We closed on several high-quality acquisitions across all three of our strategic investment platforms, bringing our gross acquisition volume to $500 million in 2021.
We continue to see strong demand for space in our centers and signed a number of key leases with well-capitalized tenants, driving our accelerated signed not opened balance to almost $4 million.
And lastly, we raised or received commitments on $670 million of capital from our equity, debt and joint venture partners, strengthening our liquidity profile and balance sheet.
I am very pleased with GIC's recent commitment of an additional $500 million to our core grocery-anchored R2G platform, positioning that platform to scale up to $1.7 billion.
We also recently obtained commitments for $130 million in the debt private placement market and received another $40 million through our ATM, demonstrating our ability to access multiple sources of capital to accretively fund our growth plans.
Regarding the acquisition environment, we are currently experiencing a very competitive landscape to acquire high-quality shopping centers, where cap rates for grocery-anchored centers in top U.S. metros are down approximately 50 basis points over the past few months.
As a result, we believe the $500 million of acquisitions that we closed on so far could be up as much as 10% relative to our transacted prices.
We continue to see a healthy pipeline of deals for grocery-anchored centers, smaller strips and wealthy infill suburbs in our core communities and larger high-quality centers over $70 million, where we can allocate the real estate between our platforms.
We are in lease negotiation with a premier investment-grade grocer to take that space, which will drive the occupancy to about 99%, resulting in an estimated stabilized yield on cost of 7% in a 5% cap rate market.
Earlier this week, we closed on the sale of Market Plaza in the Chicago market for $30 million.
We received 11 offers and sold the property at a high 5% buyer's cap rate.
We also signed a new medical tenant, Piedmont Urgent Care, that replaces a sit-down restaurant at Promenade at Pleasant Hill just outside of Atlanta, swapping a high-COVID-risk tenant for an essential tenant at a mid-20% spread to the old brand.
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Notably, we have seen a major pickup in demand in Detroit over the past few quarters and are in negotiations on over half a dozen grocery deals and another eight to 10 box leases with discount apparel, pet, outdoor recreation and homegood retailers.
Third quarter operating FFO per share of $0.27 was up $0.05 over last quarter primarily due to about $0.04 of higher NOI from acquisitions, $0.01 from lower rent not probable of collection and about $0.01 from higher lease termination fees, partially offset by lower straight-line rent.
Notably, our collection rate for the third quarter was 98% as of the end of October.
We signed 52 leases totaling 280,000 square feet at a blended comparable releasing spread of 8.2%, including a 5.2% renewal and 16% new lease spread.
They don't capture future contractual rent steps, which were 160 basis points for the leases signed during the quarter.
Leasing activity in the third quarter pushed our signed not opened balance to $3.8 million, up 19% over last quarter's $3.2 million backlog, which we expect to open over the next 15 months.
On the remerchandising and outlet front, we delivered two projects totaling $3.3 million during the quarter at almost a 12% yield, which was ahead of budget.
We also added one new project, Ferguson gallery showroom at Providence Marketplace in Nashville, totaling $1.3 million at an expected yield in the 20% to 22% range.
This brings the active remerchandising and outlet project total to $14 million with expected yields in the 10% to 12% range.
We are in active negotiations on a number of other pipeline deals totaling about $30 million with strong box demand in Boston, Florida and Detroit.
We ended the third quarter with net debt to annualized adjusted EBITDA of 6.8 times, down from seven times last quarter.
This is a bit better than expected as a result of the $40 million raised through our ATM and due to better NOI performance.
We continue to expect our leverage to fall toward our target range of 5.5 to 6.5 times as bad debt and occupancy normalize to pre-COVID levels.
We ended the third quarter with a cash balance of approximately $10 million and have $295 million available on our unsecured line of credit.
During the fourth quarter, we expect to refinance $177 million of debt.
We expect to use proceeds from our recent private placement of unsecured notes totaling $130 million, our share of expected proceeds from mortgages placed on R2G assets that we locked rate on totaling $15 million and proceeds from the sale of Market Plaza totaling $30 million to fund these debt repayments.
Following all this activity, we will have reduced debt maturities through 2024 to just 16% of our debt stack.
Over the next two quarters, we also expect to generate $96 million in disposition proceeds from parcel sales to RGMZ, including sales from our recently acquired Northborough and Newnan Pavilion assets and the remaining seed portfolio sales.
These proceeds will effectively be used to fund our share of the debt of acquisition of $68 million and to repay amounts outstanding on our revolving line of credit.
We initiated a new range for operating FFO of $0.90 to $0.94 per share, which is up $0.02 or 2% over prior guidance.
The primary drivers of the upside were $0.01 from a prior period bad debt reversal and about another $0.01 of lease termination fees recognized in the third quarter.
Our third quarter operating FFO per share of $0.27 benefited from $0.02 related to nonrecurring items, including a prior period favorable bad debt adjustment and a one-time lease termination fee.
In addition, relative to our third quarter results, 2022 G-and-A is expected to increase by approximately $0.01 per quarter related to an uptick in travel-related expenses, similar to 2019 levels, and continued investments in talent to support our growth platforms.
And can we fund the acquisition in a way that's both accretive to earnings and pushes us closer to our target leverage range of 5.5 to 6.5 times?

Summary:
Third quarter operating FFO per share of $0.27 was up $0.05 over last quarter primarily due to about $0.04 of higher NOI from acquisitions, $0.01 from lower rent not probable of collection and about $0.01 from higher lease termination fees, partially offset by lower straight-line rent.
We initiated a new range for operating FFO of $0.90 to $0.94 per share, which is up $0.02 or 2% over prior guidance.
Our third quarter operating FFO per share of $0.27 benefited from $0.02 related to nonrecurring items, including a prior period favorable bad debt adjustment and a one-time lease termination fee.