6. Goodwill and Intangible Assets

Goodwill

Goodwill as of March 31, 2022 and September 30, 2021 consisted of the following:

The Company completed its most recent annual goodwill impairment assessment, as of September 30, 2021, and determined that its goodwill was not impaired. The amount of discount inherent in the Company’s market capitalization reported on the NYSE American exchange when compared with consolidated stockholders’ equity, or net book value, had increased since September 30, 2021; therefore, the Company performed an interim assessment of its goodwill for impairment as of December 31, 2021. The estimated fair values of its Professional Services and Industrial Services reporting units were adjusted based on qualitative and quantitative analysis so that they reconcile more precisely with the Company’s market capitalization as of December 31, 2021, plus an assumed control premium. As a result, the Company recognized a non-cash impairment charge of $2,150 during three-months ended December 31, 2021. The Company reassessed the qualitative and quantitative analysis at March 31, 2022 and determined there was no additional impairment during the three-month period ended March 31, 2022.

Intangible Assets

The following tables set forth the costs, accumulated amortization and net book value of the Company’s separately identifiable intangible assets as of March 31, 2022 and September 30, 2021 and estimated future amortization expense.

The trade names are amortized on a straight-line basis over their respective estimated useful lives of between five and ten years. Intangible assets that represent customer relationships are amortized on the basis of estimated future undiscounted cash flows or using the straight-line basis over estimated remaining useful lives of five to ten years.

The amortization expense for intangible assets was $1,015 and $2,029, and $1,015 and $2,059 for three and six-month periods ended March 31, 2022 and 2021, respectively.