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Si photonic foundry fabricated cascaded and continuous spiral shaped silicon nitride (SiN) waveguides that incorporate Bragg grating structures were explored to produce an on-chip true-time delay line. A time-domain measurement method was used to characterize the delay time of the grating waveguides near their photonic band edge where it exhibits the strongest slow light effect. The highest group index extracted from cascaded SiN grating waveguides is 19.7 corresponding to a total delay time of 5.48 ns in a full length of 12.49 cm that consumes a surface area of 2.66 mm². A continuous spiral SiN grating waveguide was also fabricated which produces a delay time of 3.78 ns in a length of 5.47 cm with a surface area consumption of 0.88 mm².