After 14.4 time faults over the course, Powell is in 14th place on Mac Macdonald on 66.7 penalties - some 14.2 penalties from the leader, Britain's Badminton winner Oliver Townend on Jackson D'allez.
Powell's Apapa is in 21st place with 72.6 penalties, after also amassing time faults on the cross-country.
All riders had time faults on the course.
Hugh Lochore (GBR), the US-based course designer, had set an enticing test, which he described as a "balance of technical and attacking", reminiscent of Ireland's hunting tradition and with big bold fences set naturally in the hedge lines. Indeed, the Irish riders rose to the fore, with 5 of them in the top 10 after Cross-Country. Mary King commented: "I thought it was refreshingly old-fashioned with natural fences - it felt like proper cross-country."
The country had suffered a lot of rain, but after considerable work and commitment on the part of organiser George Mernagh and his team, although the course had some soft patches, the going was excellent and horses were finishing well. The track was little changed overall from last year, but Lochore said that he had "beefed up" some of the combinations and riders considered it an appropriately demanding test.
Husband-and-wife Trish and Michael Ryan, finished strongly to take up attacking positions in the top six for the home side.
Olympian Trish, riding Carol and Tom Henry's Irish-bred Fernhill Clover Mist, recovered from a mid-ranked dressage score to sweep into fourth place after collecting just 6.8 time penalties on the cross country course. Husband Michael, meanwhile, incurred only 3.6 penalties to place seventh with John Butler's Old Road at the end of yesterday's phase.
It was not only the veteran campaigners, like the Ryan horses who went well, but 3-star newcomers like William Fox-Pitt's Sonate V and Pippa Funnell's Mirage d'Elle. Patricia Ryan said: "It was very quick; the time was difficult and you just had to keep thinking and concentrating all the way round."
First on course, Oliver Townend and Golden Hue, seventh after dressage, were submerged in the water complex at 21 when the horse missed his footing on landing in the lower part of the split-level obstacle. Katie O'Sullivan (IRL) and Snannondale Que also fell at this fence.
Halfway through the competition, Catherston Defender, ridden by Italy's Alberto Guigni, fell at the fence, breaking his foreleg. Spectators reported that a bystander leapt to Guigni's aid as the horse struggled to keep his head above water. The 13-year-old gelding was euthanised in the water in front of a large crowd.
The fence was removed from the competition by Technical Delegate Neil Clinton (AUS) and the Ground Jury, after the remaing riders demanded it be taken out. The timing was adjusted accordingly and all riders who had already jumped the fence had 4sec (1.6 penalties) taken off their times.
The track at Tattersalls, site of the premier bloodstock auction house in County Meath, is predominantly flat, but it contains a spectacular man-made HSBC bank complex at 11 and 12 which involved a bounce up to an undulating ridge over a log and followed by an "into-space" drop. Although it proved a popular spectator attraction, the obstacle rode well and only caused one fault, for Polly Stockton on first ride Westwood Joker, whom she subsequently retired.
The most influential fence turned out to be a pair of brush corners at 8ab which claimed two notable scalps in luckless World Champion Zara Phillips on Secret Legacy and Mark Todd (NZL), riding in his first major competition this year, on his Olympic horse Gandalf. Both riders retired, Todd having already withdrawn Land Vision after dressage.
In the placings after the cross-country, close behind is George Russell and Young Man in eighth and Declan Cullen with Glenhill Gold in ninth, while Ciaran Glynn drops to 10th place on Killossery Kruisita, giving Ireland a total of five top ten places ahead of Sunday's final show jumping phase.
The 2008 winner, Capt. Geoff Curran, withdrew his winning mount Kilkishen, but is still placed well at 13th with Maurice Cassidy's The Jump Jet.
The event wraps up today with the showjumping.
• Kiwis fared better in the two-star class over the cross-country, with Andrew Nicholson maintaining his third place on Calico Joe (44.1), just behind leaders Oliver Townend (Waterview, 43.6) and Chole Newton (Cast Away II, 43.6).
A more relaxed time limit meant most riders got through without penalty, and only a handful had refusals.
Nicholson is also sixth on Tristar II (47.1), and Todd and Grass Valley 14th with 53.1 penalties. Nicholson's Shady Grey is at the tail of the field, with 83.4 penalties after a jump fault and time penalties.
Nicholson is also in fifth place in the one-star class on Quimbo, with 45.9 penalties, behind leader William Fox-Pitt and Oslo, on 38.0 penalties.