ANSI/NSF Standard 61 Finally Finalized
After years of careful evaluation of data, the National Sanitation Foundation (NSF) standards review board, has modified the standard with respect to concrete in contact with drinking water.
ANSI/NSF Standard 61 Finally Finalized
By Joy Eldredge, Water General Manager, City of Napa
After years of careful evaluation of data provided by the CA-NV American Water Works Association (AWWA) and industry professionals, the National Sanitation Foundation (NSF) standards review board, which performs testing and establishes the criteria for American National Standards Institute ANSI Standard 61 (Drinking water system components Health effects), has modified the standard with respect to concrete in contact with drinking water.
HistoryIn December 2012, NSF International proposed an increase in the testing requirements for concrete and other items. As a representative of the drinking water industry, CA-NV AWWA commented on the process for changing the standard and requested the data and rationale that drove the proposed changes. The issue had been a recurrent subject at CA-NV AWWA's annual spring and fall conferences because California Water Regulations require all items in contact with drinking water to be in compliance with ANSI/NSF 61.
The proposed changes posed a significant challenge to CA -NV members, and an ad hoc subcommittee was established in the Water Quality Division to develop guidance on complying with existing California regulations. The committee engaged California's State Water Resources Control Board's Division of Drinking Water (DDW) about the challenges of complying with the requirements as written.
Over a five-year time period, the Ad Hoc Subcommittee on Standard 61, DDW regulators, NSF joint committee members, and NSF staff were able to compile data, conduct analysis and collectively develop modified language for concrete compliance. The following provides an over view of the changes to the ANSI/NSF 61 with regard to concrete.
Section 3.3.2 Minimum Test Batteries
- Uncoated concrete storage tanks of 350,000 gallons or larger a re exempt from ANSI/NSF 61.
- Uncoated concrete with a diluted surface area-to volume ratio less than or equal to 0.8 in2/L for static conditions or 0.08 in2/L for flowing conditions are exempt.
In both exemptions, individual admixtures still need to be certified for compliance with ANSI/NSF 61. The requirement for admixtures to comply with Standard 61 has not been an obstacle to the drinking water industry since products that have been pre-certified by NSF 61 have be en readily available in California. Pre-certification requires coordination testing and routine facility inspection by NSF to maintain certification. Another reason admixture certification has been required is because formulas for admixes change frequently with advances in materials and products.
Section 5.1 Barrier Materials
- Concrete aggregate sampling is required only if the method for testing for individual concrete components is used. Aggregate sampling is not required if concrete cylinders are tested for the constituents in Portland and hydraulic cements.
As municipalities have two common ways to confirm concrete compliance: confirm constituent compliance or soak testing, language was developed to provide clarification on testing procedures that apply to each case. This clarification was incorporated because the previously developed guidance gaining compliance through testing individual components that make up the concrete, i.e., aggregate, cement, admixtures, did not explicitly state that soaking of the final concrete would not be required. This assumes that the individual components are found to be compliant. The revised guidance also clarified that when confirming compliance with the concrete cylinder soak test method, the agency was not required to also test the constituents of the mix, including aggregate.
The option of analyzing individual constituents of the concrete was designed to overcome the logistics and impracticality of certifying concrete cylinders prior to construction or cores after the concrete was pour ed in the field. Pre-construction concrete cylinder testing on some projects was found to require eight to 12 weeks to produce analytical results. Testing cylinders prior to construction posed significant schedule impacts, and testing cores aft er the concrete was placed in the field posed a significant risk to the agency. For constituent testing it is typically found that the concrete supplier has NSF certified cement and admixtures available, allowing for the aggregate to be sent to an ANSI certified laboratory to test for compliance.
Section 5.7.2 Normalization for Concrete Aggregate
- Clarification of the formula for normalization that recognizes only 10 percent of the aggregate exposed within the top one-inch surface of the concrete is exposed to drinking water in low-pressure situations found in storage tanks.
- (The previous assumption was that 80 percent of all aggregate was exposed.)
- Table 5.6 Lists calculated values of surface area- to -volume ratios for tanks or storage vessels for tanks from 5 million to 10 million gallons.
- Table 5.8 Lists values for calculating the aggregate field use for tanks from 1,000 to 250,000 gallons.
The ballot has been adopted, approved and took effect March 17, 2017. The revised NSF/ANSI Standard 61 is scheduled for publication soon.
Where to From HereThe next step is to continue to gather data and monitor newly constructed tanks and structures, focusing on tanks and structures smaller than 350,000 gallons, and determine whether the exemption can be applied to a smaller threshold of vessels. This will take time, and the ad hoc committee on Standard 6 1 would greatly appreciate receiving data from projects of this size so it can determine whether the threshold can safely be lowered. Send information to Jeldredge@cityofnapa.org or Kevin Peacock (email@example.com).
Special thanks to industry representative Kevin Peacock of DN Tanks, who assisted by gathering data and analyses performed on recent projects and providing it to the analytical team at NSF, and to Eugene Leung at DDW who managed the interim data-centric monitoring approach to achieve compliance with the standard when certified products were not available in the market. Mr. Leung also served as a resource within DDW to advise and review the interim alternate method the ad hoc committee established. Also thank you to Charley Rea of California Construction and Industrial Materials Association ( CalCIMA), who assisted in addressing this problem, raised awareness among CalCIMA members, including large material suppliers, and facilitated understanding of the road map for performing analyses that addressed the lack of ANSI/NSF 61 certified materials available in the California materials market.