear tube upside down and take a reading at the location where the ball bearing travel is restricted by the ice. Observers are requested to report Depth of Frost Penetration and Depth of Surface Frost Thawed at each report; however, Depth of Surface Frost Thawed need only be reported if there are at least 2 inches of frost depth. Observations should be rounded to the nearest inch. Depth of Frost Penetration is defined as the distance from the zero reading on the flexible clear tube to the end of the frozen zone (clear) on the frost-depth gauge. As a second check, this is the location where the ball bearing meets the ice in the tube. Depth of Surface Frost Thawed is defined as the length of thawed (green) liquid that extends from the ground level or zero to the top of a frozen zone of liquid (clear) on the frost-depth gauge. Depth of Surface Frost Thawed is only recorded when there is at least 2 inches of total frost depth. Depth of Surface Frost Thawed may not exist during periods of persistent cold. Figure 4. An example gauge reading that shows 9 in of Depth of Frost Penetration and 2 in of Depth of Surface Frost Thawed. Depth of Surface Frost Thawed needs only be reported if there are at least 2 inches of frost depth present. The frost-depth readings should be reported and SHEF encoded through WXCODER. In WXCODER, these elements are listed and SHEF encoded as Depth of Frost Penetration (GD) and Depth of Surface Frost Thawed (GT), respectively. Frequency and Timing: CO-OP observers should take readings and report every day, if possible. At a minimum, CO-OP observers should take readings twice per week on Monday and Thursday mornings before noon. All observations should be submitted through WXCODER. Weather Forecast Offices should take readings and report twice a week. Readings should be taken on Monday and Thursday mornings before noon and should be submitted through WXCODER. Special Precautions and Troubleshooting: Try to keep snow or rain from falling into the outside tube of the frost-depth gauge. The flexible tube should be kept in a dry environment. If water does get into the outside tube, try to remove it. A stick with a sponge secured to the end can be utilized to remove any moisture/dirt that may have seeped into the outside tube of the gauge. The screw cap may freeze up and become difficult to remove in cold weather. This problem can be eliminated by lubricating the cap threads lightly with white lithium grease or Vaseline. The cap should also be tightened only enough to keep moisture from entering the measurement instrument. The gage may be difficult to locate in deep snow. A marker or flag that sits above the snow pack will help with the location of the device. Appendix MSDS Safety Sheet for Green fluorescein liquid dye Note: The fluorescein dye and distilled water in the clear tube have been mixed at a ratio of 1 part fluorescein dye to 750 parts distilled water. See attached “MSDS.pdf” for the Material Safety Data Sheet.
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