The project is being managed by Paul Chapman from Tierra Ltd, who was also involved in the initial indoor arena built in 2002.
Chapman, who is also board chairman of Tauranga Riding for the Disabled, said the cover over the outdoor arena would weather-proof clients' experiences.
"It is quite difficult at the moment as it is too hot in summer and too wet in winter, and we needed more all-weather riding spaces for our clients," he said.
Chapman said it was an "exciting project" which would not only benefit existing and future clients but also making the centre more user-friendly for community groups.
Olds said the extension project would enable RDA to meet the increasing demand for equestrian therapy programmes and help to reduce the growing waiting list.
"Presently on average 140 riders use the facilities each week and we also have up to 170 riders on our waiting list," she said.
Olds said the extension project was made possible because of the fantastic support from TECT, Pub Charity, NZ Community Trust and several major private donors.
"This expansion supports our goal to assist more riders and contributes to enriching the lives of people with disabilities, and those risk in our community," she said.
"We are continually evolving to meet our clients' needs and have big plans in the next two years."
Olds said the aim was to increase the number of riders to about 200, add more intensive therapeutic programmes, and increase the number of international students.
"We have 16 therapy horses and 135 volunteers but RDA always needs more volunteers and to expand the programmes we also need to add more coaches and horses," she said.
Tauranga central resident Fiona Fullerton, who became a Tauranga RDA volunteer last April, said it was a great opportunity for her to give something back to the community.
"It's incredibly rewarding to be involved with RDA, especially when you see the growth of the children and the kinship that flows from that growth. It's amazing to be part it."
