HomeMy WebLinkAboutENG_Drywell_Capacity_Verification_TestingMitchell D. Roth 81*:.^3S2Z^A.: *1§ Stephen M. Pause, P.E.Mayor ^ •^BS^^'-/ /^ DirectorDeanna S. Sako ~voa3sy' Malia Kekai^^. ^^ nf^n^fi DWDm'"DEPARTMENT OF PUBLIC WORKSAupuai Center101 Pauahi Street, Suite 7 • Hilo, Hawai'i 96720-4224(808)961-8321 • Fax (808) 961-8630public_works@hawaiicounty.govENGINEERING DIVISIONMEMORANDUMTo: PublicFrom: Alan Keone Thompson, P.E.Date: August 29, 2024Subject: Drywell Capacity Verification TestingThe procedures below shall be followed for the capacity verification testing of all newlyinstalled drywells intended to control rainfall runoff in the County of Hawaii:• Upon completion of construction of the drywell, the following steps shall be taken.Verification testing shall be done in the presence of the Engineer or a representative.All processes and results shall be documented by the contractor on the attachedform.o Pretest: Inject a minimum of 2,000 gallons of potable water into the drywell.o First Test: Within two hours of the completion of the previous step, inject aminimum of 2,000 gallons of potable water into the drywell at the maximumflowrate allowable by the equipment used.• Record volume, start time of injection, time to complete the injection, and thetime required for the water to fall each of three 24" increments.• Calculate the rate of infiltration for each 24" increment and the average rate ofinfiltration for the three increments combined.o Second Test: Within two hours of the completion of the previous step, inject aminimum of 2,000 gallons of potable water into the drywell at the maximumflowrate allowable by the equipment used.County ofHawai'i is an Equal Opportunity Provider and Employer.
• Record volume, start time of injection, time to complete the injection, and thetime required for the water to fall each of three 24" increments.• Calculate the rate of infiltration for each 24" increment and the average rate ofinfiltration for the three increments combined.Average infiltration rates for the measured tests must be within 0.5 cubic feet persecond of each other or a third test must be conducted within two hours of the end ofthe second. If a third test is required, the average of the results of the second andthird tests shall be used to determine the capacity of the drywell.If standing water is observed at the bottom of the drywell and/or the bottom of thedrywell is at or below 10' above Mean Sea Level, an additional 500 gallons of watermust be added to each of the testing quantities and the bottom of the lowest readingmust be at least 24" above the observed standing water level or the bottom of thedrywell, whichever is higher.County ofHawai'i is an Equal Opportunity Provider and Employer.
Project NameDate of TestDrywell LocationDiameter of DrywellFirst Injection (Pretest)VolumeStart TimeSecond Injection (First Test)VolumeStart TimeAverage Injection Rate (gal/sec)Time to drop first 24"Time to drop second 24"Time to drop third 24"Third Injection (Second Test)VolumeStart TimeAverage Injection Rate (gal/sec)Time to drop first 24"Time to drop second 24"Time to drop third 24"End TimeTime to Complete (sec)Infiltration Rate ((TTr2x24")/time)Infiltration Rate ((TTr2x24")/time)Infiltration Rate ((nr2x24")/time)Average Infiltration RateTime to Complete (sec)Infiltration Rate ((nr2x24")/time)Infiltration Rate ((nr2x24")/time)Infiltration Rate ((nr x24")/time)Average Infittration RateContractor's Name / SignatureDPW Representative Name / Signature